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Megarachne Servinei
''Megarachne'' is a genus of eurypterid, an extinct group of aquatic arthropods. Fossils of ''Megarachne'' have been discovered in deposits of Late Carboniferous age, from the Gzhelian stage, in San Luis, Argentina. The fossils of the single and type species ''M. servinei'' have been recovered from deposits that had once been a freshwater environment. The generic name, composed of the Ancient Greek μέγας (''megas'') meaning "great" and Ancient Greek ἀράχνη (''arachne'') meaning "spider", translates to "great spider", because the fossil was misidentified as a large prehistoric spider. With a body length of , ''Megarachne'' was a medium-sized eurypterid. If the original identification as a spider had been correct, ''Megarachne'' would have been the largest known spider to have ever lived. Eurypterids such as ''Megarachne'' are often called "sea scorpions", but the strata in which ''Megarachne'' has been found indicates that it dwelled in freshwater and not in marine envi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gzhelian
The Gzhelian ( ) is an age in the ICS geologic timescale or a stage in the stratigraphic column. It is the youngest stage of the Pennsylvanian, the youngest subsystem of the Carboniferous. The Gzhelian lasted from to Ma. It follows the Kasimovian age/stage and is followed by the Asselian age/stage, the oldest subdivision of the Permian system. The Gzhelian is more or less coeval with the Stephanian Stage of the regional stratigraphy of Europe. Name and definition The Gzhelian is named after the Russian village of Gzhel (russian: Гжель), nearby Ramenskoye, not far from Moscow. The name and type locality were defined by Sergei Nikitin (1850–1909) in 1890. The base of the Gzhelian is at the first appearance of the Fusulinida genera '' Daixina'', '' Jigulites'' and '' Rugosofusulina'', or at the first appearance of the conodont ''Streptognathodus zethus''. The top of the stage (the base of the Permian system) is at the first appearance of the conodont ''Strepto ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Woodwardopterus
''Woodwardopterus'' is a genus of prehistoric eurypterid, or sea scorpion, classified as part of the family Mycteroptidae. The genus contains one confirmed species, ''W. scabrosus'', from the Carboniferous of Glencartholm, Scotland. Originally classified as ''Eurypterus scabrosus'', it was later found to be generically distinct and placed as a member of the family Mycteroptidae. Later in 2005, was assigned to its own genus, and linked to a new own family, Woodwardopteridae inside Mycteropoidea, probably as a sister taxon of ''Megarachne''. W. scarabrosus had carapace length about and estimated total length about . A possible second species, ?''W. freemanorum'' was named in 2021 and comes from the Changhsingian (Late Permian) beds of the Baralaba Coal Measures, Bowen Basin, central Queensland, Australia. This possible second species is important due to be the geologically youngest eurypterid discovered (at least 11 Ma younger than any previously known relative), showing ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gladius
''Gladius'' () is a Latin word meaning "sword" (of any type), but in its narrow sense it refers to the sword of ancient Roman foot soldiers. Early ancient Roman swords were similar to those of the Greeks, called '' xiphe'' (plural; singular ''xiphos''). From the 3rd century BC, however, the soldiers of the Roman Republic adopted a sword based on the celtic sword used by the Celtiberians in Hispania late into the Punic Wars, known in Latin as the ''gladius hispaniensis'', meaning "Hispanic-type sword". New variants of the gladius, such as the "Mainz gladius" and the "Pompeii gladius", were used from the first century AD and during the early centuries of the Roman Empire; in the third century AD the gladius was replaced by the " spatha". A fully equipped Roman legionary after the reforms of Gaius Marius was armed with a shield (''scutum''), one or two javelins ('' pila''), a sword (''gladius''), often a dagger ('' pugio''), and, perhaps in the later empire period, darts (''plumbat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Telson
The telson () is the posterior-most division of the body of an arthropod. Depending on the definition, the telson is either considered to be the final segment of the arthropod body, or an additional division that is not a true segment on account of not arising in the embryo from teloblast areas as other segments. It never carries any appendages, but a forked "tail" called the caudal furca may be present. The shape and composition of the telson differs between arthropod groups. Crustaceans In lobsters, shrimp and other decapods, the telson, along with the uropods, forms the tail fan. This is used as a paddle in the caridoid escape reaction ("lobstering"), whereby an alarmed animal rapidly flexes its tail, causing it to dart backwards. Krill can reach speeds of over 60 cm per second by this means. The trigger time to optical stimulus is, in spite of the low temperatures, only 55 milliseconds. In the Isopoda and Tanaidacea (superorder Peracarida), the last abdom ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Prosoma
The cephalothorax, also called prosoma in some groups, is a tagma of various arthropods, comprising the head and the thorax fused together, as distinct from the abdomen behind. (The terms ''prosoma'' and ''opisthosoma'' are equivalent to ''cephalothorax'' and ''abdomen'' in some groups.) The word ''cephalothorax'' is derived from the Greek words for head (, ') and thorax (, '). This fusion of the head and thorax is seen in chelicerates and crustaceans; in other groups, such as the Hexapoda (including insects), the head remains free of the thorax. In horseshoe crabs and many crustaceans, a hard shell called the carapace covers the cephalothorax. Arachnid anatomy Fovea The fovea is the centre of the cephalothorax and is located behind the head (only in spiders).Dalton, Steve (2008). ''Spiders; The Ultimate Predators''. A & C Black, London. P.p. 19. . It is often important in identification. It can be transverse or procurved Smith, A. M. (1990c). Baboon spiders: Tarantulas of Afr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mycteroptidae
Mycteroptidae are a family of eurypterids, a group of extinct chelicerate arthropods commonly known as "sea scorpions". The family is one of three families contained in the superfamily Mycteropoidea (along with Hibbertopteridae and Drepanopteridae), which in turn is one of four superfamilies classified as part of the suborder Stylonurina. Mycteroptids were sweep-feeding eurypterids known from the Late Carboniferous to the Late Permian. Description Mycteroptids were medium-sized to fairly large mycteropoids with parabolic prosoma and a hastate telson with paired ventral keels. They had a culticular ornament of scales or mucrones and unlike the hibbertopterids, appendage IV was non-spiniferous. The first and second opisthosomal tergites were strongly developed and elongated. The heads of mycteroptids were subtrapezoid in shape with small compound eyes. 1955. Merostomata. ''Treatise on Invertebrate Paleontology, Part P Arthropoda 2, Chelicerata'', P39. Mycteroptids only use ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dorsal (anatomy)
Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position provides a definition of what is at the front ("anterior"), behind ("posterior") and so on. As part of defining and describing terms, the body is described through the use of anatomical planes and anatomical axes. The meaning of terms that are used can change depending on whether an organism is bipedal or quadrupedal. Additionally, for some animals such as invertebrates, some terms may not have any meaning at all; for example, an animal that is radially symmetrical will have no anterior surface, but can still have a description that a part is close to the middle ("proximal") or further from the middle ("distal"). International organisations have determined vocabularies that are often used as standard vocabularies for subdisciplines of anat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Opisthosoma
The opisthosoma is the posterior part of the body in some arthropods, behind the prosoma ( cephalothorax). It is a distinctive feature of the subphylum Chelicerata (arachnids, horseshoe crabs and others). Although it is similar in most respects to an abdomen (and is often referred to as such), the opisthosoma is differentiated by its inclusion of the respiratory organs ( book lungs or book gills) and the heart. Segments The number of segments and appendages on the opisthosoma vary. Scorpions have 13, but the first is only seen during its embryological development. Other arachnids have fewer; harvestmen, for instance, have only ten. In general, appendages are absent or reduced, although in horseshoe crabs they persist as large plate-like limbs, called opercula or branchiophores, bearing the book gills, and that function in locomotion and gas exchange. In most chelicerates the opisthosomal limbs are greatly reduced and persist only as specialized structures, such as the silk-produ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aquatic Ecosystem
An aquatic ecosystem is an ecosystem formed by surrounding a body of water, in contrast to land-based terrestrial ecosystems. Aquatic ecosystems contain communities of organisms that are dependent on each other and on their environment. The two main types of aquatic ecosystems are marine ecosystems and freshwater ecosystems. Freshwater ecosystems may be lentic (slow moving water, including pools, ponds, and lakes); lotic (faster moving water, for example streams and rivers); and wetlands (areas where the soil is saturated or inundated for at least part of the time). Types Marine ecosystems Marine coastal ecosystem Marine surface ecosystem Freshwater ecosystems Lentic ecosystem (lakes) Lotic ecosystem (rivers) Wetlands Functions Aquatic ecosystems perform many important environmental functions. For example, they recycle nutrients, purify water, attenuate floods, recharge ground water and provide habitats for wildlife. Aquatic ecosystems are also used ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carapace
A carapace is a dorsal (upper) section of the exoskeleton or shell in a number of animal groups, including arthropods, such as crustaceans and arachnids, as well as vertebrates, such as turtles and tortoises. In turtles and tortoises, the underside is called the plastron. Crustaceans In crustaceans, the carapace functions as a protective cover over the cephalothorax (i.e., the fused head and thorax, as distinct from the abdomen behind). Where it projects forward beyond the eyes, this projection is called a rostrum. The carapace is calcified to varying degrees in different crustaceans. Zooplankton within the phylum Crustacea also have a carapace. These include Cladocera, ostracods, and isopods, but isopods only have a developed "cephalic shield" carapace covering the head. Arachnids In arachnids, the carapace is formed by the fusion of prosomal tergites into a single plate which carries the eyes, ocularium, ozopores (a pair of openings of the scent gland of Opiliones) a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cuticle
A cuticle (), or cuticula, is any of a variety of tough but flexible, non-mineral outer coverings of an organism, or parts of an organism, that provide protection. Various types of "cuticle" are non- homologous, differing in their origin, structure, function, and chemical composition. Human anatomy In human anatomy, "cuticle" can refer to several structures, but it is used in general parlance, and even by medical professionals, to refer to the thickened layer of skin surrounding fingernails and toenails (the eponychium), and to refer to the superficial layer of overlapping cells covering the hair shaft ( cuticula pili), consisting of dead cells, that locks the hair into its follicle. It can also be used as a synonym for the epidermis, the outer layer of skin. Cuticle of invertebrates In zoology, the invertebrate cuticle or cuticula is a multi-layered structure outside the epidermis of many invertebrates, notably roundworms and arthropods, in which it forms an exoskeleto ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Biological Ornament
A biological ornament is a characteristic of an animal that appears to serve a decorative function rather than a utilitarian function. Many are secondary sexual characteristics, and others appear on young birds during the period when they are dependent on being fed by their parents. Ornaments are used in displays to attract mates, which may lead to the evolutionary process known as sexual selection. An animal may shake, lengthen, or spread out its ornament in order to get the attention of the opposite sex, which will in turn choose the most attractive one with which to mate. Ornaments are most often observed in males, and choosing an extravagantly ornamented male benefits females as the genes that produce the ornament will be passed on to her offspring, increasing their own reproductive fitness. As Ronald Fisher noted, the male offspring will inherit the ornament while the female offspring will inherit the preference for said ornament, which can lead to a positive feedback loop ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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