Produced by the Population Genetics and Evolution class, Furman University

The Silurian: Platyceras
Platyceras is an extinct genus of gastropod from the family Playceratidae that lived from the Ordovician to the Permian (Sutton et al. 2006). Its shell has a typical spiral form of helical spires but is extremely flattened (Silurian Software 2009). The fossils of Platyceras are usually found alongside the fossils of crinoids or cystoids (Bowsher 1955). Currently, they are believed to be sedentary mollusks that attached to near the anus of crinoids and fed on the excreted waste. The waste of modern crinoids is highly nutritious, containing microorganisms and algae (Sutton et al. 2006). Platyceras became highly specialized, gaining more pronounced morphological adaptations to aid them in attaching to their hosts (Bowsher 1955). Classification of gastropods, including Platyceras, can be difficult because usually only the shell is fossilized (Silurian Software 2009). The main schools of thought are that they are related to true limpets (Sutton et al. 2006). Another source of controversy is whether the relationship between the crinoids and Platyceras is commensal or parasitic. There is a possibility that Platyceras were kleptoparasites, extracting partially digested pellets from the anus of the crinoids before they were extreted (Sutton et al. 2006).

Page by Laura Snyder
Platyceras. Photo credit: Ludlow Library and Museum Resource Centre, Shopshire, UK

Sutton MD, Briggs DEG, Siveter DJ, Sivieter DJ. 2006. Fossilized soft tissues in a Silurian Platyceratid gastropod. Proc Roy Soc., Biol Sci 273:1039-1044. Accessed Feb. 18, 2010.

Bowsher AL. 1955. Origin and adaptations of Platyceratid gastropods. UK Palenontological Contributions 1-11. Accessed Feb. 18, 2010

Silurian Software. 2009. Tilehurst, Reading {UK). Accessed Feb. 18, 2010.