Produced by the Population Genetics and Evolution class, Furman University

The Ordovician: Eurypterids and Megalograptus
Commonly known as sea scorpions, eurypterids are an extinct class of arthropods that are distantly related to modern day arachnids (Wikipedia 2010a). They include some of the largest arthropods to have ever lived, with the largest discovered at 2.5 meters long (Wikipedia 2010b). Eurypterids either crawled in shallow waters or swam using broad paddle-like structures. Earlier eurypterids swam in marine environments, while later eurypterids living lived in brackish and fresh water. Eurypterids were active predators or scavengers (Lamesdell 2009). Megalograptus, a subgenre of the eurypterids, were known to eat their own kind as well as giant orthocones and also other eurypterids (BBC 2010). Megalograptus is historically important because they were the first animals to ever move from water to land (BBC 2010). They also molted their exoskeletons to increase their size. During the molting process, Megalograptus gathered in shallow waters for protection and for an opportunity to mate (Lamesdell 2009). The closest livings relative to the eurypterids are horseshoe crabs.

Page by Julia Bobo
Eurypterid, artist interpretation. From:

Lamesdell J. 2009. Eurypterids. Accessed Feb 6, 2010.

BBC Science and Nature. 2010.Sea Scorpion. Date Accessed: Feb 6, 2010.

Wikipedia. 2010a. Eurypterids. Accessed Feb. 6, 2010.

Wikipedia. 2010b. Jaekelopterus rhenaniae. Accessed Feb. 6, 2010