Metriorhynchidae Temporal range: Middle Jurassic-Early Cretaceous, 170–135 Ma |
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Dakosaurus maximus skull, Staatliches Museum für Naturkunde Stuttgart | |
Scientific classification | |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Reptilia |
Superorder: | Crocodylomorpha |
Suborder: | †Thalattosuchia |
Superfamily: | †Metriorhynchoidea |
Family: | †Metriorhynchidae Fitzinger, 1843 |
subfamily | |
Synonyms | |
Metriorhynchidae is an extinct family of metriorhynchoid crocodyliforms from the Middle Jurassic to the Early Cretaceous period (Bajocian - Valanginian stages) of Europe, North America and South America. Metriorhynchids are fully aquatic crocodyliforms. Their forelimbs were small and paddle-like, and unlike living crocodilians, they lost their osteoderms ("armour scutes"). Their body shape maximised hydrodynamy (swimming efficiency), as did having a shark-like tail fin.[2]
Metriorhynchids were the only group of archosaurs to become fully adapted to the marine realm, becoming pelagic in lifestyle.[3]
The name Metriorhynchidae was coined by the Austrian zoologist Leopold Fitzinger in 1843.[4] It contains two subfamilies, the Metriorhynchinae and the Geosaurinae.[5][6]
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The family has a wide geographic distribution, with material found in Argentina, Chile, Cuba, England, France, Germany, Italy, Mexico, Poland, Russia and Switzerland.[6][3]
Phylogenetic analyses published during the 2000s cast doubt on the idea that many traditional metriorhynchid genera formed natural groups (i.e., include all descendants of a common ancestor). The traditional species of Geosaurus,[7][8][9] Dakosaurus[7] and Cricosaurus[7] were found to represent unnatural groups, and the species traditionally classified in these genera were reshuffled in a study published in November 2009 by Mark T. Young and Marco Brandalise de Andrade.[5] The monophyly of Metriorhynchus [7][8][10] and Teleidosaurus[7][9] is also unsupported, and the species of these genera are pending reclassification.[5]
The classification presented by Young and Andrade in 2009 was approved in later studies of the Metriorhynchidae.[11][6][12] Metriorhynchidae is a node-based taxon defined in 2009 as the least inclusive clade consisting of Metriorhynchus geoffroyii and Geosaurus giganteus.[5] The cladogram below follows the topology from a 2011 analysis by Andrea Cau and Federico Fanti with clade names from Young et al. 2011 and reduced to genera only.[11][6]
Metriorhynchidae |
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The type genus of the family Metriorhynchidae is Metriorhynchus from the Middle to Late Jurassic.[3] Other genera included within this family are Cricosaurus, Geosaurus, and Dakosaurus. Though once considered a metriorhynchid, Teleidosaurus has since been found to be slightly more distantly related to these animals within the superfamily Metriorhynchoidea.
Within this family, the genus Neustosaurus is considered nomen dubium ("doubtful name").[13]
The genus Capelliniosuchus was once thought to be a metriorhynchid similar to Dakosaurus.[14] However, Sirotti demonstrated that it is a junior synonym of Mosasaurus.[15]
Genus | Status | Author | Age | Location | Description | Synonyms | Images |
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Valid | Wagner, 1858 | middle Oxfordian to upper Valanginian |
Argentina, Chile, Cuba, England, France, Germany, Mexico, Russia and Switzerland. |
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Valid | von Quenstedt, 1856 | lower Oxfordian to lower Berriasian |
Argentina, England, France, Germany, Mexico, Poland, Switzerland and possibly Russia. |
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Valid | Cuvier, 1824 | upper Kimmeridgian to upper Valanginian |
France, Germany, Italy and Switzerland. |
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Valid | Young et al., 2010 | lower Kimmeridgian |
France (Normandy) |
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Valid | von Meyer, 1830 | lower Callovian to upper Kimmeridgian. |
England, France, Germany and Switzerland. |
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Valid | Cau & Fanti, 2011 | late Bajocian to earliest Bathonian |
Italy |
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nomen dubium | — potential senior synonym of Cricosaurus | ||||||
Valid | Rusconi, 1948 | lower Callovian to lower Tithonian |
Argentina and Chile. |
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Valid | von Meyer, 1831 | lower Tithonian |
Germany |
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Valid | Lydekker, 1890 | lower Callovian to lower Oxfordian |
England and France. |
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Valid | Andrade et al., 2010 | upper Kimmeridgian |
England |
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