A sclerite (Greek skleros meaning "hard") is a hardened body part. Greek (el ελληνική γλώσσα or simply el ελληνικά — "Hellenic" is an Indo-European language, spoken today by 15-22 million people mainly Hardness refers to various properties of Matter in the Solid phase that give it high resistance to various kinds of shape change when Force The term is used in various branches of biology for various structures including hardened portions of sponges, but it is most commonly used for the hardened portions of arthropod exoskeletons. The sponges or poriferans (from Latin porus "pore" and ferre "to bear" are Animals Arthropods are Animals belonging to the Phylum Arthropoda (from Greek ἄρθρον arthron, " Joint " An exoskeleton is an external Skeleton that supports and protects an animal's body in contrast to the internal Endoskeleton of for example a Human.
In arthropods, this hardening is accomplished by the cross-linking of the protein chains in the exocuticle, a process called sclerotization. The procuticle is the major portion of the Exoskeleton of an Insect (and various other Arthropods; its exact composition and structure may differ somewhat Thus, the arthropod exoskeleton is divided into numerous sclerites, joined by unsclerotized, membranous regions. The precise shapes and arrangement of the different sclerites provide the vast majority of morphological features that are used as characters when reconstructing the phylogenetic relationships among different lineages; they provide the foundation for arthropod systematics, primarily through the ability of the systematist to accurately assess the homologies of the different sclerites, as to how they may be lost, gained, fused, divided, or otherwise modified from one lineage to another. Biological systematics is the study of the diversity of Life on the planet Earth both past and present and the relationships among living things through time In Evolutionary biology, homology has come to mean any similarity between characters that is due to their shared ancestry. For example, the sclerite called the mandible in insects varies dramatically in form between orders, but all the different variations are homologous. The mandible (from Latin mandibula, "jawbone" or inferior maxillary bone forms the lower Jaw and holds the lower teeth in place This article is about the taxonomic rank for the sequence of species in a taxonomic list see Taxonomic order In scientific classification used
One specialized usage is to describe hollow Calcium Carbonate, Calcium Sulfate or Calcium Phosphate plates grown as body armor by a number of Early Cambrian animals. 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 Unlike sponge spicules, Early Cambrian sclerites appear to be external armor rather than internal structural elements. The sponges or poriferans (from Latin porus "pore" and ferre "to bear" are Animals 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 Sclerites are found on a curious collection of early animals including a common spongelike animal called Chancelloria; an armored slug-like form Wiwaxia; an armored worm with a pair of brachiopod-like shells Halkieria; and another armored worm Microdictyon that is generally considered to be a lobopod/onychophore. See also Halwaxiida Wiwaxia is genus of soft-bodied scale-covered animals known from Burgess shale type dating from the Early to Middle Cambrian Brachiopods (from Latin brachium, arm + New Latin -poda, foot are a small phylum of Benthic Invertebrates Also See also Halwaxiida Halkieria ( IPA: hælˈkɪˌriʌ is a genus of fossil organisms from the Lower to Middle Cambrian. Microdictyon is an extinct "armored Worm " coated with dot-like scleritic scales known from the Early Cambrian Maotianshan shale Lobopodia is a group of poorly understood animals which mostly fall as a Stem group of Arthropods. The velvet worms ( Onychophora — literally "claw bearers" form a Clade within the Ecdysozoa and can be simply described as " Worms
It has been suggested that the sclerites of the Cambrian Wiwaxia are homologous with the bristles of annelid worms (Butterfield 1990). 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 See also Halwaxiida Wiwaxia is genus of soft-bodied scale-covered animals known from Burgess shale type dating from the Early to Middle Cambrian The annelids, collectively called Annelida (from Latin anellus "little ring" are a large phylum of Animals comprising At least one modern gastropod mollusc living near deep sea hydrothermal vents has structures made of iron sulfides (Bengtson and Warén, 2003) similar to some Cambrian sclerites, although presumably not homologous in structure. The class Gastropoda or the gastropods, also previously known as gasteropods, or univalves, and more commonly known as Snails Molluscs are animals belonging to the phylum Mollusca. There are around 250000 extant Species within the phylum with an estimated 70000
References
Butterfield, N. J. (1990). "A Reassessment of the Enigmatic Burgess Shale Fossil Wiwaxia corrugata (Matthew) and Its Relationship to the Polychaete Canadia spinosa Walcott". Paleobiology 16 (3): 287-303.
Dapyx Software network: MP3 Explorer | Ebook Manager | Zenithic