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Chasmataspidida
Chasmataspidids, sometime referred to as chasmataspids, are a group of extinct chelicerate arthropods that form the order Chasmataspidida. Chasmataspidids are probably related to horseshoe crabs (Xiphosura) and/or sea scorpions (Eurypterida), while more recent studies suggest that they form a clade ( Dekatriata) with Eurypterida and Arachnida. Chasmataspidids are known sporadically in the fossil record through to the mid-Devonian, with possible evidence suggesting that they were also present during the late Cambrian. Chasmataspidids are most easily recognised by having an opisthosoma divided into a wide forepart (preabdomen) and a narrow hind part (postabdomen) each comprising 4 and 9 segments respectively. There is some debate about whether they form a natural (i.e. monophyletic) group. Distribution Chasmataspidids survived at least since Ordovician to mid-Devonian in age. As of 2019, most chasmataspidids (with a total of 9 species) are known from the Devonian strata, while the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dvulikiaspis
''Dvulikiaspis'' is a genus of chasmataspidid, a group of extinct aquatic arthropods. Fossils of the single and type species, ''D. menneri'', have been discovered in Deposition (geology), deposits of the Early Devonian Period (geology), period (Lochkovian Epoch (geology), epoch) in the Krasnoyarsk Krai, Siberia, Russia. The name of the genus is composed by the Russian language, Russian word wiktionary:двуликий, двуликий (''dvulikij''), meaning "two-faced", and the Ancient Greek word wiktionary:ἀσπίς, ἀσπίς (''aspis''), meaning "shield". The species name honors the discoverer of the holotype of ''Dvulikiaspis'', Vladimir Vasilyevich Menner. Its prosoma (head) was subquadrate (almost square) to parabolic (nearly U-shaped), with (bean-shaped) to subovate (nearly oval) Compound eye, eyes and surrounded by a marginal rim. The Abdomen#Other animals, abdomen was composed by a fused buckler and a postabdomen that occupied most of the body length, while the te ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chelicerate
The subphylum Chelicerata (from Neo-Latin, , ) constitutes one of the major subdivisions of the phylum Arthropoda. Chelicerates include the sea spiders, horseshoe crabs, and arachnids (including harvestmen, scorpions, spiders, solifuges, ticks, and mites, among many others), as well as a number of extinct lineages, such as the eurypterids (sea scorpions) and chasmataspidids. Chelicerata split from Mandibulata by the mid-Cambrian, as evidenced by stem-group chelicerates like Habeliida and '' Mollisonia'' present by this time. The surviving marine species include the four species of xiphosurans (horseshoe crabs), and possibly the 1,300 species of pycnogonids (sea spiders), if the latter are indeed chelicerates. On the other hand, there are over 77,000 well-identified species of air-breathing chelicerates, and there may be about 500,000 unidentified species. Like all arthropods, chelicerates have segmented bodies with jointed limbs, all covered in a cuticle ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chasmataspis
''Chasmataspis'' is a genus of chasmataspidid, a group of extinct aquatic chelicerate arthropods. It was found in the Early Ordovician deposits of Tennessee, United States. Morphology Just like other chasmataspidids, the body of ''Chasmataspis'' compose of a prosoma and a 13-segmented opisthosoma, with the latter subdivided into a 4-segmented preabdomen and a 9-segmented postabdomen. Dorsal to the carapace were pairs of ridges, lateral eyes and median ocelli. ''Chasmataspis'' characterized by a semicircular carapace (prosomal dorsal shield) with pointed genal spines and preabdomen with fused body segments. Rows of tubercles and spines run through the axial and lateral regions of opisthosoma. The body terminated with a spine-like telson. There is no body fossils of ''Chasmataspis'' with unambiguous appendages being discovered. The only evidence were 2 specimens of disarticulated, claw-bearing appendages discovered from the same stratum In geology and related fields, a stra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kiaeria Limuloides
''Kiaeria'' is a genus of chasmataspidid, a group of extinct aquatic arthropods. It was originally classified as a xiphosuran of the monotypic family Kiaeriidae. However, in 2019, the British geologist and paleobiologist James C. Lamsdell assigned the genus to the order Chasmataspidida, possibly being a member of the family Chasmataspididae. Only one species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ... has been assigned to this genus, ''K. limuloides''. References Prehistoric chelicerates Chasmataspidida {{Paleo-arthropod-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eurypterid
Eurypterids, often informally called sea scorpions, are a group of extinct marine arthropods that form the Order (biology), order Eurypterida. The earliest known eurypterids date to the Darriwilian stage of the Ordovician period, 467.3 Myr, million years ago. The group is likely to have appeared first either during the Early Ordovician or Late Cambrian period. With approximately 250 species, the Eurypterida is the most diverse Paleozoic Chelicerata, chelicerate order. Following their appearance during the Ordovician, eurypterids became major components of marine faunas during the Silurian, from which the majority of eurypterid species have been described. The Silurian genus ''Eurypterus'' accounts for more than 90% of all known eurypterid specimens. Though the group continued to diversify during the subsequent Devonian period, the eurypterids were heavily affected by the Late Devonian extinction event. They declined in numbers and diversity until becoming extinct during the Permi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eurypterida
Eurypterids, often informally called sea scorpions, are a group of extinct marine arthropods that form the order Eurypterida. The earliest known eurypterids date to the Darriwilian stage of the Ordovician period, 467.3 million years ago. The group is likely to have appeared first either during the Early Ordovician or Late Cambrian period. With approximately 250 species, the Eurypterida is the most diverse Paleozoic chelicerate order. Following their appearance during the Ordovician, eurypterids became major components of marine faunas during the Silurian, from which the majority of eurypterid species have been described. The Silurian genus ''Eurypterus'' accounts for more than 90% of all known eurypterid specimens. Though the group continued to diversify during the subsequent Devonian period, the eurypterids were heavily affected by the Late Devonian extinction event. They declined in numbers and diversity until becoming extinct during the Permian–Triassic extinction e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hoplitaspis
''Hoplitaspis'' is a genus of chasmataspidid, an extinct group of aquatic arthropods. Fossils of ''Hoplitaspis'' have been discovered in Late Ordovician deposits of the Lagerstätte of the Big Hill Formation exposed at Stonington Peninsular in Michigan's Upper Peninsula, United States. Its generic name is derived from the hoplites (Ancient Greek citizen-soldiers) and the Ancient Greek word άσπίς (''aspis'', meaning "shield"). The specific name ''hiawathai'' honors Hiawatha, a Native American leader and co-founder of the Iroquois Confederacy The Iroquois ( ), also known as the Five Nations, and later as the Six Nations from 1722 onwards; alternatively referred to by the Endonym and exonym, endonym Haudenosaunee ( ; ) are an Iroquoian languages, Iroquoian-speaking Confederation#Ind .... References Diploaspididae Late Ordovician first appearances Ordovician chasmataspidids Chasmataspidids of North America Fossils of the United States Fossil taxa described in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arthropods
Arthropods ( ) are invertebrates in the phylum Arthropoda. They possess an arthropod exoskeleton, exoskeleton with a cuticle made of chitin, often Mineralization (biology), mineralised with calcium carbonate, a body with differentiated (Metamerism (biology), metameric) Segmentation (biology), segments, and paired jointed appendages. In order to keep growing, they must go through stages of moulting, a process by which they shed their exoskeleton to reveal a new one. They form an extremely diverse group of up to ten million species. Haemolymph is the analogue of blood for most arthropods. An arthropod has an open circulatory system, with a body cavity called a haemocoel through which haemolymph circulates to the interior Organ (anatomy), organs. Like their exteriors, the internal organs of arthropods are generally built of repeated segments. They have ladder-like nervous systems, with paired Anatomical terms of location#Dorsal and ventral, ventral Ventral nerve cord, nerve cord ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Xiphosura
Xiphosura (; , in reference to its sword-like telson) is an order of arthropods related to arachnids. They are more commonly known as horseshoe crabs (a name applied more specifically to the only extant family, Horseshoe crab, Limulidae). They first appeared in the Hirnantian (Late Ordovician). Currently, there are only four living species. Xiphosura contains one suborder, Xiphosurida, and several stem-genera. The group has hardly changed in appearance in hundreds of millions of years; the modern horseshoe crabs look almost identical to prehistoric genera and are considered to be living fossils. The most notable difference between ancient and modern forms is that the abdominal segments in present species are fused into a single unit in adults. Xiphosura were historically placed in the class Merostomata, although this term was intended to encompass also the Eurypterida, eurypterids, whence it denoted what is now thought to be an unnatural (paraphyletic) group (although this is a gr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dekatriata
Dekatriata is a clade of planatergan chelicerates including the groups Arachnida, Chasmataspidida, Eurypterid Eurypterids, often informally called sea scorpions, are a group of extinct marine arthropods that form the Order (biology), order Eurypterida. The earliest known eurypterids date to the Darriwilian stage of the Ordovician period, 467.3 Myr, mil ...a and additionally two stem-genera '' Winneshiekia'' and '' Houia''. Dekatriata is defined by an opisthosoma with 13 segments as groundplan (the number proposed to be secondarily reduced in most arachnid orders) and fused, plate-like appendages on the first opisthosomal segment (somite VII). References Middle Ordovician first appearances {{Chelicerata-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
