Metriorhynchus BW.jpg

''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.

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. 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''. ''Metriorhynchus superciliosus'' has recently been shown to be distinct from the type species, ''M. brevirostris'', and now has its own genus '' Thalattosuchus''.

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 conceived off in the 1860s-2010.Young MT. 2007. The evolution and interrelationships of Metriorhynchidae (Crocodyliformes, Thalattosuchia). ''Journal of Vertebrate Paleontology'' 27 (3): 170A.

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.''

Unnamed species

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

See also

*List of marine reptiles

References

{{Taxonbar, from=Q132722

Late Jurassic crocodylomorphs of Europe
Prehistoric pseudosuchian genera
Prehistoric marine crocodylomorphs
Late Jurassic genus extinctions
Thalattosuchians
Fossil taxa described in 1832