Early Jurassic basal mammals
August 25, 2014

Early Jurassic Basal Mammals Were Specialized Eaters

John Hopton for redOrbit.com - Your Universe Online

Researchers from several British universities have found that small Jurassic mammals chose very specific diets from among the smorgasbord of insects available to them, with creatures of a similar type having distinct food choices.

Using a combination of technologies and comparisons with living animals, the researchers were able to study patterns of wear and tear on the mammals’ teeth in fossils. The observations showed that some “shrew-sized” mammals from the early Jurassic period ate harder insects such as beetles, while others consumed softer ones like scorpion flies.

The study of the creatures, which had lived in the South Wales area of the UK around 200 million years ago and had previously been thought to be “generalized insectivores,” assists in our broader understanding of evolutionary processes at a time when new characteristics were developing in mammals, such as better hearing and teeth capable of precise chewing.

The researchers from the universities of Bristol, Leicester and Southampton studied jaw mechanics and fossil teeth in two mammals, Morganucodon and Kuehneotherium, and reported in the journal Nature that they had developed specialized diets. They said that the mammals had different techniques for catching prey as well as for chewing it.

Specialist procedures were required in order to conduct the study, and according to Dr. Pamela Gill from Bristol, "None of the fossils of the earliest mammals have the sort of exceptional preservation that includes stomach contents to infer diet, so instead we used a range of new techniques which we applied to our fossil finds of broken jaws and isolated teeth. Our results confirm that the diversification of mammalian species at the time was linked with differences in diet and ecology."

The team used synchrotron X-rays and CT scanning to uncover a level of previously unavailable detail in the anatomy of jaws, which were of a tiny 2cm in length. The jaws were in broken sections, but scans allowed them to be 'stitched together' to make a complete digital reconstruction. A technique was also used to design hip joints and bridges known as finite element modeling was used to perform a "computational analysis of the strength of the jaws." Comparison with analyses previously carried out on the teeth of modern day insect-eating bats allowed researchers to assess the “very different patterns of microscopic pits and scratches, known as 'microwear'.”

Study co-author, Dr. Neil Gostling from the University of Southampton said of the technology involved: “The improvement in CT scanning, both in the instrumentation, at Light Source at the Paul Scherrer Institute in Switzerland where we scanned or even the µ-VIS Centre at Southampton, along with access for research of this kind, allows us to make inroads into understanding the biology and the ecology of animals long dead. The questions asked of the technology do not produce ‘speculation’, rather the results show a clearly defined answer based on direct comparison to living mammals. This would not be possible without the computational techniques we have used here.”

Professor Mark Purnell of the University of Leicester added that, "This is the first time that tooth wear patterns have been used to analyze the diet of mammals this old. That their tooth wear compares so closely to bats that specialize on different kinds of insects gives us really strong evidence that these early mammals were not generalists when it came to diet, but were quite definite in their food choices.”


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