The newly-identified species is closely related to the Chinese alligator (Alligator sinensis), the only living representative of Alligatoridae (the crown-group of caimans and alligators) outside the Americas.
An artistic reconstruction of Alligator munensis. Image credit: Márton Szabó.
Named Alligator munensis, the new species lived less than 230,000 years ago in Thailand.
The reptile’s nearly complete skull, missing only a few elements of the right side, was found at the Ban Si Liam locality in the Thai province of Nakhon Ratchasima.
Eberhard Karls Universität Tübingen paleontologist Gustavo Darlim and colleagues investigated the evolutionary relationships between Alligator munensis and other species.
They compared the fossil with 19 specimens from four extinct alligator species, as well as the living American alligator (Alligator mississippiensis), the Chinese alligator, and the spectacled caiman (Caiman crocodilus).
They also reviewed previously published research on the skeletal characteristics of, and evolutionary relationships between, alligator species.
The researchers identified several skull features that are unique to Alligator munensis, including a broad and short snout, a tall skull, reduced number of tooth sockets and nostrils that are positioned far from the tip of the snout.
They also noted similarities between the skulls of Alligator munensis and the Chinese alligator, such as the presence of a small opening in the roof the mouth, a ridge on the top of the skull, and a raised ridge behind the nostrils.
Skull of Alligator munensis, holotype. Scale bar – 10 cm. Image credit: Darlim et al., doi: 10.1038/s41598-023-36559-6.
“The two species are closely related and may have shared a common ancestor in the lowlands of the Yangtze-Xi and Mekong-Chao Phraya river systems,” the scientists said.
“Increases in the elevation of the southeastern Tibetan Plateau between 23 and five million years ago may have led to the separation of different populations and evolution of two separate species.”
“Alligator munensis has large tooth sockets towards the back of its mouth, which indicates that it may have possessed large teeth that could have been capable of crushing shells.”
“As a result of this, Alligator munensis may have eaten hard-shelled prey, such as snails, in addition to other animals.”
The discovery is reported in a paper in the journal Scientific Reports.
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G. Darlim et al. 2023. An extinct deep-snouted Alligator species from the Quaternary of Thailand and comments on the evolution of crushing dentition in alligatorids. Sci Rep 13, 10406; doi: 10.1038/s41598-023-36559-6
