Related Research Articles
Agnatha is an infraphylum of jawless fish in the phylum Chordata, subphylum Vertebrata, consisting of both present (cyclostomes) and extinct species. Among recent animals, cyclostomes are sister to all vertebrates with jaws, known as gnathostomes.
Protaspididae is an extinct family of pteraspidid heterostracan agnathans. Fossils of the various genera are found in early Devonian-aged marine strata. Protaspidids were once thought to represent a transitional form between the Pteraspididae and the Psammosteida, bearing the broad head shield shape of the latter, due to a more benthic (bottom-dwelling) existence, but recent phylogenical comparisons demonstrate that the protaspidids are actually highly derived pteraspidids, and that the anchipteraspidids, the most primitive of pteraspidids, are the sister-group of the Psammosteids.
Thelodonti is a class of extinct jawless fishes with distinctive scales instead of large plates of armor.
Macrodontophion is the name given to a dubious genus of lophotrochozoan from the Early Devonian Dniester Series of Podolia, Ukraine. It was described by Adalbert Zborzewsky in 1834, but was never given a species epithet, and is considered a nomen dubium, because it is based only on fragments, such as the holotype, a shell of 25 millimetres (0.98 in).
Semipodolaspis is an extinct genus of jawless fish.
Palanasaspis chekhivensis is an extinct species of pteraspidid heterostracan agnathan which existed during the Pragian epoch of the early Devonian period in what is now Podolia, Ukraine. It is known primarily from a wide rostral plate, which is referenced in the generic name, a compound word combining the Latin words pala, "shovel," and nasus, "nose," with the Greek suffix aspis, "a small shield." Although the rostral plate clearly marks the creature as a pteraspidoid heterostracan, that literally nothing else of its anatomy is known forces researchers to leave it as incertae sedis.
Podolaspis is an extinct genus of pteraspidid heterostracan agnathan which existed during the early Devonian period. It was originally described by Zych in 1931, and contains the species P. lerichei, and P. danieli.
Lechriaspis is an extinct genus of poraspid heterostracan agnathan known from the Early Devonian of northern Utah, western United States.
Podoliacanthus is an extinct genus of Acanthodii which existed in what is now Greenland and Ukraine during the early Devonian period. It was described by Victor Voichyshyn and Hubert Szaniawski in 2012, and the type species is Podoliacanthus zychi. It also contains three presently undescribed species.
Ariaspis is an extinct genus of cyathaspidiform heterostracan agnathan. Fossils are found in marine strata of Canada and Europe from the late Silurian period until its extinction during the Early Devonian. A new species, A. arctata, was described by David K. Elliott and Sandra Swift in 2010.
Plectodonta is an extinct genus of brachiopods which existed during the Devonian to Silurian of the United States, Australia, Canada, China, the Czech Republic, Czechoslovakia, Germany, Kazakhstan, Morocco, Poland, Spain, Ukraine, Argentina, Bolivia, Sweden, the United Kingdom, and Venezuela. It was described by Kozlowski in 1929, and the type species is P. mariae. A new extinct subspecies, P. mariae pantherae, was described by Andrzej Baliński in 2012, from the early Devonian of Ukraine.
Skenidioides is an extinct genus of brachiopods which existed during the Ordovician, Silurian, and Devonian of what is now Australia, Canada, China, the Czech Republic, Italy, Morocco, Poland, Ukraine, the United States, Belarus, Estonia, Lithuania, Mexico, Norway, Sweden, the United Kingdom, Venezuela, Ireland, Kazakhstan, the Russian Federation, and Argentina. It was described by Schuchert and Cooper in 1931, and the type species is S. billingsi. A new species, S. tatyanae, was described by Andrzej Baliński in 2012, from the early Devonian of Ukraine. The species epithet refers to Tatyana Lvovna Modzalevskaya.
The evolution of fish began about 530 million years ago during the Cambrian explosion. It was during this time that the early chordates developed the skull and the vertebral column, leading to the first craniates and vertebrates. The first fish lineages belong to the Agnatha, or jawless fish. Early examples include Haikouichthys. During the late Cambrian, eel-like jawless fish called the conodonts, and small mostly armoured fish known as ostracoderms, first appeared. Most jawless fish are now extinct; but the extant lampreys may approximate ancient pre-jawed fish. Lampreys belong to the Cyclostomata, which includes the extant hagfish, and this group may have split early on from other agnathans.
Priscomyzon riniensis is an extinct lamprey that lived some 360 million years ago during the Famennian in a marine or estuarine environment in South Africa. This small agnathan is anatomically similar to the Mazon Creek lampreys, but is some 35 million years older. Its key developments included the first known large oral disc, circumoral teeth and a branchial basket.
Pteraspidiformes is an extinct order of heterostracan agnathan vertebrates known from extensive fossil remains primarily from Early Devonian strata of Europe and North America, and from Upper Silurian Canada.
Hibernaspis is a genus of extinct amphiaspidid heterostracan agnathans whose fossils are restricted to Lower Devonian marine strata of Siberia near the Taimyr Peninsula. In life, species of Hibernaspis were thought to be benthic animals that lived most of their lives mostly buried in the sediment of a series of hypersaline lagoons. All amphiaspids are easily distinguished from other heterostracans in that all of the plates of the cephalothorax armor are fused into a single, muff-like unit, so that, in the case of Hibernaspis, the forebody of the living animal would have looked like a large guitar pic with serrated edges, with a pair of tiny, degenerated eyes, a pair of branchial openings for exhaling, and a simple, slit-like mouth at the anterior end.
Anglaspis is an extinct genus of cyathaspidiform heterostracan agnathan. Fossils are found in marine strata of Europe, from the late Silurian period until genus' extinction during the Early Devonian. As with other cyathaspidiforms, individuals of Anglaspis had dorsal and ventral plates covering the forebody, gill pouches, and nasal openings that lay on the roof of the oral cavity.
Zenaspida is an extinct order of jawless fish. They possessed a distinct headshield, which varied in width to length ratio by species.
Wladysagitta is an extinct genus of osteostracan jawless fish that existed during the lower Devonian period of what is now Podolia, Ukraine. This taxon was named in honor of Polish paleontologist Dr. Władysław Zych (1899–1981), and from the Latin sagitta, meaning arrow, which is in reference to the arrow-like shape of its skull.
References
- ↑ L. I. Novitskaya (2007). "Evolution of generic and species diversity in agnathans (Heterostraci: Orders Cyathaspidiformes, Pteraspidiformes)". Paleontological Journal . 41 (3): 268–280. doi:10.1134/S0031030107030069. S2CID 83944269.
- ↑ Victor Voichyshyn (2011). "The early Devonian Agnathans of Podolia, Ukraine". Palaeontologia Polonica . 66: 1–211. doi: 10.4202/pp.2011.66_001 .
 | This article related to a Devonian jawless fish is a stub. You can help Wikipedia by expanding it. |