Hsianwenia
Hsianwenia wui is an extinct species of cyprinid fish of the subfamily Schizothoracinae from the Pliocene lake deposits of the Qaidam Basin on the northern Tibetan Plateau.
Taxonomy and classification
The genus and species is named in honor of Professor Hsianwen Wu, one of the founders of freshwater fish research in China. Hsianwenia and Plesioschizothorax macrocephalus were found to be intermediate between extant Schizothorax and a clade containing Ptychobarbus, Diptychus, and Gymnocypris, together comprising Schizothoracinae.Description
This species is characterised by hypercalcified or hyperostotic ribs, which occupy almost the entire body of the fish. The fish seemed to live in a hyper saline environment and the hypertrophic skeleton may have been an adaptation to this habitat; the excess salts absorbed by the fish were deposited in its bones beginning at a certain size or age, leading to "extraordinarily" thickened skeletons in specimens thought to be around 10-15 years old. Hsianwenia wui grew to "more than half a meter long", with complete specimens measuring and larger sizes are indicated from incomplete specimens; if these fish grew at a similarly slow rate to extant Schizothoracines, the larger specimens are likely to be older than a decade at the time of death.A 2022 paper elaborated further on the pachyosty; the dermal skeleton is not noticeably thickened, with only the "endoskeleton" being affected. Furthermore, the ventral intramuscular bones are thicker than the dorsal ones.