Wikipedia

Metriorhynchus

For the genus of beetles, see Metriorrhynchus.

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.[2] The name Metriorhynchus means "Moderate snout", and is derived from the Greek Metrio- ("moderate") and -rhynchos ("snout").

Metriorhynchus
Temporal range: Kimmeridgian, 157–150 Ma
Partial holotype rostrum (MHNG V-2232) of M. brevirostris as illustrated in 1824
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Clade: Archosauria
Clade: Pseudosuchia
Clade: Crocodylomorpha
Clade: Crocodyliformes
Suborder: †Thalattosuchia
Family: †Metriorhynchidae
Genus: †Metriorhynchus
von Meyer, 1832[2]
Species:
†M. brevirostris
Binomial name
†Metriorhynchus brevirostris
(Holl, 1828) vide Young et al., 2020[1]
Synonyms

Discovery and species

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Fossil specimens referrable to Metriorhynchus are known from Kimmeridgian (Late Jurassic) deposits of France.[1]

Valid species

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Only one valid species is recognized today, the type species M. geoffroyii (now called M. brevirostris).[1] "Metriorhynchus" hastifer and "M." palpebrosus are generically distinct from the Metriorhynchus type species, with hastifer being recovered as a geosaurine.[3][4] 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.[5][6] Metriorhynchus superciliosus was also shown to be generically distinct from the type species, M. brevirostris, and now has its own genus Thalattosuchus.[1]

 
Life reconstruction of Metriorhynchus brevirostris

The genera Purranisaurus and Suchodus have been considered junior synonyms of Metriorhynchus.[7] Recent phylogenetic analyses however, do not support the monophyly of Metriorhynchus, as believed during the 1860s-2010.[8][9][10][1]

Eudes-Deslongchamps (1867–69) recognized four Callovian species of Metriorhynchus: M. superciliosus, M. moreli, M. blainvillei, and M. brachyrhynchus.[11] 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.[12] 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.[13] Vignaud (1997) however, considered there to be three Callovian species: M. superciliosus, M. brachyrhynchus and M. leedsi,[14] and a 2022 study describing a new metriorhynchid specimen advocated returning to this taxonomic system, considering Gracilineustes and Thalattosuchus junior synonyms of Metriorhynchus.[15]

Unnamed species

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Fragmentary remains attributed to Metriorhynchus are known from South America during the Bajocian[16] and Bathonian (both Middle Jurassic).[17] However, phylogenetic analysis has shown that these species cannot be referred to Metriorhynchus.[5][18][1]

Description

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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.[19] Metriorhynchids also had a hip anatomy conducive for live birth and evidence from the genus Dakosaurus does show that they did this..[20] 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.[1] It was 3 meters (9.8 feet).[21]

Paleoecology

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Metriorhynchus was a carnivore, one fossil shows it having eaten the gill apparatus of giant fish known as Leedsichthys. The idea of Metriorhynchus attacking weak Leedsichthys individuals has been speculated of having been the case in the past such as in the BBC and Discovery Channel documentary, Sea Monsters.[22][23]

See also

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References

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  1. ^ a b c d e f g Young, Mark T; Brignon, Arnaud; Sachs, Sven; Hornung, Jahn J; Foffa, Davide; Kitson, James J N; Johnson, Michela M; Steel, Lorna (2020-11-03). "Cutting the Gordian knot: a historical and taxonomic revision of the Jurassic crocodylomorph Metriorhynchus". Zoological Journal of the Linnean Society. 192 (2): 510–553. doi:10.1093/zoolinnean/zlaa092. ISSN 0024-4082.
  2. ^ a b von Meyer H. (1832). Palaeologica zur Geschichte der Erde und ihrer Geschöpfe. Frankfurt am Main: Siegmund Schmerber, 560.
  3. ^ Ősi, Attila; Young, Mark T.; Galácz, András; Rabi, Márton (2018-05-10). "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". PeerJ. 6: e4668. doi:10.7717/peerj.4668. ISSN 2167-8359. PMC 5949208. PMID 29761038.
  4. ^ Foffa, Davide; Young, Mark; Brusatte, Stephen (2018). "Filling the Corallian gap: new information on Late Jurassic marine reptile faunas from England". Acta Palaeontologica Polonica. 63. doi:10.4202/app.00455.2018. hdl:20.500.11820/729f4cac-6217-4a21-b22c-8683b38c733b. ISSN 0567-7920. S2CID 52254345.
  5. ^ a b Young, Mark T.; Brusatte, Stephen L.; Ruta, Marcello; De Andrade, Marco Brandalise (2010-03-30). "The evolution of Metriorhynchoidea (mesoeucrocodylia, thalattosuchia): an integrated approach using geometric morphometrics, analysis of disparity, and biomechanics". Zoological Journal of the Linnean Society. 158 (4): 801–859. doi:10.1111/j.1096-3642.2009.00571.x. ISSN 0024-4082. S2CID 84592894.
  6. ^ Herrera, Yanina; Gasparini, Zulma; Fernández, Marta S. (2015-02-20). "Purranisaurus potens Rusconi, an enigmatic metriorhynchid from the Late Jurassic–Early Cretaceous of the Neuquén Basin". Journal of Vertebrate Paleontology. 35 (2): e904790. Bibcode:2015JVPal..35E4790H. doi:10.1080/02724634.2014.904790. hdl:11336/13737. ISSN 0272-4634. S2CID 128937976.
  7. ^ Steel R. 1973. Crocodylia. Handbuch der Paläoherpetologie, Teil 16. Stuttgart: Gustav Fischer Verlag,116 pp.
  8. ^ Young MT. 2007. The evolution and interrelationships of Metriorhynchidae (Crocodyliformes, Thalattosuchia). Journal of Vertebrate Paleontology 27 (3): 170A.
  9. ^ Gasparini, Zulma; Pol, Diego; Spalletti, Luis A. (2006-01-06). "An Unusual Marine Crocodyliform from the Jurassic-Cretaceous Boundary of Patagonia". Science. 311 (5757): 70–73. Bibcode:2006Sci...311...70G. doi:10.1126/science.1120803. hdl:11336/73480. ISSN 0036-8075. PMID 16282526. S2CID 10312971.
  10. ^ Wilkinson, Laura E.; Young, Mark T.; Benton, Michael J. (2008-11-19). "A New Metriorhynchid Crocodilian (Mesoeucrocodylia: Thalattosuchia) from the Kimmeridgian (Upper Jurassic) of Wiltshire, UK". Palaeontology. 51 (6): 1307–1333. Bibcode:2008Palgy..51.1307W. doi:10.1111/j.1475-4983.2008.00818.x. ISSN 0031-0239. S2CID 84517228.
  11. ^ Eudes-Deslongchamps E. 1867-1869. Notes Paléontologiques. Caen and Paris: 320-392.
  12. ^ Andrews CW. 1913. A descriptive catalogue of the marine reptiles of the Oxford Clay, Part Two. London: British Museum (Natural History), 206 pp.
  13. ^ Adams-Tresman SM. 1987. The Callovian (Middle Jurassic) marine crocodile Metriorhynchus from Central England. Palaeontology 30 (1): 179-194.
  14. ^ Vignaud P. (1997). La morphologie dentaire des Thalattosuchia (Crocodylia, Mesosuchia). Palaeovertebrata 26: 35-59.
  15. ^ Le Mort, Jonas; Martin, Jeremy E.; Picot, Laurent; Hua, Stéphane (2022-07-01). "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". Annales de Paléontologie. 108 (3): 102539. Bibcode:2022AnPal.10802539L. doi:10.1016/j.annpal.2022.102539. ISSN 0753-3969. S2CID 254175334.
  16. ^ Gasparini, Zulma; Vignaud, Patrick; Chong, Guillermo (2000-11-01). "The Jurassic Thalattosuchia (Crocodyliformes) of Chile; a paleobiogeographic approach". Bulletin de la Société Géologique de France. 171 (6): 657–664. doi:10.2113/171.6.657. ISSN 1777-5817.
  17. ^ Gasparini, Zulma; Cichowolski, Marcela; Lazo, Dario G. (July 2005). "First Record of Metriorhynchus (Reptilia: Crocodyliformes) in the Bathonian (Middle Jurassic) of the Eastern Pacific". Journal of Paleontology. 79 (4): 801–805. doi:10.1666/0022-3360(2005)079[0801:fromrc]2.0.co;2. ISSN 0022-3360. JSTOR 4095052. S2CID 130493042.
  18. ^ Young, Mark Thomas; De Andrade, Marco Brandalise (2009-10-26). "What is Geosaurus? Redescription of Geosaurus giganteus (Thalattosuchia: Metriorhynchidae) from the Upper Jurassic of Bayern, Germany". Zoological Journal of the Linnean Society. 157 (3): 551–585. doi:10.1111/j.1096-3642.2009.00536.x. ISSN 0024-4082. S2CID 83242976.
  19. ^ Altmühltal~mail@frederik-spindler.de, Frederik Spindler~Dinosaurier Museum; Paleontology~rene@lauerfoundationpse.org, René Lauer~Lauer Foundation for; Eichstätt~htischlinger@online.de, Helmut Tischlinger~Germany and Jura-Museum; Bayerns~maeuser@snsb.de, Matthias Mäuser~Staatliche Naturwissenschaftliche Sammlungen (2021-07-03). "The integument of pelagic crocodylomorphs (Thalattosuchia: Metriorhynchidae)". Palaeontologia Electronica. doi:10.26879/1099. Retrieved 2024-08-05.
  20. ^ Spindler, Frederik (2019). Live Birth in a Jurassic Marine Crocodile [abstract]. In: Abstracts of the 90th Annual Meeting of the Paläontologische Gesellschaft (PDF). SNSB - BSPG, München. p. 141. ISBN 978-3-946705-07-9. Archived (PDF) from the original on 2023-05-17.
  21. ^ The Complete Guide to Prehistoric Life (1 ed.). Firefly Books. 2006. ISBN 155407181X.
  22. ^ Hua, Stéphane; Liston, Jeff; Tabouelle, Jérôme (March 2024). "The Diet of Metriorhynchus (Thalattosuchia, Metriorhynchidae): Additional Discoveries and Paleoecological Implications". Fossil Studies. 2 (1): 66–76. doi:10.3390/fossils2010002. ISSN 2813-6284.
  23. ^ "BBC - Science & Nature - Sea Monsters - Fact File: Metriorhynchus". www.bbc.co.uk. Retrieved 2024-08-05.
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