Protosqualus ("Primitive Squalus") was a genus of dogfish shark that existed during the Cretaceous. Fossils have been found in Europe (mainly in France, Russia, Germany, Lithuania, The United Kingdom and Ukraine), East Asia (mainly in Japan),[5] Antarctica,[6] Australia,[7] India and South America.[8][9] The type species is Protosqualus sigei, which was found around an Albian aged deposit in France.[10] There are 6 species which can be differentiated by distinct features in their teeth. Some species show some level of heterodonty, for example Protosqualus barringtonensis shows a rather high level of heterodonty within its teeth. The oldest specimens are from the Speeton Clay Formation.[11] Protosqualus teeth are quite common in the Grey Chalk deposit of England.[12] The genus went extinct at the end of the Cretaceous during the Cretaceous–Paleogene extinction event, with the last species in the genus being Protosqualus argentinensis from southern Argentina as well as possibly being from earlier deposits in India.
| Protosqualus | |
|---|---|
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| Drawing of a Protosqualus argentinensis tooth | |
Scientific classification 
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Chondrichthyes |
| Subclass: | Elasmobranchii |
| Order: | Squaliformes |
| Family: | Squalidae |
| Genus: | †Protosqualus Cappetta, 1977 |
| Type species | |
| †Protosqualus sigei[4] Cappetta, 1977
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| Other species | |
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Discovery and Naming
editThe type specimen of Protosqualus was found in a deposit that had been known to contain shark teeth since the 1930's. The type specimen was finally named in 1977 by paleontologist and ichthyologist, Henri Cappetta. The deposit is the Mortoniceras inflatum ammonoid zone. The name Protosqualus literally means "Primitive Squalus" in reference to how it is an ancient genus related to the extant genus, Squalus. The type species, P.sigei, derives its species name from paleontologist, B.Siegé.[10]
Description
editProtosqualus, like most fossil sharks, is known from mostly dental remains.[13] Protosqualus had an undulated ventral margin of the dental crown that was distal to the apron. Unlike modern members of the genus Squalus, Protosqualus had dental crowns which did not have a great degree of labiolingual compression.[14] The holotype of P. sigei featured a tooth with small gaps between them, each with a clearly defined slanted tip. Its front ledge was well-developed and slightly raised, culminating in a rounded shape firmly attached at the base of the crown. The back of the tooth appeared flat, with a slight depression near the ledge. The root was low and thick, angled slightly in relation to the crown, and exhibited minor protrusions on both its front and rear sides. The bottom of the tooth was flat and gently curved, with the holes on the sides either separated or, less commonly, connected by a groove.[10] The teeth of P. pachyrhiza were more bulky.[15] Protosqualus glickmani had a broad cusp.[16] Protosqualus argentinensis had defined serrated cutting edges and was probably the largest member of the genus.[14] Protosqualus barringtonensis may have shown some sexual dimorphism in the teeth, however all teeth show a short cusp.[17] P.albertsi had a broad, labial protuberance.[15]
Classification
editProtosqualus is a member of the Squalidae within the Squaliformes group. Today, only two extant genera of squalids exist. Squalids tend to note have the teeth in their lower jaw not being any larger than the teeth seen in the upper jaw.[18] Below is a cladogram showing where Squalidae sits in the Squaliform clade.[19]
In 2001, Adnet & Cappetta found the following position for Protosqualus.[20]Here, it is shown to be closer to the extant dogfishes called Spurdogs.
Paleoecology
editProtosqualus lived alongside other chondrichthyans as well as other types of fish. It also lived alongside mosasaurs and plesiosaurs.[21] Fossils of Protosqualus have been found in the Speeton Clay Formation, Omagari Formation, Hunstanton Formation, Jiesia Formation, Lopez de Bertodano Formation, Burim Formation, Ferriby Formation, Karai Formation,[22] Labguva Formation, Hibernian Greensand Formation and Calafate Formation among a few others. The Calafate Formation likely had estuaries and shallow seas.[23] [24]
References
edit
- ^ "Protosqualus argentinensis". PBDB.org.
- ^ "†Protosqualus sigei". PBDB.org.
- ^ Thies, Detlev (19 August 1981). "Four new species of Neoselachian sharks from the Lower Cretaceous of NW-Germany". Neues Jahrbuch für Geologie und Paläontologie - Monatshefte. 1981 (8): 475–486. doi:10.1127/njgpm/1981/1981/475. ISSN 0028-3630.
- ^ "H. Cappetta 1977". PBDB.org.
- ^ "Rubeshibe River, locality 1 (Cretaceous of Japan)". PBDB.org.
- ^ Cione, Alberto L.; Santillana, Sergio; Gouiric-Cavalli, Soledad; Acosta Hospitaleche, Carolina; Gelfo, Javier N.; López, Guillermo M.; Reguero, Marcelo (May 2018). "Before and after the K/Pg extinction in West Antarctica: New marine fish records from Marambio (Seymour) Island". Cretaceous Research. 85: 250–265. Bibcode:2018CrRes..85..250C. doi:10.1016/j.cretres.2018.01.004. hdl:11336/99687.
- ^ Kriwet, J; Klug, S (2009), Gallucci, V; McFarlane, G; Bargmann, G (eds.), "Fossil record and origin of squaliform sharks (Chondrichthyes, Neoselachii)", Biology and Management of dogfish sharks, American Fisheries Society, Bethesda, Maryland, pp. 19–38, ISBN 978-1-934874-07-3, retrieved 29 July 2024
- ^ "Protosqualus pachyrhiza | Shark-References". shark-references.com. Retrieved 8 July 2024.
- ^ "†Protosqualus Cappetta 1977 (dogfish shark)". PBDB.org.
- ^ a b c Cappetta, Henri (1 January 1977). "Selaciens nouveaux de l'Albien superieur de Wissant (Pas-de-Calais)". Geobios. 10 (6): 967–973. Bibcode:1977Geobi..10..967C. doi:10.1016/S0016-6995(77)80085-5. ISSN 0016-6995.
- ^ "Middle B beds, Speeton (Cretaceous of the United Kingdom)". PBDB.org.
- ^ "SQUALIFORMES [Dogfish]". discoveringfossils.co.uk.
- ^ "Fossil Shark Teeth". floridamuseum.ufl.edu.
- ^ a b Bogan, Sergio; Agnolin, Federico L.; Novas, Fernando E. (3 May 2016). "New selachian records from the Upper Cretaceous of southern Patagonia: paleobiogeographical implications and the description of a new taxon". Journal of Vertebrate Paleontology. 36 (3): e1105235. Bibcode:2016JVPal..36E5235B. doi:10.1080/02724634.2016.1105235. hdl:11336/17487. ISSN 0272-4634.
- ^ a b Underwood, Charlie J.; Mitchell, S. F. (1999). "Albian and Cenomanian selachian assemblages from North East England". Special Papers in Palaeontology. 60: 9–59. ISSN 0038-6804.
- ^ "Additions to the Selachian fauna of the Russian Cretaceous. 1. A new species of Protosqualus Cappetta, 1977 (Chondrichthyes: Squalidae)" (PDF). Retrieved 8 July 2024.
{{cite journal}}: Cite journal requires|journal=(help) - ^ Guinot, Guillaume; Underwood, Charlie J.; Cappetta, Henri; Ward, David J. (August 2013). "Sharks (Elasmobranchii: Euselachii) from the Late Cretaceous of France and the UK". Journal of Systematic Palaeontology. 11 (6): 589–671. Bibcode:2013JSPal..11..589G. doi:10.1080/14772019.2013.767286. ISSN 1477-2019.
- ^ Nelson, Joseph S.; Grande, Terry C.; Wilson, Mark V. H. (22 February 2016). Fishes of the World (1 ed.). Wiley. doi:10.1002/9781119174844. ISBN 978-1-118-34233-6.
- ^ Straube, Nicolas; Li, Chenhong; Claes, Julien M.; Corrigan, Shannon; Naylor, Gavin J. P. (16 August 2015). "Molecular phylogeny of Squaliformes and first occurrence of bioluminescence in sharks". BMC Evolutionary Biology. 15 (1): 162. Bibcode:2015BMCEE..15..162S. doi:10.1186/s12862-015-0446-6. ISSN 1471-2148. PMC 4537554. PMID 26277575.
- ^ Adnet, Sylvain; Cappetta, Henri (September 2001). "A palaeontological and phylogenetical analysis of squaliform sharks (Chondrichthyes: Squaliformes) based on dental characters". Lethaia. 34 (3): 234–248. Bibcode:2001Letha..34..234A. doi:10.1111/j.1502-3931.2001.tb00052.x. ISSN 0024-1164.
- ^ "El Calafate airport (Cretaceous of Argentina)". PBDB.org.
- ^ Underwood, Charlie J.; Goswami, Anjali; Prasad, G. V. R.; Verma, Omkar; Flynn, John J. (May 2011). "Marine vertebrates from the 'middle' Cretaceous (early Cenomanian) of South India". Journal of Vertebrate Paleontology. 31 (3): 539–552. Bibcode:2011JVPal..31..539U. doi:10.1080/02724634.2011.574518. ISSN 0272-4634.
- ^ Marenssi, S.; Guler, V.; Casadío, S.; Guerstein, R.; Papú, O. (1 December 2004). "Sedimentology and palynology of the Calafate Formation (Maastrichtian), Austral Basin, Southern Patagonia, Argentina". Cretaceous Research. 25 (6): 907–918. Bibcode:2004CrRes..25..907M. doi:10.1016/j.cretres.2004.08.004. ISSN 0195-6671.
- ^ "El Calafate airport (Cretaceous of Argentina)". PBDB.org.