Parvinatator
Parvinatator Temporal range:
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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
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Parvinatator, from Latin, “parvus” little and “natator” swimmer, is an extinct
Geological information
The only known Parvinatator fossil was located in an unknown horizon from the
Discovery
Parvinatator wapitiensis was discovered in the Sulfur Mountain Formation in British Columbia, Canada, by Elisabeth 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]
Description and paleobiology
Based on analysis of tooth size relative to the skull width, Parvinatator is estimated to be less than 1 meter long,
Skull
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 the
- The retroarticular process, composed of the
- The quadratojugal is high and narrow, laterally covering the quadrate.[7][6]
- The jugal and quadratojugal have a deep notch between them, agreeing with the lack of a lower
- The postorbital is enlarged and overlaps the jugal along the posterior of the orbit, forming a natural articulation point.[8][3]
- The orbit is oval in shape, being longer than tall.[3]
- The external naris is enclosed by the premaxilla, maxilla and nasal bone, separate from a well developed lacrimal.[1][6]
Forefin
Unlike some basal ichthyosaurs, Parvinatator's forefin appears well adapted for aquatic life, although it was probably used for controlling pitch rather than locomotion.[9] On the well preserved left forefin of Parvinatator the ulna is reduced in both length and width and smaller than the radius. Several bones of digits 4 and 5 are fused together as well.[1][3]
Phylogeny
There is some disagreement about the exact location of Parvinatator among its relatives. The following
Ichthyopterygia |
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However, according to Maisch and Matzke in 2000, Parvinatator is a true ichthyosaur and more derived than Utatsusaurus and Grippia.[10]
Ichthyosauria |
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See also
- List of ichthyosaurs
- Timeline of ichthyosaur research
References
- ^ a b c d e Nicholls, E. & Brinkman, D. (1995). A new ichthyosaur from the Triassic Sulphur Mountain formation of British Columbia. Sarjeant WAS (ed.): Vertebrate fossils and the evolution of scientific concepts: 521–535 London (Gordon & Breach).
- ^ a b c Motani, R. (1999). Phylogeny of the Ichthyopterygia. Journal of Vertebrate Paleontology, 19:3, 473-496.
- ^ a b c d e f g Motani, R. (1997). Phylogeny of the Ichthyosauria (Amniota: Reptilia) with special reference to Triassic forms. Ph.D. dissertation, University of Toronto, Toronto, Ontario, Canada.
- ^ Motani, R., You, H., & Mcgowan, C. (1996). Eel-like swimming in the earliest ichthyosaurs. Nature, 382, 347-348.
- ^ Motani, R.; Rothschild, B.M.; Wahl, W. (1999). "Large eyes in deep diving ichthyosaurs". Nature. 402: 747.
- ^ a b c d Maisch, M. (2010). Phylogeny, systematics, and origin of the Ichthyosauria – the state of the art. Palaeodiversity, 3, 151–214.
- ^ a b Maisch, M.W. & Matzke, A.T. (2002). The skull of a large Lower Triassic ichthyosaur from Spitzbergen and its implications for the origin of the Ichthyosauria. Lethaia, 35, 250–256.
- ^ Cuthbertson, R. S., Russell, A. P., & Anderson, J. S. (2013). Cranial morphology and relationships of a new grippidian (Ichthyopterygia) from the Vega-Phroso Siltstone Member (Lower Triassic) of British Columbia, Canada. Journal of Vertebrate Paleontology, 33, 831-847.
- .
- ^ Maisch, M.W.; Matzke, A.T. (2000). "The Ichthyosauria". Stuttgarter Beitrage zur Naturkunde, Serie B (Geologie und Palaontologie). 298: 1–159.