Metriorhynchoidea is an extinct superfamily of thalattosuchian crocodyliforms from the Early Jurassic to the Early Cretaceous (Toarcian - Valanginian, possibly as late as early Aptian) of Europe, North America and South America. Metriorhynchids are fully aquatic crocodyliforms. Named by Fitzinger, in 1843, it contains the basal taxa like Teleidosaurus and Eoneustes and the family Metriorhynchidae. Two unnamed taxa are also known, from Oregon and Chile.
|Restoration of Teleidosaurus calvadosii|
Metriorhynchoidea is a stem-based taxon defined in 2009 as the most inclusive clade consisting of Metriorhynchus geoffroyii, but not Teleosaurus cadomensis. The cladogram below follows the topology from a 2011 analysis by Andrea Cau and Federico Fanti. Note that the same topology was obtained in Mark T. Young and Marco Brandalise de Andrade, 2009 and Mark T. Young, Stephen L. Brusatte, Marcello Ruta and Marco Brandalise de Andrade, 2010.
Aegyptosuchidae is an extinct family of eusuchian crocodyliforms from the Cretaceous period of Africa. They are characterized by their large size and flat heads. The family includes two genera, Aegyptosuchus and Aegisuchus.Atoposauridae
Atoposauridae is a family of crocodile-line archosaurs belonging to Neosuchia. The majority of the family are known from Late Jurassic to Early Cretaceous marine deposits in France, Portugal, and Bavaria in southern Germany. The discovery of the genus Aprosuchus, however, extends the duration of the lineage to the end of the Cretaceous in Romania.Brillanceausuchus
Brillanceausuchus is an extinct genus of atoposaurid crocodylomorph. Fossils have been found in Early Cretaceous–age rocks of Cameroon. The genus is notable for the position of the secondary choana within its palate. Parts of the pterygoid bones make up the rostral margin of the choana and thus separate it from the palatines, a feature also seen in the more advanced neosuchian suborder Eusuchia. This characteristic was once thought to be characteristic of Eusuchia, but its presence in Brillanceausuchus suggests that the trait is homoplasic, thus making the evolution of the position of the choana within crocodilians more complex than previously thought.Coelosuchus
Coelosuchus is an extinct genus of goniopholidid mesoeucrocodylian. Fossils have been found from the Graneros Shale of the Benton Group in Wyoming, and are of Cenomanian age. It was slightly over 1 meter in length.Eoneustes
Eoneustes (meaning "dawn swimmer") is an extinct genus of metriorhynchoid crocodyliform from Middle Jurassic (late Bajocian to early Bathonian stage) deposits of France. Eoneustes was a carnivore that lived in the oceans and spent much, if not all, its life out at sea.Eusuchia
The Eusuchia ("true crocodiles") are a clade of crocodylomorphs that first appears in the Early Cretaceous with Hylaeochampsa. Along with Dyrosauridae and Sebecosuchia, they were the only crocodyliformes who survived the K-T extinction. Since the other two clades died out 35 and 11 million years ago, all living crocodilian species are eusuchians, as are many extinct forms.Karatausuchus
Karatausuchus is an extinct genus of atoposaurid crocodylomorph. It is known from a single specimen discovered in the Late Jurassic (Oxfordian - Kimmeridgian) Karabastau Svita from the vicinity of Mikhailovka in the Karatau Mountains of southern Kazakhstan. The type specimen is PIN 25858/1, a complete but poorly preserved juvenile skeleton with some possible soft tissue preservation. It is notable for having over 90 teeth, but its other anatomical details are difficult to discern. The length of this individual is estimated at 160 millimetres (6.3 in). Karatausuchus was described in 1976 by Mikhail Efimov, and the type species is K. sharovi.Khoratosuchus
Khoratosuchus is an extinct genus of neosuchian crocodylomorph which existed in northeast Thailand during the early Cretaceous period. Its type species is Khoratosuchus jintasakuli. Khoratosuchus is the youngest and most advanced Mesozoic crocodyliform yet known from Thailand. It possesses several distinctive features that help determine its phylogenetic position among crocodylomorphs, including secondary choanae relatively posterior and almost encircled by the pterygoid bones on the palate and a smooth dorsal surface of the skull.Magyarosuchus
Magyarosuchus is an extinct monotypic genus of metriorhynchoid described for the first time from fossils discovered in the Kisgerecse Marl Formation in Hungary. The type species, Magyarosuchus fitosi, lived during the Toarcian, about 180 million years ago. Most of the skeleton is known, including parts of the jaw, torso, legs and tail.Metriorhynchidae
Metriorhynchidae is an extinct family of specialized, aquatic metriorhynchoid crocodyliforms from the Middle Jurassic to the Early Cretaceous period (Bajocian - Valanginian stages, potentially as late as early Aptian) 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.Nannosuchus
Nannosuchus (meaning "dwarf crocodile") is an extinct genus of goniopholidid mesoeucrocodylian from the Berriasian of England.Neosuchia
Neosuchia is a clade within Mesoeucrocodylia that includes all modern extant crocodilians and their closest fossil relatives. It is defined as the most inclusive clade containing all crocodylomorphs more closely related to Crocodylus niloticus (the Nile Crocodile) than to Notosuchus terrestris. Neosuchia is very diverse and may be polyphyletic, as the clade has undergone many revisions since it was first named in 1988. Neosuchians first appear in the Early Jurassic with the earliest known goniopholid Calsoyasuchus, which lived during the Sinemurian and Pliensbachian stages.Plesiosuchus
Plesiosuchus is an extinct genus of geosaurine metriorhynchid crocodyliform known from the Late Jurassic (late Kimmeridgian to early Tithonian stage) of Dorset, England and possibly also Spain. It contains a single species, Plesiosuchus manselii.Shamosuchus
Shamosuchus is an extinct genus of neosuchian crocodile that lived during the Late Cretaceous (Santonian-Campanian) period in what is now the Gobi desert of Mongolia, approximately 85 to 74 million years ago.Symptosuchus
Symptosuchus is an extinct genus of goniopholidid mesoeucrocodylian. It is known from the Late Cretaceous of Argentina. Argentine paleontologist Florentino Ameghino named the genus in 1899, along with the type species S. contortidens. It was formally described by Carlos Rusconi in 1934.Thalattosuchia
Thalattosuchia is the name given to a clade of 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.
The term Thalattosuchia was coined by Fraas in 1901. Various authors considered Thalattosuchia an infraorder or a suborder within "Mesosuchia". However, the term "Mesosuchia" is a paraphyletic group, and as such is no longer used. For consistency, the Thalattosuchia are here placed at suborder rank, although the order that contains it is unnamed.
Since Buffetaut (1982) demonstrated the shared characteristics of the early forms of Metriorhynchidae and Teleosauridae, Thalattosuchia has consisted of these two families.Some of the early members of Teleosauridae have been discovered in non-marine deposits. The systematics of the genus Pelagosaurus are confused, with differencing topologies placing it as either a teleosaurid, or as the sister taxon to a Teleosauridae + Metriorhynchidae clade. Others considered Pelagosaurus to be a basal metriorhynchid.Wahasuchus
Wahasuchus is a genus of extinct mesoeucrocodylian of the Middle Campanian age found in the Quseir Formation, Egypt. The generic name derives from the Arabic word واحة (waha), which means "oasis", and souchos from the Greek in honor of crocodile-headed god of ancient Egypt. The specific egyptensis (Lat.) means from Egypt.Fossils of skull and jaw fragments, dorsal vertebrae, and fragmentary appendicular remains have been recovered.Zoneait
Zoneait (pronounced "zone-eight" and meaning "large tooth" in the Kiowa language) is an extinct genus of thalattosuchian crocodylomorph known from a single species, Zoneait nargorum, from the Middle Jurassic of Oregon. Z. nargorum was named in 2015 by paleontologist Eric Wilberg on the basis of several partial skulls, vertebrae, and forelimb bones that were found in an outcrop of the Snowshoe Formation near the town of Izee. It is currently the oldest known member of Metriorhynchoidea, a clade of marine-adapted thalattosuchians that existed until the Early Cretaceous. The skeleton of Zoneait possesses several adaptations for offshore marine life but retains features characteristic of its land-living ancestors, indicating that it is a transitional form between the fully marine metriorhynchids of the Late Jurassic and Early Cretaceous and earlier non-marine crocodylomorphs. The Snowshoe Formation was deposited in a shallow marine environment within a tropical forearc basin, suggesting that Zoneait was a marine predator.Although Zoneait is the oldest metriorhynchoid, phylogenetic analysis indicates that the slightly younger taxa Eoneustes and Teleidosaurus are more basal than it. Wilberg found that Zoneait is the sister taxon of Metriorhynchidae, which suggests that it should have been more extensively adapted to marine life than Teleidosaurus and Eoneustes were, but less adapted than true metriorhynchids like Metriorhynchus and Cricosaurus, which were fully marine. Zoneait has a streamlined skull with eyes that faced laterally like those of metriorhychids, unlike the more upward-facing eyes of Teleidosaurus and other non-marine aquatic crocodylomorphs. The shift in eye orientation is thought to reflect changes in feeding ecology; upward-facing eyes would have been adaptive for aquatic crocodylomorphs ambushing land-living prey from beneath the surface of the water, whereas side-facing eyes would have been adaptive for marine crocodylomorphs hunting in open marine environments. The skull of Zoneait also shows evidence of salt glands in the form of enlarged passageways for the carotid artery, which would have increased bloodflow to the glands. The forelimbs are not flattened into paddles as in metriorhynchids, but the ulna (lower arm bone) is reduced in length, indicating that forelimb reduction began at the lower limb and progressed upward (the humerus or upper arm bone of Zoneait not reduced). Taken together, the transitional features of Zoneait indicate that metriorhynchoids' adaptation of a marine lifestyle began with a shift in feeding ecology and only later involved changes in swimming locomotion.
Major groups within Mesoeucrocodylia