|
Canadaspis Laevigata
''Canadaspis'' ("Shield of Canada") is an extinct genus of bivalved Cambrian arthropod, known from North America and China. They are thought to have been benthic feeders that moved mainly by walking and possibly used its biramous appendages to stir mud in search of food. They have been placed within the Hymenocarina, which includes other bivalved Cambrian arthropods. Description ''Canadaspis'' ''perfecta'' The bivalved carapaces of ''Canadaspis'' ''perfecta'' are typically in length, which taper towards the front end. The head had a small pair of eyes borne on short stalks. Between the eyes is a forward pointing spine, as well as a pair of short antennae, which appear to lack segmentation. Similar antennae are known from ''Waptia'', and are probably homologous to the hemi-ellipsoid bodies of crustaceans, and thus likely have an olfactory function. The head also has another pair of larger, segmented antennae, probably with more than 12 segments, the segments increased in lengt ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Extinct
Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point. Because a species' potential range may be very large, determining this moment is difficult, and is usually done retrospectively. This difficulty leads to phenomena such as Lazarus taxa, where a species presumed extinct abruptly "reappears" (typically in the fossil record) after a period of apparent absence. More than 99% of all species that ever lived on Earth, amounting to over five billion species, are estimated to have died out. It is estimated that there are currently around 8.7 million species of eukaryote globally, and possibly many times more if microorganisms, like bacteria, are included. Notable extinct animal species include non-avian dinosaurs, saber-toothed cats, dodos, m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arthropod Leg
The arthropod leg is a form of jointed appendage of arthropods, usually used for walking. Many of the terms used for arthropod leg segments (called podomeres) are of Latin origin, and may be confused with terms for bones: ''coxa'' (meaning hip, plural ''coxae''), ''trochanter'', ''femur'' (plural ''femora''), ''tibia'' (plural ''tibiae''), ''tarsus'' (plural ''tarsi''), ''ischium'' (plural ''ischia''), ''metatarsus'', ''carpus'', ''dactylus'' (meaning finger), ''patella'' (plural ''patellae''). Homologies of leg segments between groups are difficult to prove and are the source of much argument. Some authors posit up to eleven segments per leg for the most recent common ancestor of extant arthropods but modern arthropods have eight or fewer. It has been argued that the ancestral leg need not have been so complex, and that other events, such as successive loss of function of a ''Hox''-gene, could result in parallel gains of leg segments. In arthropods, each of the leg segments ar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crustacean
Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group can be treated as a subphylum under the clade Mandibulata. It is now well accepted that the hexapods emerged deep in the Crustacean group, with the completed group referred to as Pancrustacea. Some crustaceans (Remipedia, Cephalocarida, Branchiopoda) are more closely related to insects and the other hexapods than they are to certain other crustaceans. The 67,000 described species range in size from '' Stygotantulus stocki'' at , to the Japanese spider crab with a leg span of up to and a mass of . Like other arthropods, crustaceans have an exoskeleton, which they moult to grow. They are distinguished from other groups of arthropods, such as insects, myriapods and chelicerates, by the possession of biramous (two-parted) limbs, and by th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Charles Doolittle Walcott
Charles Doolittle Walcott (March 31, 1850February 9, 1927) was an American paleontologist, administrator of the Smithsonian Institution from 1907 to 1927, and director of the United States Geological Survey.Wonderful Life (book) by Stephen Jay Gould published in 1989, Chapter 4 He is famous for his discovery in 1909 of well-preserved fossils, including some of the oldest soft-part imprints, in the Burgess Shale of British Columbia, Canada. Early life Charles Doolittle Walcott was born on March 31, 1850 in New York Mills, New York. His grandfather, Benjamin S. Walcott, moved from Rhode Island in 1822. His father, also Charles Doolittle Walcott, died when Charles Jr. was only two. Walcott was the youngest of four children. He was interested in nature from an early age, collecting minerals and bird eggs and, eventually, fossils. He attended various schools in the Utica area but left at the age of eighteen without completing high school, the end of his formal education. His intere ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Moulting
In biology, moulting (British English), or molting (American English), also known as sloughing, shedding, or in many invertebrates, ecdysis, is the manner in which an animal routinely casts off a part of its body (often, but not always, an outer layer or covering), either at specific times of the year, or at specific points in its life cycle. In medieval times it was also known as "mewing" (from the French verb "muer", to moult), a term that lives on in the name of Britain's Royal Mews where the King's hawks used to be kept during moulting time before becoming horse stables after Tudor times. Moulting can involve shedding the Epidermis (skin), epidermis (skin), pelage (hair, feathers, fur, wool), or other external layer. In some groups, other body parts may be shed, for example, the entire exoskeleton in arthropods, including the wings in some insects. Examples In birds In birds, moulting is the periodic replacement of feathers by shedding old feathers while producing new o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Metachronal Rhythm
A metachronal rhythm or metachronal wave refers to wavy movements produced by the sequential action (as opposed to synchronized) of structures such as cilia, segments of worms, or legs. These movements produce the appearance of a travelling wave. A Mexican wave is a large scale example of a metachronal wave. This pattern is found widely in nature such as on the cilia of many aquatic organisms such as ctenophores, molluscs, ciliates as well as on the epithelial surfaces of many body organs. Individual cilia, when part of a metachronal wave being used for protist locomotion, individually beat in a pattern similar to the planar stroke of a flagellum. The difference is that the recovery stroke is at 90 degrees to the power stroke, so that the cilia avoid hitting each other. Metachronal rhythms may be seen in the coordinated movements of the legs of millipedes and other multi-legged land invertebrates, as well as in the coordinated movements of social insects. Such metachronal mo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mandible (arthropod)
250px, The mandibles of a bull ant The mandible (from la, mandibula or mandĭbŭ-lum, a jaw) of an arthropod is a pair of mouthparts used either for biting or cutting and holding food. Mandibles are often simply called jaws. Mandibles are present in the extant subphyla Myriapoda (millipedes and others), Crustacea and Hexapoda (insects etc.). These groups make up the clade Mandibulata, which is currently believed to be the sister group to the rest of arthropods, the clade Arachnomorpha (Chelicerata and Trilobita). Unlike the chelicerae of arachnids, mandibles can often be used to chew food. Mandibulates also differ by having antennae, and also by having three distinct body regions: head, thorax and abdomen. (The cephalothorax (or prosoma) of chelicerates is a fusion of head and thorax.) Insects Insect mandibles are as diverse in form as their food. For instance, grasshoppers and many other plant-eating insects have sharp-edged mandibles that move side to side. Most ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Microbial Mat
A microbial mat is a multi-layered sheet of microorganisms, mainly bacteria and archaea, or bacteria alone. Microbial mats grow at interfaces between different types of material, mostly on submerged or moist surfaces, but a few survive in deserts. A few are found as endosymbionts of animals. Although only a few centimetres thick at most, microbial mats create a wide range of internal chemical environments, and hence generally consist of layers of microorganisms that can feed on or at least tolerate the dominant chemicals at their level and which are usually of closely related species. In moist conditions mats are usually held together by slimy substances secreted by the microorganisms. In many cases some of the bacteria form tangled webs of filaments which make the mat tougher. The best known physical forms are flat mats and stubby pillars called stromatolites, but there are also spherical forms. Microbial mats are the earliest form of life on Earth for which there is good fossi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Derek Briggs
Derek Ernest Gilmor Briggs (born 10 January 1950) is an Irish palaeontologist and taphonomist based at Yale University. Briggs is one of three palaeontologists, along with Harry Blackmore Whittington and Simon Conway Morris, who were key in the reinterpretation of the fossils of the Burgess Shale. He is the Yale University G. Evelyn Hutchinson Professor of Geology and Geophysics, Curator of Invertebrate Paleontology at Yale's Peabody Museum of Natural History, and former Director of the Peabody Museum. Education Briggs was educated at Trinity College Dublin where he graduated with a Bachelor of Arts degree in Geology in 1972. He went on to the University of Cambridge to work under British palaeontologist Harry Blackmore Whittington. He was awarded a PhD in 1976 on ''Arthropods from the Burgess Shale, Middle Cambrian, Canada''. Research and Career While at the University of Cambridge, Briggs worked on the fossils of the Middle Cambrian Burgess Shale of British Columbia alongsi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Exopod
The arthropod leg is a form of jointed appendage of arthropods, usually used for walking. Many of the terms used for arthropod leg segments (called podomeres) are of Latin origin, and may be confused with terms for bones: ''coxa'' (meaning hip, plural ''coxae''), ''trochanter'', ''femur'' (plural ''femora''), ''tibia'' (plural ''tibiae''), ''tarsus'' (plural ''tarsi''), ''ischium'' (plural ''ischia''), ''metatarsus'', ''carpus'', ''dactylus'' (meaning finger), ''patella'' (plural ''patellae''). Homologies of leg segments between groups are difficult to prove and are the source of much argument. Some authors posit up to eleven segments per leg for the most recent common ancestor of extant arthropods but modern arthropods have eight or fewer. It has been argued that the ancestral leg need not have been so complex, and that other events, such as successive loss of function of a ''Hox''-gene, could result in parallel gains of leg segments. In arthropods, each of the leg segments artic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Endopod
The arthropod leg is a form of jointed appendage of arthropods, usually used for walking. Many of the terms used for arthropod leg segments (called podomeres) are of Latin origin, and may be confused with terms for bones: ''coxa'' (meaning hip, plural ''coxae''), ''trochanter'', ''femur'' (plural ''femora''), ''tibia'' (plural ''tibiae''), ''tarsus'' (plural ''tarsi''), ''ischium'' (plural ''ischia''), ''metatarsus'', ''carpus'', ''dactylus'' (meaning finger), ''patella'' (plural ''patellae''). Homologies of leg segments between groups are difficult to prove and are the source of much argument. Some authors posit up to eleven segments per leg for the most recent common ancestor of extant arthropods but modern arthropods have eight or fewer. It has been argued that the ancestral leg need not have been so complex, and that other events, such as successive loss of function of a ''Hox''-gene, could result in parallel gains of leg segments. In arthropods, each of the leg segments artic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tergites
A ''tergum'' (Latin for "the back"; plural ''terga'', associated adjective tergal) is the dorsal ('upper') portion of an arthropod segment other than the head. The anterior edge is called the 'base' and posterior edge is called the 'apex' or 'margin'. A given tergum may be divided into hardened plates or sclerites commonly referred to as tergites. In a thoracic segment, for example, the tergum may be divided into an anterior notum and a posterior scutellum. Lateral extensions of a tergite are known as paranota (Greek for "alongside the back") or ''carinae'' (Latin for "keel"), exemplified by the flat-backed millipedes of the order Polydesmida. Kinorhynchs have tergal and sternal plates too, though seemingly not homologous with those of arthropods. Tergo-tergal is a stridulatory mechanism in which fine spines of the abdominal tergites are rubbed together to produce sound. This process is known as abdominal telescoping. Examples File:Andrena spiraeana abdomen.jpg , Abdominal t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
.jpg "Click for more on -> Extinct")
