Metriorhynchus

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Metriorhynchus
Temporal range: Kimmeridgian, 157–150  Ma
Metriorhynchus brevirostris.jpg
Partial holotype rostrum (MHNG V-2232) of M. brevirostris as illustrated in 1824
Scientific classification OOjs UI icon edit-ltr.svg
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 [1]
Species:
M. brevirostris
Binomial name
Metriorhynchus brevirostris
(Holl, 1828) vide Young et al., 2020 [2]
Synonyms

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

Contents

Discovery and species

Fossil specimens referrable to Metriorhynchus are known from Kimmeridgian (Late Jurassic) deposits of France. [2]

Valid species

Only one valid species is recognized today, the type species M. geoffroyii (now called M. brevirostris). [2] "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 . [2]

Life reconstruction of Metriorhynchus brevirostris Life reconstruction of Metriorhynchus brevirostris.png
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] [2]

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

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] [2]

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. [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. [2] It was 3 meters (9.8 feet). [21]

Paleoecology

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

Related Research Articles

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<i>Dakosaurus</i> Metriorhynchid reptile genus from the Late Jurassic / Early Cretaceous period

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. The genus was established by Friedrich August von Quenstedt in 1856 for an isolated tooth named Geosaurus maximus by Theodor Plieninger in 1846. Dakosaurus was a carnivore that spent much, if not all, its life out at sea. The extent of its adaptation to a marine lifestyle means that it is most likely that it mated at sea, but since no eggs or nests have been discovered that have been referred to Dakosaurus, whether it gave birth to live young at sea like dolphins and ichthyosaurs or came ashore like turtles is not known yet. The name Dakosaurus means "biter lizard", and is derived from the Greek dakos ("biter") and σαῦρος -sauros ("lizard").

<span class="mw-page-title-main">Metriorhynchidae</span> Extinct family of reptiles

Metriorhynchidae is an extinct family of specialized, aquatic metriorhynchoid crocodyliforms from the Middle Jurassic to the Early Cretaceous period of Europe, North America and South America. The name Metriorhynchidae was coined by the Austrian zoologist Leopold Fitzinger in 1843. The group contains two subfamilies, the Metriorhynchinae and the Geosaurinae. They represent the most marine adapted of all archosaurs.

<i>Enaliosuchus</i> Dubious extinct genus of sauropsids

Enaliosuchus is a dubious genus of extinct marine crocodyliform within the family Metriorhynchidae that lived during the Valanginian stage of the Early Cretaceous. It is known from fossil remains found in France and Germany and it was first described in 1883.

<i>Geosaurus</i> Extinct genus of reptiles

Geosaurus is an extinct genus of marine crocodyliform within the family Metriorhynchidae, that lived during the Late Jurassic and the Early Cretaceous. Geosaurus was a carnivore that spent much, if not all, its life out at sea. No Geosaurus eggs or nests have been discovered, so little is known of the reptile's lifecycle, unlike other large marine reptiles of the Mesozoic, such as plesiosaurs or ichthyosaurs which are known to give birth to live young out at sea. Where Geosaurus mated, whether on land or at sea, is currently unknown. The name Geosaurus means "Mother of Giants lizard", and is derived from the Greek Ge- and σαῦρος -sauros ("lizard"). The name Geosaurus was established by the French naturalist Georges Cuvier in 1824.

<span class="mw-page-title-main">Thalattosuchia</span> Clade of marine crocodylomorphs

Thalattosuchia is a clade of mostly marine crocodylomorphs from the Early Jurassic to the Early Cretaceous that had a cosmopolitan distribution. They are colloquially referred to as marine crocodiles or sea crocodiles, though they are not members of Crocodilia and records from Thailand and China suggest that some members lived in freshwater. The clade contains two major subgroupings, the Teleosauroidea and Metriorhynchoidea. Teleosauroids are not greatly specialised for oceanic life, with back osteoderms similar to other crocodyliformes. Within Metriorhynchoidea, the Metriorhynchidae displayed extreme adaptions for life in the open ocean, including the transformation of limbs into flippers, the development of a tail fluke, and smooth, scaleless skin, and probably gave live birth, seemingly uniquely among archosaurs.

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<i>Rhacheosaurus</i> Extinct genus of reptiles

Rhacheosaurus is an extinct genus of marine crocodyliform belonging to the family Metriorhynchidae. The genus was established by Christian Erich Hermann von Meyer in 1831 for skeletal remains from the Tithonian of Germany. It was a relatively small reptile, measuring between 1.39 and 1.57 m long.

<i>Suchodus</i> Extinct genus of reptiles

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<i>Pelagosaurus</i> Extinct genus of reptiles

Pelagosaurus is an extinct genus of thalattosuchian crocodyliform that lived during the Toarcian stage of the Lower Jurassic, around 183 Ma to 176 Ma, in shallow epicontinental seas that covered much of what is now Western Europe. The systematic taxonomy of Pelagosaurus has been fiercely disputed over the years, and was assigned to Thalattosuchia after its systematics within Teleosauridae were disputed. Pelagosaurus measured 2–3 m (6.6–9.8 ft) long.

<i>Cricosaurus</i> Extinct genus of reptiles

Cricosaurus is an extinct genus of marine crocodyliforms of the Late Jurassic. belonging to the family Metriorhynchidae. The genus was established by Johann Andreas Wagner in 1858 for three skulls from the Tithonian of Germany. The name Cricosaurus means "Ring lizard", and is derived from the Greek Krikos- ("ring") and σαῦρος -sauros ("lizard"). It was a relatively small reptile, with C. suevicus and C. araucanensis measuring 2 m (6.6 ft) and 3.2 m (10 ft) in total body length, respectively.

<i>Steneosaurus</i> Extinct genus of reptiles

Steneosaurus is a dubious genus of teleosaurid crocodyliform from the Middle or Late Jurassic of France. The genus has been used as a wastebasket taxon for thalattosuchian fossils for over two centuries, and almost all known historical species of teleosauroid have been included within it at one point. The genus has remained a wastebasket, with numerous species still included under the label ‘Steneosaurus’, many of which are unrelated to each other.

<span class="mw-page-title-main">Metriorhynchoidea</span> Extinct superfamily of reptiles

Metriorhynchoidea is an extinct superfamily of thalattosuchian crocodyliforms from the Early Jurassic to the Early Cretaceous of Europe, North America and South America. Metriorhynchids are fully aquatic crocodyliforms. Named by Fitzinger, in 1843, it contains the basal taxa like Teleidosaurus, Zoneait and Eoneustes and the family Metriorhynchidae. An unnamed taxon is known from Chile.

<i>Torvoneustes</i> Extinct genus of reptiles

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<span class="mw-page-title-main">Metriorhynchinae</span> Extinct subfamily of reptiles

Metriorhynchinae is a subfamily of metriorhynchid crocodyliforms from the late Middle Jurassic to the Early Cretaceous of Europe, North America and South America. Named by Fitzinger, in 1843, it contains the metriorhynchids Maledictosuchus, Gracilineustes, Metriorhynchus, Cricosaurus and Rhacheosaurus. The last three taxa form a tribe within Metriorhynchinae, the Rhacheosaurini. Metriorhynchinae is one of two subfamilies of Metriorhynchidae, the other being Geosaurinae.

<i>Maledictosuchus</i> Extinct genus of reptiles

Maledictosuchus is an extinct genus of marine crocodyliform belonging to the family Metriorhynchidae. It is the most basal member of the Rhacheosaurini Tribe with a relatively short body length, measuring 2.95 m (9.7 ft) based on the type specimen.

<i>Zoneait</i> Extinct genus of reptiles

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<i>Thalattosuchus</i> Extinct genus of reptiles

Thalattosuchus is an extinct genus of marine crocodyliform that lived in the oceans during the Middle to Late Jurassic. Thalattosuchus was named in 2020. Thalattosuchus was a carnivore that spent much, if not all, its life out at sea. No Thalattosuchus eggs or nests have been discovered, so little is known of the reptile's life cycle, unlike other large marine reptiles of the Mesozoic, such as plesiosaurs or ichthyosaurs which are known to have given birth to live young out at sea. Where Thalattosuchus mated, whether on land or at sea, is currently unknown. The name Thalattosuchus means "sea crocodile".

References

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