Muraenosaurus Seeley, 1874

Sauropterygia > Eosauropterygia > Eusauropterygia > Pistosauroidea > Plesiosauria > Plesiosauroidea > Euplesiosauria > Cryptocleidoidea > Cryptoclididae

Synonyms

'Picrocleidus', 'Tremamesacleis'

M. leedsii Seeley, 1874 (type species)

Species synonyms

C. 'oxoniensis'

Material

-

M. beloclis Seeley, 1892

Material

-

Distribution

Lower Oxford Clay, Late Jurassic of Dorset, (England).

images

Anterior cervical vertebra:

Posterior cervical vertebrae:

Dorsal or back vertebrae. The cervical series merges into the dorsal series through a transitionary series of pectoral vertebrae. During this transition the rib facets finally migrate from the centrum (as in cervicals) to the neural arch, and become transverse process in the dorsal vertebrae. These support long ribs. the centra are often distinctly spool shaped. Dorsal vertebra from front:

Caudal or tail vertebrae. From the dorsal series we pass through the pelvic to the caudal series where the ribs return to the centrum. The caudal vertebrae also bear chevrons on their venral surfaces, and the vertebrae are usually more angular when viewed from end-on. Caudal vertebra:

The paraxial skeleton. The pectoral (shoulder) girdles of plesiosaurs are expanded in thin plates ventrally, the main element in the pectoral girdle are the coracoids and the scapulae - where these meet on the lateral (outside) surface they form a glenoid cavity to accomodate the forelimb the scapulae may or may not meet on the midline depending on the species.

The pelvic girdle. As in the pectoral girdle the elements have expanded into plates, the pubis anteriorly and the ischium posteriorly. The illium is a small element which bridges the gap between the girdle and the sacral ribs - it only contacts the ischium in plesiosaurs.

The limbs. Both the fore and hind limbs have developed into wing-like flippers, and closely resemble each other. The propodial (humerus/femur) is relatively long, the epipodials (radius, ulna/ tibia, fibula) are shortened, becoming wider than long is some taxa. The mesopodials are disk-like. The metapodials and phalanges (finger bones) are quite short and waisted. Plesiosaurs show hyperphalangy (increase in the number of finger bones).There may or may not be s number of accessory bones in the epi-mesopodial area, depending on the species. Hindlimb (A) and forelimb (B):

Discussion