View source for Squalidae

{{Short description|Family of sharks in the order Squaliformes}}
{{Redirect-distinguish|Squalid|Squalor (disambiguation){{!}}Squalor}}
{{Use British English|date=March 2023}}
{{Automatic taxobox
| name = Dogfish sharks
| fossil_range = {{Fossil range|Early Cretaceous|Recent}}<ref name=FB/><ref>{{cite web |title=Sample UB3, Speeton (Cretaceous of the United Kingdom) |url=https://paleobiodb.org/classic/basicCollectionSearch?collection_no=213573&is_real_user=1 |website=PBDB.org}}</ref>
| image = Squalus_acanthias.jpg
| image_caption = [[Spiny dogfish]], [[Spiny dogfish|''Squalus acanthias'']]
| taxon = Squalidae
| authority = [[Charles Lucien Bonaparte|Bonaparte]], 1834
| subdivision_ranks = Genera
| subdivision =
*''[[Cirrhigaleus]]''
*''[[Squalus]]''
}}

'''Squalidae''', more commonly known as '''dogfish''', '''dog sharks''', or '''spiny dogfish''',<ref>{{ITIS|id=160604|taxon=''Squalidae''|access-date=16 November 2013}}</ref> are one of several families of sharks categorized under [[Squaliformes]], making it the second largest order of sharks, numbering 119 species across 7 families.<ref>{{cite journal |last1=Straube |first1=N. |last2=Li |first2=C. |last3=Claes |first3=J.M. |title=Molecular phylogeny of Squaliformes and first occurrence of bioluminescence in sharks. |journal=BMC Evolutionary Biology |date=2015 |volume=15 |issue=162 |doi=10.1186/s12862-015-0446-6|doi-access=free |pmc=4537554 }}</ref> Having earned their name after a group of fishermen reportedly observed the species chasing down smaller fish in dog-like packs,<ref name=":0">{{Cite web|url=https://oceana.org/marine-life/sharks-rays/spiny-dogfish|title=Spiny Dogfish|website=Oceana|language=en|access-date=2019-04-12}}</ref> dogfish have slender, streamlined bodies, usually more compact in comparison to other species, and a pointed snout. Dogfish likewise have two dorsal fins, each with smooth spines, but no anal fin, and their skin is generally rough to the touch.<ref name=FB>{{FishBase_family|family=Squalidae|year=2009|month=January}}</ref> As the species reaches adulthood, males usually measure a maximum of {{convert|39|in|cm|-1|abbr=in|order=flip}}, while females typically measure {{convert|49|in|cm|round=5|abbr=in|order=flip}} long. The species therefore exhibits female-dominant [[sexual dimorphism]].

Dogfish sharks have slate-grey or grey-brown skin with white dots that become paler (almost white) around the belly region. These sharks are characterized by teeth in upper and lower jaws similar in size; a [[caudal peduncle]] with lateral keels; the upper precaudal pit is usually present; and the [[caudal fin]] is without a  subterminal notch.

They are carnivorous, principally preying upon organisms smaller than themselves. Some of their prey include [[herring]], [[mackerel]], and [[capelin]]. In special cases, they may consume [[jellyfish]] and [[squid]]. Even at a young age, spiny dogfish pups may hunt fish two or three times their size.{{citation needed|date=June 2019}} Unlike virtually all other shark species, dogfish sharks possess [[venom]] which coats their dorsal spines; this venom is mildly toxic to humans and would be harmful if the shark were to be mishandled. The livers and stomachs of the Squalidae contain the compound [[squalamine]], which possesses the property of reducing small blood vessel growth in humans.<ref>{{cite magazine|title=From the Belly of a Shark, a Cancer Cure?|work=National Geographic|date=June 1998|volume=193|number=6|page=202|url=https://archive.org/details/june199886|access-date=2 January 2023}}</ref> Dogfish sharks use their strong jaw and sharp teeth to consume their prey.

The spiny dogfish has broken several records in the areas of migration and gestation. This shark tends to be a highly migratory species: one shark was recorded as travelling {{convert|5000|mi|km|abbr=in|order=flip}} after being tagged in Washington state, United States, and found again later in Japan. In addition to its long distance migration, the spiny shark holds the record for the longest gestation period of any other vertebrate at 22–24 months. Females produce eggs and give birth to live young that measure to be {{convert|20-33|cm|in|0|abbr=in}}. The mating cycle of Squalidae consists of multiple paternity, where multiple males can [[Fertilisation|fertilize]] a single litter. This allows for increased [[genetic variation]], which is essential for the conservation of the species, given their susceptibility to fishing.<ref>{{Cite journal |last=Verissimo |first=A. |last2=Grubbs |first2=D. |last3=McDowell |first3=J. |last4=Musick |first4=J. |last5=Portnoy |first5=D. |date=2011-01-01 |title=Frequency of Multiple Paternity in the Spiny Dogfish Squalus acanthias in the Western North Atlantic |url=https://academic.oup.com/jhered/article-lookup/doi/10.1093/jhered/esq084 |journal=Journal of Heredity |language=en |volume=102 |issue=1 |pages=88–93 |doi=10.1093/jhered/esq084 |issn=0022-1503}}</ref>

== Taxonomy ==
Dogfish are scientifically classified as the Squalidae family, categorized under the [[Squaliformes|Squaliform]] order, which encompasses seven families in total, including Squalidae. The Squalidae family itself contains two separate genera: ''[[Cirrhigaleus]]'' and ''[[Spurdog|Squalus]]'', numbering 37 species between the two. Some extinct genera such as †''[[Protosqualus]]'' have been documented.

'''Order''': [[Squaliformes]]
'''Family''':
Within Squaliformes, there are seven families
* [[Centrophoridae|Centrophoridae – gulper sharks]]
* [[Dalatiidae|Dalatiidae – kite-fin sharks]]
* [[Echinorhinus|Echinorhinidae – bramble sharks]]
* [[Etmopteridae|Etmopteridae – lantern sharks]]
* [[Oxynotus|Oxynotidae – rough sharks]]
* [[Somniosidae |Somniosidae – sleeper sharks]]
* Squalidae – dogfish sharks
 
'''Genus''':
Within the Squalidae dogshark family, are two known genera
* ''[[Spurdog|Squalus]]'': The ''Squalus'' genus encompasses 34 different species of dogfish, or spurdogs, home to waters all around the world. With the exception of one – ''Squalus margaretsmithae'', or Smith's dogfish shark, known to be a maximum of {{convert|21.3|in|cm|round=5|abbr=in|order=flip}} in length <ref>{{cite journal |first1=S. T.|last1=de F. L. Viana|first2=M. W.|last2=Lisher|first3=M. R.|last3=de Carvalho|title=Two new species of short-snouted dogfish sharks of the genus ''Squalus'' Linnaeus, 1758, from southern Africa (Chondrichthyes: Squaliformes: Squalidae) |journal=Marine Biodiversity |date=2018 |volume=48 |pages=1787–1814 |doi=10.1007/s12526-017-0673-8}}</ref> – species classified under the genus are known to range from {{convert|22|to|63|in|cm|abbr=in|order=flip}} in length.<ref>{{cite web |last1=Froese|first1=R.|last2=Pauly|first2=D.|title=Genus: ''Squalus'' |url=https://www.fishbase.in/identification/SpeciesList.php?class=Elasmobranchii&order=Squaliformes&famcode=13&subfamily=&genus=Squalus&areacode=&c_code=&depth=&spines=&fins=&TL=&BD=&resultPage=1&sortby=species |website=fishbase.org |publisher=FishBase}}</ref> While the majority of the species are characterized by their slate or blue-grey body coloration and white underbelly, only 2 – [[Spiny dogfish|''Squalus acanthias'']] and [[Pacific spiny dogfish|''Squalus suckleyi'']] – are more easily recognizable by the notable, evenly-spaced array of small white dots decorating their darker dorsal sides.<ref>{{cite journal |last1=Ebert |first=D. A.|title=Resurrection and redescription of ''Squalus suckleyi'' (Girard, 1854) from the North Pacific, with comments on the ''Squalus acanthias'' subgroup (Squaliformes: Squalidae). |journal=Zootaxa |date=2010 |volume=2612 |issue=1 |pages=22–40}}</ref>
* ''[[Cirrhigaleus]]'': In contrast to its counterpart genus, ''Cirrhigaleus'' currently includes only 3 species, the most recent of which, [[Southern Mandarin dogfish|''Cirrhigaleus australis'']], was discovered and classified in 2007.<ref>{{cite journal |first1=W. T.|last1=White|first2=P. R.|last2=Last|first3=J. D.|last3=Stevens. |title=Cirrhigaleus australis n. sp., a new Mandarin dogfish (Squaliformes: Squalidae) from the south-west Pacific. |journal=Zootaxa |date=2007 |volume=1560 |issue=1 |pages=19–30 |doi=10.11646/ZOOTAXA.1560.1.2}}</ref> Cirrhigaleus species are typically the larger of the two Squalidae genera, ranging from {{convert|47|to|49.5|in|cm|round=5|abbr=in|order=flip}} in length (although the largest species of {{convert|63|in|cm|abbr=in|order=flip}}, ''Squalus acanthias'', is classified under the ''Squalus'' genus, the vast majority of the species within the same genus remain under or around {{convert|39|in|cm|-1|abbr=in|order=flip}} in length, whereas only 3 of 34 total species exceed {{convert|47|in|cm|abbr=in|order=flip}}.<ref>{{cite web |last1=Froese|first1=R.|last2=Pauly|first2=D.|title=Genus: Cirrhigaleus |url=https://www.fishbase.in/identification/SpeciesList.php?class=Elasmobranchii&order=Squaliformes&famcode=13&subfamily=&genus=Cirrhigaleus&areacode=&c_code=&depth=&spines=&fins=&TL=&BD=&resultPage=1&sortby=species |website=fishbase.org |publisher=FishBase}}</ref> The genus likewise shares many phenotypic similarities with its ''Squalus'' counterpart, namely the blue-grey body coloration, white underbelly, and basic morphology, however with some variation; common body coloration may also be a grey-brown hue, and most notably, ''Cirrhigaleus'' differs from ''Squalus'' in having extremely long [[Barbel (anatomy)|nasal barbels]], and small black instead of white spots in a similar pattern.<ref>{{cite journal |last1=Tanaka |first1=Shigeho |title=Three new species from Japan |journal=Zoology |date=1917 |volume=29 |pages=225–226}}</ref>

For a full list of species in each genera: [[list of sharks]]

[[File:Squalus acanthias2.jpg|thumb|''[[Spiny dogfish|Squalus acanthias]]'', or the spiny dogfish (adult), with grey-brown body coloration, decorated by evenly-spaced, small, white dots, and lighter underbelly.|left|290x290px]]
[[File:Mandarin dogfish2.jpg|thumb|''[[Mandarin dogfish|Cirrhigaleus barbifer]]'', or the Mandarin dogfish (adult), pictured with grey-brown body coloration, decorated in an array of speckled black dots, with a lighter underbelly, and elongated [[Barbel (anatomy)|nasal barbels.]]|248x248px]]
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== References ==
{{Portal|Sharks}}
{{Reflist}}

== Further reading ==
* {{FishBase family | family = Squalidae | month = February | year = 2011}}
* {{Cite book|author-link=Leonard Compagno|last1=Compagno|first1=Leonard J. V.|last2=Dando|first2=Mark|last3=Fowler|first3=Sarah L.|title=Sharks of the World|location=New Jersey|publisher=[[Princeton University Press]]|year=2005|isbn=0-691-12072-2}}

{{Selachimorpha|S.}}
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[[Category:Squalidae| ]]
[[Category:Taxa named by Charles Lucien Bonaparte]]
[[Category:Shark families]]
[[Category:Extant Late Cretaceous first appearances]]