Atopodentatus unicus

Overview

Atopodentatus unicus is a reptile interpreted as having fed on plant material in the sea. The front of both upper and lower jaws expanded sideways like a hammer. New fossils dramatically changed interpretations of its unusual face.^[1]

Key facts

Its snout was initially interpreted as curving downward. A 2016 study used new specimens to present jaws expanded laterally at the front. Better-preserved bones prompted a fresh view of the previously unfamiliar face.^[1]

Time and place

This is a Middle Triassic marine reptile from the Guanling Formation in present-day China. A museum account places its setting at approximately 242 million years ago. It offers a view of the world in which marine reptiles developed diverse bodies and feeding strategies after a major extinction.^[2][3]

The time range describes source context, not the complete duration of this species.

Size, form and skeleton

The front of the jaws bears teeth interpreted as having been used for scraping, while densely packed needle-like teeth lie farther back. The original description reported a total length of 2.75 m for one type specimen. Forefeet, hind feet, and laterally expanded jaws together form a distinctive body.^[1][2]

Habitat and reproduction

Researchers inferred that it scraped algae from the bottom with sturdy front teeth, sucked them in with water, and filtered them using the dense needle-like tooth rows farther back. This interpretation assigns scraping and filtering to different teeth within one mouth. Its unusual jaws provide a way to investigate feeding on marine plant material.^[1]

Fossil discovery

In 2014, the snout was interpreted as curving downward, but two new specimens reported in 2016 revealed hammer-shaped jaws. Both came from the Guanling Formation in Luoping County, present-day Yunnan Province, China; one exposes the dorsal side and the other the ventral side. Fossils preserved in different orientations changed the interpretation of the face.^[1]

References

1. Chun et al. (2016) — The broad jaws and plant diet of Atopodentatus
2. A new marine reptile from the Triassic of China, with a highly specialized feeding adaptation
3. Field Museum (2016) — A herbivorous marine reptile with a hammer-like head
4. Study — Aerodynamics of Late Triassic British kuehneosaurids

Research questions

What foods could densely packed small teeth process? Researchers compared the broad jaw regions with tooth shapes and proposed scraping and filtering functions. Studying small body regions thus led to research into a new feeding strategy in marine ecosystems.^[1]

Observation

First examine how the jaws expand sideways rather than vertically. Then consider the elongated body and forelimbs and hind limbs to understand where the unusual face fits into the whole animal.^[1]