An echinoderm is any animal of the phylum Echinodermata, which includes starfish, brittle stars, sea urchins, sand dollars and sea cucumbers, as well as the sessile sea lilies or "stone lilies". While bilaterally symmetrical as larvae, as adults echinoderms are recognisable by their usually five-pointed radial symmetry, and are found on the sea bed at every ocean depth from the intertidal zone to the abyssal zone. The phylum contains about 7,600 living species, making it the second-largest group of deuterostomes after the chordates, as well as the largest marine-only phylum. The first definitive echinoderms appeared near the start of the Cambrian.
Crinoids are marine invertebrates that make up the class Crinoidea. Crinoids that remain attached to the sea floor by a stalk in their adult form are commonly called sea lilies, while the unstalked forms, called feather stars or comatulids, are members of the largest crinoid order, Comatulida. Crinoids are echinoderms in the phylum Echinodermata, which also includes the starfish, brittle stars, sea urchins and sea cucumbers. They live in both shallow water and in depths of over 9,000 metres (30,000 ft).
Blastoids are an extinct type of stemmed echinoderm, often referred to as sea buds. They first appear, along with many other echinoderm classes, in the Ordovician period, and reached their greatest diversity in the Mississippian subperiod of the Carboniferous period. However, blastoids may have originated in the Cambrian. Blastoids persisted until their extinction at the end of Permian, about 250 million years ago. Although never as diverse as their contemporary relatives, the crinoids, blastoids are common fossils, especially in many Mississippian-age rocks.
Gogia is a genus of primitive eocrinoid blastozoan from the early to middle Cambrian.
Edrioasteroidea is an extinct class of echinoderms. The living animal would have resembled a pentamerously symmetrical disc or cushion. They were obligate encrusters and attached themselves to inorganic or biologic hard substrates. A 507 million years old species, Totiglobus spencensis, is actually the first known echinoderm adapted to live on a hard surface after the soft microbial mats that covered the seafloor were destroyed in the Cambrian substrate revolution.
The stylophorans are an extinct, possibly polyphyletic group allied to the Paleozoic Era echinoderms, comprising the prehistoric cornutes and mitrates. It is synonymous with the subphylum Calcichordata. Their unusual appearances have led to a variety of very different reconstructions of their anatomy, how they lived, and their relationships to other organisms.
Crinozoa is a subphylum of mostly sessile echinoderms, of which the crinoids, or sea lilies and feather stars, are the only extant members. Crinozoans have an extremely extensive fossil history.
The taxonomy of commonly fossilized invertebrates combines both traditional and modern paleozoological terminology. This article compiles various invertebrate taxa in the fossil record, ranging from protists to arthropods. This includes groups that are significant in paleontological contexts, abundant in the fossil record, or have a high proportion of extinct species. Special notations are explained below:
Eleutherozoa is a subphylum of echinoderms. They are mobile animals with the mouth directed towards the substrate. They usually have a madreporite, tube feet, and moveable spines of some sort. It includes all living echinoderms except for crinoids. The monophyly of Eleutherozoa has been proven sufficiently well to be considered "uncontroversial."
Pentacrinites is an extinct genus of crinoids that lived from the Hettangian to the Bathonian of Asia, Europe, North America, and New Zealand. Their stems are pentagonal to star-shaped in cross-section and are the most commonly preserved parts. Pentacrinites are commonly found in the Pentacrinites Bed of the Early Jurassic of Lyme Regis, Dorset, England. Pentacrinites can be recognized by the extensions all around the stem, which are long, unbranching, and of increasing length further down, the very small cup and 5 long freely branching arms.
Paracrinoidea is an extinct class of blastozoan echinoderms. They lived in shallow seas during the Early Ordovician through the Early Silurian. While blastozoans are usually characterized by types of respiratory structures present, it is not clear what types of respiratory structures paracrinoids likely had. Despite the taxon's name, the paracrinoids are not closely related to crinoids.
Camptostroma roddyi is an extinct echinoderm from the Bonnia-Olenellus Zone of the Early Cambrian Kinzers Formation near York and Lancaster, Southeastern Pennsylvania. It is the only known species in the genus Camptostroma, as other species referred to this genus "do not appear to be cogeneric."
Homalozoa is an obsolete extinct subphylum of Paleozoic era echinoderms, prehistoric marine invertebrates. They are also referred to as carpoids.
Pelmatozoa was once a clade of Phylum Echinodermata. It included stalked and sedentary echinoderms. The main class of Pelmatozoa were the Crinoidea which includes sea lily and feather star.
Fossils of many types of water-dwelling animals from the Devonian period are found in deposits in the U.S. state of Michigan. Among the more commonly occurring specimens are bryozoans, corals, crinoids, and brachiopods. Also found, but not so commonly, are armored fish called placoderms, snails, sharks, stromatolites, trilobites and blastoids.
Cincta is an extinct class of echinoderms that lived only in the Middle Cambrian epoch. Homostelea is a junior synonym. The classification of cinctans is controversial, but they are probably part of the echinoderm stem group.
Diploporita is an extinct group of blastozoans that ranged from the Ordovician to the Devonian. These echinoderms are identified by a specialized respiratory structure, called diplopores. Diplopores are a double pore system that sit within a depression on a single thecal (body) plate; each plate can contain numerous diplopore pairs.
Paleontology or palaeontology is the study of prehistoric life forms on Earth through the examination of plant and animal fossils. This includes the study of body fossils, tracks (ichnites), burrows, cast-off parts, fossilised feces (coprolites), palynomorphs and chemical residues. Because humans have encountered fossils for millennia, paleontology has a long history both before and after becoming formalized as a science. This article records significant discoveries and events related to paleontology that occurred or were published in the year 2018.
Vetulocystidae is the only family of the taxon Vetulocystida, which is a group of extinct deuterostomes of uncertain phylogenetic position. Vetulocystidae is made up of the genera Vetulocystis, Dianchicystis and Thylacocercus.
