Phylum: Mollusca Phylum: Mollusca Class: Gastropoda Common Name or members: snails, nudibranchs, sea hares and garden slugs Habitat: All habitats: marine, freshwater, terrestrial Periods of Existence: Cambrian to Recent Description: Most Gastropod shells, especially from the Paleozoic, are preserved as internal molds (steinkerns), external molds, or casts. The typical Gastropod shell is “trochospiral” or a spiraled cone shape with a solid spire running through the center, and a aperture or opening. One complete turn of the coil is called a whorl. Gastopod shells contain only a single spiraled chamber – the animal’s body coils up and fills the entire interior of the shell. Conus Cypraea Platyceras Fossils to ID 2016 - Set B.doc 1 of 8 12/4/2015 12:54:00 PM Turritella Worthenia Fossils to ID 2016 - Set B.doc 2 of 8 12/4/2015 12:54:00 PM Phylum: Echinodermata Description: ‘Spiny skinned’ (Greek) marine animals with 5 point radial (pentaradial) symmetry as adults. Echinoderms have an endoskeleton of calcite plates (ossicles), each of which is a single stereom crystal; a water vascular system used for gas exchange, feeding, sensory reception and locomotion; and ambulacral grooves with cilia and hydraulically driven tube feet to manipulate captured food down the grooves to the mouth. Phylum: Echinodermata Class: Asteroidea Common Name or members: sea stars, starfish Habitat: Marine Periods of Existence: Ordovician to Recent Description: Sea stars are radially symmetrical, with arms radiating out from the body center. Most species have five arms, however sun stars can have as many as 40 arms or more! Most sea stars are small usually measuring 12-24 cm across, but there are some species that can be very small or very large. Sea stars are active predators that move using thousands of tube feet controlled by the hydrostatic pressure of their water vascular system. Starfish Fossils to ID 2016 - Set B.doc 3 of 8 12/4/2015 12:54:00 PM Phylum: Echinodermata Class: Blastoidea Common Name or members: blastoids Habitat: Marine Periods of Existence: Silurian through Permian Description: Blastoids were small, stalked filter feeders that lived attached to the sea floor. Their heads, or “thecas”, were covered by regularly arranged calcite plates and are usually the only part of the creature preserved. When alive, blastoids had thin “arms” called brachioles that stood up erect and encircled the star-shaped mouth at the top of the theca to trap food particles and bring them to the mouth. Extending downward from the mouth were food grooves or ambulacra resembling five petals on the upper side of the theca. Blastoid (Class) Pentremites (Genus) Phylum: Echinodermata Class: Crinoidea Common Name or members: sea lillies Habitat: Marine Periods of Existence: Lower Ordovician to Recent Description: Crinoids were stalked filter feeders similar to Blastoids, but with longer, sturdier and more complex, branching arms. The ambulacral grooves extend onto the arms, which thus have tube feet along their inner surfaces. Most crinoid fossils are formed only from the stems of crinoids. These stems have been broken into discs, which are usually round but may be elliptical or five sided. The flat part of the disc is covered with radiating grooves and ridges that may extend from the hole to periphery or may cover only part of the surface. Some thick limestone beds dating to the mid- to late-Paleozoic are almost entirely made up of disarticulated crinoid fragments. Fossils to ID 2016 - Set B.doc 4 of 8 12/4/2015 12:54:00 PM Calyx and arms Stems ‘Columnals’ Stem Pieces ‘Columnals’ Fossils to ID 2016 - Set B.doc 5 of 8 12/4/2015 12:54:00 PM Phylum: Echinodermata Class: Echinoidea Common Name or members: sea urchins, heart urchins, sea biscuits, and sand dollars Habitat: Marine Periods of Existence: Ordovician to Recent Description: Echinoids are ‘regular’- globular (sea urchins) or ‘irregular’ - disc-shaped (heart urchins and sand dollars). Primitive echinoids display five-part symmetry and more recent ones show bilateral symmetry (heart urchins and sand dollars). The ‘test’ consists of small, thin, interlocking plates that are polygonal in shape arranged in ten narrow bands radiating from the top of the shell around to the mouth on the bottom. Five of the bands contain plates with holes or slits (ambulacra) from which the tube feet project. These may form a five-petalled flower pattern on top of the shell. Alternating bands contain plates without such holes. Sea urchins feed mainly on algae by grinding with a set of teeth or mouth plates that form a "Aristotle's lantern". Many sea urchins are completely covered with long moveable spines. Sand dollars are flattened, burrowing urchins covered with tiny, velvety spines covered with cilia. Sand dollars live buried in the sediment and eat mud and detritus. Sea urchin Heart urchin/sea biscuit Fossils to ID 2016 - Set B.doc 6 of 8 12/4/2015 12:54:00 PM Sand dollar Phylum: Echinodermata Class: Ophiuroidea Common Name or members: brittle stars (also serpent or snake stars) Habitat: Marine, benthic Periods of Existence: Ordovician to Recent Description: Ophiuroids are the most speciose group of echinoderms with over 2000 described species in two large clades: Ophiurida (brittle stars) and Euryalida (basket stars). They are easily distinguished from Asteroidea (sea stars) by having five arms arranged radially (pentaradial) around a central disk-shaped body that is clearly demarcated from their long, slender, flexible, whip-like arms. Ophiuroid arms are composed of spiny calcite plates – those of the subclade Basket stars (Euryalida) are highly forked and branched and even more flexible than those of Brittle stars. Their arms readily break off, but soon regrow thus earning them the nick name ‘brittle’ stars. They use this ability to escape predators, in a way similar to lizards, Brittle stars use their arms for rapid locomotion by snake-like or rowing movements, earning them a name (Ophiuroid) meaning “serpent” in Greek. They thrust the body forward in a series of rapid jerks - extending one arm forward, while the other four act as anchors and levers. Their tube feet are used only as sensory tentacles (light and odor), and do not have suction like sea stars. However, they tend to cling and attach themselves to the sea floor, sponges or corals. Ophiuroids are scavengers or detritivores but may also prey on small crustaceans or worms. They typically hide under rocks or in crevices during the day and emerge at night to feed. Their arms are used to rhythmically sweep food to the mouth and small organic particles are moved into the mouth by the tube feet. Fossils to ID 2016 - Set B.doc 7 of 8 12/4/2015 12:54:00 PM Brittle star or Serpent Star Fossils to ID 2016 - Set B.doc 8 of 8 12/4/2015 12:54:00 PM .