Thalattosuchia is a

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...

of marine

crocodylomorph Crocodylomorpha is a group of pseudosuchian archosaurs that includes the crocodilians and their extinct relatives. They were the only members of Pseudosuchia to survive the end-Triassic extinction. During Mesozoic and early Cenozoic times, cro ...

s from the

Early Jurassic The Early Jurassic Epoch (geology), Epoch (in chronostratigraphy corresponding to the Lower Jurassic series (stratigraphy), Series) is the earliest of three epochs of the Jurassic Period. The Early Jurassic starts immediately after the Triassic-J ...

to the

Early Cretaceous The Early Cretaceous ( geochronological name) or the Lower Cretaceous (chronostratigraphic name), is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 145 Ma to 100.5 Ma. Geology Pro ...

that had a

cosmopolitan distribution In biogeography, cosmopolitan distribution is the term for the range of a taxon that extends across all or most of the world in appropriate habitats. Such a taxon, usually a species, is said to exhibit cosmopolitanism or cosmopolitism. The ext ...

. They are colloquially referred to as marine crocodiles or sea crocodiles, though they are not members of

Crocodilia Crocodilia (or Crocodylia, both ) is an order of mostly large, predatory, semiaquatic reptiles, known as crocodilians. They first appeared 95 million years ago in the Late Cretaceous period ( Cenomanian stage) and are the closest living ...

and records from Thailand and China suggest that some members lived in freshwater. The clade contains two major subgroupings, the

Teleosauroidea Teleosauroidea is an extinct superfamily of thalattosuchian crocodyliforms living from the Early Jurassic to the Early Cretaceous The Early Cretaceous ( geochronological name) or the Lower Cretaceous (chronostratigraphic name), is the earlier o ...

and

Metriorhynchoidea 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 a ...

. Teleosauroids are not greatly specialised for oceanic life, with back

osteoderms Osteoderms are bony deposits forming scales, plates, or other structures based in the dermis. Osteoderms are found in many groups of extant and extinct reptiles and amphibians, including lizards, crocodilians, frogs, temnospondyls (extinct ...

similar to other crocodyliformes. Within Metriorhynchoidea, the

Metriorhynchidae Metriorhynchidae is an extinct family of specialized, aquatic metriorhynchoid crocodyliforms from the Middle Jurassic to the Early Cretaceous period (Bajocian to early Aptian) of Europe, North America and South America. The name Metriorhync ...

displayed extreme adaptions for life in the open ocean, including the transformation of limbs into flippers, the development of a tail fluke, and smooth, scaleless skin.

Discovery and naming

The term Thalattosuchia was coined by Fraas in 1901.Fraas E. 1901. Die Meerkrokodile (Thalattosuchia n. g.) eine neue Sauriergruppe der Juraformation. ''Jahreshefte des Vereins für vaterländische Naturkunde, Württemberg'' 57: 409-418. Various authors considered Thalattosuchia an infraorder or a suborder within " Mesosuchia". However, the term "Mesosuchia" is a

paraphyletic In taxonomy (general), taxonomy, a group is paraphyletic if it consists of the group's most recent common ancestor, last common ancestor and most of its descendants, excluding a few Monophyly, monophyletic subgroups. The group is said to be pa ...

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. The exact phylogenetic position of Thalattosuchia is uncertain, with them either being interpreted as members of

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' ...

or basal members of Crocodylomorpha, with the similarities to neosuchians possibly being due to

convergence Convergence may refer to: Arts and media Literature *''Convergence'' (book series), edited by Ruth Nanda Anshen * "Convergence" (comics), two separate story lines published by DC Comics: **A four-part crossover storyline that united the four Wei ...

. Since Buffetaut (1982) demonstrated the shared characteristics of the early forms of

and

Teleosauridae Teleosauridae is a family of extinct typically marine crocodylomorphs similar to the modern gharial that lived during the Jurassic period. Teleosaurids were thalattosuchians closely related to the fully aquatic metriorhynchoids, but were less ad ...

, Thalattosuchia has consisted of these two families.Buffetaut, E. 1982. Radiation évolutive, paléoécologie et biogéographie des Crocodiliens mésosuchienes. ''Mémoires Societé Geologique de France'' 142: 1–88. The oldest records of thalattosuchians date to the

Sinemurian In the geologic timescale, the Sinemurian is an age and stage in the Early or Lower Jurassic Epoch or Series. It spans the time between 199.3 ± 2 Ma and 190.8 ± 1.5 Ma (million years ago). The Sinemurian is preceded by the Hettangian and is ...

and

Pliensbachian The Pliensbachian is an age of the geologic timescale and stage in the stratigraphic column. It is part of the Early or Lower Jurassic Epoch or Series and spans the time between 190.8 ± 1.5 Ma and 182.7 ± 1.5 Ma (million years ago). The Plien ...

stages, represented by indeterminate remains from Argentina, Chile, and India. The latest records date to the

. Some of the early members of Teleosauridae have been discovered in non-marine deposits. The systematics of the genus ''

Pelagosaurus ''Pelagosaurus'' (meaning "lizard of the open sea") is an extinct genus of thalattosuchian crocodyliform that lived during the Toarcian stage of the Lower Jurassic, around 183 Ma to 176 Ma (million years ago), in shallow epicontinental seas that ...

'' are confused, with differencing topologies placing it as either a teleosaurid,Gasparini Z, Pol D, Spalletti LA. 2006. An unusual marine crocodyliform from the Jurassic-Cretaceous boundary of Patagonia. ''Science'' 311: 70-73. or as the sister taxon to a Teleosauridae + Metriorhynchoidea clade. Others considered ''Pelagosaurus'' to be a basal metriorhynchoid.

References

External links

"Ancient ocean-going crocodiles mimicked whales and dolphins"
at The Guardian, 20 Apr 2020 {{Taxonbar, from=Q2300406 Prehistoric animal suborders Tetrapod suborders Prehistoric marine crocodylomorphs Jurassic crocodylomorphs Early Cretaceous crocodylomorphs Sinemurian first appearances Early Cretaceous extinctions

Discovery and naming

See also

References

Further reading

External links