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You are here:   OldClasses > 2012 > Cymodoce pelsarti | Amelia Armstrong






Fact Sheet



Physical Description


Life History & Behaviour

Anatomy & Physiology

Evolution & Systematics

Biogeographic Distribution

Conservation & Threats

References & Links

Evolution & Systematics

Cymodoce pelsarti is a member of the phylum Arthropoda. Within the Arthropods exists a class called Malacostraca. This class contains over half of the known species of crustaceans. In this class usually thoracic segments fuse to form a cephalothorax, and the first five pairs of abdominal appendages are biramous pleopods. Malacostraca is further separated into sub-orders, with the class Isopoda falling under Peracarida. The sub-order Peracarida has seven orders, containing over 12,000 species. The defining characteristic is the presence of a ventral marsupium (brood pouch), in which females develop their young. Members of Isopoda have had at least one abdominal segment undergo fusion with the telson, creating a pleotelson (Ruppert et al. 2004)
 (See figure in Physical Description). 

 Phylogeny adapted from Brandt and Poore (2003). The order Isopoda is a monophyletic group (Poore, 2005). The family Sphaeromatidae has 94 genera and 619 species, the most of any other within isopoda (Poore & Bruce, 2012). This group contains many distinct morphologies that will possibly generate the creation of new families (Poore & Bruce, 2012). There are very few phylogenetic studies below the level of superfamily and it therefore difficult to explain evolutionary relationships. Relationships between selected groups are detailed (left) in a phylogeny adapted from Brandt and Poore (2003).

There is a great deal of uncertainty surrounding isopods in the fossil record as modern classification does not allow many to be placed in extant families (Feldmann, 2009; Guitnot et al. 2005). However, there is a moderately strong fossil record for the Sphaeromatidea with a samples identified in France from the Jurassic. Although these records exist, due to the limitations imposed by modern taxomony, very little information on diversity and evolution can be gained (Poore & Bruce, 2012).