Edgarosaurus

Extinct genus of reptiles

Edgarosaurus
Temporal range: Early Cretaceous, Albian
PreꞒ
O
S
D
C
P
T
J
K
Pg
N
Type specimen of Edgarosaurus muddi on display in the Museum of the Rockies
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Superorder: Sauropterygia
Order: Plesiosauria
Family: Polycotylidae
Genus: Edgarosaurus
Druckenmiller, 2002
Species:
E. muddi
Binomial name
Edgarosaurus muddi
Druckenmiller, 2002

Edgarosaurus is a genus of polycotylid plesiosaur from the Thermopolis Shale, containing one species, E. muddi.[1] The type specimen was found in Early Cretaceous (late Albian) rocks in the state of Montana in the United States.[1] At the time, this location was covered by part of the Western Interior Seaway. Edgarosaurus was one of the first polycotylids that evolved to become native to the Western Interior Seaway.

The holotype (which is currently the only known specimen) consists of the skull, neck, parts of the spine and the left front flipper.[1]

History of study

The well-preserved holotype specimen of Edgarosaurus (MOR 751) was found in the Shell Creek Member, the uppermost of the three members of the Thermopolis Shale, during the spring of 1993. The specimen's skull is complete and was preserved in articulation with a series 25 cervical (neck) vertebrae. An additional cervical vertebra, three pectoral (shoulder) vertebrae, and two dorsal (back) vertebrae were found isolated at the site, but articulate to form a series with the other 25 cervical vertebrae. Three other dorsal vertebrae were also recovered, though they do not seem to belong to this string of vertebrae. An almost complete front paddle is also known. Edgarosaurus muddi was named in 2002 by Pat S. Druckenmiller. The generic name refers to the nearby location of Edgar, Montana, while the specific name honors Kevin Mudd.[1]

Description

Life restoration

Druckenmiller estimated the total length of Edgarosaurus to be roughly 3.2–3.7 meters (10–12 ft), a figure derived from the proportions of Dolichorhynchops and Peloneustes. The cranium of the holotype specimen of Edgarosaurus is 47.5 centimetres (1.56 ft) long. Each premaxilla (front upper tooth bearing bone) contains either six or seven teeth. The top of skull of Edgarosaurus possesses a small opening towards its back known as a pineal foramen. The back of the skull is vertical, rather than sloping. Each side of the braincase is perforated by a circular hole. The front ends of each half of the mandible are fused together to form a mandibular symphysis. There are six tooth pairs situated on the symphysis, a low number for a polycotylid. Edgarosaurus has large, fang-like teeth.[1]

The neck of Edgarosaurus is short for a plesiosaur, containing a total of 26 vertebrae. The neck and skull together were estimated by Druckenmiller to comprise up to 45% of the animal's length. The lower arm bones of Edgarosaurus are very short and wide. The first digit of its forelimb consists of seven bones, the second eleven, and the third ten, while the fourth and fifth bear nine.[1]

See also

  • iconpaleontology portal

Sources

  1. ^ a b c d e f Druckenmiller, PS, 2002. "Osteology of a new plesiosaur from the lower Cretaceous (Albian) Thermopolis Shale of Montana". Journal of Vertebrate Paleontology 22: 29-42. (Abstract)
  • v
  • t
  • e
Sauropsida
    • see Sauropsida
Sauropterygia
    • see below↓
Helveticosauridae?
Saurosphargidae?
Placodontia
Cyamodontoidea
Eosauropterygia
    • see below↓
Helveticosaurus zollingeri Placochelys placodonta
Pachypleurosauria
Nothosauroidea
Simosauridae
Nothosauridae
Pistosauroidea
Plesiosauria
    • see below↓
Keichousaurus hui

Nothosaurus mirabilis

Pistosaurus longaevus
Rhomaleosauridae
Pliosauridae
Thalassophonea
Brachaucheninae
Plesiosauroidea
Microcleididae
Cryptoclidia
    • see below↓
Macroplata tenuiceps

Attenborosaurus conybeari

Hydrorion brachypterygius
Cryptoclididae
Colymbosaurinae
Cryptoclidinae
Muraenosaurinae
Leptocleidia
Leptocleididae
Polycotylidae
Palmulasaurinae
Occultonectia
Polycotylinae
Dolichorhynchia
Euelasmosaurida
Elasmosaurinae
Weddellonectia
Aristonectinae
Cryptoclidus eurymerus

Leptocleidus capensis

Elasmosaurus platyurus
Taxon identifiers
Edgarosaurus muddi