Abstract:

The Tsinghsutung Formation near Balang village, Jianhe County, Guizhou Province, belonging to the eastern Guizhou
lithozone,  is more  than 300 m  in  thickness and mainly composed of dark grey  thin bedded  limestones and mudstones, which
is different  from  the  light grey  thick bedded dolostones and  limestones in  the western Guizhou  lithozone. The upper part of  the
formation is rich in trilobites, including 9 genera, 7 species, 2 conformis species and 2 indefinite species, i.e. Redlichia (Redlichia)
guizhouensis, R.  (R.) nobilis, Eoptychoparia  jinshaensis, Antagmus dapingensis, Nangaops brevis, Olenoides hupeiensis, Kootenia
sp.，  Ovatoryctocara sp.， Changaspis elongata， C. cf. elongata and Duyunaspis cf. duyunensis, of which Redlichia and Antagmidae
are most common and  typical of  the Redlichia  (R.) guizhouensis-Redlichia  (R.) nobilis Acme Zone  in  the upper part of  the
Tsinghsutung Formation. The oryctocephalid trilobites Changaspis elongate and Duyunaspis cf. duyunensis formerly reported from
the underlying Balang Formation are described for the first time in this paper from the upper part of the Tsinghsutung Formation.Moreover, Ovatoryctocara sp.， a form closely similar to Ovatoryctocara granulata from the overlying beds (lower part of the Kaili
Formation) may  likely be an ancestral species of O. granulata. The new discovery of  the oryctocephalid  trilobites  is  therefore
significant for the further work on the global boundary stratotype section and point (GSSP) for the base of Cambrian Series 3

Key words:  Tsinghsutung Formation, oryctocephalid trilobites, Cambrian, Guizhou Province