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

• Introduction
• Characters/Anatomy
• Major Suborders
  • Suborder Phacopina
  • Suborder Cheiruina
• Fossil Record
• Modern Forms
• Geological Timescale
• Glossary
• Literature and web links

Author: Sarah Vinnell
Last updated: 21/11/05
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