Thalattosuchia
Encyclopedia
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 sometimes colloquially referred to as marine crocodiles or sea crocodiles, though they are not actually members of Crocodilia
.
The term Thalattosuchia was coined by Fraas in 1901. Various authors have considered Thalattosuchia to be either 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 presently 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 suggesting thalattosuchians 'moved' from being semi-aquatic freshwater forms to fully marine forms. 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. Other authors have considered Pelagosaurus to be a basal metriorhynchid.
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
of marine crocodylomorphs from the Early Jurassic
Jurassic
The Jurassic is a geologic period and system that extends from about Mya to Mya, that is, from the end of the Triassic to the beginning of the Cretaceous. The Jurassic constitutes the middle period of the Mesozoic era, also known as the age of reptiles. The start of the period is marked by...
to the Early Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
that had a cosmopolitan distribution. They are sometimes colloquially referred to as marine crocodiles or sea crocodiles, though they are not actually members of Crocodilia
Crocodilia
Crocodilia is an order of large reptiles that appeared about 84 million years ago in the late Cretaceous Period . They are the closest living relatives of birds, as the two groups are the only known survivors of the Archosauria...
.
The term Thalattosuchia was coined by Fraas in 1901. Various authors have considered Thalattosuchia to be either an infraorder or a suborder within "Mesosuchia
Mesosuchia
"Mesosuchia" is an obsolete name for a group of terrestrial, semi-aquatic, or fully aquatic crocodylomorph reptiles. The marine crocodile Metriorhynchus had paddle-like forelimbs, Dakosaurus andiniensis had a skull that was adapted to eat large sea reptiles, and Shamosuchus was adapted for eating...
". 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 presently unnamed.
Metriorhynchidae
Metriorhynchidae is an extinct family of metriorhynchoid crocodyliforms from the Middle Jurassic to the Early Cretaceous period of Europe, North America and South America. Metriorhynchids are fully aquatic crocodyliforms. Their forelimbs were small and paddle-like, and unlike living crocodilians,...
and Teleosauridae
Teleosauridae
The teleosaurids were marine crocodyliforms similar to the modern gharial that lived from the Early Jurassic to the Early Cretaceous. They had long snouts, indicative of piscivory and were the closest relatives to the Metriorhynchidae, the Mesozoic crocodilians that returned to the sea and evolved...
, Thalattosuchia has consisted of these two families. Some of the early members of Teleosauridae have been discovered in non-marine deposits suggesting thalattosuchians 'moved' from being semi-aquatic freshwater forms to fully marine forms. The systematics of the genus Pelagosaurus
Pelagosaurus
Pelagosaurus is an extinct genus of thalattosuchian crocodyliform that lived during the Toarcian stage of the Lower Jurassic, around 183 Ma to 175 Ma , in shallow epicontinental seas that covered much of what is now Western Europe...
are confused, with differencing topologies placing it as either a teleosaurid , or as the sister taxon to a Teleosauridae + Metriorhynchidae clade. Other authors have considered Pelagosaurus to be a basal metriorhynchid.
Suggested further reading
- Fraas, E. (1902). Die Meer-Krocodilier (Thalattosuchia) des oberen Jura unter specieller Berücksichtigung von Dacosaurus und Geosaurus. Paleontographica 49: 1-72.