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Traquairaspidiformes is an order of extinct 
The head-shield and body armor of most traquairaspids form an almond shape. Plates have a distinctive ornamentation of tubercles: this ornamentation is very similar to the plate ornamentation of the heterostracan '' Weigeltaspis''. This similarity of ornamentation creates much confusion over the taxonomical placement of ''Weigeltaspis'', in addition to confusion over whether or not an isolated plate is of ''Traquairaspis'', or of ''Weigeltaspis''. Intact specimens of ''Weigeltaspis'' suggest a living animal similar to psammosteids like '' Drepanaspis''.Tarlo, Halstead. "LB t1965) Psammosteiformes tAgnatha)—A review with descriptions of new material from the Lower Devonian of Poland, II. Systematic Part." Palaeontologia Polonica 15: 168. Pages 20-21 The armor of ''Phialaspis symmondsi'' (once considered as species of ''Traquairaspis'') is shaped like a jet plane or paper airplane, with pointed wing-like crests and a dorsal crest near the posterior end of the armor. The body of "Yukonaspis," ''Traquairaspis angusta'', is greatly elongated, based on the holotype, a ventral plate.
Most species of traquairaspids are placed within the type genus '' Traquairaspis''; most of the other genera, such as ''Phialaspis'', ''Toombsaspis'', and "Yukonaspis," have been synonymized into ''Traquairaspis''. ''Weigeltaspis'' is sometimes placed within Traquairaspidiformes on account of the plate ornamentation being almost identical to that of ''Traquairaspis''.
heterostracan
Heterostraci (Ancient Greek, ἕτερος+ὄστρακον "those itha different shell" i is pl. of -us is an extinct subclass of pteraspidomorph jawless vertebrate that lived primarily in marine and estuary environments. Heterostraci exi ...
agnatha
Agnatha (, Ancient Greek 'without jaws') is an infraphylum of jawless fish in the phylum Chordata, subphylum Vertebrata, consisting of both present (cyclostomes) and extinct (conodonts and ostracoderms) species. Among recent animals, cyclosto ...
n fish
Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of ...
known from the Silurian and Early Devonian periods. Fossils are predominantly known from Late Silurian fluvial deposits from Wales
Wales ( cy, Cymru ) is a country that is part of the United Kingdom. It is bordered by England to the east, the Irish Sea to the north and west, the Celtic Sea to the south west and the Bristol Channel to the south. It had a population in ...
and England
England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe b ...
: some species were also found in strata representing shallow water marine environment
Shallow water marine environment refers to the area between the shore and deeper water, such as a reef wall or a shelf break. This environment is characterized by oceanic, geological and biological conditions, as described below. The water in thi ...
in Canada
Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...
and North America.
The head-shield and body armor of most traquairaspids form an almond shape. Plates have a distinctive ornamentation of tubercles: this ornamentation is very similar to the plate ornamentation of the heterostracan '' Weigeltaspis''. This similarity of ornamentation creates much confusion over the taxonomical placement of ''Weigeltaspis'', in addition to confusion over whether or not an isolated plate is of ''Traquairaspis'', or of ''Weigeltaspis''. Intact specimens of ''Weigeltaspis'' suggest a living animal similar to psammosteids like '' Drepanaspis''.Tarlo, Halstead. "LB t1965) Psammosteiformes tAgnatha)—A review with descriptions of new material from the Lower Devonian of Poland, II. Systematic Part." Palaeontologia Polonica 15: 168. Pages 20-21 The armor of ''Phialaspis symmondsi'' (once considered as species of ''Traquairaspis'') is shaped like a jet plane or paper airplane, with pointed wing-like crests and a dorsal crest near the posterior end of the armor. The body of "Yukonaspis," ''Traquairaspis angusta'', is greatly elongated, based on the holotype, a ventral plate.
Most species of traquairaspids are placed within the type genus '' Traquairaspis''; most of the other genera, such as ''Phialaspis'', ''Toombsaspis'', and "Yukonaspis," have been synonymized into ''Traquairaspis''. ''Weigeltaspis'' is sometimes placed within Traquairaspidiformes on account of the plate ornamentation being almost identical to that of ''Traquairaspis''.
Taxonomy
* Family Phialaspididae White 1946 ** Genus '' Munchoaspis'' Tarrant 1991 ** Genus '' Phialaspis'' Wills 1935 ** Genus '' Toombsaspis'' Tarrant 1991 * Family Traquairaspididae Kiær 1932 corrig. ** Genus '' Pseudotraquairaspis'' Broad 1968 ** Genus '' Rimasventeraspis'' Tarrant 1991 'Yukonaspis'' Obručhev 1964 non Kobayashi 1936 non Stensiö 1964** Genus '' Traquairaspis'' Kiær 1932 'Orthaspis'' Brotzen 1934; ''Lophaspis'' Brotzen 1934 non Redtenbacher 1895; ''Lophaspiscis'' Whitley 1951* ?Family Weigeltaspididae Brotzen 1933/Tarlo 1962 ** ?Genus '' Weigeltaspis'' Brotzen 1933References
Heterostraci Prehistoric jawless fish orders Devonian jawless fish Silurian jawless fish Silurian first appearances Pridoli taxonomic orders Early Devonian taxonomic orders Early Devonian extinctions {{silurian-animal-stub