Produced by the Population Genetics and Evolution class, Furman University

The Devonian: Cladoselache
Cladoselache are one of the most well-known early sharks, and they resemble the modern mackerel shark (Martin 2003). They lived in the warmer waters over eastern North America (Miller 2000) and their fossils were first found in the Cleveland Shale. Many of the fossils that have been found are actually whole, and some even include remnants of internal organs (Coates 2010). These sharks grew to be about three feet long, and had several unique characteristics. They had weaker jaws than modern sharks; however the muscles used to close their jaws were very strong. Another interesting feature is that they had large forked tails, which probably aided them in swimming faster. This means that they were most likely preyed upon by larger fish, such as Dunkleosteus (Miller 2000). However, they were predators for other fish as well, as some smaller fish fossils have been found within the stomachs of these sharks (Coates 2010). Cladoselache, unlike most other sharks, were not covered in dermal denticles (Martin 2003). In fact, they are only known to have compound scales around their head and fins, which is a very odd characteristic for sharks. Perhaps even more unique, however, is the fact that Cladoselache do not appear to have claspers, which is a male internal reproductive structure. As a result, little is known to how they reproduced; but they clearly managed to reproduce somehow (Coates 2010)!

Page by Lindsay Gerzel
Cladoselache. Image from: Martin 2003.

Coates M. 2010. Cladoselache. AccessScience@McGraw-Hill. Accessed February 24, 2010

Martin RA.2003. Ancient Sharks: Cladoselache. Biology of Sharks and Rays. Accessed February 24, 2010.

Miller DW. 2000. Cladoselache. Discovery Education. Accessed February 24, 2010.