Ptychagnostidae

Ptychagnostidae
Temporal range: Cambrian Stage 5 - Paibian
Ptychagnostus gibbus
Ptychagnostus cuyanus
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: †Trilobita
Order: †Agnostida
Superfamily: †Agnostoidea
Family: †Ptychagnostidae
Kobayashi, 1939
Type genus
Ptychagnostus
Jaekel, 1909
Genera

See text.

Ptychagnostidae is a family of agnostid trilobites from the 5th Stage to the Paibian Age of the Cambrian (~509 to ~497 million years ago).[1] The family includes several important index fossils.

Description

Like all agnostids, ptychagnostids have cephalons and pygidia that are more or less uniform in size and shape (isopygous). The thorax is composed of two body segments (somites). They are completely blind.[2]

Distribution and age range

Ptychagnostidae has a cosmopolitan distribution. They existed during the 5th Stage of the Series 3 Epoch to the Paibian Age of the early Furongian Epoch in the Cambrian (~509 to ~497 million years ago).[1] The earliest member of the family is Ptychagnostus praecurrens from the Burgess Shale fauna.[3]

Taxonomy

Ptychagnostidae is classified under the superfamily Agnostoidea of the suborder Agnostina, order Agnostida. The family was first established by the Japanese paleontologist Teiichi Kobayashi in 1939. Its name comes from the type genus, Ptychagnostus, which is itself derived from Ancient Greek πτυχος (ptychos, "folded") and άγνωστος (ágnostos, "unknown"). It includes the following genera (with their taxonomic synonyms):[2]

= Miagnostus
= Agnostonymus
=Triplagnostus, Huarpagnostus, Solenagnostus, Pentagnostus, Aristarius, Aotagnostus, Acidusus, Canotagnostus, Zeteagnostus

References

  1. ↑ 1.0 1.1 "Ptychagnostidae". Paleobiology Database. Retrieved 18 November 2012.
  2. ↑ 2.0 2.1 Samuel M. Gon III. "Agnostida Fact Sheet". A Guide to the Orders of Trilobites. Retrieved 18 November 2012.
  3. ↑ Richard A. Robison (1984). "Cambrian trilobites of east-central Alaska". Cambrian Agnostida of North America and Greenland: Part I: Ptychagnostidae. The University of Kansas Paleontological Contributions: Paper 109. Paleontological Institute, University of Kansas. pp. 1–60. ISSN 0075-5052.

External links