o Eureptilia `--o DIAPSIDA |--Araeoscelidia (paraphyletic?) `--+?--Avicephala `--o Neodiapsida |?-Coelurosauravidae `--+--Apsisaurus `--+?-Claudiosaurus `--o==Younginiformes (paraphyletic?) `--+?-Ichthyopterygia `--o Sauria |--Lepidosauromorpha `--Archosauromorpha
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 maneouverability 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 By the later part of the Middle Triassic they were extinct, having been replaced by their descendents the true ichthyosaurs.
o Diapsida `--o ICHTHYOPTERYGIA |?-Hupehsuchus nanchengensis |?-Thaisaurus chonglakmanii |?-Pessopteryx |--Utatsusaurus hataii |--Parvinatator wapitiensis `--o Eoichthyosauria |--o Grippidae | |--Grippia longirostris | `--Chaohusaurus geishanensis `--Ichthyosauria
Characters: euryapsid skull; primitive tooth implantation probably subthecodont [M97]; replacement teeth outside pulp cavity [M97]; uniquely down-turned vertebral column that enters the lower lobe of its caudal fin; flippers for limb; live birth.
References: Motani (1997) [M97]; Motani et al. (1998) (M+98)
- Superorder Ichthyopterygia
- 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.
- Ryosuke Motani's detailed Ichthyosaur homepage, with vivid graphics
- "Ichthyosauromorpha" - Mikko's Phylogeny Archive