Ptychagnostus atavus

Ptychagnostus atavus is a species of agnostid trilobite. It belongs to the genus Ptychagnostus in the family Ptychagnostidae. It was originally described by Swedish paleontologist Sven Axel Tullberg as Agnostus atavus in 1880.[1] It is used in biostratigraphy as an index fossil. Its first appearance at the GSSP section in the Wheeler Shale of Utah is defined as the beginning of the Drumian Age (around 504.5 million years ago) of the Miaolingian (Middle Cambrian).[2][3]

Ptychagnostus atavus Temporal range: Drumian PreꞒ Ꞓ O S D C P T J K Pg N ↓
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	†Trilobita
Order:	†Agnostida
Family:	†Ptychagnostidae
Genus:	†Ptychagnostus
Species:	†P. atavus
Binomial name
†Ptychagnostus atavus (Tullberg, 1880)
Synonyms
Acidusus atavus (Tullberg, 1880) Agnostus atavus Tullberg 1880

References

1. "Ptychagnostus atavus". Paleobiology Database. Retrieved 16 November 2012.
2. Babcock, L. E.; Robison, R. A.; Rees, M. N.; Peng, S.; Saltzman, M. R. (2007). "The Global boundary Stratotype Section and Point (GSSP) of the Drumian Stage (Cambrian) in the Drum Mountains, Utah, USA" (PDF). Episodes. 30 (2): 85–95.
3. Ogg, G. "GSSP for Drumian Stage". Geologic TimeScale Foundation. Retrieved 16 November 2012.