View source for Sauropodomorpha

{{Short description|Extinct clade of dinosaurs}}
{{Automatic taxobox
| name = Sauropodomorphs
| fossil_range = {{fossil range|233.23|66|ref=<ref name=langer18>{{cite journal|last1=Langer|first1=M.C.|last2=Ramezani|first2=J.|last3=Da Rosa|first3=Á.A.S.|year=2018|title=U-Pb age constraints on dinosaur rise from south Brazil|journal=Gondwana Research|volume=X|issue=18|pages=133–140|doi=10.1016/j.gr.2018.01.005|bibcode=2018GondR..57..133L}}</ref>}}
| image = {{multiple image
|perrow=2/2/2
|total_width=300
|image1=Apatosaurus louisae - CM.jpg
|image2=Eoraptor Deep Time.jpg
|image3=Lessemsaurus Senckenberg.jpg
|image4=Leonerasaurus.jpg
|image5=Argentinosaurus skeleton, PLoS ONE.png
|image6=Plateosaurus Skelett 2.jpg
|border=infobox
}}
| image_caption = Six sauropodomorphs (clockwise from top left):  ''[[Apatosaurus]]'', ''[[Eoraptor]]'', ''[[Leonerasaurus]]'', ''[[Plateosaurus]]'', ''[[Argentinosaurus]]'', ''[[Lessemsaurus]]''
| image_upright = 1.3
| taxon = Sauropodomorpha
| authority = [[Friedrich von Huene|Huene]], 1932
| subdivision_ranks = Subgroups
| subdivision = * {{extinct}}''[[Ahvaytum]]''?
* {{extinct}}''[[Buriolestes]]''
* {{extinct}}''[[Eoraptor]]''
* {{extinct}}''[[Mbiresaurus]]''
* {{extinct}}''[[Xixiposaurus]]''?
* {{extinct}}'''[[Guaibasauridae]]'''
* {{extinct}}'''[[Saturnaliidae]]'''
* {{extinct}}'''Bagualosauria'''  <small>Langer et al., 2019</small>
** {{extinct}}''[[Arcusaurus]]''
** {{extinct}}''[[Asylosaurus]]''
** {{extinct}}''[[Bagualosaurus]]''
** {{extinct}}''[[Efraasia]]''
** {{extinct}}''[[Huayracursor]]''
** {{extinct}}''[[Nambalia]]''
** {{extinct}}''[[Pantydraco]]''
** {{extinct}}''[[Plateosauravus]]''
** {{extinct}}''[[Ruehleia]]''
** {{extinct}}'''[[Thecodontosauridae]]'''
** {{extinct}}'''Plateosauria''' <small>[[Gustav Tornier|Tornier]], 1913</small>
*** {{extinct}}'''[[Plateosauridae]]'''
*** {{extinct}}'''[[Unaysauridae]]'''
*** {{extinct}}'''Massopoda''' <small>Yates, 2007</small>
**** {{extinct}}''[[Ignavusaurus]]''
**** {{extinct}}''[[Kholumolumo]]''
**** {{extinct}}''[[Musankwa]]''
**** {{extinct}}''[[Sarahsaurus]]''
**** {{extinct}}''[[Wudingloong]]''
**** {{extinct}}'''[[Massospondylidae]]'''
**** {{extinct}}'''[[Riojasauridae]]'''
**** {{extinct}}'''[[Sauropodiformes]]'''
{{Collapse top|title=Possible sauropodomorphs |left=yes|padding=0|border=0|border2=0|bg=clear|bg2=clear}}
* {{extinct}}''[[Agnosphitys]]''
* {{extinct}}''[[Ahvaytum]]''
* {{extinct}}''[[Alwalkeria]]''
* {{extinct}}''[[Nyasasaurus]]''
* {{extinct}}'''[[Herrerasauridae]]'''
{{Collapse bottom}}
}}

'''Sauropodomorpha''' ({{IPAc-en|ˌ|s|ɔːr|ə|ˌ|p|ɒ|d|ə|ˈ|m|ɔːr|f|ə}}{{refn|Cf. {{cite web |url=https://www.oxforddictionaries.com/definition/english/sauropodomorph |archive-url=https://web.archive.org/web/20151101224803/http://www.oxforddictionaries.com/definition/english/sauropodomorph |archive-date=November 1, 2015 |title=sauropodomorph - definition of sauropodomorph in English from the Oxford dictionary |publisher=[[OxfordDictionaries.com]] |access-date=2016-01-20 }}}} {{respell|SOR|ə|POD|ə|MOR|fə}}; from Greek, meaning "lizard-footed forms") is an extinct [[clade]] of [[saurischian]] dinosaurs that includes the long-necked, [[herbivorous]] [[Sauropoda|sauropod]]s and their ancestral relatives. Early, more [[basal (phylogenetics)|basal]] sauropodomorphs (traditionally termed '''prosauropods''') were [[biped]]al, and the earliest show evidence of [[omnivorous]] or [[carnivorous]] diets. Over time, sauropodomorph evolution resulted in a shift to herbivorous diets, larger body sizes, and [[quadruped]]al locomotion. The sauropods themselves generally grew to very large sizes, had long necks and tails, and became the largest animals to ever walk the Earth. The sauropods were the dominant terrestrial herbivores throughout much of the [[Mesozoic Era]], from their origins in the [[Late Triassic]] (approximately 230 [[Myr|Ma]]) until their decline and extinction at the end of the [[Cretaceous]].

==History of study==

===Early study===
Gigantic bones of [[sauropods]] have been known for thousands of years and become part of [[legend]]s and [[culture]]s but the beginning of their scientific study was in the 1830s.<ref name="hallett2016"/> Most of the early [[taxonomy]] was based on incomplete and disarticulated material as relatively complete [[skulls]] or [[skeletons]] were not discovered until closer to the end of the 19th century.<ref name="sereno2007"/> The French [[anatomist]] [[Georges Cuvier]] studied large fossils from the [[Jurassic]] of [[Stonesfield Slate]] in England, believing them to have belonged to ancient relatives of [[whales]] up to his death in 1832. However, British [[paleontologist]] [[Richard Owen]] instead classified these large bones, which he gave the name ''[[Cetiosaurus]]'' in 1841, as [[marine life|marine]] whale-like [[crocodilians]]. This was the second [[genus]] of sauropod to be named, following his earlier description of a single isolated tooth as the taxon ''[[Cardiodon]]''.<ref name="hallett2016"/> At the same time, the first early sauropodomorphs were being described, with ''[[Thecodontosaurus]]'' named in 1836 for material from England and Wales, and ''[[Plateosaurus]]'' named in 1837 for material from Germany. Owen would even name the early sauropodomorph ''[[Massospondylus]]'' in 1854 for partial specimens from southern [[Africa]], though all these early taxa were considered carnivorous [[theropods]] rather than relatives of sauropods.<ref name="sereno2007"/> Owen's interpretation of ''Cetiosaurus'' as a marine crocodilian, which he specifically excluded from [[Dinosauria]] when he named it in 1842, began to be disputed with additional discoveries of limb bones of both ''Cetiosaurus'' and the new sauropod ''[[Pelorosaurus]]'', with the classification of "cetiosaurs" as dinosaurs firmly established by 1874 by which time many the other genera including ''[[Aepisaurus]]'' and ''[[Astrodon]]'' had been named.<ref name="hallett2016"/>

The limited samples of material of sauropods and sauropodomorphs were followed by abundant discoveries in the late 19th and early 20th centuries from North America and east Africa. In the United States, American paleontologists [[Othniel Charles Marsh]] and [[Edward Drinker Cope]] began substantial excavations and competition that would be termed the [[Bone Wars]].<ref name="hallett2016"/><ref name="wilson2006"/> From this, Marsh and Cope would name and describe exemplars of the first complete sauropod skulls and skeletons, as well as the mostly complete skull and skeleton of the sauropodomorph ''[[Anchisaurus]]''.<ref name="sereno2007"/><ref name="wilson2006"/> Many of the most iconic sauropods-''[[Apatosaurus]]'', ''[[Brontosaurus]]'', ''[[Camarasaurus]]'', and ''[[Diplodocus]]''-were all named during this time.<ref name="hallett2016"/> In 1859 Owen had named the group [[Opisthocoelia]] to unite the "cetiosaurs" ''Cetiosaurus'' and ''[[Streptospondylus]]'' as crocodilians, followed by the naming of [[Ceteosauria]] by [[Harry Govier Seeley]] in 1874 for "cetiosaurs" as dinosaurs. Marsh ignored both of these older names to create the group Sauropoda in 1878 (from the [[Ancient Greek]] words ''sauros'' and ''podus'' as "saurian/lizard feet"), which became the accepted name following his work on their classification throughout the end of the 19th century and is now the term used.<ref name="hallett2016"/> The early forms of sauropodomorphs were united within Prosauropoda by German paleontologist [[Friedrich von Huene]] in 1920 as a primitive stock to give rise to both theropods and sauropods, with Sauropodomorpha being named in 1932 by Huene to unite prosauropods and sauropods as the sister to [[Carnosauria]].<ref name="sereno2007"/><ref name="huene1932"/>

==Anatomy==
===Body size===
{{Main|Dinosaur size#Sauropodomorphs}}
[[File:Buriolestes schultzi size comparison.png|thumb|left|Size of ''Buriolestes'' (the oldest known sauropodomorph) compared to a human]]
The earliest and most primitive sauropodomorphs—animals like ''[[Buriolestes]]'' and ''[[Pampadromaeus]]''—were small bipedal animals that were in the range of {{convert|1-2|m|ft|abbr=on}} in length and weighed around {{convert|2-5|kg|lbs|abbr=on}}.  These earliest forms were either fully carnivorous or omnivorous, but herbivory quickly became the dominant feeding strategy of sauropodomorphs.  Over the course of the [[Triassic Period]], they increased in size, leading to the evolution of animals like ''[[Plateosaurus]]'' and ''[[Gresslyosaurus]]'', which could reach {{convert|7-8|m|ft|abbr=on}} long and weighed around 2-2.5 tons.  During this period, all sauropodomorphs were obligate bipeds, which was the ancestral condition for dinosaurs.  The largest bipedal sauropodomorph known from substantial remains was ''[[Lishulong]]''.  Only the head and neck of ''Lishulong'' are preserved, but this was enough to estimate a total length of about {{convert|13|m|ft|abbr=on}},<ref name=Lishulong>{{Cite journal|last1=Zhang |first1=Q. |last2=Jia |first2=L. |last3=Wang |first3=T. |last4=Zhang |first4=Y. |last5=You |first5=H. |title=The largest sauropodomorph skull from the Lower Jurassic Lufeng Formation of China |year=2024 |journal=PeerJ |volume=12 |article-number=e18629 |doi=10.7717/peerj.18629 |doi-access=free |pmid=39677945 |pmc=11646418 }}</ref> which is about twice the size of the related ''[[Yunnanosaurus]]'', which is known from more complete remains and weighed about 3 tons.<ref name="luetal2007">Lu, J., Li, T., Zhong, S., Azuma, Y., Fujita, M., Dong, Z., and Ji, Q. (2007). "New yunnanosaurid dinosaur (Dinosauria, Prosauropoda) from the Middle Jurassic Zhanghe Formation of Yuanmou, Yunnan Province of China." ''Memoir of the Fukui Prefectural Dinosaur Museum'', '''6''': 1-15.</ref>  However, there is a large but relatively incomplete sauropodomorph (specimen BP/1/5339) discovered in South Africa that has not yet been fully described.  Andrew Yates and Matthew Wedel have suggested that the morphology of its arm bones meant it was probably an obligate biped.  Scaling based on the sympatric genus ''Aardonyx'' and femur allometry, this bipedal sauropodomorph would have weighed between 10-15 tons, making it comparable in size to ''[[Diplodocus]]'' and possibly one of the largest bipedal animals ever.<ref>Wedel, M.J., and Yates, A.M. 2011. "[https://sauroposeidon.wordpress.com/wp-content/uploads/2010/04/wedel-and-yates-2011-wavp-a-diplodocus-sized-bipedal-basal-sauropodomorph-from-south-africa.pdf A Diplodocus-sized bipedal basal sauropodomorph from the Late Triassic of South Africa]". Symposium for Vertebrate Palaeontology and Comparative Anatomy, 2011 meeting proceedings.</ref>
[[File:Vulcanodon Size Comparison by PaleoGeek.svg|thumb|Size diagram of ''Vulcanodon'', one of the earliest sauropodomorphs to have columnar limbs]]
The evolution of obligatory quadrupedality enabled the true sauropods and their closest relatives to achieve very large sizes.  The oldest confidently quadrupedal sauropodomorph, ''[[Melanorosaurus]]'' is not known from very complete remains, and Paul Barrett and Jonah Choiniere declined to suggest a mass estimate in their osteology of ''Melanorosaurus'' published in 2024.  However, [[Gregory S. Paul]] estimated ''Melanorosaurus'' to have been about {{convert|8|m|ft|abbr=on}} long and weighed around a ton, which is comparable to many bipedal sauropodomorphs.  By the end of the Triassic, the 7 ton ''[[Lessemsaurus]]'' had evolved, marking the origin of the oldest true sauropods.<ref name=ingentia>{{cite journal |doi=10.1038/s41559-018-0599-y |title=An early trend towards gigantism in Triassic sauropodomorph dinosaurs |date=2018 |last1=Apaldetti |first1=Cecilia |last2=Martínez |first2=Ricardo N. |last3=Cerda |first3=Ignacio A. |last4=Pol |first4=Diego |last5=Alcober |first5=Oscar |journal=Nature Ecology & Evolution |volume=2 |issue=8 |pages=1227–1232 |pmid=29988169 |bibcode=2018NatEE...2.1227A |hdl=11336/89332 |hdl-access=free }}</ref>  The early Jurassic saw the evolution of the even larger ''[[Ledumahadi]]'', which weighed around 12 tons.<ref name=mcphee2018>{{cite journal |title=A giant dinosaur from the earliest Jurassic of South Africa and the transition to quadrupedality in early sauropodomorphs |last1=McPhee |first1=Blair W. |last2=Benson |first2=Roger B.J. |last3=Botha-Brink |first3=Jennifer |last4=Bordy |first4=Emese M. |last5=Choiniere |first5=Jonah N. |name-list-style=amp |journal=Current Biology |volume=28 |issue=19 |pages=3143–3151.e7 |year=2018 |doi=10.1016/j.cub.2018.07.063 |pmid=30270189 |doi-access=free |bibcode=2018CBio...28E3143M |url=https://ora.ox.ac.uk/objects/uuid:70de4052-c736-4737-a4d7-6ef8ab2b21b0/files/m8e3f7c7b635474911e65e3da30edadac |archive-date=2025-06-03 |access-date=2025-06-03 |archive-url=https://web.archive.org/web/20250603053827/https://ora.ox.ac.uk/objects/uuid:70de4052-c736-4737-a4d7-6ef8ab2b21b0/files/m8e3f7c7b635474911e65e3da30edadac |url-status=live }}</ref>

The final anatomical bottleneck on the size of the true sauropods was the anatomy of their limbs.  Columnar limbs evolved at some point in the early Jurassic.  The oldest sauropod known to have had columnar limbs was ''[[Vulcanodon]]'', which lived in what is now Zimbabwe around 199-188 million years ago.  Earlier sauropods may have had columnar limbs, but their remains are too incomplete to determine if this is the case.  ''Vulcanodon'' has been estimated to have weighed up to 10 tons, making it one of the largest terrestrial animals of its time.<ref name=mcphee2018 />  Most sauropods during this period—such as ''[[Barapasaurus]]'', ''[[Rhoetosaurus]]'', and ''[[Patagosaurus]]''—weighed between 7-10 tons.<ref name=goodbook>{{Cite book |last1=Molina-Pérez |first1=Rubén |last2=Larramendi |first2=Asier |date=29 September 2020 |title=Dinosaur Facts and Figures: The Sauropods and Other Sauropodomorphs |translator-last1=Donaghey |translator-first1=Joan |others=Illustrated by Andrey Atuchin and Sante Mazzei |publisher=Princeton University Press |isbn=978-0-691-19069-3 |url=https://books.google.com/books?id=d-HFDwAAQBAJ |doi=10.2307/j.ctvt7x71z}}</ref>  True gigantism emerged at the beginning of the [[Late Jurassic]]; genera like ''[[Turiasaurus]]'' and ''[[Mamenchisaurus]]'' were up to {{convert|20-25|m|ft|abbr=on}} long and may have weighed up to 30 tons.  During the Late Jurassic and throughout the [[Cretaceous Period]], true gigantism evolved independently several times in distantly related sauropod groups.  Giants like ''[[Brachiosaurus]]'', ''[[Dreadnoughtus]]'', and ''[[Ruyangosaurus]]'' are believed to have exceeded {{convert|30-35|m|ft|abbr=on}} in length and weighed in excess of 50 tons, making them the largest land animals of all time.<ref name=overview>{{cite book |last1=Hallett |first1=Mark |last2=Wedel |first2=Matthew J. |date=2016 |chapter=Parting of the Ways |title=The Sauropod Dinosaurs: Life in the Age of Giants|location=Baltimore, Maryland |pages=19–35 |publisher=Johns Hopkins University Press |isbn=978-1-4214-2028-8}}</ref>  Higher mass estimates have been made for very poorly-known taxa such as ''[[Maraapunisaurus]]'' and ''[[Bruhathkayosaurus]]'', but these remain controversial.<ref name="Bruhathkayosaurus2023">{{Cite journal |last1=Paul |first1=Gregory S. |last2=Larramendi |first2=Asier |date=11 April 2023 |title=Body mass estimate of ''Bruhathkayosaurus'' and other fragmentary sauropod remains suggest the largest land animals were about as big as the greatest whales |journal=Lethaia |language=en |volume=56 |issue=2 |pages=1–11 |doi=10.18261/let.56.2.5 |bibcode=2023Letha..56..2.5P |s2cid=259782734 |issn=0024-1164|doi-access=free }}</ref>  
[[File:Longest dinosaurs2.svg|thumb|left|Several of the largest sauropods compared in size to a human]]
Sauropods reached a variety of different body proportions, so the "largest" individual species will vary based on the measurement concerned.  The longest known sauropod was probably ''[[Supersaurus]]'', which may have exceeded {{convert|40|m|ft|abbr=on}} in length.<ref name ="Woodruff et al. 2024">{{cite journal|last1=Woodruff|first1=D.C.|last2=Curtice|first2=B.D.|last3=Foster|first3=J.R.|year=2024|title=Seis-ing up the Super-Morrison formation sauropods|journal=Journal of Anatomy|volume=247 |issue=3–4 |pages=682–698 |doi=10.1111/joa.14108|pmid=38978276 |pmc=12397078 |pmc-embargo-date=July 8, 2026 }}</ref>  The tallest sauropodomorph was probably ''[[Sauroposeidon]]'', which had a relatively erect posture and may have been able to reach a height of between {{convert|16.5|–|18|m|ft|abbr=on}}.<ref name="Wedeletal2000b">{{cite journal|last=Wedel|first=Mathew J.|author2=Cifelli, R. L.|author3=Sanders, R.. K.|s2cid=59141243|year=2000|title=Osteology, paleobiology, and relationships of the sauropod dinosaur ''Sauroposeidon''|url=https://pdfs.semanticscholar.org/9efe/8db6eb32247f90a760110d5a9695977fb761.pdf|archive-url=https://web.archive.org/web/20200626075134/https://pdfs.semanticscholar.org/9efe/8db6eb32247f90a760110d5a9695977fb761.pdf|archive-date=June 26, 2020|journal=Acta Palaeontologica Polonica|volume=45|pages=343–388}}</ref>  The longest neck of any sauropod known from complete remains is that of ''[[Xinjiangtitan]]'', which had a neck {{cvt|14.9|m|ft}} meters long.<ref name="Zhang2018">{{cite journal|first1=Xiao-Qin |last1=Zhang |first2=Da-Qing |last2=Li |first3=Yan |last3=Xie |first4=Hai-Lu |last4=You|year=2020|title=Redescription of the cervical vertebrae of the Mamenchisaurid Sauropod ''Xinjiangtitan shanshanesis'' Wu et al. 2013|journal=Historical Biology|volume=32|issue=6|pages=803–822|doi=10.1080/08912963.2018.1539970|bibcode=2020HBio...32..803Z |s2cid=91680936 }}</ref>  Very large isolated cervical vertebrae from taxa like ''[[Hudiesaurus]]'' and ''[[Mamenchisaurus]]'' have been found, but the incompleteness of these remains makes it difficult to assess the total length of their necks.<ref name="dong1997">Dong, Z. (1997). "A gigantic sauropod (''Hudiesaurus sinojapanorum'' gen. et sp. nov.) from the Turpan Basin, China." Pp. 102-110 in Dong, Z. (ed.), ''Sino-Japanese Silk Road Dinosaur Expedition''. China Ocean Press, Beijing.</ref><ref name=":13">{{Cite journal|last=Paul|first=Gregory|date=2019-12-31|title=Determining the Largest Known Land Animal: A Critical Comparison of Differing Methods for Restoring the Volume and Mass of Extinct Animals|journal=Annals of Carnegie Museum|volume=85|issue=4|page=335|doi=10.2992/007.085.0403|bibcode=2019AnCM...85..335P |s2cid=210840060|issn=0097-4463}}</ref>  The most massive sauropodomorph known from relatively complete remains is generally accepted to be ''[[Argentinosaurus]]'', which may have exceeded 70 tons in weight.<ref name="Bruhathkayosaurus2023" />

The smallest sauropodomorphs were the oldest and earliest-diverging taxa.  Genera like ''[[Pampadromaeus]]'' and ''[[Eoraptor]]'' may have been {{convert|1.5|m|ft|abbr=on}} long or shorter and weighed as little as {{convert|10|kg|lbs|abbr=on}}.<ref name=sereno13>{{cite journal | last1 = Sereno | first1 = Paul C. | last2 = Martínez | first2 = Ricardo N. | last3 = Alcober | first3 = Oscar A. | s2cid = 86006363 | year = 2013 | title = Osteology of ''Eoraptor lunensis'' (Dinosauria, Sauropodomorpha). Basal sauropodomorphs and the vertebrate fossil record of the Ischigualasto Formation (Late Triassic: Carnian-Norian) of Argentina | journal = Journal of Vertebrate Paleontology Memoir | volume = 12 | pages = 83–179 | doi = 10.1080/02724634.2013.820113 }}</ref>  Sauropods were generally much larger, but several sauropods are believed to have been examples of [[insular dwarfism]].  ''[[Magyarosaurus]]'', ''[[Europasaurus]]'', and ''[[Petrustitan]]'' are the smallest sauropods known from adult remains; they were between {{convert|3-5|m|ft|abbr=on}} long and weighed less than a ton.<ref name="sander06">{{Cite journal |last1=Sander |first1=P.M. |last2=Mateus |first2=O.V. |last3=Laven |first3=T. |last4=Knötschke |first4=N. |year=2006 |title=Bone histology indicates insular dwarfism in a new Late Jurassic sauropod dinosaur |journal=Nature |volume=441 |issue=7094 |pages=739–741 |doi=10.1038/nature04633 |pmid=16760975|bibcode=2006Natur.441..739M |s2cid=4361820 }}</ref><ref name="Petrustitan">{{Cite journal |last1=Díez Díaz |first1=V. |last2=Mannion |first2=P. D. |last3=Csiki-Sava |first3=Z. |last4=Upchurch |first4=P. |year=2025 |title=Revision of Romanian sauropod dinosaurs reveals high titanosaur diversity and body-size disparity on the latest Cretaceous Haţeg Island, with implications for titanosaurian biogeography |journal=Journal of Systematic Palaeontology |volume=23 |issue=1 |at=2441516 |doi=10.1080/14772019.2024.2441516|doi-access=free |bibcode=2025JSPal..2341516D }}</ref>  Other small sauropods existed throughout the Mesozoic including ''[[Haplocanthosaurus]]'', ''[[Bonatitan]]'', and ''[[Ohmdenosaurus]]'', which were each between 1-2 tons.<ref name=goodbook />

===Skull and tooth morphology===
[[File:Sauropodomorpha skull comparison.jpg|thumb|Diagrams of the skulls of various sauropodomrophs in lateral view]]
The skulls of sauropodomorphs are generally small in relation to body size and generally had large bony [[nares]].  However they vary considerably in most other aspects of their morphology.  Prosauropods had very narrow skulls (when viewed from above), and the skull morphology of prosauropods was generally conservative.<ref name=morphometrics />  Some prosauropods like ''[[Ngwevu]]'' and ''[[Yizhousaurus]]'' evolved relatively wide and robust skulls, but these were the exception.<ref name="Chappel-etal-2019">{{Cite journal |last1=Chapelle |first1=Kimberley E. J. |last2=Barrett |first2=Paul M. |last3=Botha |first3=Jennifer |last4=Choiniere |first4=Jonah N. |date=August 5, 2019 |title=''Ngwevu intloko'': a new early sauropodomorph dinosaur from the Lower Jurassic Elliot Formation of South Africa and comments on cranial ontogeny in ''Massospondylus carinatus'' |journal=[[PeerJ]] |volume=7 |article-number=e7240 |doi=10.7717/peerj.7240 |pmid=31403001 |pmc=6687053 |doi-access=free}}</ref><ref name=Chatterjee2018>{{cite journal|doi=10.1038/s41598-018-31874-9|title=A new sauropodiform dinosaur with a 'sauropodan' skull from the Lower Jurassic Lufeng Formation of Yunnan Province, China|journal=Scientific Reports|volume=8|year=2018|last1=Zhang|first1=Qian-Nan|last2=You|first2=Hai-Lu|last3=Wang|first3=Tao|last4=Chatterjee|first4=Sankar|issue=1|page=13464|pmc=6128897|pmid=30194381|bibcode=2018NatSR...813464Z}}</ref>  It was not until the diversification of the true sauropods that a wider variety of skull dimensions evolved.  Wide and robust skulls evolved on multiple occasions within Sauropoda.  The [[Rebbachisauridae|rebbachisaurid]] ''[[Nigersaurus]]'' had a relatively wide skull, and similarly wide and robust skulls evolved in [[Camarasauridae]], [[Brachiosauridae]], [[Euhelopodidae]], and other [[somphospondyli|somphospondylans]].  More basal sauropods, like ''[[Shunosaurus]]'', ''[[Mamenchisaurus]]'', and members of [[Diplodocidae]], retained relatively narrow and lightly built skulls.  However, the study of these trends is complicated by the relative rarity of sauropod skulls in the fossil record.<ref name=morphometrics />

Study of sauropodomorph tooth [[morphometrics]] has been used to divide sauropodomorphs into several evolutionary grades.  The first of these, basal sauropodomorphs (including taxa like ''[[Eoraptor]]'', ''[[Pampadromaeus]]'', and ''[[Saturnalia]]''), show a relatively wide disparity in tooth morphology.  This is used to infer a wider variety of dietary preferences.  Some of these taxa are inferred to have been omnivorous or possibly even carnivorous, and the transition to herbivory took place within this grade.  The next grade, the "core prosauropods", includes the large bipedal herbivorous taxa that became abundant during the Late Triassic (''[[Plateosaurus]]'', ''[[Massospondylus]]'', ''[[Thecodontosaurus]]'', etc).  The core prosauropods, with only a few exceptions, have very similar tooth morphology; their teeth are generally non-recurved and are closely spaced to form a relatively continuous cutting edge along the whole length of the jaw.  These traits, alongside the generally high mechanical advantage of their jaws, are generally correlated with herbivory, which has been used to infer a broadly similar dietary ecology for the core prosauropods.  They were likely very generalized herbivores which may have been facultatively omnivorous.  The exception to this general trend is ''[[Riojasaurus]]'', which had much more specialized teeth.  This suggests that ''Riojasaurus'' was a relatively specialized herbivore in comparison to some of its close relatives.<ref name=craniodental>{{cite journal |doi=10.1017/pab.2017.4 |title=Craniodental functional evolution in sauropodomorph dinosaurs |date=2017 |last1=Button |first1=David J. |last2=Barrett |first2=Paul M. |last3=Rayfield |first3=Emily J. |journal=Paleobiology |volume=43 |issue=3 |pages=435–462 |bibcode=2017Pbio...43..435B |hdl=1983/ae3d42f3-c115-4a9a-abcd-ece397f0d265 |hdl-access=free }}</ref>
[[File:Plateosaurus skull TFA.jpg|thumb|left|The skull of ''Plateosaurus'', an archetypal "prosauropod"]]
The evolution of basal sauropodiformes (called "near-sauropods" by some sources)<ref name=overview /> saw a diversification in tooth and jaw functionality.  Taxa like ''[[Jingshanosaurus]]'' possessed relatively uniform and recurved teeth, which may reflect a renewed importance of meat in their diet.  Conversely, ''[[Yunnanosaurus]]'' evolved very narrow teeth which did not occlude with each other; this is believed to be an adaptation for a very specialized herbivorous diet.  More derived near-sauropods like ''[[Anchisaurus]]'' and ''[[Mussaurus]]'' retained the generalist anatomy of the core prosauropods, and likely had similarly generalist diets.  The evolution of the true sauropods saw the emergence of the "broad-crowned" sauropod teeth, which are associated with more robust skulls and higher bite forces.  This grade includes the bulk of early sauropod diversity, and until the evolution of diplodocoids and titanosaurs, would remain relatively conservative in morphology.<ref name=craniodental />

The ability for sauropodomorphs to increase in size so rapidly is attributed to the evolution of "bulk-browsing".  This feeding method is typified by the presence of three skull characteristics.  Firstly, the tooth-bearing bones of the skull (the premaxillae, maxillae, and dentaries) developed plates along their {{dinogloss|alveolus|alveolar}} margins to brace these bones against the stresses that occur while feeding.  Secondly, the skull itself broadened to allow for greater volumes of food to be eaten at any given time.  Thirdly, the soft tissues around the mouth (including cheeks) reduced to allow for a wider gape.  The last of these three can only be observed indirectly, since the soft cheek tissues are not preserved in the fossils.  The lack of cheeks is inferred by the lack of neurovascular foramina along the areas of the skull from which the cheeks would grow.  These three traits would become more elaborate and specialized with the evolution of true sauropods, which developed wider skulls and large gaping capabilities.<ref name=aardonyx />
[[File:Sauropodomorph functional skull evolution.png|thumb|Diagram showing the evolution of skull functionality in sauropodomorphs]]
Over the course of their evolution, sauropodomorph skulls tended to develop more robust muscle attachment sites, which have been used to infer a trend towards higher bite forces in both absolute and relative terms.  This trend coincided with the evolution of more precise dental occlusion, which likely made it easier to take bites of large masses of vegetation.  This increase in the robustness of the jaw musculature co-evolved with a similar increase in the size and robustness of the tooth-bearing bones of the skull and a reduction in sizes of the {{dinogloss|antorbital fossa}} and the {{dinogloss|mandibular fossa}}.  The evolution of the true sauropods also saw the migration of the {{dinogloss|ectopterygoid}}s towards the anterior portion of the jaw, which would have allowed for the development of larger jaw adduction muscles, whichalso increased bite forces.  Some researchers have suggested that these evolutionary trends formed a feedback-loop, with each adaptation reinforcing and enhancing the feeding utility of the others.<ref name=plateocamaro />

The absolute increase in size of the true sauropods in comparison to prosauropods naturally led to the evolution of higher bite forces.  However, these adaptations also led to a significant relative advantage in the functionality of their feeding apparatus.  The skulls of ''Plateosaurus'' and ''[[Camarasaurus]]'', while very similar in size, differed considerably in their ability to withstand the forces that feeding would have exerted on the skull.  A [[finite element analysis]] conducted in 2016 by David Button and colleagues found that, especially in the posterior portion of the jaw, the skull of ''Camarasaurus'' could withstand forces an order of magnitude higher than that of ''Plateosaurus'' while feeding.  This was likely due to the robustness of the skull bones themselves, but was also impacted by the general dimensions of the skull.  ''Plateosaurus'' and prosauropods generally had longer and narrower skulls than derived sauropods.  Their analysis also found that the forces able to be exerted by ''Plateosaurus''—and presumably other prosauropods—varied considerably along the length of their jaw, which suggests that different portions of the jaw served different purposes during feeding.  This is in contrast to the bulk-feeding methods of the true sauropods, which prioritized volume and efficiency in feeding, leading to the teeth gradually shifting towards being concentrated in the front of the mouth, with few or no teeth towards the posterior portions of the jaw.  This line of evidence was also used to suggest that prosauropods like ''Plateosaurus'' may have retained some of the carnivorous dietary habits of their more primitive ancestors.<ref name=plateocamaro>{{cite journal |doi=10.1111/pala.12266 |title=Comparative cranial myology and biomechanics of ''Plateosaurus'' and ''Camarasaurus'' and evolution of the sauropod feeding apparatus |date=2016 |last1=Button |first1=David J. |last2=Barrett |first2=Paul M. |last3=Rayfield |first3=Emily J. |last4=Benson |first4=Roger |journal=Palaeontology |volume=59 |issue=6 |pages=887–913 |bibcode=2016Palgy..59..887B |doi-access=free }}</ref>

Some uncertainties remain regarding the evolution of soft tissue anatomy in sauropodomorphs.  Some prosauropods skulls have been suggested to preserve osteological correlates associated with cheeks, but true sauropods are generally believed to have lacked cheeks.  When this transition occurred remains an unanswered question.<ref name=morphometrics>{{cite book |doi=10.1007/978-3-540-95853-6_11 |chapter=Macroevolutionary Trends in the Skull of Sauropodomorph Dinosaurs – the Largest Terrestrial Animals to Have Ever Lived |title=Morphometrics for Nonmorphometricians |series=Lecture Notes in Earth Sciences |date=2010 |last1=Young |first1=Mark T. |last2=Larvan |first2=Matthew D. |volume=124 |pages=259–269 |isbn=978-3-540-95852-9 }}</ref>  Uniquely, some of the features on the [[maxilla]]e of ''Riojasaurus'' suggest that it may have had a [[rhamphotheca]].<ref name=craniodental />

===Neck anatomy===
{{See also|Sauropod neck posture}}
[[File:Lishulong (holotype cervical vertebrae, left lateral).png|thumb|Neck vertebrae of ''[[Lishulong]]'', which had the longest neck of any known prosauropod]]
Neck elongation was among the first anatomical trends to evolve that differentiated sauropodomorphs from their [[theropod]] relatives.  Within at least the first 8 million years of sauropodomorph evolution, proportional neck length grew from around one-third of trunk length to almost the same as trunk length.  The [[Late Triassic]] [[Santa Maria Formation]] of Brazil preserves this transition.  The morphologically conservative ''[[Buriolestes]]'' is known from around 233 million years ago, and by 225 million years ago, the "core prosauropod" bodyplan had emerged with the evolution of the long-necked ''[[Macrocollum]]''.  Intermediate forms, such as the moderately elongated neck of ''[[Bagualosaurus]]'' indicate that this was a gradual process.  This initial phase of neck elongation occurred via the elongation of the cervical vertebrae themselves, rather than an increase in the number of vertebrae (both ''Buriolestes'' and ''Macrocollum'' had 8 cervical vertebrae).<ref>{{cite journal |doi=10.1002/ar.25107 |title=The elongated neck of sauropodomorph dinosaurs evolved gradually |date=2024 |last1=Damke |first1=Lísie V. S. |last2=Bem |first2=Fabiula P. |last3=Doering |first3=Mariana |last4=Piovesan |first4=Tamara R. |last5=Müller |first5=Rodrigo T. |journal=The Anatomical Record |volume=307 |issue=4 |pages=1060–1070 |pmid=36285778 }}</ref>  This elongation coincided with a shrinking of the skull, probably to reduce the muscular strain on the neck that a large head would create.<ref>{{cite journal |doi=10.1080/08912969909386586 |title=On the head size of sauropodomorph dinosaurs: Implications for ecology and physiology |date=1999 |last1=Christiansen |first1=Per |journal=Historical Biology |volume=13 |issue=4 |pages=269–297 |bibcode=1999HBio...13..269C }}</ref>

The elongation of sauropodomorph necks is suggested to have provided a comparative advantage versus other large herbivores such as [[aetosaur]]s and [[dicynodont]]s in allowing them to feed on a wider variety of vegetation.  This process of neck elongation closely mirrored the evolution of sauropodomorph teeth, which saw a trend towards adaptations for herbivory during this same interval.<ref name=macrocollum>{{cite journal |doi=10.1098/rsbl.2018.0633 |title=An exceptionally preserved association of complete dinosaur skeletons reveals the oldest long-necked sauropodomorphs |date=2018 |last1=Müller |first1=Rodrigo Temp |last2=Langer |first2=Max Cardoso |last3=Dias-Da-Silva |first3=Sérgio |journal=Biology Letters |volume=14 |issue=11 |pmid=30463923 |pmc=6283919 }}</ref>

The evolution of long necks required a suite of adaptations to sauropodomorph vertebrae.  A long neck is necessarily more massive than a short neck, and therefore the evolution of long necks coincided with the development of broad cervical vertebrae to accommodate the expansion of neck muscles.  Primitive sauropodomorphs with short necks had weak {{dinogloss|diapophyses}} and small or no {{dinogloss|parapophyses}}.  These features of the vertebrae grew broad in sauropodomorphs with longer necks and likely served as attachment sites for large [[trapezius]] muscles.  These expanded muscles were necessary for sauropodomorphs to hold their necks and heads up, and the presence of large trapezii is also supported by broad muscle attachment sites on the shoulders of these taxa.  The evolution of true sauropods saw an increase in the development of broad and robust cervical vertebrae to facilitate the evolution of increasingly long and massive necks.<ref name=correlates>{{cite journal |doi=10.1371/journal.pone.0198988|doi-access=free |title=Forelimb musculature and osteological correlates in Sauropodomorpha (Dinosauria, Saurischia) |date=2018 |last1=Otero |first1=Alejandro |journal=PLOS ONE |volume=13 |issue=7 |article-number=e0198988 |pmid=29975691 |pmc=6033415 |bibcode=2018PLoSO..1398988O }}</ref>

===Skeletal pneumaticity===
[[File:Sauropodomorph skeletal pneumaticity cladogram.png|thumb|left|Diagram showing the evolution of invasive air sacs in sauropodomorphs]]
Sauropodomorphs possessed a system of [[air sac]]s throughout their body which were connected to the respiratory system.  During development, these air sacs expanded via branching structures called "diverticula" (singular "diverticulum") which invaded and carved holes into parts of the skeleton.  These invasive diverticula formed structures called [[pleurocoel]]s and pneumatic [[fossa (anatomy)|fossa]]e, which are preserved in the fossils and can be used by researchers to infer the presence of these air sacs.  These adaptations are also seen in [[bird]]s, non-avian [[theropod]]s, and [[pterosaur]]s, but are completely absent in [[ornithischia]]ns.  This has led to the suggestion that pneumatic skeletons are ancestral to [[Avemetatarsalia|bird-line archosaurs]] and were secondarily lost in ornithischians.  However, an analysis of the skeletons of three dinosaurs including two sauropodomorphs (''[[Buriolestes]]'', ''[[Gnathovorax]]'', and ''[[Pampadromaeus]]'') conducted in 2022 found that none of the taxa studied possessed signs of an invasive air-sac system in their vertebrae.  This led the authors of the study to the conclusion that this respiratory apparatus evolved independently in pterosaurs, theropods, and sauropodomorphs.<ref name=multipleorigins>{{cite journal |doi=10.1038/s41598-022-25067-8 |title=The absence of an invasive air sac system in the earliest dinosaurs suggests multiple origins of vertebral pneumaticity |date=2022 |last1=Aureliano |first1=Tito |last2=Ghilardi |first2=Aline M. |last3=Müller |first3=Rodrigo T. |last4=Kerber |first4=Leonardo |last5=Pretto |first5=Flávio A. |last6=Fernandes |first6=Marcelo A. |last7=Ricardi-Branco |first7=Fresia |last8=Wedel |first8=Mathew J. |journal=Scientific Reports |volume=12 |issue=1 |page=20844 |pmid=36494410 |pmc=9734174 |bibcode=2022NatSR..1220844A }}</ref>

An important genus in the study of pneumaticity in early sauropodomorphs is ''[[Macrocollum]]'', from the Triassic of Brazil.  It is one of the earliest sauropodomorphs to achieve sizes larger than {{convert|3|m|ft|abbr=on}}, and the skeletal remains of the genus also preserve some of the oldest evidence of pneumatic vertebrae in this group.  Earlier taxa are either fully apneumatic (lacking invasive air sacs) or with only very minor pneumaticity, but ''Macrocollum'' possessed signs of an invasive air sac system in both the lower [[cervical vertebra]]e and upper [[thoracic vertebra|dorsal vertebrae]].  It is notable however that the evolution of vertebral pneumaticity in sauropodomorphs was not a linear process.  Taxa that evolved after ''Macrocollum'' including ''[[Plateosaurus]]'' possessed invasive pneumaticity in the cervical vertebrae, but seemed to lack this adaptation in the dorsal vertebrae.  The [[Early Jurassic]] genus ''[[Aardonyx]]'' had an extensive air sac system in the lower dorsal vertebrae and [[sacrum]], but had entirely apneumatic cervical vertebrae.  It appears that extensive pneumaticity along the entire vertebral column did not become established until the evolution of the true sauropods.<ref name=pneumorigin>{{cite journal |doi=10.1002/ar.25209 |title=The origin of an invasive air sac system in sauropodomorph dinosaurs |date=2024 |last1=Aureliano |first1=Tito |last2=Ghilardi |first2=Aline M. |last3=Müller |first3=Rodrigo T. |last4=Kerber |first4=Leonardo |last5=Fernandes |first5=Marcelo A. |last6=Ricardi-Branco |first6=Fresia |last7=Wedel |first7=Mathew J. |journal=The Anatomical Record |volume=307 |issue=4 |pages=1084–1092 |pmid=36971057 |doi-access=free }}</ref>  The exact locations of pneumatic elements on the bones are highly variable even within taxa, which is a consequence of these elements developing in tandem with the circulatory system, rather than the development of the skeleton itself.<ref>{{cite journal |doi=10.32388/1G6J3Q.5 |date=2021 |last1=Taylor |first1=Mike |last2=Wedel |first2=Mathew |title=Why is vertebral pneumaticity in sauropod dinosaurs so variable? |journal=Qeios |volume=3 |issue=1 |article-number=1G6J3Q.5 |doi-access=free }}</ref>
[[File:Apatosaurus caudal vertebrae.png|thumb|The tail bones of ''[[Apatosaurus]]'', with the pneumatic fossae clearly visible]]
The researchers Matt Taylor and Mike Weddel have written extensively about variation in the invasive air sac systems of sauropodomorphs.  Weddel conducted a general review of sauropodomorph skeletal pneumaticity in 2007 which surmised that the ribs and vertebrae of prosauropods were generally much less extensively pneumatized than those of the true sauropods.  Some prosauropods, including ''[[Pantydraco]]'' (then called ''[[Thecodontosaurus|Thecodontosaurus caudus]]'') possessed excavations in their cervical vertebrae which were described as "pleurocoel-like", but may or may not have been true pleurocoels created by pneumatic diverticula.  Other vertebral structures indicative of pneumaticity in true sauropods ([[lamina (anatomy)|lamina]]e and fossae on the vertebrae) are present in various prosauropods such as ''Plateosaurus'' and ''Pantydraco'', but these are not interpreted as signs of true pneumaticity because the texture of the bone associated with these structures generally does not differ from fully apneumatic bone.  Similar laminae and fossae are present in a variety of other archosaurs including [[pseudosuchia]]ns (which do not have any pneumatic elements in the skeleton), which may indicate that these structures are ancestral to archosaurs and evolved independently of an invasive air sac system.<ref name=propneum>{{cite journal |last1=Wedel |first1=Matthew |title=What Pneumaticity Tells us About 'Prosauropods', and Vice Versa |journal=Special Papers in Palaeontology |date=2007 |volume=77 |pages=207–222 |url=https://www.researchgate.net/publication/272152712}}</ref>

Skeletal pneumaticity may also have evolutionary benefits in lightening the skeleton.  The invasive air sacs made the bones as a whole less-dense, allowing them to increase in size without having to invest the same volume of resources as if the bones were completely solid.  This may have been a contributing factor in allowing sauropodomorphs to evolve large sizes in such a short time.<ref>{{cite journal |doi=10.1002/jez.548 |title=Evolution of archosaurian body plans: Skeletal adaptations of an air-sac-based breathing apparatus in birds and other archosaurs |date=2009 |last1=O'Connor |first1=Patrick Michael |journal=Journal of Experimental Zoology Part A: Ecological Genetics and Physiology |volume=311A |issue=8 |pages=629–646 |pmid=19492308 |bibcode=2009JEZA..311..629O }}</ref><ref name=archosaurresp>{{cite journal |doi=10.1002/jmor.10470 |title=Postcranial pneumaticity: An evaluation of soft-tissue influences on the postcranial skeleton and the reconstruction of pulmonary anatomy in archosaurs |date=2006 |last1=O'Connor |first1=Patrick M. |journal=Journal of Morphology |volume=267 |issue=10 |pages=1199–1226 |pmid=16850471 |bibcode=2006JMorp.267.1199O }}</ref>

===Arms and claws===
[[File:Plateosaurus engelhardti hand 1.JPG|thumb|left|Hand bones of ''Plateosaurus'', showing the enlarged claw on the first finger]]
Like all dinosaurs, sauropodomorphs evolved from bipedal ancestors with five digits on each hand.  They did not however possess claws on all of their digits.  Early sauropodomorphs only had claws on the first three digits (sometimes called the "thumb"), and their early evolution was marked by an increase in the size of the first digit and its associated claw.  As the transition to [[quadrupedal]]ity took place throughout the [[Triassic]] and into the [[Jurassic]], the claws on the second and third digits reduced in size and disappeared.  However, even into the [[Late Cretaceous]], large sauropods retained a large claw on the first digit of the hand.<ref name=overview />

The first major radiation of sauropodomorphs (the "core prosauropods"), retained the relatively short forelimbs of their more primitive ancestors.  ''[[Plateosaurus]]'' and its relatives had forelimbs that were less than half the length of their hind limbs.  This meant they were obligate bipeds and used their arms exclusively for non-locomotory purposes.  This is further supported by the limited wrist mobility of their hands, which would have prevented them from pronating their hands to plant them on the ground.  Functions for their arms, including the large claws on their hands, include for use in feeding and defense from predators, which would have included primitive [[theropod]]s and large [[rauisuchia]]ns.<ref name=overview />
[[File:Diplodocus foot J1.jpg|thumb|The hand of ''[[Diplodocus]]'', showing the enlarged claw on the first finger, which was inhereted from its prosauropod ancestors]]
A detailed study of the arm musculature of the core prosauropod ''[[Unaysaurus]]'' suggested that the adduction-abduction range of motion for the forelimbs was between about 74-130 degrees relative to the body.  The humerus likely had a range of motion between 105-153 degrees relative to the [[coracoid]], and the elbow likely had a range of motion between about 70-137 degrees relative to the humerus.<ref>{{cite journal |doi=10.1016/j.jsames.2014.09.024 |title=Functional and biomechanic aspects of the scapular girdle and forelimbs of Unaysaurus tolentinoi Leal et al., 2004 (Saurischia: Sauropodomorpha) |date=2015 |last1=Vargas-Peixoto |first1=Dilson |last2=Da-Rosa |first2=Átila Augusto Stock |last3=Gallo De França |first3=Marco Aurélio |journal=Journal of South American Earth Sciences |volume=61 |pages=129–133 |bibcode=2015JSAES..61..129V }}</ref>  Range of motion for the forelimbs changed considerably during the course of sauropodomorph evolution.  A more derived prosauropod, ''[[Mussaurus]]'' (which was also bipedal) was likely able to pronate its arms to some degree, and the mobility of its elbow joint was likely much greater than in earlier prosauropods.  This was a precursor to the evolution of the fuller pronation which was necessary for quadrupedality to evolve.<ref name=mussaurusarms>{{cite journal |doi=10.7717/peerj.3976|doi-access=free |title=Forelimb muscle and joint actions in Archosauria: Insights from ''Crocodylus johnstoni'' (Pseudosuchia) and ''Mussaurus patagonicus'' (Sauropodomorpha) |date=2017 |last1=Otero |first1=Alejandro |last2=Allen |first2=Vivian |last3=Pol |first3=Diego |last4=Hutchinson |first4=John R. |journal=PeerJ |volume=5 |article-number=e3976 |pmid=29188140 |pmc=5703147 }}</ref>

The size of the arms relative to the body in sauropodomorphs increased generally during their early evolution.  Even fully bipedal taxa like ''[[Aardonyx]]'' had arms which were similar in length to their hind legs.  This saw its culmination with the evolution of ''[[Melanorosaurus]]'' and the true sauropods, which were believed to have been an obligate quadrupeds and would have used their limbs more exclusively for locomotion.<ref name=aardonyx>{{cite journal |doi=10.1098/rspb.2009.1440 |title=A new transitional sauropodomorph dinosaur from the Early Jurassic of South Africa and the evolution of sauropod feeding and quadrupedalism |date=2010 |last1=Yates |first1=Adam M. |last2=Bonnan |first2=Matthew F. |last3=Neveling |first3=Johann |last4=Chinsamy |first4=Anusuya |last5=Blackbeard |first5=Marc G. |journal=Proceedings of the Royal Society B: Biological Sciences |volume=277 |issue=1682 |pages=787–794 |pmid=19906674 |pmc=2842739 }}</ref>  However, even in the largest [[Early Jurassic]] sauropodomorphs, such as ''[[Ledumahadi]]'', the forelimbs were not fully columnar, and they still retained a degree of mobility in their elbows and wrists that would have been impossible for the true sauropods.<ref name=mcphee2018 />

==Paleobiology and behavior==
Sauropodomorphs reached the age of sexual maturity well before they were fully grown adults.<ref>{{cite journal | last1 = Sander | first1 = PM | year = 2000 | title = Long bone histology of the Tendaguru sauropods: implications for growth and biology | journal = Paleobiology | volume = 26 | issue = 3 | pages = 466–488 | doi = 10.1666/0094-8373(2000)026<0466:lhotts>2.0.co;2 | bibcode = 2000Pbio...26..466S | s2cid = 86183725 | url = http://doc.rero.ch/record/16668/files/PAL_E2877.pdf | archive-date = 2023-01-25 | access-date = 2023-01-20 | archive-url = https://web.archive.org/web/20230125164507/https://doc.rero.ch/record/16668/files/PAL_E2877.pdf | url-status = live }}</ref><ref name=Griebeler13>{{cite journal | last1 = Griebeler | first1 = EM | last2 = Klein | first2 = N | last3 = Sander | first3 = PM | year = 2013 | title = Aging, Maturation and Growth of Sauropodomorph Dinosaurs as Deduced from Growth Curves Using Long Bone Histological Data: An Assessment of Methodological Constraints and Solutions | journal = PLOS ONE | volume = 8 | issue = 6| article-number = e67012 | doi = 10.1371/journal.pone.0067012 | pmid = 23840575 | pmc = 3686781 | bibcode = 2013PLoSO...867012G | doi-access = free }}</ref> A study by Griebeler et al. (2013) concluded that the maximum growth rates of sauropodomorphs were comparable to those of precocial birds and the black rhinoceros but lower than the growth rates of average mammals.<ref name=Griebeler13/>

===Senses===
[[File:Rebbachisaurid endocasts.jpg|thumb|left|upright=0.8|Endocasts of several [[Rebbachisauridae|rebbachisaurid]] sauropods in dorsal view with the olfactory bulbs labeled (ob)]]
Inferring the sensory capabilities of extinct animals is difficult due to the lack of soft tissue preservation, so any study of these fields must necessarily rely on skeletal proxies for these sensory systems.  One of the methods available is the study of the [[braincase]]s of taxa with well-preserved skull remains.  The brains of [[archosaur]]s generally have large [[olfactory bulb]]s which comprise the front-most portion of the brain.  Well-preserved braincases are rare in fossil vertebrates, but in cases where they do exist, researchers can create endocasts—3D models of the brain based on the internal structure of the braincase.  Rodrigo Müller conducted one such study in 2022 on sauropodomorphs specifically.  He sampled the braincases of over 30 dinosaur species including several primitive sauropodomorphs, core prosauropods, and derived true sauropods in order to measure the "olfactory ratios" (ORs) of these taxa (an established estimate for the volume of the brain dedicated to smell).  The absolute and proportional size of this region of the brain varied considerably among the sampled taxa.  Notably, ''[[Buriolestes]]'' had very large olfactory bulbs, which is a condition shared by ''[[Saturnalia]]'', ''[[Panphagia]]'', and ''[[Pampadromaeus]]''.  ''[[Plateosaurus]]'' had very small olfactory bulbs, but ''[[Massospondylus]]'' (which lived more recently that ''Plateosaurus'') had a very high OR, similar to ''[[Macrocollum]]'' (which lived much earlier than both), which suggests that the evolution of olfactory capacity in sauropodomorphs was complex and did not exhibit a linear progression.<ref name=smell>{{cite journal |doi=10.1080/08912963.2021.1914600 |title=Olfactory acuity in early sauropodomorph dinosaurs |date=2022 |last1=Müller |first1=Rodrigo Temp |journal=Historical Biology |volume=34 |issue=2 |pages=346–351 |bibcode=2022HBio...34..346M }}</ref>

For the taxa which had published mass estimates (''Buriolestes'', ''Macrocollum'', ''[[Diplodocus]]'', ''[[Camarasaurus]]'', and ''[[Nigersaurus]]''), Müller compared these ORs to their total body mass, and these relationships were in turn compared to the OR-to-body-mass ratios for [[theropod]]s and [[ornithischian]]s.  He found that ''Butiolestes'', ''Macrocollum'', and ''Camarasaurus'' had very high OR-to-body-mass ratios compared to most of the other dinosaurs sampled.  This suggests that smell was an important sense for a wide variety of sauropodomorph taxa regardless of absolute body size.  The earliest sauropodomorph taxa are believed to have been carnivores, and smell likely served a predatory function in taxa like ''Buriolestes''.  However, the continued prevalence of the olfactory bulbs in fully herbivorous taxa suggests that it remained important for other reasons.  Suggested functions include distinguishing edible plants from inedible plants, detecting predators, or using smell in social interactions.<ref name=smell />
[[File:Riojasaurus skull.jpg|thumb|The skull of ''Riojasaurus'', with the scleral ring clearly visible in the eye socket]]
A study in 2011 by Lars Schmitz and Ryosuke Motani examined another skeletal feature believed to correlate with sensory function, the [[scleral ring]]s in the eyes of extinct archosaurs.  Schmitz and Motani examined 33 taxa including five sauropodomorphs from which the scleral morphology is known (''Diplodocus'', ''[[Lufengosaurus]]'', ''[[Nemegtosaurus]]'', ''Plateosaurus'', and ''[[Riojasaurus]]'').  The thickness and diameter of the scleral ring is correlated strongly to both the absolute and relative sizes of the [[pupil]]s and [[lens (anatomy)|lens]]es in the eyes of modern animals, and it can therefore be used to approximate the ability for an extinct animal to see in the dark.  Schmitz and Motani discovered that the scleral morphology of the sauropodomorphs studied indicated that they were likely capable of seeing in most light conditions.  This suggests that they were likely active for long periods both during the day and night.  They hypothesized that this was a result of their large size and herbivorous, because they found a similar in large herbivorous ornithischians.  The absolute size of even early sauropodomorphs (exceeding one metric ton) necessitated that they would have likely had to feed for 12 or more hours every day, which likely meant they had to be habitually active in low-light conditions as well as during the day.  One of the sauropodomorphs studied, ''Lufengosaurus'', may have even been primarily active during the night, but this finding was ambiguous.<ref>{{cite journal|author1=Schmitz, L. |author2=Motani, R. |year=2011 |title=Nocturnality in Dinosaurs Inferred from Scleral Ring and Orbit Morphology |journal=Science |volume = →→→§332 |issue= 6030|pages= 705–8|doi=10.1126/science.1200043 |pmid=21493820|bibcode=2011Sci...332..705S |s2cid=33253407 }}</ref>

The hearing abilities of sauropodomorphs have not been the subject of extensive study.  Michael Hanson and colleagues published a study of reptile [[inner ear]] morphology in 2021 in which they examined the bony ear structure of numerous reptiles including the sauropodomorph ''[[Thecodontosaurus]]''.  Archosaur [[cochlea]]r shape elongated in a relatively linear fashion on the line towards birds, which was suggested by Hanson and colleagues to be a [[paedomorphosis|paedomorphic]] adaptation to hear the high-pitched vocalizations of juveniles of the same species.  This line of evidence is also used to suggest that parental care evolved early in the evolution of archosaurs, and therefore would have been present in sauropodomorphs.  The high-pitched calls of juvenile sauropodomorphs would have been distinct and differentiable to the parents' ears from other ambient noise.  ''Thecodontosaurus'' fit into the general category that Hanson and colleagues called "Semicircular Canal Morphotype 2", with dimensions similar to other non-avian [[dinosaur]]s and [[palaeognaths]], suggesting the general hearing capabilities of these groups were broadly similar.<ref name=birdears>{{cite journal |doi=10.1126/science.abb4305 |title=The early origin of a birdlike inner ear and the evolution of dinosaurian movement and vocalization |date=2021 |last1=Hanson |first1=Michael |last2=Hoffman |first2=Eva A. |last3=Norell |first3=Mark A. |last4=Bhullar |first4=Bhart-Anjan S. |journal=Science |volume=372 |issue=6542 |pages=601–609 |pmid=33958471 |bibcode=2021Sci...372..601H }}</ref>

===Diet and digestion===
{{multiple image
| align             = left
| direction         = vertical
| width             = 200
| image1            = Irisosaurus life restoration.jpg
| image2            = Smallest Diplodocid.png
| footer            = Life restorations of sauropodomorphs feeding (''[[Irisosaurus]]'' on top, ''[[Diplodocus]]'' on bottom)
}}

Sauropodomorphs exhibited a wide variety of diets over the 160 million years during which they existed.  Sauropodomorphs are believed to have been ancestrally [[carnivorous]], with later genera evolving to be [[omnivorous]].  The largest prosauropods and the true sauropods are believed to have been the first group of [[dinosaur]]s to become fully [[herbivory|herbivorous]], with this dietary shift contributing to their general increase in body size.<ref name=overview />  There were exceptions to this trend including the prosauropod ''[[Jingshanosaurus]]'', which had slender recurved teeth, pointing to a possibly carnivorous diet.<ref name=craniodental />  Herbivory in most prosauropods is well attested by a suite of tooth adaptations many sauropodomorphs possessed.  These include spatulate (leaf-shaped) teeth with serrations similar to extant herbivorous lizards, the orientation of the teeth to form a continuous cutting edge well suited for slicing vegetation, and a marked decrease in tooth size along the length of the jaw.  These adaptations are seen in most of the core prosauropods (e.g. ''[[Massospondylus]]'', ''[[Plateosaurus]]'', and their relatives) and are broadly conserved in more advanced prosauropods as well as the true sauropods.<ref>{{cite journal |doi=10.1111/j.1502-3931.1985.tb00690.x |title=Diet of prosauropod dinosaurs from the late Triassic and early Jurassic |date=1985 |last1=Galton |first1=Peter M. |journal=Lethaia |volume=18 |issue=2 |pages=105–123 |bibcode=1985Letha..18..105G |url=http://doc.rero.ch/record/16135/files/PAL_E2923.pdf |archive-date=2024-11-18 |access-date=2025-06-04 |archive-url=https://web.archive.org/web/20241118101012/https://doc.rero.ch/record/16135/files/PAL_E2923.pdf |url-status=live }}</ref>

Throughout the course of their evolution, sauropodomorphs never evolved the ability to [[chew]].  Scientists have inferred this from the relatively simple jaw joints they possessed.  Chewing requires a relatively complex jaw morphology to allow the jaws to flex along multiple planes of motion in order to achieve the grinding action that makes chewing possible, and no sauropodomorph skulls appear to preserve the ability to perform this range of motion.  This inability to chew distinguishes sauropodomorphs from large herbivorous mammals and also from the large herbivorous [[ornithischia]]ns with which they coexisted.<ref>{{cite journal |doi=10.1671/0272-4634(2005)025[0320:DMITAI]2.0.CO;2|issn=0272-4634 |date=2005 |volume=25 |page=320 |title=Dental microwear in Triassic amniotes: Implications for paleoecology and masticatory mechanics |last1=Goswami |first1=Anjali |last2=Flynn |first2=John J. |last3=Ranivoharimanana |first3=Lovasoa |last4=Wyss |first4=André R. |journal=Journal of Vertebrate Paleontology |issue=2 }}</ref>  Some scientists have suggested that the long necks of sauropodomorphs imposed constraints on the evolution of their heads which prevented the robust jaws and musculature necessary to evolve the ability to chew.  Over the course of their evolution, sauropodomorphs evolved other methods of assisting with the digestion of large amounts of plant matter.<ref name=overview />  
[[File:NHM - Gastrolithe.jpg|thumb|Gastroliths believed to belong to a sauropod on display in Vienna]]
One method that may have evolved to circumvent the inability to chew was the use of [[gastroliths]] (literally "stomach stones") in which animals deliberately swallow small stones to grind and process plant matter after it has been swallowed.  Gastroliths are known to have been used by a variety of animal groups including [[plesiosaur]]s, [[birds]], and other non-avian [[dinosaur]]s.<ref name=gastroliths>{{cite journal |doi=10.1080/10420940601050030 |title=Evidence for Prosauropod Dinosaur Gastroliths in the Bull Run Formation (Upper Triassic, Norian) of Virginia |date=2007 |last1=Weems |first1=Robert E. |last2=Culp |first2=Michelle J. |last3=Wings |first3=Oliver |journal=Ichnos |volume=14 |issue=3–4 |pages=271–295 |bibcode=2007Ichno..14..271W }}</ref>  Gastroliths can be difficult to distinguish from other rocks in the fossil record, but they are generally smooth and relatively uniform in size within a single animal.  The presence of gastroliths in sauropodomorphs had evolved by the [[Early Jurassic]] because several taxa including ''Massospondylus'' and ''Ammosaurus'' (possibly a [[junior synonym]] of ''[[Anchisaurus]]'') have been found with stones preserved inside their body cavities that are believed to be gastroliths.  However, this adaptation was not necessarily widespread among prosauropods.  Members of [[Plateosauridae]] are well represented in the fossil record—being known from hundreds of specimens—but there are few unambiguous examples of gastroliths preserved in these fossils.  Some authors have suggested that the use of gastroliths did not become widespread until after the common ancestor of [[Massospondylidae]] and [[Sauropoda]] had already diverged from their common ancestor with Plateosauridae.<ref name=gastroliths />

Subsequent review of the function of gastroliths in a wide variety of extant and extinct taxa has called into question the interpretation of gastroliths in non-avian taxa as serving a digestive function.  Oliver Wings, in a 2007 publication, recounted that previous authors suggested they may have served to assist in balance for bipedal sauropodomorphs.  However, the total mass of the gastroliths discovered associated with bipedal sauropodomorphs was probably too low to have any impact on their balance.  These gastroliths may have simply been swallowed accidentally during feeding, which explains their rarity and inconsitence in their association with sauropodomorph fossils.<ref>{{cite journal |last1=Wings |first1=Oliver |title=A review of gastrolith function with implications for fossil vertebrates and a revised classification |journal=Acta Palaeontologica Polonica |date=2007 |volume=52 |issue=1 |pages=1–16 |url=https://www.app.pan.pl/article/item/app52-001.html |archive-date=2021-04-14 |access-date=2025-06-12 |archive-url=https://web.archive.org/web/20210414154709/https://www.app.pan.pl/article/item/app52-001.html |url-status=live }}</ref>

===Metabolism and thermoregulation===
[[File:Pampadromaeus life.png|thumb|left|The basal sauropodomorph ''[[Pampadromaeus]]'', here depicted with a speculative coat of feathers]]
Metabolic strategies in extant animals are quite varied and cannot be neatly categorized.  The general distinction between [[ectotherm]]y ("cold-bloodedness") and [[endotherm]]y ("warm-bloodedness") is based on the dramatic metabolic differences between extant mammals and birds (which have very high metabolic rates) and modern reptiles, which have very slow metabolic rates by comparison.  Some researchers have suggested that this simple dichotomy does not account for the full range of possible variation, especially in the fossil record, because they both represent derived metabolic conditions.  [[Archosaur]]s (and possibly [[amniote]]s more generally) may have had significantly higher metabolic rates than modern crocodilians and [[squamate]]s—a metabolic condition which is sometimes called [[mesotherm]]y.  It is unclear when the avian metabolic condition evolved, but it is believed to have been present in most theropods based on [[histology|histological]] data.<ref>{{cite journal |doi=10.1093/sysbio/syw033 |date=2016 |last1=Legendre |first1=Lucas J. |last2=Guénard |first2=Guillaume |last3=Botha-Brink |first3=Jennifer |last4=Cubo |first4=Jorge |title=Palaeohistological evidence for ancestral high metabolic rate in archosaurs |journal=Systematic Biology |volume=65 |issue=6 |pages=989–996 |publisher=Dryad |pmid=27073251 }}</ref>

The presence of feathers is often used as a proxy measure of an endothermic metabolism.  [[Pterosaur]]s, theropods, and ornithischians are all known to have possessed feathers or feather-like filaments, which has led some researchers to suggest that feathers may have been an ancestral trait for [[Avemetatarsalia|bird-line archosaurs]].  If this is true, it would imply that sauropodomorphs were ancestrally feathered, which itself may have implied an endothermic (or at least moderately high) metabolism.  However, researchers who have studied the question concluded that it is not likely, given the current evidence, that feathers were an ancestral trait for bird-line archosaurs, and it is more probable that feathers or filaments evolved independently in pterosaurs, theropods, and ornithischians.  This implies that sauropodomorphs were ancestrally scaly.<ref>{{cite book |doi=10.1007/978-3-030-27223-4_12 |chapter=On the Ancestry of Feathers in Mesozoic Dinosaurs |title=The Evolution of Feathers |series=Fascinating Life Sciences |date=2020 |last1=Campione |first1=Nicolás E. |last2=Barrett |first2=Paul M. |last3=Evans |first3=David C. |pages=213–243 |isbn=978-3-030-27222-7 }}</ref>
[[File:Sauropodomorph climatic cladogram.png|thumb|Evolutionary regimes along the temperature axis (in degrees C) are shown for Sauropodomorpha]]
Other proxies for metabolism in sauropodomorphs inclued inferences based on their paleobiogeography.  [[Palynology]] and other plant fossils can be used to infer climatic data for various paleoenvironments in which sauropodomorphs were present.  Global sampling of fossil data indicates that sauropodomorphs generally were more common at lower latitudes, which may be indicative of lower metabolic rates and a higher reliance on environmental conditions to maintain a high internal temperature.  However, this correlation may also be non-causal because plant matter is also generally more abundant in lower latitudes and sauropodomorphs (due to their generally large size) would have needed much more plant matter to sustain their size regardless of their metabolic proclivities.  This apparent sauropodomorph preference for lower latitudes could also reflect a [[sampling bias]] in the fossil record, and should not necessarily be interpreted as indicative of anything by itself.<ref>{{cite journal |doi=10.1016/j.cub.2024.04.051 |title=Early Jurassic origin of avian endothermy and thermophysiological diversity in dinosaurs |date=2024 |last1=Chiarenza |first1=Alfio Alessandro |last2=Cantalapiedra |first2=Juan L. |last3=Jones |first3=Lewis A. |last4=Gamboa |first4=Sara |last5=Galván |first5=Sofía |last6=Farnsworth |first6=Alexander J. |last7=Valdes |first7=Paul J. |last8=Sotelo |first8=Graciela |last9=Varela |first9=Sara |journal=Current Biology |volume=34 |issue=11 |pages=2517–2527.e4 |pmid=38754424 |bibcode=2024CBio...34.2517C |doi-access=free }}</ref>  Some researchers have also used regression analyses of metabolic rates in extant vertebrates based on body mass to estimate that most dinosaurs, including sauropodomorphs, were mesotherms.<ref>{{cite journal |doi=10.1126/science.1253143 |title=Evidence for mesothermy in dinosaurs |date=2014 |last1=Grady |first1=John M. |last2=Enquist |first2=Brian J. |last3=Dettweiler-Robinson |first3=Eva |last4=Wright |first4=Natalie A. |last5=Smith |first5=Felisa A. |journal=Science |volume=344 |issue=6189 |pages=1268–1272 |pmid=24926017 |bibcode=2014Sci...344.1268G }}</ref>

Some researchers have suggested that it would be impossible for animals as large as sauropods to exhibit endothermy because they were too large and would overheat.  This was subsequently called into question by Eva Maria Griebeler, who used data from extant animals and from dinosaurs with known [[ontogeny|ontogenetic]] series and published mass estimates to approximate the internal temperatures of dinosaurs at various points in their lives.  While her findings were not meant to determine precise body temperature estimates, she did find that the body temperature of large dinosaurs did not scale directly with their size beyond a certain mass, meaning that endothermic sauropods would not necessarily overheat.  This finding did not conclusively determine whether or not sauropodomorphs were endotherms, but it did disprove the overheating hypothesis.<ref>{{cite journal |doi=10.1371/journal.pone.0074317|doi-access=free |title=Body Temperatures in Dinosaurs: What Can Growth Curves Tell Us? |date=2013 |last1=Griebeler |first1=Eva Maria |journal=PLOS ONE |volume=8 |issue=10 |article-number=e74317 |pmid=24204568 |pmc=3812988 |bibcode=2013PLoSO...874317G }}</ref>  Other authors have examined the skull vasculature of sauropods and found that the large {{dinogloss|antorbital fenestra}} present in most sauropod genera could have served as efficient sites for heat exchange.  This meant that the brains of sauropods could be kept cooler than the rest of the body, and this temperature differential could have allowed for higher body temperatures to be non-lethal.<ref>{{cite journal |doi=10.1002/ar.24234 |title=Vascular Patterns in the Heads of Dinosaurs: Evidence for Blood Vessels, Sites of Thermal Exchange, and Their Role in Physiological Thermoregulatory Strategies |date=2020 |last1=Porter |first1=William Ruger |last2=Witmer |first2=Lawrence M. |journal=The Anatomical Record |volume=303 |issue=4 |pages=1075–1103 |pmid=31618532 }}</ref>  Some researchers have also suggested a thermoregulatory role for the respiratory [[air sac]]s, but other researchers have dismissed these as lacking sufficient evidence.<ref name=archosaurresp />

===Respiratory system===
[[File:Macrocollum skeletal pneumaticity.png|thumb|left|Skeletal reconstruction of the prosauropod ''Macrocollum'', with the probable position of the lungs and air sacs illustrated]]
Because sauropodomorphs are only known from skeletal remains, any reconstruction of their respiratory system must be based on inferences drawn from its effects on the bones themselves.  Living birds have a complex respiratory apparatus that differs considerably from mammals.  Whereas mammal respiration is performed by lungs and the diaphragm, birds have multiple [[air sac]]s in addition to their lungs and these air sacs are incorporated into the skeleton through structures called pneumatic diverticula (singular "diverticulum").  Since modern birds and sauropodomorphs share a common ancestor, the structure of sauropodomorph bones can be used to infer the existence of analogous structures.  Problems in making such inferences arise from the fact that numerous soft tissue structures—including muscles, nerves, and blood vessels—are incorporated into the skeletons of vertebrates, so it is not always clear which structures in extinct animals may have been caused by each of these organs.  A review of the skeletal correlates in [[archosaur]] respiratory systems was publiushed by Patrick O'Connor in 2006 wherein he suggested that {{dinogloss|foramina|foraminae}} and {{dinogloss|fossa|fossae}} with large internal chambers are the most likely structures to be indicative of these invasive air sacs.<ref name=archosaurresp />

Sauropodomorphs likely had a heterogenous respiratory system.  This means that there were multiple organs responsible for the process of respiration that served different functions.  The lungs themselves would have been filled with the [[parenchyma]]l tissues necessary for oxygen to diffuse into the blood.  However, secondary organs, the air sacs, would have been involved in helping to circulate air through the lungs, but they probably lacked parenchymal tissues and would not have been used to absorb oxygen into the blood directly.  This style of respiratory system is seen in modern birds and some [[squamates]] and was likely present in both sauropodomorphs and non-avian [[theropod]]s.  The lungs of sauropodomorphs were likely directly attached to the spine, which is evidenced by the presence of invasive tissues in the [[thoracic vertebra|dorsal vertebra]]e which were possibly diverticula of the lungs themselves.<ref name=archosaurresp />  Sauropodomorphs likely possessed large air sacs in front of and behind the lungs, which is the condition seen in modern birds.  These are called the cervical (front) and abdominal (back) air sacs, respectively, and they would have assisted the circulation of air through the lungs in the absence of a [[Thoracic diaphragm|diaphragm]] (which sauropodomorphs did not have).  More advanced sauropods may have possessed additional air sacs in the head, tail, shoulder, and hip regions of the body, although this remains uncertain due to the difficulty in interpreting the presence of various pneumatic structures in their bones.<ref name=archosaurresp /><ref name=pneumorigin />
[[File:Dino bird h.jpg|thumb|A diagram illustrating the flwo-through lungs present in birds, and possibly also sauropodomorphs]]
The exact mechanism that sauropodomorphs used to breathe has been controversial among scientists.  Birds are their closest living relatives, but the complex evolution of the avian respiratory apparatus—as shown by the wide variety of pneumatic structures seen in non-avian theropods—means that the avian respiratory condition may not have evolved before the theropod-sauropodomorph split.  Some scientists have argued that sauropodomorphs, and non-avian dinosaurs generally, may have breathed in a manner more similar to crocodiles or turtles, which is more comparable to tidal breathing of mammals.  Matthew Wedel published a review of the breathing capabilities of extinct archosaurs in 2009 and he concluded that, in order for any animal to possess an avian-like flow-through lung, in which fresh air enters the lungs during both inhalation and exhalation, it must have specific anatomical adaptations.  These adaptations should include:  lungs that function as tubes rather than sacs, air sacs both anterior and posterior to the lungs, and muscles capable of driving ventilation in a single direction.  He noted that sauropodomorphs (and [[saurischia]]ns more broadly) probably possessed all of these adaptations.  However, Wedel also noted that the presence of these does not necessarily mean that they must have breathed in this manner, just that it was possible.  Absent any living members to observe, the exact manner of sauropodomorph breathing remains uncertain.<ref>{{cite journal |doi=10.1002/jez.513 |title=Evidence for bird-like air sacs in saurischian dinosaurs |date=2009 |last1=Wedel |first1=Mathew John |journal=Journal of Experimental Zoology Part A: Ecological Genetics and Physiology |volume=311A |issue=8 |pages=611–628 |pmid=19204909 |bibcode=2009JEZA..311..611W }}</ref>

===Gait and locomotion===
The early evolution of saurodomorphs was marked by a change in leg proportions away from the cursorial adaptations which characterized basal genera like ''[[Buriolestes]]'' and ''[[Pampadromaeus]]''.  The first sauropodomorphs to achieve larger body sizes had already shifted away from this locomotor style — change which would only compound throughout the [[Triassic]].<ref name=macrocollum />  Even after sauropodomorphs began increasing in size, they are believed to have remained obligate bipeds.  Genera like ''[[Plateosaurus]]'', ''[[Massospondylus]]'', and their relatives had relatively short arms and wrists not capable of the protation movement necessary to plant them on the ground for locomotion.<ref name=overview />  Later bipedal taxa, like ''[[Aardonyx]]'', generally developed a more elongated body and longer arms.<ref name=aardonyx />  This evolutionary trend coincided with the development of more complex wrist anatomy that allowed some degree of pronation for the forelimbs, which is a necessary prerequisite for planting the hands on the ground to bear weight.<ref name=mussaurusarms />
[[File:Sauropodomorph body plan cladogram.png|left|thumb|A simplified cladogram showing steps in the evolution of quadrupedality in sauropodomorphs]]
One of the few prosauropod taxa with direct evidence for quadrupedality is ''[[Mussaurus]]'', which is known from multiple specimens of all ages (embyros, hatchlings, juvelines, and adults).  Fully-grown ''Mussaurus'' individuals are fairly typical prosauropods; they have relatively short arms and were probably obligate bipeds.  However, hatchling individuals possessed arms that were more-or-less the same length as their legs.  Otero and colleagues modeled individuals of ''Mussaurus'' at various ages and determined that the center-of-mass of these hatchling individuals was about halfway down the length of the trunk.  This is significantly anterior to the hips, suggesting that it was impossible for these hatchlings to walk bipedally, making them obligate quadrupeds.<ref name=mussauruspostureshift>{{cite journal |last1=Otero |first1=Alejandro |last2=Cuff |first2=Andrew R. |last3=Allen |first3=Vivian |last4=Sumner-Rooney |first4=Lauren |last5=Pol |first5=Diego |last6=Hutchinson |first6=John R. |title=Ontogenetic changes in the body plan of the sauropodomorph dinosaur Mussaurus patagonicus reveal shifts of locomotor stance during growth |journal=Scientific Reports |date=2019 |volume=9 |issue=1 |article-number=7614 |doi=10.1038/s41598-019-44037-1 |pmid=31110190 |pmc=6527699 |bibcode=2019NatSR...9.7614O }}</ref>  The prosauropod ''Massospondylus'' is also known from embryos, which have relatively long arms, similar to those of the embryos of ''Mussaurus''.  Suggestions of quadrupedality in young ''Massospondylus'' is complicated by the much simpler wrist anatomy of the taxon, which would have made wrist pronation impossible.  However, [[trace fossil]]s from the same locality as the ''Massospondylus'' embryos show clear evidence of quadrupedal locomotion, with hand imprints clearly distinct from footprints.  These handprints show that the hands were rotated outwards (thus unpronated), suggesting that quadrupedality as a feature of prosauropod juveniles significantly predated the evolution of complex wrists.<ref name="reisz2010">{{cite journal | bibcode=2010JVPal..30.1653R | date=November 1, 2010 | first1=Robert R. | last1=Reisz | title=Embryonic Skeletal Anatomy of the Sauropodomorph Dinosaur Massospondylus from the Lower Jurassic of South Africa | last2=David C. Evans | last3=Hans-Dieter Sues | last4=Diane Scott | journal=Journal of Vertebrate Paleontology | volume=30 | issue=6 | pages=1653, 1664 | issn=0272-4634 | doi=10.1080/02724634.2010.521604 | s2cid=84599991}}</ref>

It is not clear how many times quadrupedal locomotion evolved independently among adult sauropodomorphs, but Kimberly Chapelle and colleagues suggested in 2020 that this happened at least twice.  The first of these occurrences would have been some time after the diversification of Massopoda but before the evolution of ''Mussaurus''.<ref name=postureshift>{{cite journal|last1=Chapelle |first1=Kimberley E. J. |last2=Benson |first2=Roger B. J. |last3=Stiegler |first3=Josef |last4=Otero |first4=Alejandro |last5=Zhao |first5=Qi |last6=Choiniere |first6=Jonah N. |last7=Porro |first7=Laura |title=A quantitative method for inferring locomotory shifts in amniotes during ontogeny, its application to dinosaurs and its bearing on the evolution of posture |journal=Palaeontology |date=2020 |volume=63 |issue=2 |pages=229–242 |doi=10.1111/pala.12451 |bibcode=2020Palgy..63..229C }}</ref>  This hypothesis implies that non-sauropod sauropodiformes like ''[[Anchisaurus]]'' and ''[[Riojasaurus]]'' were quadrupedal.  At some point, bipedality re-evolved in taxa like ''Mussaurus'' and ''[[Yunnanosaurus]]'', and then quadrupedality re-evolved at some point around the evolution of ''[[Melanorosaurus]]'' and [[Lessemsauridae]].<ref name=mcphee2018 />  Other authors have suggested that quadrupedality only evolved once in sauropodomorphs.  The evolution of the posterodistal tubercle on the radius has been suggested as a possible signifier for quadrupedality in sauropodomorphs.  This feature is present on the radii of several taxa that are believed to have been bipedal, such as ''Aardonyx'' and ''Mussaurus'', so this feature may not be a sufficient condition for quadrupedal locomotion.  A curved (rather than straight) radius would likely have been necessary as a precondition for fully pronating the wrists.<ref name=bookch12 />

==Classification==
Sauropodomorpha is one of the two major clades within the order [[Saurischia]]. The sauropodomorphs' sister group, the [[Theropoda]], includes bipedal carnivores like ''[[Velociraptor]]'' and ''[[Tyrannosaurus]]''; as well as birds. However, sauropodomorphs also share a number of characteristics with the [[Ornithischia]], so a small minority of [[palaeontologist]]s, like [[Robert Bakker|Bakker]], have historically placed both sets of herbivores within a group called "Phytodinosauria" or "Ornithischiformes".{{citation needed|date=June 2024}}  A summary of the possible classification schemes is shown below.
{{columns-start | num=3}}
;Conventional relationships
{{clade| style=font-size:90%;line-height:90%
|label1=[[Dinosauria]]
|1={{clade
|1=[[Ornithischia]]
|label2=[[Saurischia]]
|2={{clade
|1=[[Theropoda]]
|2='''Sauropodomorpha'''
}}
}}
}}
{{column}}
;Ornithoscelida hypothesis
{{clade| style=font-size:90%;line-height:90%
|label1=[[Dinosauria]]
|1={{clade
|1='''Sauropodomorpha'''
|label2=[[Ornithoscelida]]
|2={{clade
|1=[[Theropoda]]
|2=[[Ornithischia]]
}}
}}
}}
{{column}}
;Phytodinosauria hypothesis
{{clade| style=font-size:90%;line-height:90%
|label1=[[Dinosauria]]
|1={{clade
|1=[[Theropoda]]
|label2=[[Phytodinosauria]]
|2={{clade
|1=[[Ornithischia]]
|2='''Sauropodomorpha'''
}}
}}
}}
{{columns-end}}
In [[Linnaean taxonomy]], Sauropodomorpha (which means "lizard feet forms") is either a [[suborder]] or is left unranked. It was originally established by [[Friedrich von Huene]] in 1932, who broke it into two groups: the basal forms within [[Prosauropoda]], and their descendants, the giant [[Sauropoda]].{{citation needed|date=June 2024}}

[[Phylogenetic]] analyses by Adam Yates (2004, 2006) and others firmly placed Sauropoda within a [[paraphyletic]] "Prosauropoda". Recent cladistic analyses suggest that the clade [[Prosauropoda]], which was named by Huene in 1920 and was defined by Sereno, in 1998, as all animals more closely related to ''[[Plateosaurus engelhardti]]'' than to ''[[Saltasaurus loricatus]]'',<ref name="sereno1998">{{cite journal | last1 = Sereno | first1 = P.C. | year = 1998 | title = A rationale for phylogenetic definitions, with applications to the higher-level taxonomy of Dinosauria | journal = Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen | volume = 210 | pages = 41–83 | doi=10.1127/njgpa/210/1998/41}}</ref> is a junior synonym of [[Plateosauridae]] as both contain the same taxa.<ref name=Y07 /><ref name=Indiansaupo/>

Most modern classification schemes break the prosauropods into a half-dozen groups that evolved separately from one common lineage. While they have a number of shared characteristics, the evolutionary requirements for giraffe-like browsing high in the trees may have caused [[convergent evolution]], where similar traits evolve separately because they faced the same evolutionary pressure, instead of ([[homology (biology)|homologous]]) traits derived from a shared ancestor.<ref name=poletal2011>{{cite journal | author = Pol D. | author2 = Garrido A. | author3 = Cerda I.A. | year = 2011 | title = A New Sauropodomorph Dinosaur from the Early Jurassic of Patagonia and the Origin and Evolution of the Sauropod-type Sacrum | journal = PLOS ONE | volume = 6 | issue = 1| article-number = e14572 | doi = 10.1371/journal.pone.0014572 | pmid=21298087 | pmc=3027623 | editor1-last = Farke | editor1-first = Andrew Allen| bibcode = 2011PLoSO...614572P | doi-access = free }}</ref>

The phylogenetic analysis of Otero et al., 2015 found Sauropodomorpha to be in a polytomy with ''[[Agnosphitys]]'' and [[Theropoda]] within [[Eusaurischia]], with [[Herrerasauridae]] and ''[[Eoraptor]]'' external to it within [[Saurischia]].<ref name="otero">{{cite journal|doi=10.1111/zoj.12247|title=A new basal sauropodiform from South Africa and the phylogenetic relationships of basal sauropodomorphs|journal=[[Zoological Journal of the Linnean Society]]|volume=174|issue=3|page=589|year=2015|last1=Otero|first1=Alejandro|last2=Krupandan|first2=Emil|last3=Pol|first3=Diego|last4=Chinsamy|first4=Anusuya|last5=Choiniere|first5=Jonah|doi-access=free|hdl=11336/38019|hdl-access=free}}</ref> A large phylogenetic analysis of early dinosaurs published by Matthew Baron, [[David B. Norman|David Norman]] and Paul Barrett (2017) in the journal [[Nature (journal)|''Nature'']] redefined Sauropodomorpha and [[Saurischia]] and recovered [[Herrerasauridae]] as the [[sister group]] to Sauropodomorpha within Saurischia. This resulted from the proposed removal of [[Theropoda]] from Saurischia and the formation of [[Ornithoscelida]], a clade containing Theropoda and [[Ornithischia]].<ref name="Ornithoscelida">{{cite journal | last1 = Baron | first1 = M.G. | last2 = Norman | first2 = D.B. | last3 = Barrett | first3 = P.M. | year = 2017 | title = A new hypothesis of dinosaur relationships and early dinosaur evolution | journal = Nature | volume = 543 | issue = 7646| pages = 501–506 | doi = 10.1038/nature21700 | pmid = 28332513 | bibcode = 2017Natur.543..501B | s2cid = 205254710 }}</ref>

===Phylogeny===
Within Sauropodomorpha, there is a large clade named '''Plateosauria'''.  The name Plateosauria was first coined by [[Gustav Tornier]] in 1913.<ref>Tornier, G., 1913, "Reptilia (Paläontologie)" In: ''Handwörterbuch Naturwissenschaften'' '''8''': 337-376</ref> The name afterwards fell out of use until the 1980s.  Plateosauria is a [[node-based taxon]]. In 1998, [[Paul Sereno]] defined Plateosauria as the [[last common ancestor]] of ''[[Plateosaurus engelhardti]]'' and ''[[Massospondylus carinatus]]'', and its descendants.<ref name="sereno1998" /> [[Peter Galton]] and [[Paul Upchurch]] in 2004 used a different definition: the last common ancestor of ''Plateosaurus  engelhardti'' and ''[[Jingshanosaurus xinwaensis]]'', and its descendants. In their [[cladistic]] analysis the Plateosauria belonged to the Prosauropoda, and included the [[Plateosauridae]] subgroup. In Galton's and Upchurch's study also ''[[Coloradisaurus]]'', ''[[Euskelosaurus]]'', ''[[Jingshanosaurus]]'', ''[[Massospondylus]]'', ''[[Mussaurus]]'', ''[[Sellosaurus]]'', and ''[[Yunnanosaurus]]'' proved to be plateosaurians.<ref name=GU04>{{Cite journal|author1=Galton, P.M  |author2=Upchurch, P.  |name-list-style=amp |year=2004 |title=Prosauropoda |journal=In D. B. Weishampel, P. Dodson, & H. Osmólska (Eds.), the Dinosauria (Second edition). University of California Press, Berkeley |pages=232–258 }}</ref>

However, recent [[cladistics|cladistic]] analyses suggest that the Prosauropoda as traditionally defined is [[paraphyletic]] to [[sauropod]]s.<ref name=Y03>{{cite journal | last1 = Yates | first1 = Adam M. | year = 2003 | title = Species taxonomy of the sauropodomorph dinosaurs from the Löwenstein Formation (Norian, Late Triassic) of Germany | journal = Palaeontology | volume = 46 | issue = 2 | pages = 317–337 | doi=10.1111/j.0031-0239.2003.00301.x| s2cid = 86801904 | doi-access = free | bibcode = 2003Palgy..46..317Y }}</ref><ref name=Y07>{{cite journal | last1 = Yates | first1 = Adam M. | year = 2007 | title = The first complete skull of the Triassic dinosaur ''Melanorosaurus'' Haughton (Sauropodomorpha: Anchisauria) |editor-first1= Paul M.|editor-last1=Barrett|editor-first2=David J.|editor-last2=Batten| journal = Evolution and Palaeobiology | volume = 77 | pages = 9–55 | isbn = 978-1-4051-6933-2 }}</ref><ref name=poletal2011 /><ref name=Indiansaupo>{{Cite journal|author1=Fernando E. Novas |author2=Martin D. Ezcurra |author3=Sankar Chatterjee |author4=T. S. Kutty |year=2011 |title=New dinosaur species from the Upper Triassic Upper Maleri and Lower Dharmaram formations of central India |journal=Earth and Environmental Science Transactions of the Royal Society of Edinburgh |volume=101 |issue=3–4 |pages=333–349 |doi=10.1017/S1755691011020093|s2cid=128620874 }}</ref><ref name=Leyesaurus>{{cite journal |author1=Cecilia Apaldetti |author2=Ricardo N. Martinez |author3=Oscar A. Alcober |author4=Diego Pol |year=2011 |title=A New Basal Sauropodomorph (Dinosauria: Saurischia) from Quebrada del Barro Formation (Marayes-El Carrizal Basin), Northwestern Argentina |journal=PLOS ONE |volume=6 |issue=11 |article-number=e26964 |doi=10.1371/journal.pone.0026964 |bibcode = 2011PLoSO...626964A |pmid=22096511 |pmc=3212523|doi-access=free }}</ref> Prosauropoda, as currently defined, is a [[synonym (taxonomy)|synonym]] of [[Plateosauridae]] as both contain the same taxa by definition. The phylogenetic analysis of 2021 recovered ''[[Issi]]'' and ''[[Plateosaurus]]'' as the basal-most plateosaurs.<ref>{{Cite journal|last1=Beccari|first1=Victor|last2=Mateus|first2=Octávio|last3=Wings|first3=Oliver|last4=Milàn|first4=Jesper|last5=Clemmensen|first5=Lars B.|date=November 2021|title=Issi saaneq gen. et sp. nov.—A New Sauropodomorph Dinosaur from the Late Triassic (Norian) of Jameson Land, Central East Greenland|journal=Diversity|language=en|volume=13|issue=11|page=561|doi=10.3390/d13110561|doi-access=free|bibcode=2021Diver..13..561B |hdl=10362/128951|hdl-access=free}}</ref>  Below is a cladogram of basal sauropodomorpha after Apaldetti and colleagues, 2021.<ref name=TJboundaryphylo>{{cite journal |doi=10.1038/s41598-021-01120-w |title=Sauropodomorph evolution across the Triassic–Jurassic boundary: Body size, locomotion, and their influence on morphological disparity |date=2021 |last1=Apaldetti |first1=Cecilia |last2=Pol |first2=Diego |last3=Ezcurra |first3=Martín D. |last4=Martínez |first4=Ricardo N. |journal=Scientific Reports |volume=11 |issue=1 |page=22534 |pmid=34795322 |pmc=8602272 |bibcode=2021NatSR..1122534A }}</ref>
{{clade| style=font-size:80%;line-height:70%
|label1='''Sauropodomorpha'''
|1={{clade sequential
|1=''[[Buriolestes]]'' [[File:Buriolestes schultzi restoration.png|70px]]
|2=''[[Eoraptor]]''
|3='''[[Saturnaliidae]]''' [[File:Saturnalia tupiniquim.jpg|60px]]
|4=''[[Thecodontosaurus]]''
|5={{clade
|1=''[[Efraasia]]'' [[File:Efraasia.png|70px]]
|2={{clade
|label1=Plateosauria
|1={{clade
|1={{clade |grouplabel1='''"Core prosauropods"''' |grouplabelstyle1=vertical-align:bottom;
|1={{clade
|1='''[[Plateosauridae]]''' <div style="{{mirrorH}}">[[File:Plateosaurus TD.png|90px]]</div> |barbegin1=green
|2='''[[Unaysauridae]]''' |bar2=green
}}
|2={{clade
|label1=Massopoda
|1={{clade
|1={{clade 
|1='''[[Riojasauridae]]''' |bar1=green
|2={{clade
|1='''[[Massospondylidae]]''' [[File:Massospondylus reconstruction.png|80px]] |barend1=green
|2={{clade
|label1=[[Sauropodiformes]]
|sublabel1=''sensu lato''
|1={{clade
|1={{clade
|1=''[[Yunnanosaurus]]''
|2={{clade
|1={{clade sequential
|1=''[[Seitaad]]''
|2=''[[Chuxiongosaurus]]''
|3=''[[Jingshanosaurus]]'' <div style="{{mirrorH}}">[[File:Jingshanosaurus xinwaensis.png|90px]]</div>
}}
|2={{clade
|1=''[[Xingxiulong]]'' [[File:Xingxiulong yueorum.png|80px]]
|2={{clade
|1={{clade
|1=''[[Anchisaurus]]''
|2=''[[Leonerasaurus]]'' <div style="{{mirrorH}}">[[File:Leonerasaurus NT.jpg|80px]]</div>
}}
|2={{clade
|label1=[[Sauropodiformes]]
|sublabel1=''sensu stricto''
|1={{clade
|1={{clade sequential
|1=''[[Mussaurus]]'' [[File:Mussaurus patagonicus life restoration.png|70px]]
|2=''[[Aardonyx]]'' <div style="{{mirrorH}}">[[File:Aardonyx TD.png|90px]]</div>
|3=''[[Irisosaurus]]''
|4=''[[Melanorosaurus]]''
|5='''[[Sauropoda]]''' [[File:Diplodocus carnegii.jpg|120px]]
}}
}}
}}
}}
}}
}}
}}
}}
}}
}}
}}
}}
}}
}}
}}
}}
}}
}}
}}
'''Massopoda''' is a [[clade]] of [[sauropodomorph]] [[dinosaur]]s within Sauropodomorpha which lived during the [[Late Triassic]] to [[Late Cretaceous]] epochs. It was named by [[paleontologist]] [[Adam M. Yates]] of the [[University of the Witwatersrand]] in [[2007 in paleontology|2007]]. Massopoda is a [[stem-based taxon]], defined as all animals more closely related to ''[[Saltasaurus loricatus]]'' than to ''[[Plateosaurus engelhardti]]''.  The name Massopoda, {{etymology|la|massa|lump}}; {{etymology|grc|''πους'' (pous)|foot}}, is also contraction of [[Massospondylidae]] and [[Sauropoda]], two disparate [[taxa]] in the clade.<ref name=A.rex>{{cite journal | author=Yates, Adam M. | year = 2007 | title = Solving a dinosaurian puzzle: the identity of ''Aliwalia rex'' Galton | journal = Historical Biology | volume = 19 | issue = 1 | pages = 93–123 | doi=10.1080/08912960600866953| bibcode = 2007HBio...19...93Y | s2cid = 85202575 }}</ref> [[Sauropodiformes]] is a more exclusive stem-based clade within Massopoda, defined as "the most inclusive clade containing ''Saltasaurus'' but not ''[[Massospondylus]]''".<ref name=sauropodiformes>{{Cite journal | doi = 10.1111/zoj.12127| title = The complete anatomy and phylogenetic relationships of ''Antetonitrus'' ingenipes (Sauropodiformes, Dinosauria): Implications for the origins of Sauropoda| journal = Zoological Journal of the Linnean Society| volume = 171| pages = 151–205| year = 2014| last1 = McPhee | first1 = B. W. | last2 = Yates | first2 = A. M. | last3 = Choiniere | first3 = J. N. | last4 = Abdala | first4 = F. }}</ref>

===Subgroups===
Below are the various subgroups of sauropodomorphs alongside their accompanying definitions.
{| class="wikitable sortable" align="center" width="100%"
! Name
! Named by
! Definition
! Notes
|-
| '''Anchisauria'''
| Galton & Upchurch, 2004
| Least inclusive clade containing both ''[[Anchisaurus]]'' and ''[[Melanorosaurus]]''<ref name=bookch3 />
|
|-
| '''Bagualosauria'''
| Langer et al., 2019
| Least inclusive clade containing both ''[[Bagualosaurus]]'' and ''[[Saltasaurus]]''<ref>{{cite journal |doi=10.1371/journal.pone.0212543|doi-access=free |title=Anatomy of the dinosaur Pampadromaeus barberenai (Saurischia—Sauropodomorpha) from the Late Triassic Santa Maria Formation of southern Brazil |date=2019 |last1=Langer |first1=Max Cardoso |last2=McPhee |first2=Blair Wayne |last3=Marsola |first3=Júlio César de Almeida |last4=Roberto-Da-Silva |first4=Lúcio |last5=Cabreira |first5=Sérgio Furtado |journal=PLOS ONE |volume=14 |issue=2 |article-number=e0212543 |pmid=30785940 |pmc=6382151 |bibcode=2019PLoSO..1412543L }}</ref>
|
|-
| '''[[Eusauropoda]]'''
| Upchurch, 1995
| Least inclusive clade containing both ''[[Shunosaurus]]'' and ''[[Saltasaurus]]''<ref name=bookch3 />
| Given a formal definition by Upchurch et al., 2004<ref name=bookch3 />
|-
| '''Gravisauria'''
| Allain & Aquesbi, 2008
| Least inclusive clade containing both ''[[Tazoudasaurus]]'' and ''[[Saltasaurus]]''<ref name=bookch3 />
|
|-
| '''Massopoda'''
| Yates, 2007
| Most inclusive clade containing ''[[Saltasaurus]]'', but not ''[[Plateosaurus]]''<ref name=bookch3 />
|
|-
| '''Plateosauria'''
| Sereno, 1998
| Least inclusive clade containing both ''[[Plateosaurus]]'' and ''[[Massospondylus]]''<ref name=bookch2>{{cite book |doi=10.1007/978-3-030-95959-3_2 |chapter=Non-sauropodiform Plateosaurians: Milestones Through the "Prosauropod" Bauplan |title=South American Sauropodomorph Dinosaurs |series=Springer Earth System Sciences |date=2022 |last1=Otero |first1=Alejandro |last2=De Fabrègues |first2=Claire Peyre |pages=51–92 |isbn=978-3-030-95958-6 }}</ref>
|
|-
| '''Prosauropoda'''
| Huene, 1920
| Most inclusive clade containing ''[[Plateosaurus]]'' but not ''[[Saltasaurus]]''
| Phylogenetic definition given by Sereno in 2005, this definition may be synonymous with [[Plateosauridae]]
|-
| '''[[Sauropoda]]'''
| Marsh, 1878
| Most inclusive clade containing ''[[Saltasaurus]]'' but not ''[[Melanorosaurus]]'';<ref name=bookch2 /> least inclusive clade containing both ''[[Vulcanodon]]'' and [[Eusauropoda]]<ref name=bookch3>{{cite book |doi=10.1007/978-3-030-95959-3_3 |chapter=South American Non-Gravisaurian Sauropodiformes and the Early Trend Towards Gigantism |title=South American Sauropodomorph Dinosaurs |series=Springer Earth System Sciences |date=2022 |last1=Apaldetti |first1=Cecilia |last2=Martínez |first2=Ricardo N. |pages=93–130 |isbn=978-3-030-95958-6 }}</ref>
| Alternative definitions given by Yates, 2007 and Langer et al., 2010,<ref name=bookch2 /><ref name=bookch3 /> formerly defined as the most inclusive clade containing ''Saltasaurus'' but not ''Plateosaurus'' (this clade is now called Massopoda)<ref name=bookch5>{{cite book |doi=10.1007/978-3-030-95959-3_12 |chapter=Body Size Evolution and Locomotion in Sauropodomorpha: What the South American Record Tells Us |title=South American Sauropodomorph Dinosaurs |series=Springer Earth System Sciences |date=2022 |last1=Otero |first1=Alejandro |last2=Hutchinson |first2=John R. |pages=443–472 |isbn=978-3-030-95958-6 }}</ref>
|-
| '''[[Sauropodiformes]]'''
| Sereno, 2007
| Least inclusive clade containing ''[[Mussaurus]]'' and ''[[Saltasaurus]]''<ref name=bookch3 />
| Alternatively defined by McPhee et al., 2014 as the most inclusive clade containing ''[[Saltasaurus]]'' but not ''[[Massospondylus]]''<ref>{{cite journal |doi=10.1111/zoj.12127 |title=The complete anatomy and phylogenetic relationships of ''Antetonitrus ingenipes'' (Sauropodiformes, Dinosauria): Implications for the origins of Sauropoda |date=2014 |last1=McPhee |first1=Blair W. |last2=Yates |first2=Adam M. |last3=Choiniere |first3=Jonah N. |last4=Abdala |first4=Fernando |journal=Zoological Journal of the Linnean Society |volume=171 |pages=151–205 }}</ref>
|-
| '''Sauropodomorpha'''
| Huene, 1932
| Most inclusive clade containing ''[[Diplodocus]]'' but not ''[[Triceratops]]'' or the [[house sparrow]];<ref name=bookch3 /> most inclusive clade containing ''[[Saltasaurus]]'' but not ''[[Allosaurus]]'' or ''[[Iguanodon]]''
| Formal definition given by Sereno, 2007;<ref name=bookch3 /> definition sometimes includes ''[[Herrerrasaurus]]'' as a defining taxon<ref name=bookch2 />
|-
|}

==Evolutionary history and paleobiogeography==
[[File:Dinosaur fossil distribution over time.png|thumb|Maps of the world during various points of the Mesozoic with sauropod remains indicated by white dots]]
Among the first dinosaurs to evolve in the Late Triassic period,<ref>{{Cite journal|last1=Müller|first1=Rodrigo T.|last2=Garcia|first2=Maurício S.|date=2019-03-08|title=Rise of an empire: analysing the high diversity of the earliest sauropodomorph dinosaurs through distinct hypotheses|journal=Historical Biology|volume=32|issue=10|language=en|pages=1334–1339|doi=10.1080/08912963.2019.1587754|s2cid=92177386|issn=0891-2963}}</ref> about 230 million years ago (Mya), they became the dominant herbivores by halfway through the late Triassic (during the [[Norian]] stage). Their perceived decline in the early Cretaceous is most likely a bias in fossil sampling, as most fossils are known from Europe and North America, but sauropods were still the dominant herbivores in the [[Gondwana]]n landmasses. The spread of [[flowering plant]]s (angiosperms) and "advanced" [[ornithischia]]ns, another major group of herbivorous dinosaurs (noted for their highly developed chewing mechanisms), are most likely not a major factor in sauropod decline in the northern continents{{citation needed|date=February 2015}}. Like all non-avian dinosaurs (birds), the sauropodomorphs became extinct 66 Mya, during the [[Cretaceous–Paleogene extinction event]].

The earliest and most [[Basal (phylogenetics)|basal]] sauropodomorphs known are ''[[Chromogisaurus novasi]]'' and ''[[Panphagia protos]]'', both from the [[Ischigualasto Formation]], dated to 231.4 million years ago (late [[Carnian]] age of the Late Triassic according to the [[International Commission on Stratigraphy|ICS]]<ref name=leal2004>{{cite journal | title = A new early dinosaur (Sauropodomorpha) from the Caturrita Formation (Late Triassic), Paraná Basin, Brazil | author = Luciano A. Leal | author2 = Sergio A. K. Azevodo | author3 = Alexander W. A. Kellner | author4 = Átila A. S. da Rosa | name-list-style = amp | date = October 18, 2004 | journal = Zootaxa | volume = 690 | pages = 1–24 | url = http://www.mapress.com/zootaxa/2004f/z00690f.pdf | doi = 10.11646/zootaxa.690.1.1 | archive-date = November 19, 2023 | access-date = January 19, 2011 | archive-url = https://web.archive.org/web/20231119170743/https://www.mapress.com/zootaxa/2004f/z00690f.pdf | url-status = live }} (''Warning:'' abstract is 12 kb [[portable document format|PDF]])</ref><ref name=RMOA09>{{cite journal |last=Martínez |first=Ricardo N. |author2=Alcober, Oscar A. |year=2009 |title=A basal sauropodomorph (Dinosauria: Saurischia) from the Ischigualasto Formation (Triassic, Carnian) and the early evolution of Sauropodomorpha |journal=PLOS ONE |volume=4 |issue=2 |pages=1–12|doi=10.1371/journal.pone.0004397 |pmid=19209223 |pmc=2635939 |editor1-last=Sereno |editor1-first=Paul|bibcode=2009PLoSO...4.4397M |doi-access=free }}</ref>). Some studies have found ''[[Eoraptor lunensis]]'' (also from the Ischigualasto Formation), traditionally considered a theropod, to be an early member of the sauropodomorph lineage, which would make it the most basal sauropodomorph known.<ref name="Martinez2011">{{Cite journal|author=Ricardo N. Martinez|author2=Paul C. Sereno|author3=Oscar A. Alcober|author4=Carina E. Colombi|author5=Paul R. Renne|author6=Isabel P. Montañez|author7=Brian S. Currie|name-list-style=amp |year=2011 |title=A Basal Dinosaur from the Dawn of the Dinosaur Era in Southwestern Pangaea |url=https://www.science.org/doi/abs/10.1126/science.1198467 |journal=Science |volume=331 |issue=6014 |pages=206–210 |doi=10.1126/science.1198467 |pmid=21233386|bibcode=2011Sci...331..206M |s2cid=33506648|hdl=11336/69202 |hdl-access=free |url-access=subscription }}</ref>

Sauropodomorph remains have been found on every continent, including Antarctica.  They evolved during the existence of the supercontinent [[Pangaea]], and are believed to have been widespread on this landmass prior to its separation into multiple continents.  However, multiple intercontinental dispersal events are believed to have occurred after Pangaea began to separate, resulting in the widespread proliferation of true sauropods after they evolved.<ref name="SP07">{{cite journal |last=Smith |first=Nathan D. |author2=Pol, Diego |year=2007 |title=Anatomy of a basal sauropodomorph dinosaur from the Early Jurassic Hanson Formation of Antarctica |url=http://app.pan.pl/article/item/app52-657.html |journal=Acta Palaeontologica Polonica |volume=52 |issue=4 |pages=657–674 |archive-date=2014-02-21 |access-date=2013-03-18 |archive-url=https://web.archive.org/web/20140221164854/http://app.pan.pl/article/item/app52-657.html |url-status=live }}</ref>  Sauropods themselves are also known from every continent, including Antarctica.<ref name="CrameLondon1989">{{cite book|author1=J. J. Alistair Crame|author2=Geological Society of London|title=Origins and Evolution of the Antarctic Biota|url=https://books.google.com/books?id=oLwTAQAAIAAJ&q=%22sauropods%22%22antarctica%22|year=1989|publisher=Geological Society|isbn=978-0-903317-44-3|page=132}}</ref>

===Timeline of groups===
<timeline>
ImageSize  = width:950px height:auto barincrement:15px
PlotArea   = left:10px bottom:50px top:10px right:10px

Period      = from:-251 till:-48
TimeAxis    = orientation:horizontal
ScaleMajor  = unit:year increment:10 start:-251
ScaleMinor  = unit:year increment:1 start:-251
TimeAxis    = orientation:hor
AlignBars   = justify

Colors =
 #legends
  id:SMP	  value:green
  id:SAU 	 value:blue
  id:black        value:black
  id:white        value:white
  id:mesozoic     value:rgb(0.54,0.54,0.258)
  id:triassic     value:rgb(0.51,0.17,0.57) 
  id:earlytriassic     value:rgb(0.6,0.22,0.61) 
  id:middletriassic     value:rgb(0.73,0.53,0.71) 
  id:latetriassic     value:rgb(0.78,0.65,0.8) 
  id:jurassic     value:rgb(0.2,0.7,0.79) 
  id:earlyjurassic     value:rgb(0,0.69,0.89) 
  id:middlejurassic     value:rgb(0.52,0.81,0.91) 
  id:latejurassic     value:rgb(0.74,0.89,0.97) 
  id:cretaceous   value:rgb(0.5,0.78,0.31)
  id:earlycretaceous   value:rgb(0.63,0.78,0.65)
  id:latecretaceous   value:rgb(0.74,0.82,0.37)
  id:paleogene     value:rgb(0.99,0.6,0.32) 
  id:paleocene     value:rgb(0.99,0.65,0.37) 
  id:eocene     value:rgb(0.99,0.71,0.42) 
 
BarData=
 bar:eratop
 bar:space
 bar:periodtop
 bar:space
 bar:NAM1
 bar:NAM2
 bar:NAM3
 bar:NAM4
 bar:NAM5
 bar:NAM6
 bar:NAM7
 bar:NAM8
 bar:NAM9
 bar:NAM10
 bar:NAM11
 bar:NAM12
 bar:NAM13
 bar:NAM14

 bar:space
 bar:period
 bar:space
 bar:era

PlotData=
 align:center textcolor:black fontsize:M mark:(line,black) width:25 
 shift:(7,-4)
  
 bar:periodtop
 from: -251   till:  -245    color:earlytriassic  text:[[Early Triassic|Early]]
 from: -245   till:  -228    color:middletriassic  text:[[Middle Triassic|Middle]] 
 from: -228   till:  -199.6    color:latetriassic  text:[[Late Triassic|Late]]            
 from: -199.6    till: -175.6    color:earlyjurassic    text:[[Early Jurassic|Early]]
 from: -175.6    till: -161.2    color:middlejurassic    text:[[Middle Jurassic|Middle]]
 from: -161.2    till: -145.5    color:latejurassic    text:[[Late Jurassic|Late]]
 from: -145.5    till: -99.6    color:earlycretaceous    text:[[Early Cretaceous|Early]]
 from: -99.6    till: -65.5    color:latecretaceous    text:[[Late Cretaceous|Late]]
 from: -65.5   till:  -55.8    color:paleocene  text:[[Paleocene|Pal.]]
 from: -55.8   till:  -48   color:Eocene text:[[Eocene|Eo.]]

 bar:eratop
 from: -251   till:  -199.6    color:triassic  text:[[Triassic]]         
 from: -199.6    till: -145.5    color:jurassic    text:[[Jurassic]]
 from: -145.5    till: -65.5   color:cretaceous    text:[[Cretaceous]]
 from: -65.5   till:  -48    color:paleogene  text:[[Paleogene]]

PlotData=
 align:left fontsize:M mark:(line,white) width:5 anchor:till align:left

 color:SMP bar:NAM1  from:-233.3    till:-201 text:Primitive sauropodomorphs
 color:SMP bar:NAM3  from:-225      till:-190 text:[[Plateosauridae]]
 color:SMP bar:NAM5  from:-227      till:-176 text:[[Massospondylidae]]
 color:SMP bar:NAM7  from:-216      till:-185 text:[[Sauropodiformes|Non-sauropod sauropodiformes]]
 color:SAU bar:NAM9  from:-206      till:-167 text:[[Sauropod|Primitive sauropods]]
 color:SAU bar:NAM11  from:-184      till:-114 text:[[Eusauropoda|Non-neosauropod eusauropods]]
 color:SAU bar:NAM13  from:-168      till:-65.5 text:[[Neosaurpoda|Neosauropods]]

PlotData=
 align:center textcolor:black fontsize:M mark:(line,black) width:25

 bar:period
 from: -251   till:  -245    color:earlytriassic  text:[[Early Triassic|Early]]
 from: -245   till:  -228    color:middletriassic  text:[[Middle Triassic|Middle]] 
 from: -228   till:  -199.6    color:latetriassic  text:[[Late Triassic|Late]]            
 from: -199.6    till: -175.6    color:earlyjurassic    text:[[Early Jurassic|Early]]
 from: -175.6    till: -161.2    color:middlejurassic    text:[[Middle Jurassic|Middle]]
 from: -161.2    till: -145.5    color:latejurassic    text:[[Late Jurassic|Late]]
 from: -145.5    till: -99.6    color:earlycretaceous    text:[[Early Cretaceous|Early]]
 from: -99.6    till: -65.5    color:latecretaceous    text:[[Late Cretaceous|Late]]
 from: -65.5   till:  -55.8    color:paleocene  text:[[Paleocene|Pal.]]
 from: -55.8   till:  -48   color:Eocene text:[[Eocene|Eo.]]

 bar:era
 from: -251   till:  -199.6    color:triassic  text:[[Triassic]]         
 from: -199.6    till: -145.5    color:jurassic    text:[[Jurassic]]
 from: -145.5    till: -65.5   color:cretaceous    text:[[Cretaceous]]
 from: -65.5   till:  -48    color:paleogene  text:[[Paleogene]]

</timeline>

==References==
<references>
<ref name="huene1932">{{cite journal|last=Huene|first=F.F.v.|author-link=Friedrich von Huene|year=1932|title=Die fossile Reptil-Ordnung Saurischia, ihre Entwicklung und Geschichte|journal=Monographien zur Geologie und Palaeontologie|volume=1|issue=4|pages=1–361}}</ref>
<ref name="wilson2006">{{cite book|last=Wilson|first=J.A.|year=2006|chapter=Overview of Sauropod Phylogeny and Evolution|pages=15–49|editor-last=Curry Rogers|editor-first=K.A.|editor2-last=Wilson|editor2-first=J.A.|title=The Sauropods: Evolution and Paleobiology|publisher=University of California Press|isbn=0-520-24623-3}}</ref>
<ref name="sereno2007">{{cite journal|last=Sereno|first=P.C.|author-link=Paul Sereno|year=2007|title=Basal Sauropodomorpha: historical and recent phylogenetic hypotheses, with comments on ''Ammosaurus major'' (Marsh, 1889)|journal=Special Papers in Palaeontology|volume=77|pages=261–289}}</ref>
<ref name="hallett2016">{{cite book|last1=Hallett|first1=M.|last2=Wedel|first2=M.J.|author-link2=Matt Wedel|year=2016|chapter=Sizing Up Sauropods|pages=23–53|title=The Sauropod Dinosaurs: Life in the Age of Giants|publisher=Johns Hopkins University Press|isbn=978-1-4214-2028-8}}</ref>
</references>

==External links==
* [https://web.archive.org/web/20050115161940/http://www.palaeos.com/vertebrates/Units/Unit330/330.000.html Sauropodomorpha: Overview], from Palæos.
* [http://users.tamuk.edu/kfjab02/dinos/VPSAUROPOD.htm Sauropodmorpha] {{Webarchive|url=https://web.archive.org/web/20190702050521/http://users.tamuk.edu/kfjab02/dinos/VPSAUROPOD.htm |date=2019-07-02 }}, from When Dinosaurs Ruled Texas, by Jon A. Baskin.
* [http://www.geol.umd.edu/~tholtz/G104/10421saur.htm Geol 104 Dinosaurs: A natural history: Sauropodomorpha: Size matters], by [[Thomas R. Holtz Jr.]], from the University of Maryland.
* {{Wikispecies-inline|Sauropodomorpha}}

{{Sauropodomorpha|S.|state=autocollapse}}
{{Portal bar|Dinosaurs|Paleontology}}
{{Taxonbar|from=Q133012}}

[[Category:Sauropodomorpha| ]]
[[Category:Dinosaur clades]]