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]

Trinacromerum
Temporal range: Late Cretaceous
A cast specimen of Trinacromerum kirki at the Royal Ontario Museum
Scientific classification
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

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."[2] Its name means "three tipped femur".

Classification
Profile view of a cast of a Manitoban specimen of Trinacromerum kirki
Trinacromerum bentonianum from the Late Cretaceous of Kansas

Below is a cladogram of polycotylid relationships from Ketchum & Benson, 2011.[3]

Plesiosauroidea 
 

Cryptoclididae

 
 Leptocleidia 
 

Leptocleididae

 
 Polycotylidae 
 

Edgarosaurus

 
 
 
 

Plesiopleurodon

 
 

QM F18041

 
 
 
 
 

Eopolycotylus

 
 

Polycotylus

 
 

Thililua

 
 
 
 

Trinacromerum

 
 
 

Manemergus

 
 
 

Dolichorhynchops herschelensis

 
 
 

Dolichorhynchops

 
 

Palmulasaurus

 
 
 
 
 
 
 
 
 
 

See also

References
  1. Ellis, Richard (2003). Sea Dragons: Predators of the Prehistoric Oceans. University Press of Kansas. p. 189. ISBN 0-7006-1269-6.
  2. Ellis, 190
  3. Hilary F. Ketchum and 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. doi:10.1111/j.1475-4983.2011.01083.x.CS1 maint: uses authors parameter (link)


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