|
Halwaxiida
Halwaxiida or halwaxiids is a proposed clade equivalent to the older orders Sachitida He 1980 and Thambetolepidea Jell 1981, loosely uniting scale-bearing Cambrian animals, which may lie in the stem group to molluscs or lophotrochozoa. Some palaeontologists question the validity of the Halwaxiida clade. Definition and members The name "halwaxiid" was formed by combining the names of two members of the proposed group, '' Halkieria'' and ''Wiwaxia''. The group was defined as a set of Early to Mid Cambrian animals that had: a "chain mail" coat of three concentric bands of small armor plates that are called sclerites; in some cases, a small cap-like shell at the front end and in some cases both ends. Some scientists are unhappy with this loose definition, arguing that such traits may have arisen convergently rather than being inherited from a common ancestor. This objection implies that the group may not be monophyletic, and that their similarities are not biologically equivalent ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Halkieria
The halkieriids are a group of fossil organisms from the Lower to Middle Cambrian. Their eponymous genus is ''Halkieria'' , which has been found on almost every continent in Lower to Mid Cambrian deposits, forming a large component of the small shelly fossil assemblages. The best known species is ''Halkieria evangelista'', from the North Greenland Sirius Passet Lagerstätte, in which complete specimens were collected on an expedition in 1989. The fossils were described by Simon Conway Morris and John Peel in a short paper in 1990 in the journal ''Nature''. Later a more thorough description was undertaken in 1995 in the journal ''Philosophical Transactions of the Royal Society of London'' and wider evolutionary implications were posed. The group is sometimes equated to Sachitida, although as originally envisaged, this group includes the wiwaxiids and is thus equivalent to the Halwaxiida. History of discovery Armor plates called "sclerites" had long been known as elements of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wiwaxia
''Wiwaxia'' is a genus of soft-bodied animals that were covered in carbonaceous scales and spines that protected it from predators. ''Wiwaxia'' fossils – mainly isolated scales, but sometimes complete, articulated fossils – are known from early Cambrian and middle Cambrian fossil deposits across the globe. The living animal would have measured up to 5 cm (2 inch) when fully grown, although a range of juvenile specimens are known, the smallest being long. ''Wiwaxia's'' affinity has been a matter of debate: Researchers were long split between two possibilities. On the one hand, its rows of scales looked superficially similar to certain scale worms (annelids); conversely, its mouthparts and general morphology suggested a relationship to the shell-less molluscs. More recently, evidence for a molluscan affinity has been accumulating, based on new details of ''Wiwaxias mouthparts, scales, and growth history. The proposed clade Halwaxiida contains ''Wiwaxia'' as well a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eohalobia
The halkieriids are a group of fossil organisms from the Lower to Middle Cambrian. Their eponymous genus is ''Halkieria'' , which has been found on almost every continent in Lower to Mid Cambrian deposits, forming a large component of the small shelly fossil assemblages. The best known species is ''Halkieria evangelista'', from the North Greenland Sirius Passet Lagerstätte, in which complete specimens were collected on an expedition in 1989. The fossils were described by Simon Conway Morris and John Peel in a short paper in 1990 in the journal ''Nature''. Later a more thorough description was undertaken in 1995 in the journal ''Philosophical Transactions of the Royal Society of London'' and wider evolutionary implications were posed. The group is sometimes equated to Sachitida, although as originally envisaged, this group includes the wiwaxiids and is thus equivalent to the Halwaxiida. History of discovery Armor plates called "sclerites" had long been known as elements of t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orthrozanclus
''Orthrozanclus'' (from Greek + ( + ), "dawn scythe") is a genus of sea creatures known from two species, ''O. reburrus'' from the Middle Cambrian (~) Burgess shale and ''O. elongata'' from Early Cambrian (~) Maotianshan Shales. Animals in this genus were one to two centimeters long, with spikes protruding from their armored bodies. The placement of this genus into a specific family is not universally accepted. History of discovery Jean-Bernard Caron and Donald A. Jackson found a specimen in the Burgess Shale and in 2006 referred to it as "scleritomorph C" without a detailed description. In 2007 Caron and Simon Conway Morris published a description and named the fossil ''Orthrozanclus reburrus''. The genus name means "Dawn scythe" and derives from Greek, with the species name meaning "bristling hair" in Latin. The two known specimens of ''O. elongata'' were discovered from Maotianshan Shale in 2015 and 2016 and formally described the following year. Description ''Orthrozanclu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lomasulcachites
The halkieriids are a group of fossil organisms from the Lower to Middle Cambrian. Their eponymous genus is ''Halkieria'' , which has been found on almost every continent in Lower to Mid Cambrian deposits, forming a large component of the small shelly fossil assemblages. The best known species is ''Halkieria evangelista'', from the North Greenland Sirius Passet Lagerstätte, in which complete specimens were collected on an expedition in 1989. The fossils were described by Simon Conway Morris and John Peel in a short paper in 1990 in the journal ''Nature''. Later a more thorough description was undertaken in 1995 in the journal ''Philosophical Transactions of the Royal Society of London'' and wider evolutionary implications were posed. The group is sometimes equated to Sachitida, although as originally envisaged, this group includes the wiwaxiids and is thus equivalent to the Halwaxiida. History of discovery Armor plates called "sclerites" had long been known as elements of th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orthrozanclus Reburrus E
''Orthrozanclus'' (from Greek + ( + ), "dawn scythe") is a genus of sea creatures known from two species, ''O. reburrus'' from the Middle Cambrian (~) Burgess shale and ''O. elongata'' from Early Cambrian (~) Maotianshan Shales. Animals in this genus were one to two centimeters long, with spikes protruding from their armored bodies. The placement of this genus into a specific family is not universally accepted. History of discovery Jean-Bernard Caron and Donald A. Jackson found a specimen in the Burgess Shale and in 2006 referred to it as "scleritomorph C" without a detailed description. In 2007 Caron and Simon Conway Morris published a description and named the fossil ''Orthrozanclus reburrus''. The genus name means "Dawn scythe" and derives from Greek, with the species name meaning "bristling hair" in Latin. The two known specimens of ''O. elongata'' were discovered from Maotianshan Shale in 2015 and 2016 and formally described the following year. Description ''Orthrozanclu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wiwaxia Corrugata
''Wiwaxia'' is a genus of soft-bodied animals that were covered in carbonaceous scales and spines that protected it from predators. ''Wiwaxia'' fossils – mainly isolated scales, but sometimes complete, articulated fossils – are known from early Cambrian and middle Cambrian fossil deposits across the globe. The living animal would have measured up to 5 cm (2 inch) when fully grown, although a range of juvenile specimens are known, the smallest being long. ''Wiwaxia's'' affinity has been a matter of debate: Researchers were long split between two possibilities. On the one hand, its rows of scales looked superficially similar to certain scale worms (annelids); conversely, its mouthparts and general morphology suggested a relationship to the shell-less molluscs. More recently, evidence for a molluscan affinity has been accumulating, based on new details of ''Wiwaxias mouthparts, scales, and growth history. The proposed clade Halwaxiida contains ''Wiwaxia'' as well as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Siphogonuchites
The halkieriids are a group of fossil organisms from the Lower to Middle Cambrian. Their eponymous genus is ''Halkieria'' , which has been found on almost every continent in Lower to Mid Cambrian deposits, forming a large component of the small shelly fossil assemblages. The best known species is ''Halkieria evangelista'', from the North Greenland Sirius Passet Lagerstätte, in which complete specimens were collected on an expedition in 1989. The fossils were described by Simon Conway Morris and John Peel in a short paper in 1990 in the journal ''Nature''. Later a more thorough description was undertaken in 1995 in the journal ''Philosophical Transactions of the Royal Society of London'' and wider evolutionary implications were posed. The group is sometimes equated to Sachitida, although as originally envisaged, this group includes the wiwaxiids and is thus equivalent to the Halwaxiida. History of discovery Armor plates called "sclerites" had long been known as elements of th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Australohalkieria
''Australohalkieria'' (meaning "southern ''Halkieria''") is an extinct genus of halkieriid from Australia and Antarctica. Description ''Australohalkieria superstes'' This species, named by Porter in 2004, is the most complete and abundant Australian halkieriid species. The sclerites assigned to this species are convex on the upper surface and concave on the lower. They may also curve within their own plane, and they overlap so that the concave side of each is partly covered by the convex side of the next one. The internal cavity within ''Australohalkieria'' is more complicated that the simple tube in ''Halkieria''; about half-way up the sclerite, the cylindrical tube splits into a pair of longitudinal canals, with the central canal flattening; the canals don't seem to be connected. The walls also have a different microscopic structure. In ''A. superstes'' the central canals of sclerites are flattened on their upper surfaces, and this produces a depression on the upper surface ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
