|
Qianodus Duplicis
''Qianodus'' (from the Chinese: 黔, Qian','' the ancient name for Guizhou and the Greek: ὀδούς, ''odus'', 'tooth') is a jawed vertebrate genus that is based on disarticulated teeth from the lower Silurian ( Aeronian, c. 439 Myr) of China. The type and only species of ''Qianodus, Q. duplicis'', is known from compound dental elements called tooth whorls, each consisting of multiple tooth generations carried by a spiral-shaped base. The tooth whorls of ''Qianodus'' represent the oldest unequivocal remains of a toothed vertebrate, predating previously recorded occurrences by about 14 million years. The specimens attributed to the genus come from limestone conglomerate beds of the Rongxi Formation exposed near the village of Leijiatun, Guizhou Province, China. These horizons have been interpreted as tidal deposits1 that form part of the shallow marine sequences of the Rongxi Formation. Morphology and development ''Qianodus'' is known from 23 tooth whorls of varying state of pr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Guizhou
Guizhou (; formerly Kweichow) is a landlocked province in the southwest region of the People's Republic of China. Its capital and largest city is Guiyang, in the center of the province. Guizhou borders the autonomous region of Guangxi to the south, Yunnan to the west, Sichuan to the northwest, the municipality of Chongqing to the north, and Hunan to the east. The population of Guizhou stands at 38.5 million, ranking 18th among the provinces in China. The Dian Kingdom, which inhabited the present-day area of Guizhou, was annexed by the Han dynasty in 106 BC. Guizhou was formally made a province in 1413 during the Ming dynasty. After the overthrow of the Qing in 1911 and following the Chinese Civil War, the Chinese Communist Party took refuge in Guizhou during the Long March between 1934 and 1935. After the establishment of the People's Republic of China, Mao Zedong promoted the relocation of heavy industry into inland provinces such as Guizhou, to better prot ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crown Group
In phylogenetics, the crown group or crown assemblage is a collection of species composed of the living representatives of the collection, the most recent common ancestor of the collection, and all descendants of the most recent common ancestor. It is thus a way of defining a clade, a group consisting of a species and all its extant or extinct descendants. For example, Neornithes (birds) can be defined as a crown group, which includes the most recent common ancestor of all modern birds, and all of its extant or extinct descendants. The concept was developed by Willi Hennig, the formulator of phylogenetic systematics, as a way of classifying living organisms relative to their extinct relatives in his "Die Stammesgeschichte der Insekten", and the "crown" and "stem" group terminology was coined by R. P. S. Jefferies in 1979. Though formulated in the 1970s, the term was not commonly used until its reintroduction in 2000 by Graham Budd and Sören Jensen. Contents of the crown ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acanthodii
Acanthodii or acanthodians is an extinct class of gnathostomes (jawed fishes), typically considered a paraphyletic group. They are currently considered to represent a grade of various fish lineages leading up to the extant Chondrichthyes, which includes living sharks, rays, and chimaeras. Acanthodians possess a mosaic of features shared with both osteichthyans (bony fish) and chondrichthyans (cartilaginous fish). In general body shape, they were similar to modern sharks, but their epidermis was covered with tiny rhomboid platelets like the scales of holosteians ( gars, bowfins). A lower Silurian species, '' Fanjingshania renovata'', attributed to Climatiiformes is the oldest chondrichthyan with known anatomical features. The popular name "spiny sharks" is because they were superficially shark-shaped, with a streamlined body, paired fins, a strongly upturned tail, and stout, largely immovable bony spines supporting all the fins except the tail—hence, "spiny sharks". However ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Climatiiformes
The Climatiiformes is an order of extinct fish belonging to the class Acanthodii. Like most other "spiny sharks", the Climatiiformes had sharp spines. These animals were often fairly small in size and lived from the Late Silurian to the Early Carboniferous period. The type genus is ''Climatius''. The order used to be subdivided into the suborders Climatiida and Diplacanthida, but subsequently Diplacanthida has been elevated to a separate order, the Diplacanthiformes. The Diplacanthiformes take their name from ''Diplacanthus ''Diplacanthus'' is an extinct genus of Mid to Late Devonian fish in the class Acanthodii, known as spiny sharks. Classification The genus was named by Louis Agassiz in 1843. It was formerly regarded as belonging to the Climatiformes but r ...'', first described by Agassiz in 1843. Family Gyracanthidae is sometimes rejected from this order. References Acanthodii Prehistoric fish orders Paraphyletic groups {{Carboniferous-animal-st ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Placodermi
Placodermi (from Greek πλάξ 'plate' and δέρμα 'skin', literally ' plate-skinned') is a class of armoured prehistoric fish, known from fossils, which lived from the Silurian to the end of the Devonian period. Their head and thorax were covered by articulated armoured plates and the rest of the body was scaled or naked, depending on the species. Placoderms were among the first jawed fish; their jaws likely evolved from the first of their gill arches. Placoderms are thought to be paraphyletic, consisting of several distinct outgroups or sister taxa to all living jawed vertebrates, which originated among their ranks. In contrast, one 2016 analysis concluded that placodermi are likely monophyletic, though these analyses have been further dismissed with more transitional taxa between placoderms and modern gnathosthomes, solidifying their paraphyletic status. Placoderms were also the first fish to develop pelvic fins, the precursor to hindlimbs in tetrapods, as well ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chondrichthyes Chondrichthyes (; ) is a class that contains the cartilaginous fishes that have skeletons primarily composed of cartilage. They can be contrasted with the Osteichthyes or ''bony fishes'', which have skeletons primarily composed of bone tissue. Chondrichthyes are jawed vertebrates with paired fins, paired nares, scales, and a heart with its chambers in series. Extant chondrichthyes range in size f |
