Trinacromerum

Trinacromerum is an extinct genus of sauropterygian reptile, a member of the polycotylid plesiosaurs. It contains two species, T. bentonianum and T. kirki. Specimens have been discovered in the Late Cretaceous fossil deposits of what is now modern Kansas and Manitoba.^[1] Some fossils are also found in the Southern United States such as in the Mooreville Chalk of Alabama.^[2]

Trinacromerum Temporal range: Late Cretaceous
Mounted T. kirki cast at the Royal Ontario Museum
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Superorder:	†Sauropterygia
Order:	†Plesiosauria
Superfamily:	†Plesiosauroidea
Family:	†Polycotylidae
Genus:	†Trinacromerum Cragin, 1888
Species
†T. bentonianum Cragin, 1888 (type) †T. kirki Russell, 1935

Description

Trinacromerum with a human to scale

Trinacromerum was 3 meters (9.8 feet) long. Its teeth show that it fed on small fish.^[1]

The long flippers of Trinacromerum enabled it to achieve high swimming speeds.^[1] Its physical appearance was described by Richard Ellis as akin to a "four-flippered penguin."^[3] Its name means "three tipped femur".

Classification

T. bentonianum life restoration

Below is a cladogram of polycotylid relationships from Ketchum & Benson, 2011.^[4]

Plesiosauroidea	Cryptoclididae Leptocleidia Leptocleididae Polycotylidae Edgarosaurus Plesiopleurodon QM F18041 Eopolycotylus Polycotylus Thililua Trinacromerum Manemergus Dolichorhynchops herschelensis Dolichorhynchops Palmulasaurus

See also

• paleontology portal

• List of plesiosaur genera
• Timeline of plesiosaur research