GEOL 331 Principles of Paleontology

Fall Semester 2008
Echinodermata

Echinodermata: After molluscs and arthropods, the most commonly fossilized bilatrian taxon. Indeed, disarticulated echinoderm plates are major constituents of Phanerozoic carbonates, especially from the Mississippian. Deterostomes - thus closely related to hemichordates and chordates. Potential synapomorphies of Echinoderms and Chordates:

Echinoderm characteristics:

Traditionally all stemmed echinoderms were lumped into "Pelmatozoa", and all non-stemmed to "Eleutherozoa". A more cladistic phylogeny of Echinodermata:

Helicoplacoidea (Early Cam.)

Edrioasteroid: (Cam. - Penn)

"Eocrinoids": (Cam - Sil.)

Blastozoa

Homolazoa: (Cam. Ord.)

Echino-uglies. A problematic group of Early Paleozoic echinoderms. True apples of discord. Mono-, poly-, or paraphyletic, depending on whom you ask.

"Includes":

What we DO know

Crinoidea (sea lilies and feather stars) (Ord. - Rec.): Finally, a group with living representatives.

Echinoderm origins: Who are the closest relatives or ancestors of echinoderms? Hard to say for fossils that lack echinoderm like calcitic skeletal elements. Some possibilities:

Your call.

To Syllabus.

Last modified: 22 August 2008