(Three tipped femur).
Named By: Cragin - 1888.
Synonyms: Ceraunosaurus brownorum, Dolichorhynchops kirki, Dolichorhynchops willistoni, Trinacromerum anonymum, Trinacromerum brownorum, Trinacromerum willistoni.
Classification: Chordata, Reptilia, Sauropterygia, Plesiosauria. Polycotylidae.
Species: T. bentonianum (type), T. kirki, T. lafquenianum.
Size: 3 meters long.
Known locations: Canada - Manitoba. USA - Colorado, Kansas, Texas and Utah.
Time period: Cenomanian to Turonian of the Cretaceous.
Fossil representation: Multiple individuals.
Although not as well-known as its more famous relative Dolichorhynchops, Trinacromerum remains one of the best represented polycotylid plesiosaurs in the fossil record. Like its relatives, Trinacromerum was a plesiosaur but one with a much shorter neck and elongated jaws filled with thin needle like teeth. Living in the Western Interior Seaway of the late Cretaceous, Trinacromerum was a predator of fish that used speed and manoeuvrability to capture its prey. In turn Trinacromerum would have likely been targeted by other predators with possible candidates including large pliosaurs such as Brachauchenius.
- A plesiosaur from the Upper Cretaceous of Manitoba. - Journal of Paleontology 9(5):385-389. - L. S. Russel - 1935.