Ichthyopterygia

Ichthyopterygians Temporal range: Early Triassic - Late Cretaceous, 248–90 Ma PreЄ Є O S D C P T J K Pg N
Utatsusaurus
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Clade:	†Ichthyosauriformes
Superorder:	†Ichthyopterygia Owen, 1840
Subgroups
See text.

Ichthyopterygia ("fish flippers") was a designation introduced by Sir Richard Owen in 1840 to designate the Jurassic ichthyosaurs that were known at the time, but the term is now used more often for both true Ichthyosauria and their more primitive early and middle Triassic ancestors.^[1][2]

Basal ichthyopterygians (prior to and ancestral to true Ichthyosauria) were mostly small (a meter or less in length) with elongate bodies and long spool shaped vertebrae, indicating that they swam in a sinuous eel-like manner. This allowed for quick movements and maneuverability that were an advantage in shallow-water hunting.^[3] Even at this early stage they were already very specialised animals with proper flippers, and would have been incapable of movement on land.

These animals seem to have been widely distributed around the coast of the northern half of Pangea, as they are known the Late Olenekian and Early Anisian (early part of the Triassic period) of Japan, China, Canada, and Spitsbergen (Norway). By the later part of the Middle Triassic they were extinct, having been replaced by their descendents the true ichthyosaurs.

Taxonomy

• Superorder Ichthyopterygia
  • ? Genus Isfjordosaurus
  • ? Family Omphalosauridae
  • Family Parvinatatoridae
  • Family Thaisauridae
  • Family Utatsusauridae
  • Eoichthyosauria
    • Order Grippidia
    • Order Ichthyosauria

Phylogeny

Below is a cladogram modified from Cuthbertson et al., 2013.^[4]

Ichthyopterygia

Parvinatator wapitiensis Utatsusaurus hataii Xinminosaurus catactes Eoichthyosauria Grippidia Grippia longirostris Gulosaurus helmi Ichthyosauria sensu Motani (1999) Chaohusaurus geishanensis Cymbospondylus Mixosauria Mixosaurus cornalianus Phalarodon atavus Toretocnemidae Qianichthyosaurus zhoui Toretocnemus californicus Shastasauria Shonisaurus popularis Shastasaurus pacificus Callawayia neoscapularis Guizhouichthyosaurus tangae Besanosaurus leptorhynchus Californosaurus perrini Parvipelvia

References

1. Motani, R. (1997). "Temporal and spatial distribution of tooth implantation in ichthyosaurs". In J. M. Callaway and E. L. Nicholls (eds.). Ancient Marine Reptiles. Academic Press. pp. 81–103.
2. Motani, R.; Minoura, N.; Ando, T. (1998). "Ichthyosaurian relationships illuminated by new primitive skeletons from Japan". Nature 393 (6682): 255–257. doi:10.1038/30473.
3. Motani, R. (2000). "Rulers of the Jurassic Seas". Scientific American 283 (6): 52–9. doi:10.1038/scientificamerican1200-52. PMID 11103459.
4. 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 (4): 831. doi:10.1080/02724634.2013.755989.

General references

• Ellis, Richard, (2003) Sea Dragons - Predators of the Prehistoric Oceans. University Press of Kansas
• McGowan, C & Motani, R. (2003) Ichthyopterygia, Handbook of Paleoherpetology, Part 8, Verlag Dr. Friedrich Pfeil

External links

• Ryosuke Motani's detailed Ichthyosaur homepage, with vivid graphics
• Eureptilia: Ichthyopterygia - Palaeos