3.85" Fossil Mosasaur (Clidastes) Ischium Bone - Kansas

Fossil Mosasaur (Clidastes) Ischium Bone - Kansas #197614

This is a 3.85" long ischium bones from a Clidastes Mosasaur. It was collected from the Smoky Hill Chalk in Gove County, Kansas. The ischium is one third of the bones that comprise half of the pelvic girdle of this Mosasaur. Both halves are mirror images of each other and serve at the point of articulation for the rear limbs. The bone preservation is quite nice and exhibits minimal repair for a rarer type of bone.

Clidastes is an extinct aquatic lizard belonging to the mosasaur family. Clidastes was one of the smaller types of mosasaurs. Although some species were larger, the average length of this genus is only a few meters, or about 10 feet in length. This mosasaur was also slimmer than the others with a narrower ribcage, giving it a more sleek or eel-like look. It was probably very agile and able to chase down smaller prey.

Mosasaur size comparison

The Smoky Hill Chalk Member of the Niobrara Chalk formation is a Cretaceous conservation Lagerstätte, or fossil-rich geological formation, known primarily for its exceptionally well-preserved marine reptiles. It outcrops in parts of northwest Kansas--its most famous localities for fossils--and in southeastern Nebraska. Large, well-known fossils excavated from the Smoky Hill Chalk include marine reptiles such as plesiosaurs, large bony fish such as Xiphactinus, mosasaurs, pterosaurs, and turtles.

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