The Terminology of Amniote Temporal Vacuities

Attention is focussed upon the extensive variation in temporal vacuities of amniotes, applying terms to types exemplified in extant turtles, squamatans, birds and mammals. Turtles, long accepted as anapsid, exhibit varying degrees of temporal notching (keiroid), either posterior (opisthokeiroid) or inferior (pleurokeiroid), or both. The prefixes meio-, meso-, meta- and hyper- are used to designate appropriate degrees of notching. In squamatans, the divisions hemidiapsid (more specifically, infrahemidiapsid), anadiapsid and eudiapsid are designated. In birds the eudiapsid and suprahemidiapsid conditions are noted, and in mammals the eusynapsid and anasynapsid divisions of the synapsid condition.