Thylacocephala

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Thylacocephala
Fossil and reconstruction of Ostenocaris cypriformis

Fossil and reconstruction of Ostenocaris cypriformis

Temporal occurrence
lower Cambrian to Upper Cretaceous
529 to 83.6 million years
Locations
  • worldwide
Systematics
without rank: Bilateria
without rank: Primordial mouths (protostomia)
Over trunk : Molting animals (Ecdysozoa)
Trunk : Arthropod (arthropoda)
incertae sedis
Class : Thylacocephala
Scientific name
Thylacocephala
Pinna , Arduini , Pesarini & Teruzzi , 1982

Thylacocephala (from ancient Greek θύλακος thylakos "sack" and κεφαλή kephalē "head") is an extinct class of bivalve arthropods .

features

Thylacocephala were arthropods with a laterally compressed, shield-like shell with a length between 15 and 250 mm, which enclosed the entire body. Abdominal features such as a telson were absent. The armor was mostly oval or egg-shaped and had a rostrum and a notch at the front end , a rear rostrum was possible. The eyes were well developed, mostly spherical or teardrop-shaped, in some species also hypertrophic or stalked, and consisted of numerous small ommatidia . There may be 5 pairs of extremities on the head and 8 or more pairs on the back of the body, which became smaller as they came back.

Systematics

The class was developed by Pinna et al. Established in 1982 on the basis of Ostenia cypriformis . They gave 5 diagnostic features, but no formal definition of the class.

External system

The Thylacocephala can only be safely assigned to the arthropods. A possible relationship with the crustaceans (Crustacea), due to the shell surrounding the body, has not yet been clarified.

Internal system

Schram 1990 divided the representatives of the class Thylacocephala into two orders: the Concavicarida Briggs & Rolfe, 1983 , Thylacocephala with a rostrum overhanging the visual notch, and the Conchyliocarida Secrétan, 1983 , Thylacocephala with a weakly defined visual notch and rostrum and eyes, which are located on the Surface of a large, protruding "cephalon sack".

A distinction is currently made between 21 genera:

The genera Isoxys and Tuzoia probably also belong to the class Thylacocephala.

swell

literature

  • J. Vannier, Chen J.-Y., Huang D.-Y., S. Charbonnier, Wang X.-Q: The Early Cambrian origin of thylacocephalan arthropods . Acta Palaeontologica Polonica 51 (2), 2006: 201-214. PDF

Individual evidence

  1. ↑ G. Pinna, P. Arduini, C. Pesarini, G. Teruzzi: Thylacocephala: una nuova classe di crostacei fossili . Atti della Società Italiana di Scienze Naturali e del Museo Civico di Storia Naturale di Milano 123, 1982: 469-482.
  2. ^ FR Schram: On Mazon Creek Thylacocephala . Proceedings of the San Diego Society of Natural History 3, 1990: 1-16.

Web links

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