Cyathaspidiformes

Cyathaspidiformes
	Poraspis from the Lochkovian of Europe and Siberia.
Temporal occurrence
	Silurian to Lower Devonian
	443.4 to 393.3 million years
Locations
	North America; Europe, Russia; Brazil;
Systematics
	Neumünder (Deuterostomia)
	Chordates (chordata)
	Vertebrates (vertebrata)
	Pteraspidomorphi
	Heterostraci
	Cyathaspidiformes
Scientific name
	Cyathaspidiformes
	Kiaer , 1930

The Cyathaspidiformes are an order of extinct, fish-like, armored vertebrates that occurred from the Silurian to the Lower Devonian within a span of 50 million years.

features

The Cyathaspidiformes had an elongated body, oval in cross section and slightly flattened dorsoventrally. The head and front body were completely surrounded by armor made of bone plates, the rear body was protected by strong, roof-tile-like overlapping scales. The front back and top of the head were covered by a single strong plate. The eyes lay in an indentation on the front part of this plate. Within these bone plates were the sensory lines that opened outwards through several rows of pores. An indentation in the narrow branchial plate on the side served as a gill opening. There were some smaller plates (oral plates) around the mouth opening. The bone plates showed a ornamentation of narrow, parallel property and fine notched from dentine existing (dentin) burrs, which as a diagnostic applies feature of the group. The dentin was missing in the pits between the ridges. There were no paired fins, dorsal and anal fin, but the fish had a flattened, almost symmetrical caudal fin. The animals probably swam by winding their bodies sideways. The weight of the bone armor made them awkward and likely spent much of their lives lying on the floor.

nomenclature

The taxon was introduced in 1930 by Johan Aschehoug Kiaer under the name Cyathaspida.

Internal system

Within the Cyathaspidiformes, two subgroups are distinguished, which Nelson has the rank of families.

Amphiaspidida
- Genera: Aphataspis , Ctenaspis , Eglonaspis , Kureykaspis , Prosarctaspis
Cyathaspidida
- Genera: Anglaspis , Allocryptaspis , Anglaspis , Capitaspis , Dinaspidella , Gerronaspis , Irregularareaspis , Liliaspis , Pionaspis , Poraspis , Putoranaspis , Torpedaspis .

literature

Michael J. Benton : Paleontology of the vertebrates. 2007, Verlag Friedrich Pfeil, Munich (2007), page 61, ISBN 3-89937-072-4 .
Robert L. Carroll : Paläontologie und Evolution der Vertbeltiere , Thieme, Stuttgart (1993), page 31-32, ISBN 3-13774-401-6 .

Joseph S. Nelson : Fishes of the World . John Wiley & Sons, 2006, pp. 29-30, ISBN 0-471-25031-7 .

Hans-Peter Schultze: Pteraspidomorphi Page 184 in: Wilfried Westheide & Reinhard Rieger: Special Zoology Part 2: Vertebrae and Skull Animals , 1st edition, Spectrum Academic Publishing Heidelberg • Berlin, 2004, ISBN 3-8274-0307-3 .

Individual evidence

↑ J. Kiaer: Ctenaspis - A new Genus of Cyathaspidian Fishes. In: Skrifter om Svalbard og Ishavet , No. 33, pp. 1–7, 1930. (digitized version )

Web links

Commons : Cyathaspidiformes - collection of images, videos and audio files

Philippe Janvier. 1997. Heterostraci. in The Tree of Life Web Project
Palaeos: Cyathaspidiformes
The Paleobiology Database: Cyathaspidiformes

[Kiaer,_1930-1] J. Kiaer: Ctenaspis - A new Genus of Cyathaspidian Fishes. In: Skrifter om Svalbard og Ishavet , No. 33, pp. 1–7, 1930. (digitized version )