plesio2.jpg (87932 bytes)

Plesiosaur Skull Anatomy



Copyright 2000-2009 by Mike Everhart


Last updated 09/07/2009




LEFT: Plate IX, Andrews, C. W. 1896. On the structure of the plesiosaurian skull. Quart. Jour. Geol. Soc. London. 246-253.

This page is intended as a primer on the structural anatomy of the plesiosaur skull.  As a model I am using Plate IX from an article written by Charles W. Andrews and published in the Quarterly Journal of the Geological Society of London.  Although Plesiosaurus macropcephalus is a Jurassic plesiosaur from England, the cranial anatomy is reasonably similar to that of the late Cretaceous plesiosaurs from the Western Interior Seaway. Click here for a picture of the skeleton of Plesiosaurus dolichodeirus from Richard Forrest's Plesiosaur webpage.  You can also click on the thumbnails of the skull of Thalassomedon haningtoni below (DMNH 1588; Denver Museum of Nature and Science) for comparison. 

plesio1.jpg (145015 bytes)

List of Abbreviations:

ang. - angular;  b.oc. - basioccipital; b.sph.- basisphenoid; col. - columella cranii; ext. nar.- external nares; int. nar. - internal nares; fr. - frontal; mx.- maxilla; pal.- palatine; par.- parietal; pas; parasphlenoid; pin.for. - pineal foramen; pmx; - premaxilla; -prefrontal; ? - separate post-frontal; post. pal.vac. -posterior palatine vacuities; q. -quadrate; vom. - vomer.

Thalassomedon haningtoni (DMNH 1588; Denver Museum of Nature and Science)

1588-02a.jpg (3418 bytes)

1588-03a.jpg (2586 bytes)

1588-04a.jpg (3447 bytes)

1588-05a.jpg (3501 bytes)

T1588-06a.jpg (3077 bytes)

Reference: Andrews, C. W. 1896. On the structure of the plesiosaurian skull. Quart. Jour. Geol. Soc. London. 246-253.

GASTRAIA.jpg (16959 bytes) LEFT: A ventral view of the Jurassic plesiosaur Thaumatosaurus von Meyer 1841, showing the relationship between the pectoral and pelvic girdles, and the gastralia. The name "Thaumatosaurus" means "wonder lizard." (See Ben Creisler's Guide for more information).  Original drawing by E. Fraas (1910). Specimen was more recently attributed to Rhomaleosaurus victorThe specimen (SMNS 12478) was damaged by fire in WW II, but was repaired.

The remains are currently on exhibit in the Staatliches Museum fuer Naturkunde Stuttgart, Museum am Loewentor, Rosenstein 1, 70191 Stuttgart, Germany. (Photo by Markus Moser, 2004)

GASTRAI4.jpg (25025 bytes) LEFT: A close up of the "belly of the beast" showing the interlocking gastralia that covered the middle portion of the body. The specimen does contain some gastroliths (pers. comm., Oliver Wings, 2004).

Additional reading on the web:

Hawkins, T., 1834. Memoirs of ichthyosauri and plesiosauri, extinct monsters of the ancient Earth. Roy. fol., London. ix + 58 pp., frontisp., 28 pls.

For more information on Jurassic plesiosaurs: Adam Smith's The Plesiosaur Directory