Vernonaspis Temporal range: | |
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Vernonaspis sp. mass mortality. Late Silurian, Cape Storm Formation, Cornwallis Island, Nunavut (Canada) | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Infraphylum: | Agnatha |
Class: | † Pteraspidomorphi |
Subclass: | † Heterostraci |
Order: | † Cyathaspidiformes |
Family: | † Cyathaspididae |
Genus: | † Vernonaspis Flower and Wayland-Smith, 1952 |
Type species | |
Veronaspis allenae Flower and Wayland-Smith, 1952 | |
Other species | |
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Vernonaspis is an extinct genus of jawless fish that lived in the Silurian in the Paleozoic approximately 419 million years ago, in what is now Canada and the Northeastern United States. [1] [2]
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Heterostraci is an extinct subclass of pteraspidomorph, Ostracoderm, jawless vertebrate that lived primarily in marine and estuary environments. Heterostraci existed from the mid-Ordovician to the conclusion of the Devonian.
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.
Lepidaspis serrata is an extinct heterostracan jawless fish from Early Devonian Canada. Its scientific name refers to the fact that the armor is composed of hundreds of tiny scales with serrated edges.
Anaspida is an extinct group of jawless fish that existed from the early Silurian period to the late Devonian period. They were classically regarded as the ancestors of lampreys, but it is denied in recent phylogenetic analysis, although some analysis show these group would be at least related. Anaspids were small marine fish that lacked a heavy bony shield and paired fins, but were distinctively hypocercal.
Galeaspida is an extinct taxon of jawless marine and freshwater fish. The name is derived from galea, the Latin word for helmet, and refers to their massive bone shield on the head. Galeaspida lived in shallow, fresh water and marine environments during the Silurian and Devonian times in what is now Southern China, Tibet and Vietnam. Superficially, their morphology appears more similar to that of Heterostraci than Osteostraci, there being currently no evidence that the galeaspids had paired fins. A galeaspid Tujiaaspis vividus from the Silurian period of China was described in 2022 as having a precursor condition to the form of paired fins seen in Osteostraci and gnathostomes. Earlier than this, Galeaspida were already in fact regarded as being more closely related to Osteostraci, based on the closer similarity of the morphology of the braincase.
Drepanaspis is an extinct genus of heterostracan armoured jawless fish from the Early Devonian. Drepanaspis are assumed to have lived primarily in marine environments and is most commonly characterized by their ray-like, heavily armoured bodies, along with their lack of paired fins and jaws.
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Alainaspis platyrhina is an extinct cyathaspidid heterostracan agnathan vertebrate which existed in a marine environment in what is now the Northwest Territories of Canada, during the upper Silurian period. It was first named by David Elliott and David Dineley in 1985, and is placed in the monotypic genus Alainaspis, closely related to Boothiaspis.
Poraspis is an extinct genus of heterostracan. Fossils are found in Late Silurian and Early Devonian marine strata of Norway, Canada and the United States.
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.
Capitaspis is an extinct genus of cyathaspidine cyathaspidid heterostracan jawless vertebrate known from the Late Silurian Somerset Island Formation of the Northwest Territories, Canada. It contains a single species, Capitaspis giblingi. It is most closely related to Pionaspis.
Panamintaspis snowi is an extinct species of pteraspidid heterostracan agnathan which existed during the early Middle Devonian period of Death Valley, California. Fossils are found in Late Emsian-aged marine strata of the Lost Burro Formation. P. snowi strongly resembles Pteraspis, though while it was originally described as a member of the same family, Pteraspididae, a recent phylogenetic reassessment of the order Pteraspidiformes places P. snowi within the paraphyletic family "Protopeteraspidae," as the sister taxon of the suborder Pteraspidoidei.
Cardipeltis is an extinct genus of heterostracan agnathan from marine strata of early Devonian of Utah, and Wyoming. Species of Cardipeltis superficially resemble those of cyathaspids in having a flattened body and indistinct head covered by a large, broad, guitar pick or heart-shaped dorsal shield, and a long, scaly tail. Unlike cyathaspids, which all have a single ventral plate, however, the ventral shield of Cardipeltis is a mosaic composed of large scales.
Blieckaspis priscillae is a pteraspidid heterostracan agnathan from the Middle Devonian of North America.
Cyathaspididae is an extinct family in the heterostracan order Cyathaspidiformes.
Anchipteraspididae is an extinct family of heterostracan vertebrates restricted to Late Silurian and Early Devonian strata of Arctic Canada.