Leptocleidus

Genus:

Leptocleidus

Genus author:

Andrews, 1922b

Classification:

Age:

Valanginian to Barremian (Lower Cretaceous)

Location:

Global distribution: England; South Africa, Australia.

Referred material (sp.):

To compile

Type species:

L. superstes

Species:

L. superstes

Species author:

Andrews, 1922

Type specimen:

NHMUK R4828, skull and partial skeleton

Age:

Barremian, Lower Cretaceous

Geological formation:

Weald Clay Formation

Type location:

Berwick, East Sussex, England

Referred material:

To compile

Species:

L. capensis

Species author:

(Andrews, 1911)

Type specimen:

SAM-K5822, a complete skull and partial lower jaw

Age:

Uppermost Valanginian, Early Cretaceous

Geological formation:

Sundays River Formation

Type location:

Picnic Bush site overlooking Redhouse Farm, Swartkops River Valley, Cape Province, South Africa

Referred material:

None

Species:

L. clemai

Species author:

Cruickshank and Long, 1997

Type specimen:

WAM 92.8.1-1 to 68, a partial skeleton

Age:

Barremian, Early Cretaceous

Geological formation:

Birdrong Sandstone (top upper metre)

Type location:

Near Kalbarri, Carnarvon Basin, Western Australia

Referred material:

WAM 94.1.6-1 to 100, a partial skeleton less well preserved than the holotype

Lower Cretaceous plesiosaurs are rare, so Leptocleidus is important because it fills a gap in the fossil record of plesiosaurians. Leptocleidus was once considered to be a late surviving member of the family Rhomaleosauridae but it has recently been reidentified as a close relative of polycotylids. The fossils of all known species of Leptocleidus were preserved in inshore brackish or freshwater deposits. This led Cruickshank (1997) to speculate that the large pliosaurids that appeared during the Middle and Late Jurassic may have outcompeted the rhomaleosaurids in the open ocean and forced them to exploit near-shore niches instead.

The genus Leptocleidus and the type species L. superstes was established by Andrews (1922b) for a substantially complete specimen with a skull from the Weald Clay Formation of Sussex, England. There are presently two other valid species of Leptocleidus: L. capensis, and L. clemai. The genus ‘Peyerus’ was proposed for Leptocleidus capensis by Stromer (1935) but that name is now considered a junior synonym of Leptocleidus (Cruickshank 1997).