Metriorhynchus
Encyclopedia
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 plesiosaur
s 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").
, France
and Germany
.
.
Longirostrine
Two longirsotrine species, M. acutus and M. leedsi have been referred to the genus Gracilineustes
.
Brevirostrine
and Bathonian
(both Middle Jurassic). However, phylogenetic analysis has shown neither of these species can be referred to Metriorhynchus.
of Metriorhynchus. Some of the longirostrine forms, however, do appear to form a natural group
.
The cladogram
presented below follows an analysis by Mark Young and Marco Brandalise de Andrade, published in November 2009.
Cladogram
after Cau & Fanti (2010).
Averaging 3 metres (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.
s. 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. cephalopod
s) without dehydrating
.
. Occasionally it was also capable of capturing flying animals such as the pterosaurs and scavenging on plesiosaur
carcasses on the seafloor.
which could grow in excess of 10 meters in length. Since Metriorhynchus had lost its osteoderm
s, "Armour scutes", to become more efficient swimmers it would have had little defense against larger marine predators.
television series Sea Monsters.
A metriorhynchus named Cretaceous was one of the main antagonists in Ice Age: The Meltdown
.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of marine crocodyliform
Crocodyliformes
Crocodyliformes is a clade of crurotarsan archosaurs, the group often traditionally referred to as "crocodilians."In 1988, Michael J. Benton and James M. Clark argued that all traditional names for well-known groups of animals should be restricted to their crown clades, that is, used only for...
that lived in the oceans during the Middle
Middle Jurassic
The Middle Jurassic is the second epoch of the Jurassic Period. It lasted from 176-161 million years ago. In European lithostratigraphy, rocks of this Middle Jurassic age are called the Dogger....
to Late Jurassic
Late Jurassic
The Late Jurassic is the third epoch of the Jurassic Period, and it spans the geologic time from 161.2 ± 4.0 to 145.5 ± 4.0 million years ago , which is preserved in Upper Jurassic strata. In European lithostratigraphy, the name "Malm" indicates rocks of Late Jurassic age...
. Metriorhynchus was named by the German
Germans
The Germans are a Germanic ethnic group native to Central Europe. The English term Germans has referred to the German-speaking population of the Holy Roman Empire since the Late Middle Ages....
palaeontologist Christian von Meyer
Christian Erich Hermann von Meyer
Christian Erich Hermann von Meyer was a German palaeontologist.He was born at Frankfurt am Main.In 1832 von Meyer issued a work entitled Palaeologica, and in course of time he published a series of memoirs on various fossil organic remains: molluscs, crustaceans, fishes and higher vertebrata,...
in 1830. Metriorhynchus was a carnivore
Carnivore
A carnivore meaning 'meat eater' is an organism that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of animal tissue, whether through predation or scavenging...
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
Mesozoic
The Mesozoic era is an interval of geological time from about 250 million years ago to about 65 million years ago. It is often referred to as the age of reptiles because reptiles, namely dinosaurs, were the dominant terrestrial and marine vertebrates of the time...
, such as plesiosaur
Plesiosaur
Plesiosauroidea is an extinct clade of carnivorous plesiosaur marine reptiles. Plesiosauroids, are known from the Jurassic and Cretaceous Periods...
s 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
Ancient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...
Metrio- ("moderate") and -rhynchos ("snout").
Discovery and species
Fossil specimens referrable to Metriorhynchus are known from Middle-Late Jurassic deposits of EnglandEngland
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
, France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
and Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
.
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 CallovianCallovian
In the geologic timescale, the Callovian is an age or stage in the Middle Jurassic, lasting between 164.7 ± 4.0 Ma and 161.2 ± 4.0 Ma. It is the last stage of the Middle Jurassic, following the Bathonian and preceding the Oxfordian....
.
- 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 morphometricsMorphometricsMorphometrics refers to the quantitative analysis of form, a concept that encompasses size and shape. Morphometric analyses are commonly performed on organisms, and are useful in analyzing their fossil record, the impact of mutations on shape, developmental changes in form, covariances between...
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, France and Germany) of the Middle-Late Jurassic (Callovian and OxfordianOxfordian stageThe Oxfordian is, in the ICS' geologic timescale, the earliest age of the Late Jurassic epoch, or the lowest stage of the Upper Jurassic series. It spans the time between 161.2 ± 4 Ma and 155.7 ± 4 Ma...
); M. moreli, M. blainvillei, and M. jaekeli are junior synonyms. - M. hastifer: Western Europe (France) of the Late Jurassic (Kimmeridgian)
- M. geoffroyii: (type speciesType speciesIn biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
) Western Europe (England, France and Switzerland) of the Late Jurassic (Kimmeridgian); M. palpebrosus, and M. temporalis are junior synonyms.
Two longirsotrine species, M. acutus and M. leedsi have been referred to the genus Gracilineustes
Gracilineustes
Gracilineustes is an extinct genus of marine crocodyliform that lived in the oceans during the Middle to Late Jurassic. Gracilineustes was a carnivore that spent much, if not all, its life out at sea.-Discovery and species:...
.
Brevirostrine
- All brevirostrine species have been transferred to the genera: PurranisaurusPurranisaurusPurranisaurus is an extinct genus of marine crocodyliform from the Middle to Late Jurassic period of Chile and Argentina. Rusconi originally regarded Purranisaurus potens to be a plesiosaur; however, Gasparini demonstrated that it was in fact a metriorhynchid crocodyliform, and that may be a...
and SuchodusSuchodusSuchodus is an extinct genus of marine crocodyliform from the Middle to Late Jurassic period of England and France.-Taxonomy and phylogeny:Recent phylogenetic analysis has shown that Suchodus is a distinct metriorhynchid genus.-Valid species:...
.
Unnamed species
Fragmentary remains of Metriorhynchus are known from South America during the BajocianBajocian
In the geologic timescale, the Bajocian is an age or stage in the Middle Jurassic. It lasted from approximately 171.6 Ma to around 167.7 Ma . The Bajocian age succeeds the Aalenian age and precedes the Bathonian age....
and Bathonian
Bathonian
In the geologic timescale the Bathonian is an age or stage of the Middle Jurassic. It lasted from approximately 167.7 Ma to around 164.7 Ma...
(both Middle Jurassic). However, phylogenetic analysis has shown neither of these species can be referred to Metriorhynchus.
Taxonomy and phylogeny
The genera Purranisaurus and Suchodus have been considered junior synonyms of Metriorhynchus, Recent phylogenetic analyses however, do not support the monophylyMonophyly
In common cladistic usage, a monophyletic group is a taxon which forms a clade, meaning that it contains all the descendants of the possibly hypothetical closest common ancestor of the members of the group. The term is synonymous with the uncommon term holophyly...
of Metriorhynchus. Some of the longirostrine forms, however, do appear to form a natural group
Monophyly
In common cladistic usage, a monophyletic group is a taxon which forms a clade, meaning that it contains all the descendants of the possibly hypothetical closest common ancestor of the members of the group. The term is synonymous with the uncommon term holophyly...
.
The cladogram
Cladogram
A cladogram is a diagram used in cladistics which shows ancestral relations between organisms, to represent the evolutionary tree of life. Although traditionally such cladograms were generated largely on the basis of morphological characters, DNA and RNA sequencing data and computational...
presented below follows an analysis by Mark Young and Marco Brandalise de Andrade, published in November 2009.
Cladogram
Cladogram
A cladogram is a diagram used in cladistics which shows ancestral relations between organisms, to represent the evolutionary tree of life. Although traditionally such cladograms were generated largely on the basis of morphological characters, DNA and RNA sequencing data and computational...
after Cau & Fanti (2010).
Description
Salt glands
Recent examination of the fossil specimens of Metriorhynchus superciliosus, have shown that adults of this species had well-developed salt glandSalt gland
The salt gland is an organ for excreting excess salts. It is found in elasmobranchs, seabirds, and some reptiles. In sharks, salt glands are found in the rectum, but in birds and reptiles, they are found in or on the skull, in the area of the eyes, nostrils or mouth. In crocodiles, the salt is...
s. This means that like Geosaurus
Geosaurus
Geosaurus is an extinct genus of marine crocodyliform within the family Metriorhynchidae that lived during the Late Jurassic to the Early Cretaceous. Geosaurus was a carnivore that spent much, if not all, its life out at sea...
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. cephalopod
Cephalopod
A cephalopod is any member of the molluscan class Cephalopoda . These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles modified from the primitive molluscan foot...
s) without dehydrating
Dehydration
In physiology and medicine, dehydration is defined as the excessive loss of body fluid. It is literally the removal of water from an object; however, in physiological terms, it entails a deficiency of fluid within an organism...
.
Diet
Metriorhynchus was a versatile and opportunistic predator, predated upon both the armoured belemnites, fast moving fish and the giant filter feeding fish LeedsichthysLeedsichthys
Leedsichthys was a giant pachycormid that lived in the oceans of the Middle Jurassic period. The closest living relative of the pachycormids is the bowfin, Amia calva, but this is only very distantly related....
. Occasionally it was also capable of capturing flying animals such as the pterosaurs and scavenging on plesiosaur
Plesiosaur
Plesiosauroidea is an extinct clade of carnivorous plesiosaur marine reptiles. Plesiosauroids, are known from the Jurassic and Cretaceous Periods...
carcasses on the seafloor.
Predators
Even though Metriorhynchus was an effective predator, it was vulnerable to predation from apex predators such as LiopleurodonLiopleurodon
Liopleurodon is a genus of large, carnivorous marine reptile belonging to the Pliosauroidea, a clade of short-necked plesiosaurs. Two species of Liopleurodon lived during the Callovian stage of the Middle Jurassic Period , while the third, L. rossicus, lived during the Late Jurassic...
which could grow in excess of 10 meters in length. Since Metriorhynchus had lost its osteoderm
Osteoderm
Osteoderms are bony deposits forming scales, plates or other structures in the dermal layers of the skin. Osteoderms are found in many groups of extant and extinct reptiles, including lizards, various groups of dinosaurs , crocodilians, phytosaurs, aetosaurs, placodonts, and hupehsuchians...
s, "Armour scutes", to become more efficient swimmers it would have had little defense against larger marine predators.
In popular culture
Metriorhynchus has featured in the Jurassic episode of the BBCBBC
The British Broadcasting Corporation is a British public service broadcaster. Its headquarters is at Broadcasting House in the City of Westminster, London. It is the largest broadcaster in the world, with about 23,000 staff...
television series Sea Monsters.
A metriorhynchus named Cretaceous was one of the main antagonists in Ice Age: The Meltdown
Ice Age: The Meltdown
Ice Age: The Meltdown, also known as Ice Age 2: The Meltdown or simply as Ice Age 2, is the 2006 sequel to the 2002 computer-animated film Ice Age. It was produced by Blue Sky Studios for 20th Century Fox, and premiered in Belgium on March 1, 2006...
.
Suggested reading
- Buffetaut E. 1982. Radiation évolutive, paléoécologie et biogéographie des Crocodiliens mésosuchienes. Mémoires Societé Geologique de France 142: 1–88