Metriorhynchus

{{Speciesbox

|fossil_range = Kimmeridgian, {{Fossil range|157|150}}

|image = Metriorhynchus brevirostris.jpg

|image_caption = Partial holotype rostrum (MHNG V-2232) of M. brevirostris as illustrated in 1824

|genus = Metriorhynchus

|parent_authority = von Meyer, 1832von Meyer H. (1832). Palaeologica zur Geschichte der Erde und ihrer Geschöpfe. Frankfurt am Main: Siegmund Schmerber, 560.

|species = brevirostris

|authority = (Holl, 1828) vide Young et al., 2020

|synonyms =

Gavialis jurinii Gray, 1831
Metriorhynchus geoffroyii von Meyer, 1832
Streptospondylus geoffroyi (von Meyer, 1832)
Steneosaurus brevirostris Holl, 1829
Steneosaurus rostro-minor Geoffroy, 1825

}}

Metriorhynchus is an extinct genus of marine crocodyliform that lived in the oceans during the Late Jurassic. The type species, M. brevirostris was named in 1829 as a species of Steneosaurus before being named as a separate genus by the German palaeontologist Christian von Meyer in 1832. The name Metriorhynchus means "moderate snout", and is derived from the Greek Metrio- ("moderate") and -rhynchos ("snout").

Discovery and species

Fossil specimens referrable to Metriorhynchus are known from Kimmeridgian (Late Jurassic) deposits of France.{{Cite journal |last1=Young |first1=Mark T |last2=Brignon |first2=Arnaud |last3=Sachs |first3=Sven |last4=Hornung |first4=Jahn J |last5=Foffa |first5=Davide |last6=Kitson |first6=James J N |last7=Johnson |first7=Michela M |last8=Steel |first8=Lorna |date=2020-11-03 |title=Cutting the Gordian knot: a historical and taxonomic revision of the Jurassic crocodylomorph Metriorhynchus |url=http://dx.doi.org/10.1093/zoolinnean/zlaa092 |journal=Zoological Journal of the Linnean Society |volume=192 |issue=2 |pages=510–553 |doi=10.1093/zoolinnean/zlaa092 |issn=0024-4082|url-access=subscription }}

=Valid species=

Only one valid species is recognized today, the type species M. geoffroyii (now called M. brevirostris). "Metriorhynchus" hastifer and "M." palpebrosus are generically distinct from the Metriorhynchus type species, with hastifer being recovered as a geosaurine.{{Cite journal |last1=Ősi |first1=Attila |last2=Young |first2=Mark T. |last3=Galácz |first3=András |last4=Rabi |first4=Márton |date=2018-05-10 |title=A new large-bodied thalattosuchian crocodyliform from the Lower Jurassic (Toarcian) of Hungary, with further evidence of the mosaic acquisition of marine adaptations in Metriorhynchoidea |journal=PeerJ |language=en |volume=6 |pages=e4668 |doi=10.7717/peerj.4668 |issn=2167-8359 |pmc=5949208 |pmid=29761038 |doi-access=free }}{{Cite journal |last1=Foffa |first1=Davide |last2=Young |first2=Mark |last3=Brusatte |first3=Stephen |date=2018 |title=Filling the Corallian gap: new information on Late Jurassic marine reptile faunas from England |journal=Acta Palaeontologica Polonica |volume=63 |doi=10.4202/app.00455.2018 |s2cid=52254345 |issn=0567-7920|doi-access=free |hdl=20.500.11820/729f4cac-6217-4a21-b22c-8683b38c733b |hdl-access=free }} Species in this genus were traditionally classed into two skull groups: longirostrine (long, narrow jaws) and brevirostrine (short, broad jaws). However, most of brevirostrine species have been transferred to the genera Purranisaurus and Suchodus.{{Cite journal |last1=Herrera |first1=Yanina |last2=Gasparini |first2=Zulma |last3=Fernández |first3=Marta S. |date=2015-02-20 |title=Purranisaurus potens Rusconi, an enigmatic metriorhynchid from the Late Jurassic–Early Cretaceous of the Neuquén Basin |journal=Journal of Vertebrate Paleontology |volume=35 |issue=2 |pages=e904790 |doi=10.1080/02724634.2014.904790 |bibcode=2015JVPal..35E4790H |s2cid=128937976 |issn=0272-4634|hdl=11336/13737 |hdl-access=free }} Metriorhynchus superciliosus was also shown to be generically distinct from the type species, M. brevirostris, and now has its own genus Thalattosuchus.

File:Life reconstruction of Metriorhynchus brevirostris.png

The genera Purranisaurus and Suchodus have been considered junior synonyms of Metriorhynchus.Steel R. 1973. Crocodylia. Handbuch der Paläoherpetologie, Teil 16. Stuttgart: Gustav Fischer Verlag,116 pp. Recent phylogenetic analyses however, do not support the monophyly of Metriorhynchus, as believed during the 1860s-2010.Young MT. 2007. The evolution and interrelationships of Metriorhynchidae (Crocodyliformes, Thalattosuchia). Journal of Vertebrate Paleontology 27 (3): 170A.{{Cite journal |last1=Gasparini |first1=Zulma |last2=Pol |first2=Diego |last3=Spalletti |first3=Luis A. |date=2006-01-06 |title=An Unusual Marine Crocodyliform from the Jurassic-Cretaceous Boundary of Patagonia |url=https://www.researchgate.net/publication/7484990 |journal=Science |volume=311 |issue=5757 |pages=70–73 |doi=10.1126/science.1120803 |pmid=16282526 |bibcode=2006Sci...311...70G |s2cid=10312971 |issn=0036-8075|doi-access=free |hdl=11336/73480 |hdl-access=free }}{{Cite journal |last1=Wilkinson |first1=Laura E. |last2=Young |first2=Mark T. |last3=Benton |first3=Michael J. |title=A New Metriorhynchid Crocodilian (Mesoeucrocodylia: Thalattosuchia) from the Kimmeridgian (Upper Jurassic) of Wiltshire, UK |date=2008-11-19 |url=https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1475-4983.2008.00818.x |journal=Palaeontology |volume=51 |issue=6 |pages=1307–1333 |doi=10.1111/j.1475-4983.2008.00818.x |bibcode=2008Palgy..51.1307W |s2cid=84517228 |issn=0031-0239|url-access=subscription }}

Eudes-Deslongchamps (1867–69) recognized four Callovian species of Metriorhynchus: M. superciliosus, M. moreli, M. blainvillei, and M. brachyrhynchus.Eudes-Deslongchamps E. 1867-1869. Notes Paléontologiques. Caen and Paris: 320-392. Later, Andrews (1913) considered there to be seven valid species: M. superciliosus, M. moreli, M. brachyrhynchus, M. durobrivensis, M. cultridens, M. leedsi and M. laeve.Andrews CW. 1913. A descriptive catalogue of the marine reptiles of the Oxford Clay, Part Two. London: British Museum (Natural History), 206 pp. However, Adams-Tresman (1987), using linear morphometrics, could only distinguish between the two skull groups, so she found there to be two species from the Oxford Clay, M. superciliosus and M. brachyrhynchus.Adams-Tresman SM. 1987. The Callovian (Middle Jurassic) marine crocodile Metriorhynchus from Central England. Palaeontology 30 (1): 179-194. Vignaud (1997) however, considered there to be three Callovian species: M. superciliosus, M. brachyrhynchus and M. leedsi,Vignaud P. (1997). La morphologie dentaire des Thalattosuchia (Crocodylia, Mesosuchia). Palaeovertebrata 26: 35-59. and a 2022 study describing a new metriorhynchid specimen advocated returning to this taxonomic system, considering Gracilineustes and Thalattosuchus junior synonyms of Metriorhynchus.{{Cite journal |last1=Le Mort |first1=Jonas |last2=Martin |first2=Jeremy E. |last3=Picot |first3=Laurent |last4=Hua |first4=Stéphane |date=2022-07-01 |title=First description of the most complete Metriorhynchus aff. superciliosus (Thalattosuchia) specimen from the Callovian of the Vaches-Noires cliffs (Normandy, France) and limitations in the classification of Metriorhynchidae |journal=Annales de Paléontologie |language=en |volume=108 |issue=3 |pages=102539 |doi=10.1016/j.annpal.2022.102539 |bibcode=2022AnPal.10802539L |s2cid=254175334 |issn=0753-3969}}

=Unnamed species=

Fragmentary remains attributed to Metriorhynchus are known from South America during the Bajocian{{Cite journal |last1=Gasparini |first1=Zulma |last2=Vignaud |first2=Patrick |last3=Chong |first3=Guillermo |date=2000-11-01 |title=The Jurassic Thalattosuchia (Crocodyliformes) of Chile; a paleobiogeographic approach |journal=Bulletin de la Société Géologique de France |volume=171 |issue=6 |pages=657–664 |doi=10.2113/171.6.657 |issn=1777-5817|url=http://sedici.unlp.edu.ar/handle/10915/123708 }} and Bathonian (both Middle Jurassic).{{Cite journal |last1=Gasparini |first1=Zulma |last2=Cichowolski |first2=Marcela |last3=Lazo |first3=Dario G. |date=July 2005 |title=First Record of Metriorhynchus (Reptilia: Crocodyliformes) in the Bathonian (Middle Jurassic) of the Eastern Pacific |url=https://www.jstor.org/stable/4095052 |journal=Journal of Paleontology |volume=79 |issue=4 |pages=801–805 |doi=10.1666/0022-3360(2005)079[0801:fromrc]2.0.co;2 |jstor=4095052 |s2cid=130493042 |issn=0022-3360|url-access=subscription }} However, phylogenetic analysis has shown that these species cannot be referred to Metriorhynchus.{{Cite journal |last1=Young |first1=Mark T. |last2=Brusatte |first2=Stephen L. |last3=Ruta |first3=Marcello |last4=De Andrade |first4=Marco Brandalise |date=2010-03-30 |title=The evolution of Metriorhynchoidea (mesoeucrocodylia, thalattosuchia): an integrated approach using geometric morphometrics, analysis of disparity, and biomechanics |url=http://dx.doi.org/10.1111/j.1096-3642.2009.00571.x |journal=Zoological Journal of the Linnean Society |volume=158 |issue=4 |pages=801–859 |doi=10.1111/j.1096-3642.2009.00571.x |s2cid=84592894 |issn=0024-4082|url-access=subscription }}{{Cite journal |last1=Young |first1=Mark Thomas |last2=De Andrade |first2=Marco Brandalise |date=2009-10-26 |title=What is Geosaurus? Redescription of Geosaurus giganteus (Thalattosuchia: Metriorhynchidae) from the Upper Jurassic of Bayern, Germany |journal=Zoological Journal of the Linnean Society |volume=157 |issue=3 |pages=551–585 |doi=10.1111/j.1096-3642.2009.00536.x |s2cid=83242976 |issn=0024-4082|doi-access=free }}

Description

Metriorhynchus was a thalattosuchian, a group of marine crocodylomorphs. It was a member of the Metriorhynchidae, a group of thalattosuchians with a tail anatomy which indicates that they had a tail fluke similar to that of a shark. Unlike many other pseudosuchians, they did not have extensive osteoderms covering the body. Instead it appears that they had smoother skin similar to other marine reptiles like plesiosaurs and ichthyosaurs.{{Cite journal |last1=Altmühltal~mail@frederik-spindler.de |first1=Frederik Spindler~Dinosaurier Museum |last2=Paleontology~rene@lauerfoundationpse.org |first2=René Lauer~Lauer Foundation for |last3=Eichstätt~htischlinger@online.de |first3=Helmut Tischlinger~Germany and Jura-Museum |last4=Bayerns~maeuser@snsb.de |first4=Matthias Mäuser~Staatliche Naturwissenschaftliche Sammlungen |date=2021-07-03 |title=The integument of pelagic crocodylomorphs (Thalattosuchia: Metriorhynchidae) |url=https://palaeo-electronica.org/content/2021/3399-metriorhynchid-skin |access-date=2024-08-05 |journal=Palaeontologia Electronica |language=en |doi=10.26879/1099|doi-access=free }} Metriorhynchids also had a hip anatomy conducive for live birth and evidence from the related Dakosaurus does show that they did this.{{cite book|year=2019|author=Spindler, Frederik|url=https://www.palaeontologie.geowissenschaften.uni-muenchen.de/pdfs/palges2019_abstracts.pdf#page=141|title=Live Birth in a Jurassic Marine Crocodile [abstract]. In: Abstracts of the 90th Annual Meeting of the Paläontologische Gesellschaft|publisher= SNSB - BSPG, München|page=141|isbn=978-3-946705-07-9|archive-url=https://web.archive.org/web/20230517045802/https://www.palaeontologie.geowissenschaften.uni-muenchen.de/pdfs/palges2019_abstracts.pdf#page=141|archive-date=2023-05-17|url-status=live}} Metriorhynchus can be distinguished from other metriorhynchids in that the three front teeth get bigger from front to back, with the first being round and the third more oval-shaped. The jaws have a narrow point where different parts of the upper jaw meet, and there are at least 13 teeth before the palatine bones start. The teeth are mostly oval-shaped, but after the third one, they become rounder. The front part of the nasal bones stops near the eighth tooth, and unlike most animals, it has a single large external nostril instead of two separate ones. The opening for the nostrils begins behind the first tooth and ends just past the last one in the front section of the jaw. It was about 3 meters (9.8 feet) in body length.{{Cite book |title=The Complete Guide to Prehistoric Life |publisher=Firefly Books |year=2006 |isbn=155407181X |edition=1}}

Paleoecology

Metriorhynchus was a carnivore. One fossil shows it has eaten the gill apparatus of the giant fish Leedsichthys. The idea of Metriorhynchus attacking weak Leedsichthys individuals has been speculated to be the case in the past such as in the BBC and Discovery Channel documentary Sea Monsters.{{Cite journal |last1=Hua |first1=Stéphane |last2=Liston |first2=Jeff |last3=Tabouelle |first3=Jérôme |date=March 2024 |title=The Diet of Metriorhynchus (Thalattosuchia, Metriorhynchidae): Additional Discoveries and Paleoecological Implications |journal=Fossil Studies |language=en |volume=2 |issue=1 |pages=66–76 |doi=10.3390/fossils2010002 |doi-access=free |issn=2813-6284}}{{Cite web |title=BBC - Science & Nature - Sea Monsters - Fact File: Metriorhynchus |url=https://www.bbc.co.uk/science/seamonsters/factfiles/metriorhynchus.shtml |access-date=2024-08-05 |website=www.bbc.co.uk}}

References

Category:Late Jurassic crocodylomorphs of Europe

Category:Prehistoric pseudosuchian genera

Category:Prehistoric marine crocodylomorphs

Category:Late Jurassic genus extinctions

Category:Thalattosuchia

Category:Fossil taxa described in 1832