Tsunyidiscus
Tsunyidiscus is a trilobite belonging to the suborder Eodiscina. Tsunyidiscus appeared near the end of the Lower Cambrian, during the late Atdabanian stage of geologic time and some collections suggest it may have survived into the Botomian. The genus is very small, oculate and isopypous with a narrow dome-shaped glabella and a narrow bullet-shaped pygidial axis. Thorax consists of three segments. Tsunyidiscus is the only genus currently attributed to the family Tsunyidiscidae.
Description
Like other Agnostida the body of Tsunyidiscus is diminutive, the headshield and end-section are of approximately same size, with 3 thoracic segments in-between, each consisting of a horizontal inner portion that abruptly passes into an inclined outer portion. The cephalon has a deeply parabolic outline and maximum width usually anterior to genal angle. Glabella extremely narrow, lateral glabellar furrows usually obscure, with rounded and expanded frontal glabellar lobe. The most backward lobe of the glabella at least as long as the lobe in front of it, and is usually expanded laterally, may bear sharp, posteriorly directed spine. Long, curved posterior fixigenal spine may be present. The furrow between those two lobes is transverse and uninterrupted. The facial sutures are proparian. The free cheeks or are ½× as long as the cephalon. The pygidium has a narrow, multisegmented axis. The thorax and pygidial axis segments may carry nodes.Species and distribution
- Tsunyidiscus aclis
- Tsunyidiscus acutus
- Tsunyidiscus armatus
- Tsunyidiscus chintingshanensis
- Tsunyidiscus limbanodus Qian in Zhang et al., 1980
- Tsunyidiscus longquanensis
- Tsunyidiscus niutitangensis
- Tsunyidiscus pengshuiensis Zhang & Clarkson, 2012 was extracted from the Lower Cambrian of China.
- Tsunyidiscus pertenus Lin et al., 2004
- Tsunyidiscus yanjiazhiensis S. Zang et al. in Yin and Li, 1978
- 'Tsunyidiscus'' sp.'''
Taxonomy