Aulacopleura
Encyclopedia
Aulacopleura, also known as Arethusa, Arethusina, and Paraaulacopleura, is a genus
of trilobite
that lived during the Silurian
. The cephalon is semicircular or semielliptical, with border and preglabellar field. The glabella is short with variable eyes variable, with or without defined eye ridges, genal spines present; hypostome natant (primitive condition); exoskeleton pitted, or with small tubercles. The thorax has between 11 and 22 segments and pleural ends usually rounded. The pygidium can be small (micropygous), with even margin (Aulacopleuridae), or longer with spines (some Brachymetopidae).
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of trilobite
Trilobite
Trilobites are a well-known fossil group of extinct marine arthropods that form the class Trilobita. The first appearance of trilobites in the fossil record defines the base of the Atdabanian stage of the Early Cambrian period , and they flourished throughout the lower Paleozoic era before...
that lived during the Silurian
Silurian
The Silurian is a geologic period and system that extends from the end of the Ordovician Period, about 443.7 ± 1.5 Mya , to the beginning of the Devonian Period, about 416.0 ± 2.8 Mya . As with other geologic periods, the rock beds that define the period's start and end are well identified, but the...
. The cephalon is semicircular or semielliptical, with border and preglabellar field. The glabella is short with variable eyes variable, with or without defined eye ridges, genal spines present; hypostome natant (primitive condition); exoskeleton pitted, or with small tubercles. The thorax has between 11 and 22 segments and pleural ends usually rounded. The pygidium can be small (micropygous), with even margin (Aulacopleuridae), or longer with spines (some Brachymetopidae).