| Parvinatator | |
|---|---|
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Superorder: | †Ichthyopterygia |
| Family: | †Parvinatatoridae McGowan and Motani, 2003 |
| Genus: | †Parvinatator Nicholls and Brinkman, 1995 |
| Type species | |
| †Parvinatator wapitiensis Nicholls and Brinkman, 1995 | |
Parvinatator, from Latin, “parvus” little and “natator” swimmer, is an extinctgenus of smallichthyopterygianmarine reptile that lived during the Early to MiddleTriassic. Its fossils have been found inBritish Columbia,Canada.[1]
The only known Parvinatator fossil was located in an unknown horizon from theSulfur Mountain Formation in atalus deposit, so its exact geological age is unknown. Best estimates place the fossil somewhere between theOlenekian andLadinian age around 251-235 mya.[2] Other small ichthyosaurs have been found nearby includingGrippia,Utatsusaurus, andPhalarodon.
Parvinatator wapitiensis was discovered in the Sulfur Mountain Formation in British Columbia, Canada, byElisabeth Nicholls and Don Brinkman in 1995. The only fossil recovered of this genus is a partial skull and two forefins.[1] The skull has been tectonically deformed, partially dis-articulated and broken with the posterior section rotated forward into the orbit. The left forefin is well preserved with only minor overlapping and breakage, while the right forefin is heavily overlapped and broken.[3]
Based on analysis of tooth size relative to the skull width, Parvinatator is estimated to be less than 1 meter long,[2] approximately the same size and general shape of otherbasalichthyosaurs, although it is unknown if Parvinatator lacked adorsal fin like Utatsusaurus and Grippia. Also like other early ichthyosaurs, Parvinatator most likely used an eel-like lateral body movement for propulsion,[4] known asanguilliform. Based on jaw size and tooth shape, Parvinatator is thought to have feed on smallfish andcephalopods similarly to other basal ichthyosaurs, as opposed to hard shelled organisms such asmollusks andclams.[3] Ichthyosaurs typically had large eyes suggesting they would hunt in the dark, either at night or in deep water.[5] After the skull's dis-articulatedorbit was reconstructed, it matched the approximate shape and typical size of other ichthyosaurs eyes.[3]
The fossil of the skull is small, measuring approximately 15 cm in width by 10 cm in height. The skull had been dis-articulated, broken and tectonically deformed, but was reconstructed by Ryosuke Motani, leading to several differences from Nicholls and Brinkman's original description, including; the presence of thesquamosal,quadratojugal, and a reduced supratemporal, a lack of contact between theprefrontal andpostfrontal, as well as between thejugal and quadratojugal (which was previously identified as the squamosal).[3] Otherdiagnostic characteristics of the Parvinatator skull are as follows:
Unlike some basal ichthyosaurs,Parvinatator's forefin appears well adapted foraquatic life, although it was probably used for controllingpitch rather thanlocomotion.[9] On the well preserved left forefin ofParvinatator theulna is reduced in both length and width and smaller than theradius. Several bones ofdigits 4 and 5 are fused together as well.[1][3]
There is some disagreement about the exact location ofParvinatator among its relatives. The followingphylogeny by Motani placesParvinatator withUtatsusaurus as basal ichthyopterygians but not true ichthyosaurs.[2]
| Ichthyopterygia |
| |||||||||
However, according to Maisch and Matzke in 2000,Parvinatator is a true ichthyosaur and more derived thanUtatsusaurus andGrippia.[10]
| Ichthyosauria | |
