[PaleoIchthyology • 2015]
A Streamlined Jawless Fish (Galeapida) from the Lower Devonian of Yunnan, China and Its Taxonomic and Paleoecological Implications
A new genus and species of the Huananaspiformes (Galeaspida), Rhegmaspis xiphoidea, is described from the Posongchong Formation (Pragian, Early Devonian), Zhaotong, Yunnan Province, China. The new taxon is characterized by having a torpedo-shaped head-shield, a long rostral process, ventrolaterally set orbits, and ventrally curved branchial fossae, but no corners, inner corners, and ventral rim of head-shield. It is assigned to the family Gantarostrataspidae that include Gantarostrataspis and Wumengshanaspis. According to the new material and new observation, the Gantarostrataspidae is emended and a fresh look is prososed for Gantarostrataspis and Wumengshanaspis. As a streamlined jawless fish, Rhegmaspis displays an adaptation for a suprabenthic lifestyle with more active feeding behavior among galeaspids. The new form not only enriches the diversity of the Huananaspiformes, but also provides evidence for the last adaptive radiation of galeaspids by occupying an unexploited ecological niche during the Pragian of the Early Devonian.
Key words Zhaotong, Yunnan; Lower Devonian; Galeaspida, Huananaspiformes; taxonomy; paleoecology
Subclass: Galeaspida Tarlo, 1967
Supraorder: Polybranchiaspidida Janvier, 1996
Order: Huananaspiformes Janvier, 1975
Family: Gantarostrataspidae Wang & Wang, 1992
Genus: Rhegmaspis gen. nov.
Type species: Rhegmaspis xiphoidea sp. nov.
Etymology: Rhegma, Greek, rupture, breach; aspis Greek, shield.
Rhegmaspis xiphoidea sp. nov.
(Figs. 2−6, 9E, 10B, cover image)
Etymology: Xiphoideus (swordlike).
Holotype: A complete head-shield (IVPP V 19354.1A, B).
Paratype: A nearly complete head-shield (IVPP V 19354.2), an incomplete head-shield (V 19354.4), an incomplete endocast of skull (V 19354.3).
Horizon and type locality: Early Devonian, Pragian, Posongchong Formation,
Zhaotong, Yunnan, China.
GAI Zhi-Kun, ZHU Min, JIA Lian-Tao and ZHAO Wen-Jin. 2015. A Streamlined Jawless Fish (Galeapida) from the Lower Devonian of Yunnan, China and Its Taxonomic and Paleoecological Implications. VERTEBRATA PALASIATICA. 53(2); 93-109.
New jawless fish found from the Lower Devonian of Yunnan, China
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