Bulongosteus liui
Age
Devonian (Famennian)
371 Ma
Taxonomy
Kingdom：Animalia
Phylum：Chordata
Class：Placodermi
Order：Arthrodira
Family：Selenosteidae
Genus：Bulongosteus
Species：Bulongosteus liui
Morphological description
Bulongosteus liui is characterized by a triangular median nuchal plate, with a convex anterior margin, a distinctly concave posterior margin, and slightly concave lateral margins. The posterior end of the paranuchal plate extends beyond the posterior margin of the median nuchal plate and bears two sensory canals. The preorbital plate is enlarged to form the anterodorsal margin of the orbit, and its surface is densely covered with fine tubercles. The anterior part of the marginal plate is thickened to form the posterior margin of the orbit, with three sensory canals arranged in a distinct Y-shaped pattern. The posterior ventrolateral plate is elongate. These characteristics distinguish Bulongosteus liui from other members of the family Selenosteidae.
Etymology
The genus name Bulongosteus is derived from Bulonggor, the locality where the fossils were discovered, with "Bulong" referring to the locality and the Greek word osteus, meaning "bone" or "bony armor."
The species name liui honors Xianting Liu, one of the earliest Chinese paleichthyologists to study brachythoracid arthrodires.
Biological interpretation
The holotype of Bulongosteus liui is specimen B20-1, consisting of a median nuchal plate. Additional referred specimens include a preorbital plate, suborbital plate, paranuchal plate, median dorsal plate, ventrolateral plate, and several other dermal plates. All fossils were recovered from the upper part of the Zhulumute Formation in the Bulonggor area of western Junggar, Xinjiang, China, and date to the early Famennian.
Bulongosteus liui represents the first arthrodire discovered in Xinjiang, the first relatively complete aspinothoracid brachythoracid arthrodire known from China, and the first aspinothoracid arthrodire ever discovered in continental deposits worldwide. Previously, members of this group were known almost exclusively from marine strata. Therefore, the discovery of Bulongosteus liui greatly expands the known ecological range of aspinothoracid arthrodires.
The study suggests that Bulongosteus liui was capable of inhabiting freshwater environments during at least part of its life history and, like many Late Devonian fishes, was probably euryhaline, capable of tolerating a wide range of salinities. Sedimentological evidence indicates that it inhabited a braided river system surrounded by abundant vegetation resembling the Leptophloeum–Sublepidodendron Assemblage flora. Based on this associated plant assemblage, the researchers assigned the fossils to the early Famennian.
（Author: Bai Leng）
Reference
Yilong, L., Ruiwen, Z., Yiming, G. (2020). The first aspinothoracid arthrodire from the Late Devonian continental strata are found in western Junggar, Xinjiang. Chinese Science Bulletin.
+46.72, +86.10
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