Produced by the Population Genetics and Evolution class, Furman University

The Silurian: Acanthodians
Acanthodians were the first jawed fish. They were small, with a shark-like appearance. They are characterized by having a large mouth and eyes, meaning that they probably preyed on smaller fish (Wilson 2010). Some acanthodians had small teeth in the lower jaw, but some had no teeth at all (Acanthodian Permian fossil from Germany). Another obvious feature of the Acanthodii is their dermal spines in front of all fins but the caudal fin (Janvier 1997). In fact, this feature is so distinguishing that the name Acanthodii is actually derived from the Greek word for spine (Virtual Fossil Museum 2010). Acanthodii also had growing scales that resembled an onion-like structure, as well as streamlined bodies which enabled them to be fast swimmers (Janvier 1997). These fish, although not the first vertebrate in history, are the earliest whole vertebrates to be represented in the fossil record (Wilson 2010). However, acanthodii are still being disputed over as to which phylum they belong to as they have characteristics of both bony and cartilaginous fish (Virtual Fossil Museum 2010). Currently, they are referred to as a sister group of Osteichthyes, but they could still be paraphyletic (Janvier 1997).

Page by Lindsay Gerzel
An Acanthodii fossil. From:The Virtual Fossil Museum

Janvier P. 1997. Gnathostomata: jawed vertebrates. The Tree of Life Web Project. Accessed on February 17, 2010.

Virtual Fossil Museum. 2010. Acanthodian Permian fossil from Germany. Fossil Museum Navigation. Accessed on February 17, 2010

Wilson, MVH. 2010. Acanthodii. AccessScience Encyclopedia at McGraw-Hill. Accessed on February 17, 2010.