Marrellomorpha
Sign in to saveMarrellomorpha are an extinct group of arthropods known from the Cambrian to the Early Devonian. It is divided into two major groups, Marrellida and Acercostraca. They lacked mineralised hard parts, so are only known from areas of exceptional preservation, limiting their fossil distribution. The best known member is Marrella, with thousands of specimens found in the Cambrian aged Burgess Shale of Canada.
Article
9 sectionsContents
- Description and ecology
- Taxonomy
- Internal taxonomy
- Gallery
- Relationship to other arthropods
- Phylogeny
- Internal phylogeny
- External phylogeny
- References
Marrellomorpha are an extinct group of arthropods known from the Cambrian to the Early Devonian. It is divided into two major groups, Marrellida and Acercostraca. They lacked mineralised hard parts, so are only known from areas of exceptional preservation, limiting their fossil distribution. The best known member is Marrella, with thousands of specimens found in the Cambrian aged Burgess Shale of Canada.
==Description and ecology== The group is divided up into two major orders, Marrellida and Acercostraca. Both groups have cuticles (exoskeletons) that are not mineralised, unbranched antennae attached to the head section (cephalon) and a segmented trunk (reaching over 25 segments in adult individuals in some species) with a pair of biramous (divided into two branches) appendages attached to each trunk segment except the last. Marrellida is recognised by the possession of head shields with two or three pairs of elongate spine-like projections, and two or three attached pairs of uniramous (single-branched) head appendages (including the antennae), while Acercostraca have large ovoid dorsal shields that cover the entire upper half of the body, and up to five pairs of appendages attached to the head section.