Kwatisuchus rosai
- 演化之聲
- Mar 19
- 3 min read
Age
Triassic（between Induan and Olenekian）
251-250 Ma
Taxonomy
Kingdom: Animalia
Phylum: Chordata
Class: Amphibia
Order: Temnospondyli
Suborder: Stereospondyli
Family: Benthosuchidae
Genus: Kwatisuchus
Species: Kwatisuchus rosai
Morphological description
Kwatisuchus rosai is an Early Triassic temnospondyl amphibian belonging to the family Benthosuchidae. The holotype specimen, UNIPAMPA 0765, preserves a well-preserved anterior portion of the skull. The skull is wedge-shaped, with an elongated snout. The external nares are set back from the tip of the snout, leaving a clear gap between them and the anterior margin. The nares are oval and extend posteriorly.
The surface of the skull is covered with dense small pits and radiating ridges, along with a well-developed system of sensory canals, including the supraorbital and infraorbital sulci. The supraorbital sulcus shows a slight medial curvature and crosses the suture between the nasal and lacrimal bones, reflecting an intermediate anatomical condition between primitive and more derived morphologies. The nasals are the largest bones on the skull roof.
On the palate, the anterior palatal vacuity is slightly heart-shaped. The vomers bear a V-shaped transverse row of transvomerine teeth. The palatines also carry teeth, representing one of the autapomorphic features of this genus.
Based on the preserved material, the complete skull is estimated to have reached approximately 28 cm in length, indicating a medium to relatively small body size. Overall, Kwatisuchus rosai displays a unique combination of cranial outline, sensory canal configuration, palatal openings, and dentition patterns. These features distinguish it from typical benthosuchids such as Benthosuchus and Syrtosuchus, which are primarily known from Russian deposits.
Etymology
The generic name Kwatisuchus derives from the Tupi word akwa'tim, meaning "pointed nose", referring to its elongated and narrow snout, combined with the Greek suffix -suchus, meaning "crocodile." Although this animal is not a pseudosuchian, the suffix -suchus is commonly used in naming temnospondyl amphibians.
The specific name rosai honors the Brazilian geologist and paleontologist Dr. Átila A. Stock Da-Rosa, in recognition of his contributions to the study of Triassic geology in Brazil, particularly the Sanga do Cabral Formation.
Biological description
Kwatisuchus rosai lived during the transition between the Induan and Olenekian stages of the Early Triassic. Its fossils were discovered in the Sanga do Cabral Formation in southern Brazil, specifically near the municipality of Rosário do Sul in Rio Grande do Sul.
This formation consists of alternating layers of fine sandstone and intraclastic conglomerate, representing a high-energy fluvial system under semi-arid climatic conditions. The environment likely consisted of ephemeral river channels flowing across sandy alluvial plains.
The occurrence of Kwatisuchus rosai in South America is geographically and temporally distant from previously known benthosuchids, which were thought to be restricted to Russia. This discovery significantly expands the known distribution of the group.
Phylogenetically, Kwatisuchus rosai forms a sister group with Benthosuchus sushkini and B. gusevae, and is also closely related to the genus Syrtosuchus. This placement supports the interpretation of Benthosuchidae as one of the earliest-diverging lineages within Trematosauroidea.
The discovery of Kwatisuchus rosai enriches our understanding of tetrapod diversity and biogeographic patterns in South America following the Permian–Triassic mass extinction. It also suggests that there may have been dispersal pathways connecting faunas between Russia and South America during the Early Triassic.
（Author: Shui-Ye You）
Reference
Pinheiro FL et al. (2024). Interrelationships among Early Triassic faunas of Western Gondwana and Laurasia as illuminated by a new South American benthosuchid temnospondyl. Anat Rec (Hoboken).
-30.24, -54.93
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