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Asioaspis brachyotus
R.-R. Zhang, N. Zhang, Li, Zhu & Gai, 2026 VERTEBRATA ALASIATICA. 64(2); |
A new genus and species, Asioaspis brachyotus gen. et sp. nov. of Polybranchiaspiformes, is described from the Lower Devonian Lochkovian Xishancun Formation near Miandian Reservoir, Qujing City, Yunnan Province, China. The new genus is characterized by an elongated ovoid headshield with serrated lateral margins, a small subcircular median dorsal opening, short and laterally projecting cornual processes, an exceptionally broad ventral rim, 12 pairs of branchial fossae, and coarse granular tubercles (~3/mm²). It displays a mosaic of characters of the most primitive polybranchiaspiform (Platylomaspis), derived Polybranchiaspiformes, and even the basal members of the galeaspid family Dayongaspidae. Phylogenetic analysis resolves A. brachyotus as an intermediate taxon between the most primitive Gumuaspidae and other derived Polybranchiaspiformes. Although A. brachyotus also shares the broad ham-brim-like ventral rim with the Gumuaspidae, its other characters are more like other derived Polybranchiaspiformes. In particular, its median dorsal opening and paired orbital openings are not highly close-set on the top of the headshield as in the Gumuaspidae, but rather significantly separated from each other and close to the margin of the ventral rim as in the Pentathyraspidae, Duyunolepididae, and Polybranchiaspidae. These proportions indicate that it was unlikely to have lived a semi-infaunal lifestyle and are more consistent with the epibenthic habit typical of most galeaspids, representing an evolutionary transition from the semi-infaunal benthic to epibenthic lifestyle within Polybranchiaspiformes.
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Photograph of Asioaspis brachyotus gen. et sp. nov. from Lower Devonian Xishancun Formation, Qujing, Yunnan in ventral view
A. an incomplete headshield, paratype, IVPP V26676. 2; B. a nearly complete dorsal headshield, holotype, V26676. 1
A. an incomplete dorsal headshield, IVPP V26676.5; B. an incomplete dorsal headshield, V26676.4b |
Subclass Galeaspida Tarlo, 1967
Supraorder Polybranchiaspidida Janvier, 1996
Order Polybranchiaspiformes Liu, 1965
Family Asioaspidae fam. nov.
Type genus Asioaspis gen. nov.
Differential diagnosis: The Asioaspidae is distinguished from other families of Polybranchiaspiformes by its short, ear-like, and laterally projecting cornual processes. It resembles the Gumuaspidae in having a broad ventral rim, but differs in lacking a rostral process. It differs from the Duyunolepididae, Pentathyraspidae, and Polybranchiaspidae by the presence of a broad ventral rim and further differs from the Duyunolepididae by bearing a pair of broad inner cornual processes. Therefore, a new family, the Asioaspidae fam. nov., is herein established.
Genus Asioaspis gen. nov.
Type species Asioaspis brachyotus gen. et sp. nov.
Etymology: Asioaspis is derived from Asio (referring to owls of the genus Asio characterized by prominent ear tufts) plus aspis (Greek shield).
Diagnosis: Medium-sized polybranchiaspiform characterized by an ovoid headshield with serrated lateral margins; the rostral margin arcuate, but lacking a rostral process; the cornual processes short and projecting laterally; the inner cornual processes large and broad leaf-shaped; median dorsal opening small and subcircular in shape; orbital opening large, round, and dorsally positioned; the sensory canals are well developed, V-shaped posterior supraorbitals and four pairs of lateral transverse canals issuing from the lateral dorsal canal; ventral rim of headshield remarkably broad, 13.5–14.1 mm in width on each side (approximately one half of the width of the entire headshield); a large dome-shaped oralobranchial chamber (a composite chamber with both oral and branchial functions) with 12 pairs of branchial fossae; and ornamentation consists of coarse tubercles (~3/mm²)
Asioaspis brachyotus gen. et sp. nov.
Etymology: The brachyotus means short-eared, which is in reference to its short and laterally projecting cornual processes that resemble a pair of short ears on the headshield, as in Asio.
Type locality and horizon: Miandian Reservoir in the Triathlon Sports Park, Qilin District, Qujing City, Yunnan Province, China; Xishancun Formation, lower Lochkovian, Lower Devonian.
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Morphological comparison of Polybranchiaspiformes, Dayongaspidida, and Huananaspidiformes A. Asioaspis; B. Dayongaspis (Zhang et al., 2024); C. Foxaspis (Gai et al., 2023); D. Platylomaspis (redrawn after Gai et al., 2018); E. Rhegmaspis (Gai et al., 2015); F. Rhegmaspis (Gai et al., 2015); G. Nanningaspis (redrawn after Gai et al., 2018) A–E, G. in dorsal views; F. in ventral view.
Phylogenetic diagram of Dayongaspidida, Polybranchiaspiformes, and Huananaspidiformes
Dayongaspis (Zhang et al., 2024); Platylomaspis (redrawn after Gai et al., 2018); Nanningaspis (redrawn after Gai et al., 2018); Polybranchiaspis (Liu, 1965); Foxaspis (Gai et al., 2023); Rhegmaspis (Gai et al., 2015).
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| Life restoration of Asioaspis brachyotus gen. et sp. nov. |
ZHANG Rui-Rui, ZHANG Ning, LI Qiang, ZHU Min and GAI Zhi-Kun. 2026.
Asioaspis, A New Genus of Polybranchiaspiformes (Galeaspida, stem-Gnathostomes) from the Lower Devonian of Yunnan, China.
VERTEBRATA PALASIATICA. 64(2); 137-150. DOI:
10.19615/j.cnki.2096-9899.260113 [20 April 2026]
