Kingdom Animalia Superorder Phacopina Family Phacopidae Rank Genus | Class Trilobita Superfamily Phacopoidea Phylum Arthropoda Order Phacopida | |
Similar Phacopida, Phacopidae, Ductina, Chotecops, Phacops |
Trimerocephalus is a genus of eyeless trilobites from the order Phacopida, family Phacopidae. It lived during the final stage of the Devonian, the Famennian, and became extinct at the end of this stage, together with all other trilobites with the exception of some Proetida. It can be found in Australia, the Czech Republic, France, Germany, Iran, Kazakhstan, Morocco, Poland, the Russian Federation (Urals), Spain, and the United Kingdom (England).
Contents
Distribution
Species belonging to the genus Trimerocephalus have been found in Europe, Morocco, Iran and Australia.
Taxonomy
Acuticryphops is probably ancestral to Trimerocephalus, and mainly differs from its descendants in having an eye lobe with a small number of lenses. Crônier, 2003, erected the subgenus Trimerocephalus (Trifoliops) containing T. trifolius and T. nigritus. In order not to be polyphyletic, T. (Trifoliops) would need to include at least T. steinachensis, and preferably T. dianopsoides as well. These species are in the same clade as T. mastophtalmus however, which is the type of the genus Trimerocephalus, which would by definition be in the nominal subgenus Trimerocephalus (Trimerocephalus). This in turn would prompt the erection of an other subgenus with all remaining species shown in the cladogram.
Description
Trimerocephalus is one of several phacopid genera that is eyeless (others being Dianops, Ductina, and Trimerocephaloides). The dorsal facial sutures are not functional, so cranidia and free cheeks (or librigenae) are not found separated. The marginal ridge bordering the cheeks is wide and convex. The part of the margin that is tucked-under (or doublure) and only visible when viewing the cephalon from the belly (or ventral side), is short and flat. The vincular furrow, a groove that fits the margin of the tailpiece or pygidium when the animal was enrolled, is wide and deep. The pygidium is about 3 times wider than long.