Metriorhynchus

### Location

Normandy, France; Baden-Württemberg, Germany; Oxfordshire, and Peterborough, United Kingdom

### Taxon

Crocodylomorpha, Thalattosuchia, Metriorhynchidae

***Metriorhynchus*** is an extinct genus of marine crocodyliform that lived in the oceans during the Middle to Late Jurassic. *Metriorhynchus* was named by the German palaeontologist Christian von Meyer in 1830. *Metriorhynchus* was a carnivore that spent much, if not all, its life out at sea. No *Metriorhynchus* 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 *Metriorhynchus* mated, whether on land or at sea, is currently unknown. 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 Middle-Late Jurassic deposits of England, France, Germany, Argentina, and Chile.

### Valid species

Species in this genus are traditionally classed into two skull groups: longirostrine (long, narrow jaws) and brevirostrine (short, broad jaws). However there has been some contention as to how many of these species are valid, especially those from the Callovian.

* Eudes-Deslongchamps (1867-69) found there to be four Callovian species: *M. superciliosus*, *M. moreli*, *M. blainvillei*, and *M. brachyrhynchus*.
* Andrews (1913) considered there to be seven valid species: *M. superciliosus*, *M. moreli*, *M. brachyrhynchus*, *M. durobrivensis*, *M. cultridens*, *M. leedsi* and *M. laeve*.
* Adams-Tresman (1987) using linear morphometrics however could only distinguish between the two skull groups, so she found there to be two species: *M. superciliosus* and *M. brachyrhynchus*.
* Vignaud (1997) however, considered there to be three Callovian species: *M. superciliosus*, *M. brachyrhynchus* and *M. leedsi*.

**Longirostrine**

* *M. superciliosus*: Western Europe (England and France) of the Middle-Late Jurassic (Callovian and Oxfordian); *M. moreli*, *M. blainvillei*, and *M. jaekeli* are junior synonyms.
* *M. leedsi*: Western Europe (England) of the Middle Jurassic (Callovian); *M. laeve* is a junior synonym.
* *M. palpebrosus*: Western Europe (England) of the Late Jurassic (Kimmeridgian); *M. temporalis* is a junior synonym.
* *M. hastifer*: Western Europe (France) of the Late Jurassic (Kimmeridgian)
* *M. acutus*: Western Europe (France) of the Late Jurassic (Kimmeridgian)
* *M. geoffroyii*: (type species) Western Europe (France) of the Late Jurassic (Kimmeridgian)

**Brevirostrine**

* *M. brachyrhynchus*: Western Europe (England and France) of the Middle-Late Jurassic (Callovian and Oxfordian); *M. cultridens* is a junior synonym.
* *M. durobrivensis*: Western Europe (England and France) of the Middle Jurassic (Callovian). Was originally the type species of the genus *Suchodus*, but it was regarded as a junior synonym of *Metriorhynchus* by Andrews, 1913.
* *M. casamiquelai*: Middle Jurassic of Chile (Callovian);
* *M. westermanni*: Middle Jurassic of Chile (Callovian). Although previously considered a junior synonym of *M. casamiquelai*, it has been revalidated;
* *M. potens*: End Jurassic of Argentina (Tithonian). Was originally the type species of the genus *Purranisaurus*, but it was regarded as a possible junior synonym of *Metriorhynchus* by Gasparini.

### Unnamed species

Fragmentary remains of *Metriorhynchus* are known from South America during the Bajocian  and Bathonian (both Middle Jurassic).

## Taxonomy and phylogeny

The genera *Purranisaurus* and *Suchodus* are junior synonyms of *Metriorhynchus*, Recent phylogenetic analyses however, do not support the monophyly of *Metriorhynchus*. Some of the longirostrine forms, however, do appear to form a natural group.

## Palaeobiology

### Description

Averaging 3 meters (9.8 ft) in length, *Metriorhynchus* was of a similar size to modern crocodiles. However, it had a streamlined body and a finned tail, making it a more efficient swimmer than modern crocodilian species.

### Salt glands

Recent examination of the fossil specimens of *Metriorhynchus superciliosus*, have shown that adults of this species had well-developed salt glands. This means that like *Geosaurus* it would have been able to "drink" salt-water (necessary for a pelagic animal) and eat prey that have the same ionic concentration as the surrounding sea water (i.e. cephalopods) without dehydrating.

### Diet

*Metriorhynchus* was a versatile and opportunistic predator, predated upon both the armoured belemnites, fast moving fish and the giant filter feeding fish *Leedsichthys*. Occasionally it was also capable of capturing flying animals such as the pterosaurs and scavenging on plesiosaur carcasses on the seafloor.

## Palaeoecology

### Predators

Even though *Metriorhynchus* was an effective predator, it was vulnerable to predation from apex predators such as *Liopleurodon* which could grow in excess of 10 metres in length. Since *Metriorhynchus* had lost its osteoderms, "armour scutes", to become more efficient swimmers it would have had little defence against larger marine predators.

## Appearance in other media

### *Jurassic Park*

1. *Metriorhynchus* can be received from the DNA Rescue and can then be created in the Aquatic Park in the game *Jurassic Park: Builder*.
2. *Metriorhynchus* can be created in *Jurassic World: The Game* as a super rare amphibian even though it is a sea crocodile. In reality, *Metriorhynchus* had fins and stayed in the water unlike in the game which can be on land and had fresh water crocodyliform-like legs. The real *Metriorhynchus* also removed the classic osteoderms for better mobility in the water, while the game's *Metriorhynchus* has the osteoderms.

## Suggested reading

* Buffetaut E. 1982. Radiation évolutive, paléoécologie et biogéographie des Crocodiliens mésosuchienes. *Mémoires Societé Geologique de France* **142**: 1–88

## References

1. ↑ Cite error: Invalid `<ref>` tag; no text was provided for refs named `von Meyer, 1830`
2. ↑ 2.0 2.1 Steel R. 1973. Crocodylia. *Handbuch der Paläoherpetologie, Teil 16*. Stuttgart: Gustav Fischer Verlag,116 pp.
3. ↑ 3.0 3.1 Gasparini Z. 1975. Revison de ?*Purranisaurus potens* RUSCONI, 1948 (Crocodilia, Thalattosuchia). Los Thalattosuchia como un nuevo Infraorden de los Crocodilia. *Actas del Congreso Geologico Argentino* **5**: 423–431.
4. ↑ 4.0 4.1 Cite error: Invalid `<ref>` tag; no text was provided for refs named `Gasparini & Chong, 1977`
5. ↑ Eudes-Deslongchamps E. 1867-1869. *Notes Paléontologiques*. Caen and Paris: 320-392.
6. ↑ 6.0 6.1 6.2 Cite error: Invalid `<ref>` tag; no text was provided for refs named `Andrews, 1913`
7. ↑ Adams-Tresman SM. 1987. The Callovian (Middle Jurassic) marine crocodile Metriorhynchus from Central England. *Palaeontology* **30** (1): 179-194.
8. ↑ Vignaud P. 1997. La morphologie dentaire des Thalattosuchia (Crocodylia, Mesosuchia). *Palaeovertebrata* **26**: 35-59.
9. ↑ Cite error: Invalid `<ref>` tag; no text was provided for refs named `Lennier, 1887`
10. ↑ Cite error: Invalid `<ref>` tag; no text was provided for refs named `von Meyer, 1832`
11. ↑ 11.0 11.1 Gasparini Z, Vignaud P, Chong G. 2000. The Jurassic Thalattosuchia (Crocodyliformes) of Chile: a paleobiogeographic approach. *Bulletin Société Géologique de France* **171** (6): 657-664
12. ↑ Gasparini ZB, Paulina-Carabajal A, Chong G. 2008. Un nuevo espécimen de cocodrilo marino del Jurásico Medio del norte de Chile: revalidación de *Metriorhynchus westermanni* (Crocodyliformes: Metriorhynchidae). *Revista Geológica de Chile* **35** (2): 335-346.
13. ↑ Gasparini Z, Cichowolski M, Lazio DG. 2005. First record of *Metriorhynchus* (Reptilia: Crocodyliformes) in the Bathonian (Middle Jurassic) of the Eastern Pacific. *Journal of Paleontology* **79** (4): 801–805.
14. ↑ 14.0 14.1 Young MT. 2007. The evolution and interrelationships of Metriorhynchidae (Crocodyliformes, Thalattosuchia). *Journal of Vertebrate Paleontology* **27** (3): 170A.
15. ↑ Gasparini Z, Pol D, Spalletti LA. 2006. An unusual marine crocodyliform from the Jurassic-Cretaceous boundary of Patagonia. *Science* **311**: 70-73.
16. ↑ 16.0 16.1 Wilkinson LE, Young MT, Benton MJ. 2008. A new metriorhynchid crocodilian (Mesoeucrocodylia: Thalattosuchia) from the Kimmeridgian (Upper Jurassic) of Wiltshire, UK. *Palaeontology* **51** (6): 1307-1333.
17. ↑ Mueller-Töwe IJ. 2005. Phylogenetic relationships of the Thalattosuchia. *Zitteliana* **A45**: 211–213.
18. ↑ Massare JA. 1988. Swimming capabilities of Mesozoic marine reptiles; implications for method of predation. *Paleobiology* **14** (2):187-205.
19. ↑ Gandola R, Buffetaut E, Monaghan N, Dyke G. 2006. Salt glands in the fossil crocodile *Metriorhynchus*. *Journal of Vertebrate Paleontology* **26** (4): 1009-1010.
20. ↑ Fernández M, Gasparini Z. 2008. Salt glands in the Jurassic metriorhynchid *Geosaurus*: implications for the evolution of osmoregulation in Mesozoic crocodyliforms. *Naturwissenschaften* **95**: 79-84.
21. ↑ Forrest R. 2003. Evidence for scavenging by the marine crocodile *Metriorhynchus* on the carcass of a plesiosaur. *Proceedings of the Geologists’ Association* **114**: 363-366.