5" Fossil Mosasaur (Tylosaurus) Premaxillary - Kansas

Fossil Mosasaur (Tylosaurus) Premaxillary - Kansas #197479

This is a beautifully preserved 5" long mosasaur (Tylosaurus) premaxillary bone from Gove County, Kansas. It comes from the Cretaceous age Smoky Hill Chalk - Niobrara Formation, making it approximately 82-87 million years old. It features exceptional bone preservation and exposed foramen at the distal end. The ventral side of the premaxillary contains an unerupted tooth and multiple empty tooth sockets.

There is no gap fill restoration to this fossil, though there is a repaired crack and some natural fracturing which is visible across the superior side of the specimen.

Along with plesiosaurs, sharks, fish, and other genera of mosasaurs, Tylosaurus was a primary predator of the Western Interior Seaway during the Late Cretaceous. Among the largest of all the mosasaurs, Tylosaurus reached a maximum lengths of 14 meters (46 feet). A distinguishing characteristic is its elongated, cylindrical premaxilla (snout) from which it takes its name, and which may have been used to ram and stun prey and also for intraspecific combat. Tylosaurus was designated as one of two official Kansas state fossils in 2014.

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.