Study on Jaw Mechanism Offers Clues about Feeding Habits of Early Tetrapods

A latest analysis conducted on the jaws of one of the earliest known limbed vertebrates, tetrapods, reveal that the species that evolved from fish fed under water and not on land.

In order to gain an insight into the feeding mechanism of one of the earliest known tetrapods - Acanthostega - a team of international scientists developed a novel technique.

Acanthostega belongs to an extinct genus and is among the first vertebrates. The fossilized fragments of this new species were discovered in 1987. It belonged to the late Denovian Period (416-360 Million Years Ago). With fish-like tail and gills, the origin of tetrapods from fish is a major evolutionary transition. This includes today's amphibians like frog, birds, reptiles and other mammals.

A team of researchers from the Universities of Lincoln,  Zurich, Cambridge and Bristol  used advanced statistical techniques to study the anatomical, functional and ecological changes linked with the evolution of tetrapods.

Dr Marcello Ruta from the University of Lincoln's School of Life Sciences said, "The origin of tetrapod from fish is an iconic example of a major evolutionary transition.  The fossils of Acanthostega continue to play an unsurpassed role in our understanding of the fish-tetrapod transition."

The team's examination of the structure of the lower jaws of Acanthostega and several other tetrapods and tetrapod like fish, revealed that the jaws of the Acanthostega were suited to a more aquatic lifestyle.

"Acanthostega retained many primitive and fish-like features while also displaying unquestionable tetrapod features such as fingers and toes.  Its broad snout appears to be consistent with aquatic feeding habits (suction feeding) but its complex cranial joints appear to be similar to those of terrestrial vertebrates and would suggest direct biting on land environments as a means of prey capture. This paradox prompted our stud," said Ruta.

The researchers examined the patterns in the jaw structures of the Acanthostega , fish and tetrapods  to find the similarities in their shapes.  They did this by incorporating advanced engineering techniques to stimulate the biting movements.

The researchers saw that the lower jaw of the Acanthostega was anatomically and functionally similar to the jaws of early fish and other fish-tetrapod species.

The researchers claim that this study adds weight to the idea that these animals were among those who evolved limbs with digits and continued feeding in water rather than hunting on land.

The study was documented in the Proceedings of the Royal Society B.