Download Bell Pettigrew Museum of Natural History - synergy

Bell Pettigrew Museum
of Natural History
Interpretative Panels
Text: Dr Iain Matthews
Design: Steve Smart & Cavan Convery
A University of St Andrews Development Fund Project
School of Biology
http://biology.st-andrews.ac.uk
15:1 Echinodermata
P hy l u m
Body Plan:
• Bilaterally symmetrical, but
appearing 5 rayed
• Triploblastic
• Spacious coelomic cavity in three
parts, and through gut
• Deuterostome
• Mineral endoskelton with the
mesoderm
• Complex water vascular system
Echinodermata
S u b p hy l u m
Super class
Class
The echinoderms are united in having adults with a unique
five-rayed (pentamerous) symmetry. Internally, and in their
larvae, they show a bilateral ancestry with evidence of a tripartite
coelomic body plan. The calcareous endoskeleton is formed
from ossicles in the mesoderm, often covered with spines and
other protuberances which project through the skin.
Gut
Endoderm
Body Cavity
Mesoderm
Ectoderm
Class: Concentricycloidea
Concentricycloidea is the smallest and most recently discovered
of the classes of echinoderm. The sea daises are small (<1 cm),
disc-shaped echinoderms with podia only around the edges.
Only two species, both from deep water (> 1000 m) have so
far been found.
Another unique echinoderm system, the water vascular system,
operates a series of individual tube feet or podia, especially
for locomotion. There is no true blood vascular or excretory
system, and a very simple radially organised nervous system.
Class: Holothuroidea
Holothuroidea contains 1150 species of sea-cucumbers. They
lack arms, and their elongated, worm-like body lies on its side.
The body wall is leathery, with the endoskeleton reduced to
A morphologically diverse phylum, the 6750 extant species, spicules.
which are all marine and virtually all benthic, are contained Class: Asteroidea
in six classes:
The 1500 species of asteroid, which includes the starfish and
seastars , have flattened bodies with five or more stout arms.
Class: Crinoidea
Crinoidea contains around 625 extant species of sea lilies and Most species are scavengers or predators with a downward
feather stars (e.g. Antedon ). They are usually stalked and pointing mouth and an anus on the upper surface.
attached to the substrate with an upward pointing mouth Classification
within
and a U–shaped gut. Their arms branch repeatedly, forming
Echinodermata
a filter feeding basket covered with podia and cilia.
Class: Echinoidea
The 950 species of echinoid, including the sea urchins , and
sand dollars , are spherical, possessing large body cavities
but lacking arms. Their ossciles are fused into a rigid skeleton,
called a test. Echinoids, most of which are benthic detritivores,
have a downward pointing mouth, complex jaws (Aristotle’s
lantern), and an anus on the upper surface.
Class: Ophiuroidea
The 2000 species of ophiuroid, which includes the brittlestars
and basketstars, are superficially similar to the asteroids.
However their five arms are clearly demarcated from the central
disc-shaped body. Most species are scavengers having a
downward pointing mouth, but lacking an anus.
Class: Echinoidea
Order: Cidaroida
Order: Echinothuroida
Order: Diadematoida
Order: Pedinoida
Order: Salenoida
Order: Phymosomatoida
Order: Arbacioida
Order: Temnopleuroida
Order: Echinoida
Order: Holectypoida
Order: Clypeasteroida
Order: Cassiduloida
Order: Spantangoida
Order: Neolampadoida
Order: Holasteroida
Class: Holothuroidea
Order: Dendrochirotida
Order: Dactylochirotida
Order: Aspidochirotida
Order: Elasipoda
Order: Apodida
Order: Molpadiida
Class: Crinoidea
Order: Isocrinida
Order: Comatulida
Order: Millericrinida
Order: Bourgueticrinida
Order: Cyrtocrinida
Class: Asteroidea
Order: Brisingida
Order: Forcipulatida
Order: Valvatida
Order: Notomyotida
Order: Paxillosida
Order: Velatida
Order: Spinulosida
Class: Ophiuroidea
Order: Oegophiurida
Order: Phrynophiurida
Order: Ophiurida
Class: Concentricycloidea
Order: Peripodida
See specimen.
Brittlestars, sea urchins and sea cucumbers
The phylum Echinodermata contains animals with an amazingly
wide variety of shapes. It includes the starfish and brittlestars
, the sea lilies , urchins
and the sea-cucumbers .
The echinoderms get their name from the Latin for
‘hedgehog skin’.
The crinoids, or sea lilies, now make up only a small part of
the phylum. However they are extremely abundant in the fossil
record .