Phylum Echinodermatastarfish, sea urchin, sea brittle, sea lilies, sea cucumber, sea feather

Phylum Echinodermata (Intro)Cambrian to RecentThe echinoderms (or "spiny skins") are a diverse group of completely marine animals (shallow to very deep marine). have a soft body encased in a hard rigid shell or exoskeleton, called a test.The body is made of individual plates (or ossicles). made up of numerous thin plates.Many echinoderms have spines covering their test (e.g. the sea urchin). there are some 6000 recent species, distributed among five classes.echinoderm appearance is with pentameral a 5 fold - radial symmetry.

have a complex and unique water-vascular (or ambulacral) system; a hydrostatic skeleton of internal water-filled canals.Ambulacral system is a food collecting and transporting device, in starfish and sea urchins used for movement and also be used to grip objects,Many early echinoderms were not pentameral at all, some types were able to crawl by nudging themselves along the sea floor with a sort of "tail".

General Morphology

Echinoderm skeletons are made up of interlocking calcium carbonate plates and spines. This skeleton is enclosed by the epidermis - endoskeleton.In sea urchins, the plates fit together tightly. In starfish, the plates are more loosely bound, In sea cucumbers the plates are usually microscopic.whatever their shape, the plates of echinoderms have a very typical microstructure: electron microscopy reveals just fine networks of calcium carbonate forming a structure known as stereom. each skeletal element of an echinoderm is actually a single crystal of calcium carbonate, very finely branched and structured. All echinoderms have a water-vascular system, a set of water-filled canals branching from a ring canal that encircles the gut.Echinoderms also have a spacious coelom (an open, fluid-filled body cavity)

Life History and Ecology

Cambrian-RecentAll echinoderms are marineAll have internal mesodermal skeletons of porous calcite plates and spiny. Pentameral symmetry (five ray skeleton)water vascular system, tube feet (podia) funtions as locomotion, respiration and feeding.With a few exceptions, echinoderms are all benthic (bottom-dwellers); most Paleozoic echinoderms were sessile, while most living echinoderms can creep from place to place. Few can swim or float.like many starfish are predators; holothurians, sand dollars, and ophiuroids often feed on detritus; crinoids are filter-feeders; sea urchins scrape algae from rocks. Starfish and sea urchins may be common in very shallow water, while the floor of the deep sea may swarm with ophiuroids or holothurians. Reproduction in echinoderms is typically by external fertilization; eggs and sperm are freely discharged into the water.Most echinoderms go through several planktonic larval stages before settling down.

Subphylum Blastozoa Class Eocrinoidea (Cambrian-Silurian),Class Parablastoidea (Ordovician),Class Rhombifera = Cystoidea in part (Ordo - Devon),Class Diploporita = Cystoidea in part (Ordo - Devo),Class Blastoidea (Silurian - Permian) Subphylum Homalozoa Class Stylophora (Camb. - Devon)Class Homoiostelea (Camb. - Devon) Class Homostelea (Cambrian)Class Ctenocystoidea (Cambrian) Subphylum Asterozoa (= Stelleroidea) Class Asteroidea - starfish - (E. Ordo-Rec.)Class Ophiuroidea - Brittle Stars -(Ordo- Recent) Subphylum Echinozoa Class Echinoidea (Sea Urchins) (Ordovician - Recent)Class Holothuroidea (Sea Cucumbers) (Ordovician - Recent)Class Edrioasteroidea (E.Camb-Carbon) Class Edrioblastoidea (Ordovician)Class Helicoplacoidea (Cambrian)Class Cyclocystoidea (Ordo - Devon) Subphylum Crinozoa Class Crinoidea - sea lilies (Cambrian? Early Ordovician Recent)Class Paracrinoidea (Ordovician - Silurian Phylum Echinodermata Classification

ClassificationClass BlastoideaClass EdrioasteroideaClass HelicoplacoideaClass HomalozoaClass HolothuroideaClass Echinoidea Class OphiuroideaClass CrinoideaClass Asteroidea

Class Blastoidea (Cambrian-Permian) Subphylum Blastozoaan extinct taxon of echinoderms. Originating in the Ordovician along with many other echinoderm classes, they reached their greatest diversity in the Mississippian, or early Carboniferous, and persisted until the end of Permian. blastoids are common fossils in many Mississippian-age rocks. Like crinoids, blastoids were high-level stalked suspension feeders, filtering food particles out of the water column.In life, the theca of a typical blastoid was attached to a stalk, or column, made up of stacked disc-shaped plates. other end of the column attached to the ocean floor -- very much like stalked crinoids Pentremites godoni, Mississippian (Carboniferous)

The mouth was located at the tip of the theca.Radiating from the center like flower petals were five food grooves, or ambulacra. In life, each ambulacrum had many long, thin, fine structures called brachioles, which were used to trap food particles and bring them to the mouth.Brachioles were delicate structures, and usually they are not preserved in place. The five holes surrounding the star-shaped mouth, are the anus (the largest hole of the five) and the entrances to a set of five complex folded respiratory organs known as the hydrospires.

(E.Camb-Carbon)five rays organism, like a starfish. It is in fact Isorophus, an extinct echinoderm. It is sessile - attached to a substrate by a short thick stalk covered with plates. Their ambulacra - the five radiating feeding grooves in the upper part of the organism, covered by large plates - grew in a curved, Ambulacra plates often spiral or nearly spiral pattern.

Class Edrioasteroidea Subphylum Echinozoa

Class Edrioasteroidea Subphylum Echinozoa Carneyella ulrichi (Ordovician)Agelacrinites pulaskensis Late Ordovician

Class Helicoplacoidea

Lower Cambrian group (the earliest echinoderms)shaped like a slender football or a fat cigar, Their "skin" was covered in spirals of overlapping ossicles that functioned like armor; their "mouth" was a long groove that also spiralled around their body. Not much is known and fossils are rare, and there are no living species. It is thought that helicoplacoids lived in burrows.

Helicoplacus gilbertiLate CambrianClass Helicoplacoidea

Class Homalozoa

Cambrian to the Late Ordovician radially symmetrical with five similar sections (as in sea-stars), the homalozoa were secondarily bilateral (as in sand dollars), or even asymmetical. Their body is flattened, with an arm-like aulacophore at one end. for feeding; or foot on which the animal stood (much like the stalk of crinoids); or suggested for swimming (much like primitive chordates).The current classification system recognizes two orders: Cornuta and Ankyroida

Rhenocystis latipedunculata Early DevonianClass Homalozoa

Class Holothuroidea

sea cucumber is an echinoderm. This holothurians are generally long and wormlike; they don't look much like starfish or sea lilies. However, retain pentameral (five-rayed) symmetry, with five rows of tube feet running from the mouth along the body (three are visible in the picture at the left; the other two are on the other side of the body). Holothurians are common in the oceans of today; in fact, in certain parts of the deep sea and in shallow-water habitats such as tidepools. The spicules of holothurians are found as fossils, but they have not received much study compared to other types of microfossils. Body fossils of whole holothurians are rare, eg Achistrum,

Achistrum sp.Achistrum sp.Middle PennsylvanianClass Holothuroidea

Class Echinoidea (Ordovocian - recent) Echinoid skeletons are almost always made up of tightly interlocking plates that form a rigid structure or test -- in contrast with the more flexible skeletal arrangements of starfish, brittle star and sea cucumber. Test shapes range from nearly globular, as in some sea urchins, to highly flattened, as in sand dollars. Living echinoids are covered with spines, which are movable and anchored in sockets in the test. These spines may be long and prominent, as in typical sea urchins. In sand dollars and heart urchins, however, the spines are very short. The mouth of most echinoids is provided with five hard teeth arranged in a circlet, forming an apparatus known as Aristotle's lantern. Echinoids are classified by the symmetry of the test, the number and arrangement of plate rows making up the test, and the number and arrangement of respiratory pore rows called petals.

Traditionally, echinoids have been divided into two subgroups: regular echinoids - with nearly perfect pentameral (five-rayed) symmetry. Regular echinoids include the Cidaroida (pencil urchins) and Echinoida (sea urchins). irregular echinoids - with bilateral symmetry. The Clypeasteroida (sand dollars and sea biscuits), the Spatangoida (heart urchins), and the Cassiduloida make up the irregular echinoids.Based on arrangements of ambulacral and interambulacral plates echinoidea can be classified into two subclasses:Subclass Perischoechinoidea (Ordovician - recent) - regular echinoid with two or more columns of ambulacral and interambulacral plates, weak lantern and sometimes large calcitic spines.Order Cidaroida - e.g. Cidaris. Subclass Euechinoidea (Triassic - recent) - regular or irregular echinoid with only two columns of ambulacral and interambulacral plates, different types of lantern.Order Echinoida - two regular and two irregular super-families.

(Eocene Epoch) sea biscuit Eupatagus ocalanus (Pliocene Epoch) sand dollar Millitella californicus(Lower Miocene) sea urchin, Tripnuestes parkinson

Class Ophiuroidea

Ophiuroids are a large group (over 1600 species) of echinoderms that includes the brittle stars (Ophiurida) and basket stars (Euryalida). The more familiar Ophiurida, or brittle stars, usually have five arms and superficially resemble true starfish (Asteroidea). brittle stars have long, flexible arms, other common name for ophiuroids, "snake stars" The body and arms are also protected by calcium carbonate plates, and the arms generally bear delicate spines.Basket stars (Euryalida) have a similar structure to brittle stars, their arms are very highly forked and branched, Ophiuroids can be found in most parts of the world, from the Arctic and Antarctic to the tropics.Ophiuroids are common in many shallow-water marine habitats, and include a few species which can adapt to brackish water, which is quite unusual for echinoderms. Most ophiuroids are scavengers and detritus feeders, although they also prey on small live animals such as small crustaceans and worms.

Ophiopetra sp. Brittlestar (Jurassic)(Jurassic )Starfish Bed Palaeocoma egertoni

Class Asteroidea

classified in the Asteroidea, Most starfish are predators, feeding on sessile or slow-moving prey such as mollusks and barnacles.The aptly named crown-of-thorns starfish, specializes on corals, and may do considerable damage to coral reefs.

Compsaster formosus (Carboniferous)Astropecten matilijaensis Upper EoceneHudsonaster sp. Ordovician

Class Crinoidea Sea lilies and feather they dominated the Paleozoic fossil record of echinoderms and shallow marine habitats until the Permo-Triassic extinction, Stalked crinoids, or "sea lilies", lived attached to the bottom, and filtered food particles from the currents flowing past them. The living stalked crinoids mostly inhabit deep water and are therefore difficult for the average underwater enthusiast to observe.

Agaricocrinus americanus, (Carboniferous)Pentacrinites fossilis (Jurassic)

Class Eocrinoidea

Eocrinoids are among the earliest groups of echinoderms to appear, ranging from the Early Cambrian to the Silurian. Most eocrinoids were sessile and fed with their long brachioles (the arm-like structures, which in this specimen are spirally twisted). The body was covered by plates; in early eocrinoids the holdfast was also covered by plates, but later eocrinoids evolved a stalk with columnals, like crinoids and blastoids.