| Chelicerata Fossil range: Cambrian - recent | ||||||
|---|---|---|---|---|---|---|
 | ||||||
| Scientific classification | ||||||
| ||||||
| Classes | ||||||
The Subphylum Chelicerata constitutes one of the major subdivisions of the Phylum Arthropoda, including the arachnids, horseshoe crabs, and related forms. The Cambrian is a geologic period and system that began about Ma (million years ago at the end of the Proterozoic eon and ended about Ma with The horseshoe crab or Atlantic horseshoe crab ( Limulus polyphemus) is a marine Chelicerate Arthropod. Arthropods are Animals belonging to the Phylum Arthropoda (from Greek ἄρθρον arthron, " Joint " Richard Heymons ( 1867 - 1943) was a German zoologist Studied in Berlin from 1886 to 1891 and provided overall direction of the Institute of Zoology Arachnids are a class ( Arachnida) of joint-legged Invertebrate Animals in the subphylum Chelicerata. Xiphosura is a class of marine chelicerates which includes a large number of extinct lineages and only four recent species in the family Limulidae, which Sea spiders, also called Pantopoda or pycnogonids ('pycnogonid' = Greek for 'thick knee' are marine Arthropods of class Pycnogonida The eurypterids (sea scorpions include the largest known Arthropod that ever lived (with the possible exception of Arthropleuridae) Arthropods are Animals belonging to the Phylum Arthropoda (from Greek ἄρθρον arthron, " Joint " Arachnids are a class ( Arachnida) of joint-legged Invertebrate Animals in the subphylum Chelicerata. The horseshoe crab or Atlantic horseshoe crab ( Limulus polyphemus) is a marine Chelicerate Arthropod. These mainly predatory arthropods ultimately outlasted the now extinct trilobites, the common marine arthropod of the Cambrian era. Trilobites ("three-lobes" are extinct Arthropods that form the class Trilobita. The Cambrian is a geologic period and system that began about Ma (million years ago at the end of the Proterozoic eon and ended about Ma with Most of the marine chelicerates, including all of the eurypterids, are now extinct. The chelicerates and their closest fossil relatives (mostly originally included in the Xiphosura) are grouped together with the trilobites to form the taxon Arachnomorpha. Xiphosura is a class of marine chelicerates which includes a large number of extinct lineages and only four recent species in the family Limulidae, which A taxon (plural taxa) or taxonomic unit, is a name designating an organism or a group of Organisms In Biological nomenclature according to Arachnomorpha ("Spider Form" Lameere 1890 is a subdivision of Arthropoda, containing the monophyletic group formed by the trilobites and other trilobite-like
Characteristics
In the Chelicerata, the body is divided into an anterior prosoma (or cephalothorax) composed of eight segments plus a presegmental acron and a posterior opisthosoma (or abdomen) composed of twelve segments plus a postsegmental telson. In fields of Anatomy, anatomical terms of location are descriptive terms to help identify relative positions or directions within a species The cephalothorax (call prosoma in some groups is an anatomical term used in Arachnids and Malacostracan Crustaceans for the In fields of Anatomy, anatomical terms of location are descriptive terms to help identify relative positions or directions within a species The opisthosoma is the posterior portion of the Arachnids body behind the Prosoma (cephalothorax The telson is the last division of the body of a Crustacean. It is not considered a true segment because it does not arise in the embryo from teloblast areas As in other arthropods, the mouth lies between the second and third segments, but whereas in other groups there is usually a pair of antennae on the last preoral segment, here there are none. The prosoma usually has eyes. The first two segments of the prosoma bear no appendages; the third bears the chelicerae. The Chelicerae are mouth parts of the Chelicerata, an Arthropod Subphylum that includes Arachnids, Merostomata the fourth segment bears legs or pedipalps, and all subsequent segments bear legs. The arthropod leg is a form of jointed Appendage of Arthropods usually used for Walking. Pedipalps, are the second pair of Appendages of the Prosoma in the subphylum Chelicerata.
The chelicerae, which give the group its name, are pointed appendages that grasp the food in place of the chewing mandibles most other arthropods have. Most are unable to ingest anything solid, so they drink blood or spit or inject digestive enzymes into their prey. Enzymes are Biomolecules that catalyze ( ie increase the rates of Chemical reactions Almost all enzymes are Proteins The legs on the prosoma are either uniramous or have a very reduced gill branch, and are adapted for walking or swimming. The arthropod leg is a form of jointed Appendage of Arthropods usually used for Walking. A gill is an anatomical structure found in many aquatic organisms The appendages on the opisthosoma, in contrast, are either absent or are reduced to their gill branch.
Classification
_Lorryia_formosa_2_edit.jpg/180px-Yellow_mite_(Tydeidae)_Lorryia_formosa_2_edit.jpg)
Lorryia formosa
The Chelicerata are divided into five classes:
- Arachnida (spiders, scorpions, mites, etc. A class is the Taxonomic rank in the Biological classification of organisms in Biology below phylum and above order. Arachnids are a class ( Arachnida) of joint-legged Invertebrate Animals in the subphylum Chelicerata. Spiders are Predatory Invertebrate Animals that have two body segments, eight legs no chewing mouth parts and no wings Scorpions are eight-legged Carnivorous Arthropods They are members of the order Scorpiones within the class Arachnida. Mites, along with Ticks belong to the subclass Acarina (also known as Acari and the class Arachnida Mites are among the most diverse and successful )
- Xiphosura (horseshoe crabs)
- Eurypterida (sea scorpions, extinct)
- Chasmataspidida (chasmataspids, extinct)
- Pycnogonida (sea spiders)
The Pycnogonida actually show some strong differences from the body plan as described above, and it has been suggested that they represent an independent line of arthropods. Xiphosura is a class of marine chelicerates which includes a large number of extinct lineages and only four recent species in the family Limulidae, which The horseshoe crab or Atlantic horseshoe crab ( Limulus polyphemus) is a marine Chelicerate Arthropod. The eurypterids (sea scorpions include the largest known Arthropod that ever lived (with the possible exception of Arthropleuridae) The eurypterids (sea scorpions include the largest known Arthropod that ever lived (with the possible exception of Arthropleuridae) Sea spiders, also called Pantopoda or pycnogonids ('pycnogonid' = Greek for 'thick knee' are marine Arthropods of class Pycnogonida Sea spiders, also called Pantopoda or pycnogonids ('pycnogonid' = Greek for 'thick knee' are marine Arthropods of class Pycnogonida They may have diverged from the other chelicerates early on, or represent highly modified forms. Sometimes they are excluded from the Chelicerata but grouped with them as the Cheliceriformes. The name Merostomata should be avoided because in all recent cladistic hypotheses it refers to a paraphyletic group composed by the Xiphosura + Eurypterida. Merostomata is a class of marine Chelicerata which includes Horseshoe crabs and Eurypterids It includes only four living Species but dozens In Phylogenetics, a group of organisms is said to be paraphyletic if the group contains its most recent common ancestor but does not contain all
The Burgess shale animal Sanctacaris, and perhaps the aglaspids, may also belong here. See also Burgess shale type fauna The Burgess Shale is famous for the exceptional preservation of the fossils found within it in which the soft parts are preserved Sanctacaris is a Middle Cambrian arthropod from the Burgess shale of British Columbia. The Aglaspida, more correctly termed Aglaspidida, were a group of small horseshoe crab-like Arthropods that were once regarded as basal or ancestral Horseshoe These are extinct forms that arose in the Cambrian; the aglaspids are believed to have died out during the Silurian. The Cambrian is a geologic period and system that began about Ma (million years ago at the end of the Proterozoic eon and ended about Ma with The Silurian is a geologic period and system that extends from the end of the Ordovician period about 443 After them, the oldest group of chelicerates are the Eurypterida, found from the Ordovician onwards. The eurypterids (sea scorpions include the largest known Arthropod that ever lived (with the possible exception of Arthropleuridae) The Ordovician is a geologic period and system, the second of six of the Paleozoic era, and covers the time between 488 When young, these show a resemblance to the trilobites, suggesting a possible relationship between these two groups. Trilobites ("three-lobes" are extinct Arthropods that form the class Trilobita.
Dapyx Software network: MP3 Explorer | Ebook Manager | Zenithic