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From Eldredge (1991)
The phylum Echinodermata consists
of several types of complex organisms which show a general
pentameral symmetry and have a well developed water vascular
system. Echinoderms are also characterized by their
mesodermal skeleton. Echinoderms occur in a variety of
morphologies including free-living forms such as starfish
and sand dollars as well stalked forms such as sea lilies
which are attached to the sea floor. The first part of the lab will
concentrate on the stalked echinoderms also called
pelmatozoans. Pelmatozoans are exclusively marine and live
in a variety of habitats of normal salinity. They are all
filter-feeders. As a group, the pelmatozoans have been quite
abundant in the geologic past especially the Paleozoic, yet
since the close of the Mesozoic they have mainly relegated
to deep-water, cryptic environments. The second part of this lab will
concentrate on the very diverse non-stalked echinoderms
belonging to the subphyla Asterozoa and Echinozoa, and
collectively referred to as free-living echinoderms. Similar
to the pelmatozoans, the free-living echinoderms all have a
mesodermal skeleton comprised of calcite plates and a
complex water-vascular system including tube-feed. Unlike
the pelmatozoans, the groups of this lab are quite abundant
in the modern seas, occupying a large number environments by
an equally large number of life-habits. Because of their
abundance and diversity, the echinozoans will be the largest
part of the lab.
Phylum
Echinodermata (Precambrian
-Recent) Subphylum
Crinozoa (Cambrian-Recent) Class
Crinoidea (Cambrian-Recent) Subphylum
Blastozoa (Cambrian-Permian) Class
Blastoidea (Silurian-Permian) Class
Rhombifera (Ordovician-Devonian) Subphylum
Asterozoa (Ordovician-Recent) Class
Asteroidea (Ordovician - Recent) Class
Ophiuroidea (Ordovician - Recent) Subphylum
Echinozoa (Precambrian?,
Camb-Rec.) Class
Echinoidea (Ordovician - Recent) Class
Edioasteroidea
(Cambrian-Carboniferous)
PELMATOZOAN
GENERAL MORPHOLOGY In general, the pelmatozoan
skeleton can be dived into two main parts: The stem and the
calyx. The stalk or stem is composed of numerous disks
called columnals
which have a central hole called the lumen. 
Stems are often secured to the substrate by means of a
holdfast or root system. 
The calyx (sometimes called theca), a cup-like structure as
shown in these specimens, 
which may or may not support a variety of arms.
As outlined below, the calyx is usually composed of a number
of different kinds of plates, grooves, and pores; some of
which are quite specialized
Appendage
and Calyx Morphology Ambulacral groove: one of
the 5 radially arranged regions specialized for food
gathering. Brachial plates: arm plates;
several different types depending on position relative to
arm branch e.g., primibrachials and secundibrachials. See
these fossil specimens. Brachioles: small erect food
gathering appendages surrounding the edge of the ambulacrual
area in blastoids. Pinnules: small linear
hair-like branches that may occur on each arm plate and also
aid in food gathering. Basal plates: the circlet of
plates below and off-set to, and joining, the radial
plates. Infrabasal plates: secondary
plates below basals. Radial plates: below lowest
brachial and above basal plates where ray
terminates. Interray plates: plates that
are added between rays. Lancet: ambulacral plate of
blastoid, usually site of brachiole attachment. Deltoid: small triangular or
rhombahedral plate above the radial plates in
blastoids. Pores: openings for tube
feet. Tegmen: Part of calyx
occasionally with plates that resides above the attachment
points of arms. Sometimes elevated into a anal
pyramid. Ray: trace of plates from
arm through calyx; there are usually five (or multiples
thereof) rays in pelmatozoans; ray terminates with radial
plates (note the larger arrows in the figure
below).
Modified from McRoberts (1991)
