BSCI392
11-02-07
Calcichordates or Homalozoans?

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We shift to the last major bilaterian group - Deuterostomia.

An odd group of disparate taxa, yet strongly supported by morphological, developmental, and molecular synapomorphies. Includes vertebrates and echinoderms plus minor groups.

The major Deuterostome groups are Echinodermata, Chordata, and Hemichordata. The focus of this presentation is on a particularly enigmatic group of early echinoderms, but first, some preliminaries.

Hemichordata: Including acorn worms and pterobranchs (Remember graptilites? Ancient pterobranchs). Suspension feeders, however food capture is by means of ciliary action.

Ten years ago, the conventional wisdom was that the pharynx and gill slits were synapomorphies of hemichordates and chordates. Since then, several molecular analyses have strongly supported a sister-taxon relationship of hemichordates and echinoderms.

Potential morphological synapomorphies of hemichordates and echinoderms:

But now, Echinoderms....

Major groups

Crinoidea (sea lilies and feather stars) (Ordovician - Recent)