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''Thalattoarchon'' is an extinct genus of
''Thalattoarchon'' is a large-bodied ichthyosaur, measuring at least long and weighing . The only known skeleton of ''Thalattoarchon'' is incomplete, but it can be inferred on the basis of other early ichthyosaurs to have had an elongated body and a weakly developed caudal fin. ''Thalattoarchon'' is diagnosed by a single distinguishing feature that is unique among ichthyosaurs: large, thin teeth that bear two cutting edges and that have smooth
ichthyosaur
Ichthyosaurs (Ancient Greek for "fish lizard" – and ) are large extinct marine reptiles. Ichthyosaurs belong to the order known as Ichthyosauria or Ichthyopterygia ('fish flippers' – a designation introduced by Sir Richard Owen in 1842, altho ...
from the Middle Triassic of the western United States. The type species ''Thalattoarchon saurophagis'' (meaning "lizard-eating sovereign of the sea" in Greek) was discovered in Nevada, USA, in 2010 and formally described in 2013. It is known from a single skeleton, holotype FMNH PR 3032, consisting of a partial skull, vertebral column, hip bones, and parts of the hind fins. The total length of ''Thalattoarchon'' is estimated to have been at least . ''Thalattoarchon'' is thought to have been one of the first marine macropredators capable of eating prey that was similar in size to itself, an ecological role that can be compared to that of modern orcas. ''Thalattoarchon'' lived four million years after the first appearance of ichthyosaurs in the Early Triassic and is therefore the oldest known marine reptile
Marine reptiles are reptiles which have become secondarily adapted for an aquatic or semiaquatic life in a marine environment.
The earliest marine reptile mesosaurus (not to be confused with mosasaurus), arose in the Permian period during the ...
to have been an apex predator. It lived eight million years after the Permian-Triassic extinction event, indicating a fast recovery of marine ecosystems after the mass extinction.
Description
''Thalattoarchon'' is a large-bodied ichthyosaur, measuring at least long and weighing . The only known skeleton of ''Thalattoarchon'' is incomplete, but it can be inferred on the basis of other early ichthyosaurs to have had an elongated body and a weakly developed caudal fin. ''Thalattoarchon'' is diagnosed by a single distinguishing feature that is unique among ichthyosaurs: large, thin teeth that bear two cutting edges and that have smooth tooth crown
In dentistry, crown refers to the anatomical area of teeth, usually covered by tooth enamel, enamel. The crown is usually visible in the mouth after tooth development, developing below the gingiva and then tooth eruption, erupting into place. ...
s. Most later ichthyosaurs have much smaller cone-shaped teeth. The Late Triassic ichthyosaur ''Himalayasaurus tibetensis
''Himalayasaurus'' is an extinct genus of ichthyosaur from the Late Triassic Qulonggongba Formation of Tibet. The type species ''Himalayasaurus tibetensis'' was described in 1972 on the basis of fragmentary remains, including teeth, limb bones, ...
'' also has large teeth with cutting edges, but can be distinguished from ''Thalattoarchon saurophagis'' by the presence of grooves across the surfaces of its tooth crowns. ''Thalattoarchon'' is very similar in appearance to ''Cymbospondylus
''Cymbospondylus'' (a Greek word meaning "boat vertebrae") was a basal early ichthyosaur that lived between the early and middle Triassic period (249-237 million years ago). Previously, the genus was classified as a shastasaurid, but more rec ...
'', another large-bodied Middle Triassic ichthyosaur, but differs in having a head that is about twice as large as that of ''Cymbospondylus'' relative to its body.
Classification
Below is a cladogram from Fröbisch ''et al.'' (2013): A 2016 cladistic analysis recovers ''Thalattoarchon'' as acymbospondylid
Cymbospondylidae is an extinct family of Hueneosaurian Ichthyosaurs known from the Middle Triassic of Europe, North America, and Asia.
Taxonomy
Cymbospondylidae is a basal clade of ichthyosaurs. In 2000, Maischand and Matzke recovered cymbospond ...
rather than a basal merriamosaur.Jiang, Da-Yong; Motani, Ryosuke; Huang, Jian-Dong; Tintori, Andrea; Hu, Yuan-Chao; Rieppel, Olivier; Fraser, Nicholas C.; Ji, Cheng; Kelley, Neil P.; Fu, Wan-Lu; Zhang, Rong (23 May 2016). "A large aberrant stem ichthyosauriform indicating early rise and demise of ichthyosauromorphs in the wake of the end-Permian extinction". Scientific Reports 6. 26232.
See also
*List of ichthyosaurs
This list of ichthyosaurs is a comprehensive listing of all genera that have ever been included in the order Ichthyosauria or the parent clade Ichthyopterygia, excluding purely vernacular terms. The list includes all commonly accepted genera, but a ...
* Timeline of ichthyosaur research
This timeline of ichthyosaur research is a chronological listing of events in the history of paleontology focused on the ichthyosauromorphs, a group of secondarily aquatic marine reptiles whose later members superficially resembled dolphins, shar ...
References
{{Taxonbar, from=Q2756895 Middle Triassic ichthyosaurs Middle Triassic reptiles of North America Triassic United States Extinct reptiles Ichthyosauromorph genera