Ichthyopterygia

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Ichthyopterygians Fossil range: Early Triassic - Late Cretaceous
Utatsusaurus
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Subclass:	Diapsida
Superorder:	Ichthyopterygia Owen, 1840
Orders
Grippidia Ichthyosauria

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 (Motani 1997, Motani et al. 1998).

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 (Motani 2000). 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 By the later part of the Middle Triassic they were extinct, having been replaced by their descendents the true ichthyosaurs.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
  • Family Utatsusauridae
  • Family Parvinatatoridae
  • Order Grippidia
  • Order Ichthyosauria

Phylogeny

Cladogram after Motani (1998, 1999) and Nicholls & Manabe (2001).

Neodiapsida
 |--Sauria
 '-?Ichthyopterygia
      |-?Hupehsuchus
      |-?Thaisaurus
      |--Utatsusaurus
      |--Parvinatator
      '--Eoichthyosauria
            |--Grippidae
            '--Ichthyosauria
                  |-?Mikadocephalus
                  |-?Wimanius
                  |--Cymbospondylus
                  '--+--Mixosauridae
                     '--Merriamosauria
                           |--+-?Mixosaurus
                           |  '--+-?Cymbospondylus
                           |     '--Shastasauridae
                           '--Euichthyosauria
                                 |--Toretocnemidae
                                 '--+--Californosaurus
                                     '--Parvipelvia
                                           |--Macgovania
                                           '--+--Hudsonelpidia
                                              '--+--Suevoleviathan
                                                 '--+--Temnodontosaurus
                                                       |--Eurhinosauridae
                                                       '--Thunnosauria
                                                             |-?Chacaicosaurus
                                                             |--Stenopterygius
                                                             '--+--Ichthyosaurus
                                                                '--Ophthalmosauridae

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
• Motani, R. (1997), Temporal and spatial distribution of tooth implantation in ichthyosaurs, in JM Callaway & EL Nicholls (eds.), Ancient Marine Reptiles. Academic Press. pp. 81-103.
• Motani, R. (2000), Rulers of the Jurassic Seas, Scientific American vol.283, no. 6
• Motani, R., Minoura, N. & Ando, T. (1998), Ichthyosaurian relationships illuminated by new primitive skeletons from Japan. Nature 393: 255-257.

External links

• Ryosuke Motani's detailed Ichthyosaur homepage, with vivid graphics
• Eureptilia: Ichthyopterygia - Palaeos
• "Ichthyosauromorpha" - Mikko's Phylogeny Archive