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Diandongichthys ocellatus Xu & Ma, 2024 |
Abstract
Ginglymodians (e.g. gars) are a group of holostean fishes with a rich fossil history in the Mesozoic. The resolution of interrelationships among extinct ginglymodians is central to the problem of understanding the origin of this clade. Here, a new fossil ginglymodian, Diandongichthys ocellatus gen. et sp. nov., is described based on 13 well-preserved specimens from the Early-Middle Triassic (Anisian) marine deposits exposed in Luoping, eastern Yunnan, China. The discovery documents one of the oldest and smallest ginglymodians hitherto known from the Middle Triassic, with a maximum standard length of 41 mm. Diandongichthys, although displaying several synapomorphies of ginglymodians, retains some primitive states with respect to other early ginglymodians (e.g. a short snout without anterior infraorbitals, a maxilla ending below the orbit, and a median gular); consequently, it is nested at the base of the Ginglymodi in this phylogenetic study. Besides body shape, some autapomorphies on the cranial bones and caudal fin easily distinguish Diandongichthys from other members of this clade. The discovery provides new insights into the origin and early diversification of ginglymodian fishes.
China, Middle Triassic, neopterygian, osteology, phylogeny
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Diandongichthys ocellatus gen. et sp. nov., holotype (IVPP V25610). |
Systematic palaeontology
Actinopterygii Cope, 1887,
Neopterygii Regan, 1923,
Holostei Müller, 1844 (sensuGrande, 2010)
Ginglymodi Cope, 1872 (sensuGrande, 2010)
Diandongichthys gen. nov.
Etymology: The generic epithet ‘Diandong’, the Chinese Pingyin for the eastern Yunnan, and the Greek suffix ‘ιχθύς’, ichthys, fish.
Geographical distribution and age: Luoping, Yunnan, China; Pelsonian, Anisian, Middle Triassic.
Diandongichthys ocellatus sp. nov.
Etymology: The specific epithet ‘cyclotus’ refers to the nearly rounded profile of the caudal fin.
Locality and horizon: Luoping, Yunnan, China; Second (Upper) Member of Guanling Formation, Pelsonian (∼244 Mya), Anisian, Middle Triassic (Zhang et al. 2009).
Diagnosis: A small-sized ginglymodian distinguished from other members of the clade by the following combination of features (autapomorphies, those unique among ginglymodians, identified with an asterisk): frontal about three times as long as parietal; parietal nearly square; large pores for supraorbital sensory canal in frontal situated very close to lateral margin of this bone (*); three supraorbitals; eight infraorbitals; three suborbitals; quadrate exposed in lateral view (uncovered by cheek bones); operclular length nearly equal to ...
Guang-Hui Xu and Xin-Ying Ma. 2024. A New basal ginglymodian Fish (Holostei: Neopterygii) from the Middle Triassic (Anisian) Luoping Biota, Yunnan, China. Zoological Journal of the Linnean Society. 201(3) zlad144. DOI: doi.org/10.1093/zoolinnean/zlad144 [16 October 2023]
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