Qushiaspis, a new genus of gantarostrataspid fish (galeaspida, stem-gnathostomata) from the Lower Devonian of Yunnan, China

Abstract

ABSTRACT A new genus and species of the Galeaspida Qushiaspis elaia gen. et sp. nov. is described from the Lower Devonian Xujiachong Formation of Qujing, Yunnan Province, southwestern China. The new genus displays the diagnostic characters of Huananaspidiformes including a large oval-shaped median dorsal opening, a slender rostral process, lateral positioned orbital opening, and posteriorly projecting cornual and inner cornual processes. It bears a closer resemblance to Gantarostrataspidae than to Sanchaspidae and Huananaspidae in lacking the laterally projecting cornual processes, than to Sanqiaspidae in lacking the crescent-shaped median dorsal opening. Unlike all other galeaspids, the dermal ornamentation of Qushiaspis exhibits numerous tessera-like units composed of a central large olive-shaped tubercle surrounded by 1–2 rings of much smaller tubercles. An extended phylogenetic analysis of Galeaspida indicates that Qushiaspis, Gantarostrataspis, Wumengshanaspis, and Rhegmaspis form a monophyletic group, the family Gantarostrataspidae, and Qushiaspis is the sister taxon of all other gantarostrataspids. As a less derived gantarostrataspid, Qushiaspis sheds new light on the plesiomorphic condition of the family Gantarostrataspidae, and demonstrates the high diversity of Devonian galeaspids during the Pragian in the Qujing Basin.