Dental News - Fossil teeth trace human lineage to rat-like creature

Dental Tribune International

Tue. 14. November 2017

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PORTSMOUTH, UK: According to new research from the University of Portsmouth in England, fossils from the oldest mammals belonging to the line that led to human beings have been discovered on the Jurassic Coast of Dorset in the UK. The two teeth are from small, rat-like creatures that lived 145 million years ago in the shadow of the dinosaurs. The animals are reportedly the ancestors of almost all mammals alive today.

The discovery of the teeth was made by University of Portsmouth undergraduate student Grant Smith. Dr Steve Sweetman, a research fellow at the University of Portsmouth and the study’s lead author, said: “Grant was sifting through small samples of earliest Cretaceous rocks collected on the coast of Dorset as part of his undergraduate dissertation project in the hope of finding some interesting remains. Quite unexpectedly, he found not one but two quite remarkable teeth of a type never before seen from rocks of this age. I was asked to look at them and give an opinion and even at first glance my jaw dropped.”

The teeth were recovered from rocks exposed in cliffs near Swanage, which has given up thousands of iconic fossils. “The teeth are of a type so highly evolved that I realised straight away I was looking at remains of Early Cretaceous mammals that more closely resembled those that lived during the latest Cretaceous—some 60 million years later in geological history. In the world of palaeontology there has been a lot of debate around a specimen found in China, which is approximately 160 million years old. This was originally said to be of the same type as ours but recent studies have ruled this out. That being the case, our 145-million-year-old teeth are undoubtedly the earliest yet known from the line of mammals that lead to our own species,” said Sweetman.

Sweetman believes the mammals were small, furry creatures and most likely nocturnal. One, a possible burrower, probably ate insects and the larger may have eaten plants as well. Noting that the teeth are of a highly advanced type that can pierce, cut and crush food Sweetman said, “They are also very worn which suggests the animals to which they belonged lived to a good age for their species. No mean feat when you’re sharing your habitat with predatory dinosaurs.”

The paper, titled “Highly derived eutherian mammals from the earliest Cretaceous of southern Britain”, was published in the Acta Palaeontologica Polonica journal on 7 November.