A new alligator species dating back 230,000 years, identified in Thailand

The fossil remains are crucial for tracing the enigmatic origin of the Chinese alligator— a sole representative "outside the New World."
Sade Agard
Life reconstruction of Alligator munensis.
Life reconstruction of Alligator munensis.

Márton Szabó 

Scientists have unveiled a new species of ancient alligator discovered in Thailand, closely related to the Chinese alligator, according to a new study published in Nature on July 13. 

The species, named Alligator munensis after the nearby Mun River, was identified by examining a nearly complete fossilized skull estimated to be younger than 230,000 years old. Geologically speaking, this age fits in with the Quaternary of Thailand— or the Pleistocene and the Holocene epochs.

The authors emphasized that fossil alligator remains from Asia are critical for tracing the enigmatic evolutionary origin of the Chinese alligator, Alligator sinensis— the sole living representative of Alligatoridae "outside the New World."

Discovering A. munensis

The researchers compared the remains of A. munensis with those of 19 specimens from four extinct alligator species, as well as the Chinese alligator, American alligator, and spectacled caiman. They discovered unique skull features in A. munensis, such as a broad and short snout, a tall skull, reduced tooth sockets, and nostrils far from the snout tip.

A new alligator species dating back 230,000 years, identified in Thailand
Comparison between the skulls of (a) Alligator munensis and (b) Alligator sinensis (a Chinese alligator)in lateral view.

Notably, they found similarities between A. munensis and the Chinese alligator, suggesting a close evolutionary relationship and a possible shared ancestor in the lowlands of the Yangtze-Xi and Mekong-Chao Phraya river systems.

In a press release, the authors speculated that the elevation of the southeastern Tibetan Plateau from 23 to 5 million years ago potentially separated distinct populations and the subsequent evolution of two different species.

The researchers also noted that A. munensis exhibited large tooth sockets towards the back of the mouth, suggesting it may have had powerful teeth capable of crushing shells. This led them to propose that A. munensis potentially consumed hard-shelled prey, including snails and other animals.

The study sheds light on the evolutionary history of Asian alligators, highlighting the unique characteristics and relationships within the alligator species.

Where do alligators live globally?

Did you know in Asia, there are no naturally occurring species of alligator? Alligators are native to the Americas, mainly in the southeastern United States.

The two species of alligator are the American alligator (Alligator mississippiensis) and the Chinese alligator (Alligator sinensis). These species are found in the wild on two continents: North America and Asia.

The Chinese alligator is critically endangered and is limited to small areas in eastern China.

In ancient times, various alligator species existed worldwide. Fossil records reveal examples of ancient alligator species in North America, such as Alligator prenasalis in the Eocene epoch (56 to 33.9 million years ago), Alligator olseni during the Eocene and Oligocene (33.9 to 23 million years ago), and Alligator mcgrewi in the Miocene epoch (23 to 5.3 million years ago).

These are just a few examples of ancient alligator species that once thrived. Over time, some species went extinct, while others evolved into the modern-day alligator species we know today.

The full study was published in Nature on July 13 and can be found here.

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