Dawsonoceras

Dawsonoceras is an extinct genus of nautiloid cephalopod belonging to the order Endocerida. These marine invertebrates lived during the Ordovician period, with fossils found in North America. The most distinctive feature of Dawsonoceras is its large, straight, and often robust shell, known as a conch. This conch was typically conical in shape, tapering to a point at the apex. Internally, the shell was divided by thin walls called septa, creating chambers. The animal lived in the largest, rearmost chamber. Like other endocerids, Dawsonoceras possessed a siphuncle, a tube that ran through the shell, allowing it to control its buoyancy by regulating the amount of fluid within the chambers. The exact diet and behavior of Dawsonoceras are not fully understood, but as cephalopods, they were likely active predators in their ancient marine environments. Fossil evidence suggests they were relatively common in certain shallow marine settings of the Ordovician. The genus was first described in the early 20th century.