Ptychagnostus

Ptychagnostus is a member of the agnostida that lived during the Cambrian period. Ptychagnostidae generally do not exceed one centimetre in length.[1] Their remains are rarely found in empty tubes of the polychaete worm Selkirkia.[2] The genus probably ranged throughout the water column. It has two glabellar lobes, and three pygidial lobes,.[3]

Ptychagnostus
Temporal range: Middle Cambrian
Ptychagnostus germanus
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: †Trilobita
Order: †Agnostida
Family: †Ptychagnostidae
Genus: †Ptychagnostus
Jaekel, 1909
Synonyms[1]
  • Triplagnostus Linnarsson, 1869
  • Huarpagnostus Rusconi, 1950
  • Solenagnostus Whitehouse, 1936
  • Pentagnostus Lermontova, 1940
  • Aristarius Opik, 1979
  • Aotagnostus Opik, 1979
  • Acidusus Opik, 1979
  • Canotagnostus Rusconi, 1951
  • Zeteagnostus Opik, 1979

Type species

Agnostus punctuosus Angelin, 1851 from the Pt. punctuosus Zone of the Alum Shale (Drumian), Sweden (by original designation). Official ruling on the conservation of accepted usage of A. punctuosus as the type species was given by the International Commission on Zoological Nomenclature, 1993.

Remarks

Ptychagnostus affinis (Brøgger 1878) [4] was once considered a subspecies of Pt. punctuosus. Laurie (2008) [5] grouped punctuosus and affinis within Ptychagnostus, but preferred to place the closely related atavus within Acidusus.

Ptychagnostidae Genera

Høyberget & Bruton (2008) [6] concluded that the following genera belong in the Ptychagnostidae: Ptychagnostus, Goniagnostus, Tomagnostus, Lejopyge, Aotagnostus and Onymagnostus.

Species
  • Ptychagnostus punctuosus (Type species).
  • Ptychagnostus affinis (formerly Pt. punctuosus affinis)
  • Ptychagnostus aculeatus
  • Ptychagnostus akanthodes
  • Ptychagnostus atavus
  • Ptychagnostus cassis
  • Ptychagnostus ciceroides
  • Ptychagnostus cuyanus
  • Ptychagnostus germanus
  • Ptychagnostus gibbus
  • Ptychagnostus hybridus
  • Ptychagnostus intermedius
  • Ptychagnostus michaeli
  • Ptychagnostus praecurrens
  • Ptychagnostus seminula

References
  1. Samuel M. Gon III. "Agnostida Fact Sheet". A Guide to the Orders of Trilobites. Retrieved 18 November 2012.
  2. Brian D. E. Chatterton, Desmond H. Collins & Rolf Ludvigsen (2003). "Cryptic behaviour in trilobites: Cambrian and Silurian examples from Canada, and other related occurrences". In Philip D. Lane, Derek J. Siveter & Richard A. Fortey (ed.). Trilobites and their Relatives: contributions from the third international conference, Oxford 2001. Special Papers in Palaeontology. 70. pp. 157–173. ISBN 978-0-901702-81-4.
  3. Coppold, Murray and Wayne Powell (2006). A Geoscience Guide to the Burgess Shale, p.56. The Burgess Shale Geoscience Foundation, Field, British Columbia. ISBN 0-9780132-0-4.
  4. BRØGGER W. C. 1878. Om paradoxides-skifrene ved Krekling. Nyt Magazin for Naturvidens-kaberne 24, 18–88.
  5. LAURIE J. R. 2008. Species relationships in the Ptychagnostidae (Cambrian, Agnostina). In: Ra´bano I., Gozalo R. & GarciaBellido D. eds. Advances in trilobite research, pp. 211–218. Cuadernos del Museo Geominero 9.
  6. HØYBERGET M. & BRUTON D. L. 2008. Middle Cambrian trilobites of the suborders Agnostina and Eodiscina from the Oslo Region, Norway. Palaeontographica A286, 1–87.


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