If you need an accessible version of this item please contact JSTOR User Support

Temnodontosaurus risor Is a Juvenile of T. platyodon (Reptilia: Ichthyosauria)

C. McGowan
Journal of Vertebrate Paleontology
Vol. 14, No. 4 (Feb. 15, 1995), pp. 472-479
Stable URL: http://www.jstor.org/stable/4523589
Page Count: 8
  • Download PDF
  • Cite this Item

You are not currently logged in.

Access your personal account or get JSTOR access through your library or other institution:

login

Log in to your personal account or through your institution.

If you need an accessible version of this item please contact JSTOR User Support
Temnodontosaurus risor Is a Juvenile of T. platyodon (Reptilia: Ichthyosauria)
Preview not available

Abstract

Most ichthyosaurs from the English Lower Jurassic are dolphin-sized, with skull lengths of about 500 mm and body lengths of up to 2,500 mm. Very large ichthyosaurs are rare, and the largest and best known of these is Temnodontosaurus platyodon, with skull lengths ranging from 1,200 to 2,000 mm and body lengths of up to about 9,000 mm. Two other species are referrred to the genus Temnodontosaurus, T. eurycephalus and T. risor. The former, known from a single 950 mm long skull, is characterized by its much shortened snout. T. risor, erected upon three isolated skulls ranging in length from 655 to 800 mm, is like T. platyodon but differs in having a slightly larger orbit, smaller maxilla, and a curved snout. An almost complete, three-dimensionally preserved skeleton was recently found which can be identified as T. risor but which has a slightly longer skull than the other referred specimens. The skull is remarkably large relative to the post-cranial skeleton, suggestive of immaturity, and this is supported by size-independent osteological features. T. risor therefore represents an immature stage, but of which taxon? The most likely candidate is T. platyodon, and when comparisons are made between the new material, and specimens formerly referred to T. risor and to T. platyodon, a case can be made that they form part of a growth series. T. risor is therefore recognized as a junior synonym for T. platyodon. The new material provides valuable additonal information for T. platyodon, a rather inadequately known species, for which an emended diagnosis is given.

Page Thumbnails

  • Thumbnail: Page 
472
    472
  • Thumbnail: Page 
473
    473
  • Thumbnail: Page 
474
    474
  • Thumbnail: Page 
475
    475
  • Thumbnail: Page 
476
    476
  • Thumbnail: Page 
477
    477
  • Thumbnail: Page 
478
    478
  • Thumbnail: Page 
479
    479