
Submitted by Abigail Youngman on Mon, 03/02/2025 - 14:34
The previously hidden diversity of shrews has been revealed in research by recent Zoology MPhil graduate, Haobo Yuan and Dr Robert Asher, published in the Proceedings of the Royal Society B.
Entitled ‘The Origin and Evolution of Shrews’, the paper describes this investigation of shrews’ anatomy, palaeontology, and molecular biology which has uncovered their hidden diversity despite outwardly similar appearance.
Highlights of the findings described include a novel and mysterious bone in "Congo" and "mouse" shrews from Africa. This elongate, needle-like bone projects over the back of their necks and can be as long as their forearm. Important muscles from the shoulders, neck and head attach to this bone. It does not appear to protrude beyond the skin, and despite its needle-like appearance, it lacks an obvious conduit for venom. The function of the bone is not yet known but it is likely relevant to mobility of the head but we cannot rule out a role in defence or acoustics.
The paper also includes research on a new, 33-million-year-old fossil from Wyoming. Whereas, in the fossil record, shrews are usually known only from fragmentary jaws and teeth, the Wyoming fossil is much more complete and shows the anatomy of this ancient shrew's skull and forelimb. It shares several features with living shrews, such as its jaw joint. Instead of a single connection between the lower jaw and the rest of the skull, shrews' jaws are separated into distinct upper and lower facets. Such morphology allows these species to carry out complicated yet well-coordinated chewing movements.
In other regards, the new fossil differs from living shrews, for example in the anatomy of its nose and ear regions. These exhibit similarities to the nose and ear skeletons of moles and gymnures, and demonstrate the piecemeal evolution of these animals from a common ancestor, which is estimated to have existed over 57 million years ago.
Yuan H, Dickson ED, Martinez Q, Arnold P, Asher RJ. 2024. The Origin and Evolution of Shrews (Soricidae, Mammalia). Proceedings of the Royal Society B. DOI: 10.1098/rspb.2024.1856