Platyhystrix rugosus
- Rodrigo
- Mar 19
- 3 min read
Updated: 1 day ago
Age
Carboniferous（Gzhelian）-Permian（Kungurian）
299-279.5 Ma
Taxonomy
Kingdom: Animalia
Phylum: Chordata
Class: Amphibia
Order: Temnospondyli
Family: Dissorophidae
Genus: Platyhystrix
Species: Platyhystrix rugosus
Morphological description
Platyhystrix rugosus is an early Permian amphibian characterized by extremely elongated neural spines that form a sail-like structure along the back. The proximal portions of these spines are smooth, whereas slightly above the base they become covered with tubercles arranged in roughly longitudinal rows. These ornamented regions are bounded by ridges along the anterior and posterior margins of each spine. Further distally, the tubercles merge into a vermiculate pattern that extends toward the tips of the spines.
Along both the anterior and posterior edges of each neural spine, there is a pair of closely appressed vertical ridges. These are interpreted as attachment sites for strong interspinous ligaments, which likely bound adjacent spines tightly together and contributed to a relatively rigid dorsal column .
The "sail" of Platyhystrix rugosus was formed by a limited number of highly elongated neural spines. The number of dorsal vertebrae was probably lower than in many other labyrinthodont amphibians, resulting in a shortened and stiffened vertebral column. In cross-section, the spines are expanded in the anteroposterior direction and are closely spaced, indicating that the back was reinforced by a tightly integrated ligament system.
In addition, compared with other dissorophid amphibians, Platyhystrix rugosus possessed a relatively large skull, exceeding 19 cm in midline length, with a narrow and elongated dorsal outline. The dermal ornamentation on the skull roof and lateral surfaces is highly diverse. The dorsal margins of the orbits, the edges of cranial plates, and the cheek regions bear prominent ridges and nodular projections. These tuberculate features are especially well developed on the posterior skull roof, postorbital, squamosal, supratemporal, and tabular regions. The central dorsal surface of the skull is marked by a reticulate pattern of depressions that becomes finer toward the nasal region. This distinctive ornamentation is a key feature distinguishing Platyhystrix rugosus from other members of Dissorophidae.
Based on the marginal dentition and preserved portions of the premaxilla, the upper jaws likely bore more than 65 teeth on each side. These teeth are simple, conical, and sharply pointed.
Etymology
The genus name Platyhystrix was re-described by Wann Langston Jr. in 1953. Its taxonomic history was previously confused with other genera. The name derives from Latin, meaning "flattened spine" (platy- flat, hystrix spine), referring to its conspicuously elongated dorsal spines.
The species name rugosus means "rough," referring to the tuberculate and ridged surface ornamentation of the neural spines.
Biological description
Platyhystrix belongs to the order Temnospondyli, suborder Rhachitomi, and is closely related to the family Dissorophidae, possibly representing a member of that group. Fossils of this genus are known from Lower Permian deposits in the Four Corners region of the United States, including southeastern Utah, southwestern Colorado, and northern and southern New Mexico. All known specimens are assigned to a single species, P. rugosus.
This animal was likely more adapted to terrestrial locomotion than many other temnospondyls. The stiffened structure of the neural spines and associated ligament system probably provided enhanced support for the body during movement on land .
Although it has been proposed that the sail of Platyhystrix functioned in thermoregulation, similar to that of Dimetrodon, there is no evidence of extensive vascularization in the neural spines. Consequently, this hypothesis remains uncertain. Paleontologists generally suggest that elongation of the neural spines initially evolved to reinforce the vertebral column, and only later may have been co-opted for other functions such as sexual display.
(Author: Rodrigo)
References
Vaughn, P. P. (1971). A Platyhystrix-like amphibian with fused vertebrae, from the Upper Pennsylvanian of Ohio. Journal of Paleontology, 45(3), 464–469.
Vaughn, Peter Paul (1962). "Vertebrates from the Halgaito Tongue of the Cutler Formation, Permian of San Juan County, Utah". Journal of Paleontology. 36 (3): 529–539. ISSN 0022-3360
Case, E.C. (1910). "New or little known reptiles and amphibians from the Permian (?) of Texas". Bulletin of the American Museum of Natural History. 28: 163–181.
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