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Thyestiida
Thyestiida is an order of bony-armored jawless fish in the extinct vertebrate class Osteostraci The class Osteostraci (meaning "bony shells") is an extinct taxon of bony-armored jawless fish, termed " ostracoderms", that lived in what is now North America, Europe and Russia from the Middle Silurian to Late Devonian. Anatomically speaking, ....The origin and early evolution of the Osteostraci (Vertebrata): A phylogeny for the Thyestiida. Robert S. Sansom, Journal of Systematic Palaeontology, Volume 6, Issue 3, 2008, pages 317-332, References External links Thyestiidaat fossilworks.org (retrieved 21 April 2016) Osteostraci Prehistoric jawless fish orders {{Paleo-jawless-fish-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Auchenaspis
''Auchenaspis salteri'' is an extinct species of Osteostraci, armored jawless fish of the order (biology), order Thyestiida from the Late Silurian of England. In England, ''A. salteri'''s fossils are found in extreme abundance in the Lower Old Red Sandstone strata in Ledbury, Herefordshire. ''A. salteri'' strongly resembles the thyestiids ''Procephalaspis'' and ''Thyestes (fish), Thyestes'', and within Thyestiida, it represents a transitional form between the primitive, superficially ''Cephalaspis''-like forms, such as ''Thyestes'', and the more specialized tremataspid thyestiids, like ''Tremataspis'', ''Dartmuthia'', or ''Dobraspis'', whose headshields tend to resemble hot buns or horseshoe crabs. References Osteostraci genera Silurian fish of Europe Fossils of Great Britain {{Paleo-jawless-fish-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Osteostraci
The class Osteostraci (meaning "bony shells") is an extinct taxon of bony-armored jawless fish, termed " ostracoderms", that lived in what is now North America, Europe and Russia from the Middle Silurian to Late Devonian. Anatomically speaking, the osteostracans, especially the Devonian species, were among the most advanced of all known agnathans. This is due to the development of paired fins, and their complicated cranial anatomy. The osteostracans were more similar to lampreys than to jawed vertebrates in possessing two pairs of semicircular canals in the inner ear, as opposed to the three pairs found in the inner ears of jawed vertebrates. They are thought to be the sister-group to pituriaspids, and together, these two taxa of jawless vertebrates are the sister-group of gnathostomes. Several synapomorphies support this hypothesis, such as the presence of: sclerotic ossicles, paired pectoral fins, a dermal skeleton with three layers (a basal layer of isopedin, a middle layer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Osteostraci Janvier
The class (biology), class Osteostraci (meaning "bony shells") is an extinct taxon of bony-armored jawless fish, termed "ostracoderms", that lived in what is now North America, Europe and Russia from the Wenlock epoch, Middle Silurian to Late Devonian. Anatomically speaking, the osteostracans, especially the Devonian species, were among the most advanced of all known agnathans. This is due to the development of paired fins, and their complicated cranial anatomy. The osteostracans were more similar to lampreys than to jawed vertebrates in possessing two pairs of semicircular canals in the inner ear, as opposed to the three pairs found in the inner ears of jawed vertebrates. They are thought to be the sister-group to Pituriaspida, pituriaspids, and together, these two taxa of jawless vertebrates are the sister-group of Gnathostomata, gnathostomes. Several synapomorphies support this hypothesis, such as the presence of: sclerotic ossicles, paired pectoral fins, a dermal skeleton with ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Procephalaspis
''Procephalaspis'' is an extinct genus of jawless fish Agnatha (; ) or jawless fish is a paraphyletic infraphylum of animals in the subphylum Vertebrata of the phylum Chordata, characterized by the lack of jaws. The group consists of both extant taxon, living (Cyclostomi, cyclostomes such as hagfish .... References * Telling the Evolutionary Time: Molecular Clocks and the Fossil Record (Systematics Association Special Volume) by Philip C J Donoghue and M. Paul Smith (page 227) Osteostraci genera Silurian jawless fish {{Paleo-jawless-fish-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dartmuthia
''Dartmuthia'' is an extinct genus of primitive jawless fish that lived in the Silurian period. Fossils of ''Dartmuthia'' have been found in Himmiste Quarry, on the island of Saaremaa in Estonia Estonia, officially the Republic of Estonia, is a country in Northern Europe. It is bordered to the north by the Gulf of Finland across from Finland, to the west by the Baltic Sea across from Sweden, to the south by Latvia, and to the east by Ru .... It was first described by William Patten. ''Dartmuthia'' is one of the only osteostracans in which material of the trunk and tail behind the armored head shield have been found. Since the mouth is positioned on the underside of the head ''Dartmuthia'' is presumed to have dwelled on the ocean floor, sucking its food into its mouth. References Osteostraci genera Fossils of Estonia Silurian fish of Europe {{Paleo-jawless-fish-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
