Study Looks at Early Vertebrate Jaw Designs

Researchers at the University of Bristol, the University of Oxford and the Leiden University, all in the United Kingdom, recently took an interest in studying the first animals ever to sport jaw bones. Their latest foray into this field is detailed in the top scientific journal Nature.

Jawed animals first appeared and began diversifying some 420 million years ago. At that time, there were no vertebrates roaming Earth's landmasses. Every interaction between lifeforms took place under the waves, where weird fishes (by today's standards) ruled supreme.

The seas and oceans were controlled by jawless, toothless armor-plated fish, whose grip also most likely extended to all lakes as well. In these environments, jawed fish were insignificant actors.

It also didn't help that jawbones back then were nothing like they are now. The UK collaboration has identified some of the creatures that lived at the time that look more alien than aliens on television.

At this point in time, more than 99 percent of all vertebrate animals have jawbones. This classification also includes our species. One of the factors that may have contributed to this is the fact that the niches in which jawed creatures first developed remained stable for more than 80 million years.

This means that the animals had sufficient time to adapt and evolve when faced with the demands of their environments. Their jaws became a lot stronger, and with time they could even be used for more practical applications than ever before.

Using concepts from physics and engineering, researchers from the three universities looked at several of these early jaw designs, and then cross-referenced the data with patterns of diversity they uncovered in both jawed and jawless fish.

One of the most interesting aspects of the new study was determining whether jawed fish indeed appeared and replaced jawless fish, as many researchers propose. Despite the fact that this hypothesis is very widespread, no one actually tested it at length.

“Surprisingly, our results indicate that long-held assumptions concerning the replacement of jawless fishes by newly evolved jawed forms are likely wrong,” explains Bristol School of Earth Sciences expert Dr. Philip Anderson.

“The variety of feeding mechanisms in early jawed animals appears to have had little to no affect on the diversity of jawless fishes, which shared ecological space with the jawed fishes for at least 30 million years before beginning to notably decline,” he adds.

“When the jawless fishes do decline, we see no indication that their jawed cousins took up new functional roles, calling into question old ideas of ecological replacement,” the expert concludes.