Wednesday 11th April 2018
From 19:00 until 20:00
Venue: Dorset County Museum, High West Street, Dorchester, Dorset, DT1 1XA
Geology Revealed: Dorset landlord’s ancestor was an Early Cretaceous “rat”!!
The discovery of Man’s earliest ancestors in Durlston Bay
Dr Steve Sweetman, University of Portsmouth
In the mid-19th Century the Rev. P. B. Brodie and Mr C. Wilcox sent their combined collection of small vertebrate remains obtained from the Purbeck Group exposed in Durlston Bay to Richard Owen, soon to become Superintendent of the Natural History Departments of the British Museum. This important collection included some well-preserved mammal remains. At that time Mesozoic mammals were only known from a handful of localities worldwide and Owen immediately described one new genus and species, Spalacotherium tricuspidens. He then approached Samuel H. Beckles, a well-known south of England fossil collector, proposing that he undertake a sustained effort to recover additional material from the same locality. Beckles agreed and commenced extensive quarrying in 1856. The scale of this operation was remarkable and it probably represents one of the largest palaeontological excavations ever undertaken. Owen went on to list 16 Purbeck mammals in his 1871 Monograph of fossil Mammalia of the Mesozoic Formations.
Subsequently very few new mammal remains were reported from the Purbeck Group until 1986 when then Dorset County Museum curator Paul Ensom started bulk screening sediment samples to recover microvertebrate remains. By 2001 he had isolated more than 800 mammal specimens, mostly teeth. Among this material were a significant number of new species including Tribactonodon bonfieldi, a stem tribosphenidan - a somewhat distant and indirect ancestor to modern mammals.
In 2015, as an undergraduate dissertation project, University of Portsmouth student Grant Smith was tasked with taking further samples from the horizon so extensively sampled by Beckles in the 19th Century, now known as the ‘Mammal Bed’. He succeeded in finding a small number of teeth of taxa recorded in Owen’s Monograph but also, quite remarkably and unexpectedly, not one but two teeth of highly derived mammals belonging to the advanced line that leads directly to Man.
This presentation summarises the historical background, the techniques used to recover the new specimens and their profound significance.
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