Bruhathkayosaurus
Template:Short description Template:Use dmy dates Template:Speciesbox
Bruhathkayosaurus (Template:IPAc-en; meaning "huge-bodied lizard") is a genus of sauropod dinosaur found in the Kallamedu Formation of India. The fragmentary remains were originally described as a theropod, but it was later determined to be a titanosaurian sauropod. Length estimates by researchers exceed those of the titanosaur Argentinosaurus,<ref name=Paul1994/> as longer than Template:Convert and weighing over 80 tonnes. A 2023 estimate placed Bruhathkayosaurus as potentially weighing approximately Template:Convert, with paleontologist Michael Benton, giving Bruhathkayosaurus a length of Template:Convert.<ref name=DinosaurBehaviour>Template:Cite book</ref> If the upper estimates of the 2023 records are accurate, Bruhathkayosaurus may have rivaled the blue whale as one of the largest animals to ever exist.<ref name="Bruhathkayosaurus2023"/> However, all of the estimates are based on the dimensions of the fossils described in Yadagiri and Ayyasami (1987), and in 2017, it was reported that the holotype fossils had disintegrated and no longer exist.<ref name="YadagiriAyyasami" /><ref name=":0" />
Discovery and naming
Template:Location map The holotype of Bruhathkayosaurus, GSI PAL/SR/20, was discovered around 1978 near the southern tip of India, specifically in the Tiruchirappalli district of Tamil Nadu, northeast of Kallamedu village. It was recovered from rocks of the Kallamedu Formation, which are dated to the Maastrichtian stage of the Late Cretaceous, about 70 million years ago. The fossilized remains include hip bones (the ilium and ischium), partial leg bones (femur and tibia), a forearm (radius) and a tail bone (part of a vertebra, specifically a platycoelous caudal centrum). The remains were originally classified as belonging to a carnosaurian theropod by Yadagiri and Ayyasami in 1987 (not 1989, as some sources indicate).<ref name="YadagiriAyyasami">Yadagiri, P. and Ayyasami, K. (1987). "A carnosaurian dinosaur from the Kallamedu Formation (Maestrichtian horizon), Tamilnadu." In M.V.A. Sastry, V.V. Sastry, C.G.K. Ramanujam, H.M. Kapoor, B.R. Jagannatha Rao, P.P. Satsangi, and U.B. Mathur (eds.), Three Decades of Development in Palaeontology and Stratigraphy in India. Volume 1. Precambrian to Mesozoic. Geological Society of India Special Publication, 11(1): 523-528.</ref> The generic name chosen, "Bruhathkayosaurus", is derived from a combination of the Sanskrit word Bruhathkaya (bṛhat Template:Lang, 'huge, heavy' and kāya, काय 'body'), and the Greek sauros (lizard).<ref name=paulschneiderman>Schneiderman, P. (Nov 1994). "Report on the initial description Template:Webarchive". Dinosaur Mailing List</ref> The specific epithet, "matleyi", honours British palaeontologist Charles Alfred Matley, who discovered many fossils in India.
The monsoon season, combined with the sands and clays of the Kallamedu Formation, creates water-saturated fossils which are very friable. During the dry season, expansion during the day and contraction during the night can cause fossils to split apart. This results in poorly preserved bones that can be impossible to extract without damage. In 2017, Galton and Ayyasami reported that the Bruhathkayosaurus fossils started to disintegrate inside their field jackets before reaching the Geological Survey of India (GSI) and no longer exist.<ref name=":0">Template:Cite journal</ref>
Classification
Bruhathkayosaurus was originally classified as a carnosaur (like Allosaurus), of an uncertain position (incertae sedis). However, Chatterjee (1995) re-examined the remains and demonstrated that Bruhathkayosaurus is actually a titanosaur sauropod.<ref>Chatterjee, S. (1995). "The last dinosaurs of India". The Dinosaur Report, Fall 1995. p. 12-18.</ref> Some later studies listed Bruhathkayosaurus as an indeterminate sauropod or as a nomen dubium.<ref>Upchurch, P., Barrett, P. M. and Dodson, P. 2004. Sauropoda. pp. 259–322. in Weishampel, D. B., Dodson, P. and Osmólska, H. (eds). The Dinosauria, Second Edition. University of California Press, Berkeley, 861 pp.</ref><ref name="krauseetal2006">Template:Cite journal</ref><ref>Template:Cite journal</ref>
The original publication described little in the way of diagnostic characteristics and was only supported by a few line drawings and photographs of the fossils as they lay in the ground. This led to online speculation by researchers that the bones might actually have been petrified wood, akin to the way the original discoverers of Sauroposeidon initially believed their find to be fossilized tree trunks.<ref name="Holtz1995a">Holtz, T. (1995), http://dml.cmnh.org/1995Sep/msg00701.html Template:Webarchive "Re: Biggest predators"], discussion group, The Dinosaur Mailing List, 22 September 1995. Accessed 24 February 2019.</ref><ref name="mortimer2006">Mortimer, M. (2006), "Re:" Template:Webarchive, discussion group, The Dinosaur Mailing List, 17 November 2006. Accessed 24 February 2019.</ref><ref name="Brusatte2001a">Brusatte, S. (2001), "Re: Bruhathkayosaurus" Template:Webarchive, discussion group, The Dinosaur Mailing List, 18 June 2001. Accessed 24 February 2019.</ref> A 2022 review by Pal and Ayyasami presented additional previously unseen photographs of the tibia bone at the excavation site and in a plaster jacket, and reinforced the taxon's position within Titanosauria.<ref name=":2">Template:Cite journal</ref> However, as Mohabey and colleagues noted in 2024, "this new information has not resolved the identity of the element nor the validity of the taxon."<ref>Template:Cite journal</ref>
Size estimates
According to the published description, the shin bone (tibia) of Bruhathkayosaurus was Template:Convert long.<ref name="YadagiriAyyasami" /><ref name=":2" /> This is 29 percent larger than the fibula of Argentinosaurus, which is only Template:Cvt long. The fragmentary femur was similarly huge; across the distal end, it measured Template:Convert, 33% larger than the femur of Antarctosaurus giganteus, which measures Template:Convert. The ilium measured Template:Convert in length.<ref name="mortimer2004"/><ref name=":0" />
No total body size estimates for Bruhathkayosaurus have been published, but paleontologists and researchers have posted tentative estimates on the Internet. In a post from June 2001, Mickey Mortimer estimated that Bruhathkayosaurus could have reached Template:Convert in length and might have weighed Template:Convert, but in later posts retracted these estimates, reducing the estimated length to Template:Convert based on more complete titanosaurs (Saltasaurus, Opisthocoelicaudia and Rapetosaurus), and declined to provide a new weight estimate, describing the older weight estimates as inaccurate.<ref name="mortimer2001a">Mortimer, M. (2001), "Re: Bruhathkayosaurus" Template:Webarchive, discussion group, The Dinosaur Mailing List, 19 June 2001. Accessed 23 May 2008.</ref><ref name="mortimer2004">Mortimer, M. (2004), "Re: Largest Dinosaurs" Template:Webarchive, discussion group, The Dinosaur Mailing List, 7 September 2004. Accessed 23 May 2008.</ref><ref name="mortimer2001b">Mortimer, M. (2001), "Titanosaurs too large?" Template:Webarchive, discussion group, The Dinosaur Mailing List, 12 September 2001. Accessed 23 May 2008.</ref> In a May 2008 article for the weblog Sauropod Vertebra Picture of the Week, paleontologist Matt Wedel used a comparison with Argentinosaurus and calculated the weight of Bruhathkayosaurus at up to Template:Convert.<ref name="wedel2008">Wedel, M. "SV-POW! showdown: sauropods vs whales Template:Webarchive." [Weblog entry.] Sauropod Vertebra Picture of the Week. 20 May 2008. Accessed 23 May 2008.</ref> In 2019, Gregory S. Paul suggested that the supposed tibia was probably a degraded femur, in which case its length was slightly greater than that of Dreadnoughtus (1.91 meters) and Futalognkosaurus (1.98 meters). Its ilium is similar in length to that of Dreadnoughtus whereas the width of the distal femur appears to slightly exceed that of Patagotitan. Paul estimated its mass at around Template:Convert, much lower than any previous estimation.<ref name=":1">Template:Cite journal</ref> In 2020, Molina-Perez and Larramendi suggested that the Template:Convert long tibia is probably a fibula, and estimated the size of the animal at Template:Convert and Template:Convert.<ref>Template:Cite book</ref>
By comparison, the titanosaur Argentinosaurus is estimated to have reached Template:Cvt in length, and to have weighed 65–100 tonnes.<ref name=Paul1994>Template:Cite book</ref><ref name=":1" /><ref name=Paul1997>Template:Cite conference</ref> These sauropods are known only from partial or fragmentary remains, so the size estimates are uncertain. Length is calculated by comparing existing bones to the bones of similar dinosaurs, which are known from more complete skeletons and scaling them up isometrically. However, such extrapolation can never be more than an educated guess and the length of the tail, in particular, is often hard to judge. Determining mass is even more difficult because little evidence of soft tissues survives in the fossil record. In addition, isometric scaling is based on the assumption that body proportions remain the same, which is not necessarily the case. In particular, the proportions of the titanosaurs are not well known, due to a limited number of relatively complete specimens.<ref name="mortimer2004"/>
If the upper size estimates for Bruhathkayosaurus are accurate, it would even rival the size of the largest recorded blue whale. Mature blue whales can reach Template:Convert in length, and the record-holder blue whale was recorded at Template:Convert,<ref name="pop">Template:Cite web</ref> with estimates of up to Template:Convert.<ref>Template:Cite journal</ref>
Another poorly known sauropod that shares similar size estimates to Bruhathkayosaurus is Maraapunisaurus fragillimus, which is based on a now-missing dorsal vertebra. In 2006, Kenneth Carpenter used Diplodocus as a guide and estimated Maraapunisaurus to be Template:Convert in length and weigh only about Template:Convert.<ref name="carpenter2006">Carpenter, K. (2006). "Biggest of the big: a critical re-evaluation of the mega-sauropod Amphicoelias fragillimus." In Foster, J.R. and Lucas, S.G., eds., 2006, Paleontology and Geology of the Upper Jurassic Morrison Formation. New Mexico Museum of Natural History and Science Bulletin 36: 131–138.</ref> In 2018, however, Carpenter estimated Maraapunisaurus to be Template:Convert in length based upon comparisons with rebbachisaurids.<ref>Template:Cite journal</ref> In 2019, Paul gave a higher estimation of Template:Convert and a weight of Template:Convert.<ref name=":1" />
Paul and Larramendi (2023) suggested that Bruhathkayosaurus may have weighed within the range of Template:Convert, though they stated that it would have likely weighed between Template:Convert. Whilst its most liberal estimate was 240 tons when scaled with Patagotitan, they considered any estimate over Template:Convert to be unlikely.<ref name="Bruhathkayosaurus2023">Template:Cite journal</ref> Nevertheless, Paul stressed that the idea of these 'super-sauropods' or 'land-whales' aren't as far-fetched as one would think given the long period of sauropod existence as well as their very efficient body-plan (i.e. small heads, large body, efficient ventilated air-sacs, strong and flexible muscle and bone structure, and large source of static food), indicating that the existence of 150+ ton sauropods such as Bruhathkayosaurus and Maraapunisaurus are in the realm of possibility.<ref name="Bruhathkayosaurus2023"/>
See also
References
External links
- Report on the initial description from the Dinosaur Mailing List