Order Phacopida:

Suborder Calymenina


This suborder was identified by Swinnerton in 1915. The cephalon is semicircular to subtriangular usually with gonatoparian sutures. Genal spines can be well developed but are usually lacking. The galbella tapers anteriorally, with four or five pairs of lateral lobes which diminish in size forwards. The hypostoma is subrectangular. The eyes are small and holochroal. The thorax, narrowing slightly towards the posterior, contains 11-13 segments with rounded tips. The pygidium is semicircular or triangular. Diagram and photographs below highlight the main features of this suborder.

 

 

 

Suborder Calymenina 

Family Calymenidae

Subfamily Pharostomatinae

Genus Pharostoma

Species pulchrum

 Pharostoma pulchrum illustrating main features of this suborder

 

 
 

 Homalonotos sp. showing semicircular, smooth pygidium, no axial furrows present

Homalonotos sp. cephalon showing small holochroal eyes and forward tapering glabella

 

 

 Calymenes sp. side view showing small cephalon and small eyes

 Calymenes sp. top view showing posteriorally narrowing thorax and slight enrollment of the pygidium



Author: Sarah Vinnell
Last updated: 21/11/05
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Websites produced by students on the MSc Palaeobiology programme in the Department of Earth Sciences at the University of Bristol for academic year 2005-6