The Ordovician caryocaridid phyllocarids (Crustacea): diversity and evolutionary tendencies

摘要

An overall look at the Ordovician phyllocarid representatives assigned to the Family Caryocarididae led to the recognition of an unexpected biodiversity during the Tremadocian –Hirnantian time interval. Three new genera are described: Jellicaris n.g. from Australia, Saltericaris n. g. from Bohemia, and Soomicaris n. g. from South Africa, which add to the three previously described taxa, namely Caryocaris, Janviericaris, and Ivocaris; hence the Family Caryocarididae now includes six genera. The stratigraphical range of these genera, with respect to the graptolite zonation, displays that morphological characters vary accordingly, which is considered to reflect evolutionary tendencies which are exposed and discussed herein. Hypothetical phyletic relationships between caryocaridid genera are briefly discussed and are suggestive of two parallel lineages within the Family Caryopcarididae.