A new graptolite species of Cyrtograptus from the uppermost Llandovery of Ziyang, Shaanxi Province, China

A new species of Cyrtograptus, C. fui n. sp., from Bajiaokou-A section in Ziyang, southern Shaanxi Province, China, is described and illustrated. Compared with other Cyrtograptus species, C. fui is characterized by a rhabdosome that forms a low helical spiral with 1.5 tightly coiled whorls proximal and distal parts of which bear 3–4 primary cladia; proximal and mesial thecae triangulate with apertural hooks twisted to the right and furnished with dorso-lateral spines; a first cladium originating from the 17th–19th theca, a six thecal separation between the first and second cladium; 9–10 thecae occuring between the second and third cladium; and second-order cladia occuring occasionally in mature rhabdosomes. Based on associated graptolite species, C. fui occurs in the latest Llandovery. The identification of the new species helps clarify evolutionary relations within Cyrtograptus in the late Llandovery and early Wenlock of China and provides new material for the palaeontology and biostratigraphy of C. insectus–C. centrifugus Biozone of northern Yangtze Plate of China.