Paraceratodus

Paraceratodus is a genus of ancient jawless fishes that lived during the Ordovician period, approximately 450-420 million years ago. Fossils of Paraceratodus have been found in Europe and North America, with the most significant discoveries made in Belgium and Canada.

Paraceratodus is a member of the Anaspida clade, a group of extinct, jawless fishes that were characterized by their branchial styles and lack of paired fins. These ancient creatures were likely small in size, ranging from a few inches to about a foot in length. The specimens found so far suggest that Paraceratodus had a broad, flat skull and a long, slender or anguilliform body.

The name Paraceratodus was given to this genus by a French paleontologist, in 1970. The name is derived from two Greek words - "para" meaning alongside or beside, and "keras" meaning horn, referring to the horn-like shape of the nasal capsule in some specimens. Other notable characteristics include the presence of several suspensorial hyobranchial arches and the absence of paired fins.

The Paraceratodus fossils are significant because they provide clues about the evolution of early vertebrates. They share some characteristics with modern fish such as hagfish, while others are distinct and offer insights into the complexities of primitive fish architecture.