Belantsea montana
- 演化之聲
- Mar 19
- 2 min read
Updated: 1 day ago
Age
Carboniferous（Serpukhovian）
330.9-323.2 Ma
Taxonomy
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Order: Petalodontiformes
Family: Belantseidae
Genus: Belantsea
Species: Belantsea montana
Morphological description
The fossil of Belantsea montana was discovered in the Bear Gulch Limestone Member of Montana, USA. Its dentition consists of a symmetrical symphysial tooth family accompanied by three lateral tooth families. All teeth possess denticulations. Compared with B. occidentalis, B. montana exhibits relatively longer and more pointed crowns, with a greater number of denticulations (7–14). The crowns are extremely thin and blade-like, bearing two to three basal lingual ridges and one to two basal labial ridges. The holotype represents an adult individual measuring 24 cm in total length, with a maximum body height of 9 cm. The body is laterally compressed and equipped with two large, aspinous dorsal fins supported by radial elements. The pectoral and pelvic fins are broad, with the pelvic fins positioned close to the caudal fin, and an anal fin is absent.
Scales cover the entire body and all fins. Scales adjacent to the upper and lower jaws are thick and elevated, featuring irregular serrated ridges, whereas other scales are leaf-like or blade-shaped, highly variable in form, and typically possess thickened margins or a central ridge. The orbits are positioned far posteriorly on the neurocranium, and an elongated ethmoid region extends anterior to the eyes. The pectoral girdle and posterior jaw region show clear calcification, but overall endoskeletal calcification is limited.
The holotype specimen is catalogued as MV 7698.
Etymology
Belantsea: derived from the self-designation of the Crow people of Montana.
montana: referring to the U.S. state of Montana, where the fossil was discovered.
Biological description
The laterally compressed body, combined with large, flexible fins supported by radial elements and well-developed musculature, suggests that Belantsea montana possessed strong maneuverability rather than capacity for sustained long-distance swimming. It was likely adapted to sheltered environments, possibly inhabiting confined or benthic shallow marine settings. Its movement through the water was probably slow, and it may have concealed itself beneath rocks to avoid predators.
The enlarged scales surrounding the mouth are interpreted as protective structures against abrasion during feeding. This morphology implies a feeding strategy involving scraping or crushing rough substrates such as algae or the hard exoskeletons of small benthic invertebrates.
The absence of mobile lips and the clearly heterodont dentition further support a specialized feeding mechanism. Anterior teeth are labiolingually curved and sharply blade-like, whereas posterior teeth are smaller, lower-crowned, and resemble reduced versions of the anterior teeth. Histologically, the teeth exhibit a multilayered enameloid structure, including terminal membrane enameloid, radial-bundled enameloid, and tangled-fibered enameloid, all surrounding an osteodentine core, with no orthodentine present.
The dentition indicates a relatively shortened jaw, with a size gradient decreasing from anterior to posterior. This pattern resembles that of the closely related Netsepoye. These features suggest negative allometric growth between jaws and teeth during evolution, alongside a high degree of specialization for a particular feeding strategy.
（Author: Shui-Ye You）
Reference
Lund R. (1989). New petalodonts (Chondrichthyes) from the Upper Mississippian Bear Gulch Limestone (Namurian E2b) of Montana. Journal of Vertebrate Paleontology.
46.992, -108.92
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