Trinacromerum

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

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]

Description

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

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

Leptocleidia

Polycotylidae

	Plesiopleurodon

	QM F18041

	Eopolycotylus

	Polycotylus

	Thililua

Trinacromerum

Manemergus

Dolichorhynchops herschelensis

	Dolichorhynchops

	Palmulasaurus

References

^ ^a ^b ^c Ellis, Richard (2003). Sea Dragons: Predators of the Prehistoric Oceans. University Press of Kansas. p. 189. ISBN 0-7006-1269-6.
^ Kiernan, Caitlin R. (2002-03-14). "Stratigraphic distribution and habitat segregation of mosasaurs in the Upper Cretaceous of western and central Alabama, with an historical review of alabama mosasaur discoveries". Journal of Vertebrate Paleontology. 22 (1): 91–103. doi:10.1671/0272-4634(2002)022[0091:SDAHSO]2.0.CO;2. ISSN 0272-4634.
^ Ellis, 190
^ Hilary F. Ketchum; Roger B. J. Benson (2011). "A new pliosaurid (Sauropterygia, Plesiosauria) from the Oxford Clay Formation (Middle Jurassic, Callovian) of England: evidence for a gracile, longirostrine grade of Early-Middle Jurassic pliosaurids". Special Papers in Palaeontology. 86: 109–129.