Named By: M. J. Polcyn & G. L. Bell Jr - 2005.
Classification: Chordata, Reptilia, Squamata, Mosasauridae, Russellosaurinae.
Species: R. coheni (type).
Known locations: USA, Texas - Arcadia Park Shale and Kamp Ranch Limestone.
Time period: Turonian of the Cretaceous.
Fossil representation: Skull as well as additional fragmentary remains.
represents a primitive mosasaur, marine reptiles that would go on to
achieve a variety of sizes and specialisations that would see them
becoming the dominant predators of the late Cretaceous seas.
Russelosaurus itself displays a number of features
diagnostic of more than one mosasaur group, something that suggests
that these traits were developed and lost according to the predatory
niche that a specific group or genera became accustomed too. As for
Russellosaurus it was probably a more generalist
carnivore that preyed
upon fish and other smaller marine vertebrates.
Russellosaurus is considered to be related to Yaguarasaurus and Tethysaurus, both primitive mosasaurs in their own rights that are known from deposits in South America and Africa respectively. This shows that while early mosasaurs where more primitive in form, they were still well enough adapted to marine life to spread out across the ocean. None of these mosasaurs are considered to be the earliest however, as in 2005 Polcyn and Bell also named another even more primitive form called Dallasaurus.