''Metriorhynchus'' is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of marine

crocodyliform Crocodyliformes is a clade of Crurotarsi, crurotarsan archosaurs, the group often traditionally referred to as "crocodilians". They are the first members of Crocodylomorpha to possess many of the features that define later relatives. They are the ...

that lived in the oceans during the

Late Jurassic The Late Jurassic is the third Epoch (geology), epoch of the Jurassic Period, and it spans the geologic time scale, geologic time from 161.5 ± 1.0 to 143.1 ± 0.8 million years ago (Ma), which is preserved in Upper Jurassic stratum, strata.Owen ...

. The type species, ''M. brevirostris'' was named in 1829 as a species of ''

Steneosaurus ''Steneosaurus'' (from , 'narrow' and , 'lizard') is a dubious genus of teleosaurid crocodyliform from the Middle or Late Jurassic (Callovian or early Oxfordian) of France. The genus has been used as a wastebasket taxon for thalattosuchian ...

'' before being named as a separate genus by the

German German(s) may refer to: * Germany, the country of the Germans and German things **Germania (Roman era) * Germans, citizens of Germany, people of German ancestry, or native speakers of the German language ** For citizenship in Germany, see also Ge ...

palaeontologist Paleontology, also spelled as palaeontology or palæontology, is the scientific study of the life of the past, mainly but not exclusively through the study of fossils. Paleontologists use fossils as a means to classify organisms, measure geolo ...

Christian von Meyer in 1832. The name ''Metriorhynchus'' means "moderate snout", and is derived from the

Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...

''Metrio''- ("moderate") and -''rhynchos'' ("snout").

Discovery and species

Fossil specimens referrable to ''Metriorhynchus'' are known from Kimmeridgian (Late Jurassic) deposits of

France France, officially the French Republic, is a country located primarily in Western Europe. Overseas France, Its overseas regions and territories include French Guiana in South America, Saint Pierre and Miquelon in the Atlantic Ocean#North Atlan ...

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'' was also shown to be generically distinct from the type species, ''M. brevirostris'', and now has its own genus ''

Thalattosuchus ''Thalattosuchus'' is an extinct genus of marine crocodyliformes, crocodyliform that lived in the oceans during the Middle Jurassic, Middle to Late Jurassic. Though the genus ''Thalattosuchus'' itself was named in 2020, its fossils have historic ...

''.

Life reconstruction of Metriorhynchus brevirostris

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 In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical dat ...

analyses however, do not support the

monophyly In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria: # the grouping contains its own most recent comm ...

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. 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 Morphometrics (from Greek μορΦή ''morphe'', "shape, form", and -μετρία ''metria'', "measurement") or morphometry refers to the quantitative analysis of ''form'', a concept that encompasses size and shape. Morphometric analyses are co ...

, 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 In the geologic timescale, the Bajocian is an age and stage in the Middle Jurassic. It lasted from approximately 170.9 ±0.8 Ma to around 168.2 ±1.2 Ma (million years ago). The Bajocian Age succeeds the Aalenian Age and precedes the Bathonia ...

and

Bathonian In the geologic timescale the Bathonian is an age (geology), age and stage (stratigraphy), stage of the Middle Jurassic. It lasted from approximately 168.2 ±1.2 annum, Ma to around 165.3 ±1.1 Ma (million years ago). The Bathonian Age succeeds ...

(both Middle Jurassic). However, phylogenetic analysis has shown that these species cannot be referred to ''Metriorhynchus''.

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. Metriorhynchids also had a hip anatomy conducive for live birth and evidence from the related ''

Dakosaurus ''Dakosaurus'' is an extinct genus of crocodylomorph within the family Metriorhynchidae that lived during the Late Jurassic and Early Cretaceous. It was large, with teeth that were serrated and compressed lateromedially (flattened from side to s ...

'' does show that they did this. ''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.

Paleoecology

''Metriorhynchus'' was a carnivore. One fossil shows it has eaten the gill apparatus of the giant fish ''

Leedsichthys ''Leedsichthys'' is an extinct genus of pachycormid fish that lived in the oceans of the Middle to Late Jurassic.Liston, JJ (2004). An overview of the pachycormiform ''Leedsichthys''. In: Arratia G and Tintori A (eds) Mesozoic Fishes 3 - Systema ...

''. 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 A sea monster is a mythical sea creature. Sea Monsters may refer to: Film * ''Sea Monsters: A Prehistoric Adventure'', a 2007 National Geographic 3D film Literature * ''Sea Monsters'', a 2019 novel by Chloe Aridjis Television Episodes * "Chapter ...

References