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.
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.
Mitrates are an extinct group of stem group echinoderms, which may be closely related to the hemichordates. Along with the cornutes, they form one half of the Stylophora.
Cystoidea was defined as a class of extinct paleozoic blastozoan echinoderms established to encompass stalked taxa that were neither crinoids nor blastoids. It was shown to be polyphyletic in the late 1960s but continues to be used even in recent literature to discuss both rhombiferans and diploporitans.
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.
The Eocrinidae are a family of early echinoderms that contain the genus Gogia.
The Fezouata Formation or Fezouata Shale is a geological formation in Morocco which dates to the Early Ordovician. It was deposited in a marine environment, and is known for its exceptionally preserved fossils, filling an important preservational window beyond the earlier and more common Cambrian Burgess shale-type deposits. The fauna of this geological unit is often described as the Fezouata biota, and the particular strata within the formation which exhibit exceptional preservation are generally termed the Fezouata Lagerstätte.
Dibrachicystis is an extinct genus of rhombiferan echinoderm from the early Middle Cambrian. It is a stalked echinoderm within the family Dibrachicystidae which lived in what is now northernmost Iberian Chains, northern Spain. It is known from the holotype MPZ2009/1230 and from the paratypes MPZ2011/2–6. It was found in the uppermost part of the Murero Formation at Purujosa, Moncayo Natural Park, dating to the Lower Languedocian and referred to the Solenopleuropsis thorali Zone. It was first named by Samuel Zamora and A. B. Smith in 2011 and the type species is Dibrachicystis purujoensis.
Stereom is a calcium carbonate material that makes up the internal skeletons found in all echinoderms, both living and fossilized forms. It is a sponge-like porous structure which, in a sea urchin may be 50% by volume living cells, and the rest being a matrix of calcite crystals. The size of openings in stereom varies in different species and in different places within the same organism. When an echinoderm becomes a fossil, microscopic examination is used to reveal the structure and such examination is often an important tool to classify the fossil as an echinoderm or related creature.
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.
Soluta is an extinct class of echinoderms that lived from the Middle Cambrian to the Early Devonian. The class is also known by its junior synonym Homoiostelea. Soluta is one of the four "carpoid" classes, alongside Ctenocystoidea, Cincta, and Stylophora, which made up the obsolete subphylum Homalozoa. Solutes were asymmetric animals with a stereom skeleton and two appendages, an arm extending anteriorly and a posterior appendage called a homoiostele.
Ctenocystoidea is an extinct clade of echinoderms, which lived during the Cambrian and Ordovician periods. Unlike other echinoderms, ctenocystoids had bilateral symmetry, or were only very slightly asymmetrical. They are believed to be one of the earliest-diverging branches of echinoderms, with their bilateral symmetry a trait shared with other deuterostomes. Ctenocystoids were once classified in the taxon Homalozoa, also known as Carpoidea, alongside cinctans, solutes, and stylophorans. Homalozoa is now recognized as a polyphyletic group of echinoderms without radial symmetry. Ctenocystoids were geographically widespread during the Middle Cambrian, with one species surviving into the Late Ordovician.
Yanjiahella biscarpa is an extinct species of Early Cambrian deuterostome which may represent the earliest stem group echinoderm.
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.
Lepidocystis is a Palaeozoic genus of imbricate lepidocystoid eocrinoid, closely related to Kinzercystis, It bore a stalk, with which it attached to firm substrates; and brachioles arising as lateral branches from its arms.
