Oct 3, 2016 | By Alec

Tooth-like structures can be found in vertebrates throughout the history of the world. It is believed that the ancestors of sharks and related fish species were among the first to develop denture-like structures in their mouths, presumably rough sandpaper-like shapes on the jaw (not individual teeth) that could grind down food. Because they are so common in so many species, teeth and jaws are a very important target for evolutionary biologists, as they can aid researchers to track the evolutionary process of various animals – including humans.

By carefully studying the teeth and jaw structures of very delicate and rare fossilized remains, this focus has led researchers to the Placoderms: a group of 400 million year old fish species that were believed to be the first to develop bony jaw structures. While it was previously argued that these fish had so-called ‘real teeth’, researchers from the Australian National University have just applied 3D printing and 3D scanning to an Buchanosteus fish fossil (of the Placoderm family)– which showed that the fish actually represents a more transitional phase in teeth evolution. This, in turn, can change our understanding of the evolutionary process of human jaws.

This important biological breakthrough was realized by Australian National University (ANU) researchers Gavin Young and Yuzhi Hu, and Dr Carole Burrow from Queensland Museum, and the results have already been published in the journal Biology Letters. With their paper, entitled ‘Placoderms and the evolutionary origin of teeth: a comment on Rücklin & Donoghue (2015)’, they are disputing the real teeth conclusions of an article published in that same journal only a year ago.

To reach this updated conclusion, the ANU team relied on very rare fossil skulls and braincases of the Buchanosteus, which have been found around Lake Burrinjuck in southeast Australia – acid-etched from limestone rock. The creature, which is part of the Placoderm family that has been at the core of the tooth origin questions, was from the Early Devonian period and has now been extensively compared to earlier placoderm fish and more distantly related jawed fish.

Unfortunately, the fossil itself was excavated in such a state that it was impossible to conclude whether or not the creature had jaws or teeth. Through the application of micro CT 3D scanning and 3D printing techniques, however, the researchers were able to properly study the fossil and its jaw functions, concluding that it had a more primitive form of teeth than claimed in the earlier article. “It's great that we are able to use recent technology, such as micro-CT scanning and 3D printing, to examine some of the earliest known evidence of tooth-like structures in the most primitive jawed fishes,” said Carole Burrow. The study itself was funded by the Australian Research Council.

According to Ms Yuzhi Hu, a PhD student from the ANU Research School of Earth Sciences, this allows them to make important inroads into the major scientific questions on the origin of teeth. “We are researching this question using new evidence from an exceptionally preserved fossil fish about 400 million years old,” Hu said. Specifically, the 3D prints (scaled up to six times their original size) were used to study exactly how the jaws moved and how they enabled eating. It also allowed them, for the first time, to see whether or not these fossils actually had teeth. They were also able to conclude that some fossil remains were not, in fact, made from enameloid – unlike previously thought.

While an important breakthrough, its full impact will only be felt once they can incorporate this study into the larger question of how teeth have originated in all vertebrates – including humans. As Gavin Young, a paleontologist at the ANU Department of Applied Mathematics, explained, there is thus still a lot to be done. “We are conducting further research on the internal tissue structure of tooth-like denticles in the mouth of the fish fossil, to determine whether they represent a transitional stage in the evolution of teeth,” Young said in a news release. And 3D printing will doubtlessly play a key role in that research too.

 

 

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