Morphometric and phylogenetic analyses of the fossilised remains of the jaws and teeth of a shrew discovered in a deposit in Gran Dolina de Atapuerca, in Burgos, a city of northern Spain at the edge of the central plateau, have shown this to be a new species (Dolinasorex glyphodon) that has not previously been described. The extinct animal had red teeth, was large in size compared with mammals of the same family, and was more closely related to Asian than European shrews.

Researchers from the University of Zaragoza (UNIZAR) have discovered fossils in the TD4, TD5 and TD6 levels of the Gran Dolina deposit in Burgos that date to between 780,000 and 900,000 years ago, and have shown that these belong to a new genus and species of shrew (Dolinasorex glyphodon), from the Soricidae family (small insect-eating mammals).

"To date, all the medium to large-sized Soricidae fossils discovered in the deposits of the Sierra de Atapuerca belonged to Beremendia fissidens, a species of plio-pleistocene shrew that was distributed throughout Europe, Juan Rofes, lead author of the study that has been published recently in the Zoological Journal of the Linnean Society and a researcher in the Paleontology Department at the UNIZAR, told Servicio de Información y Noticias Científicas (SINC).

Dolinasorex glyphodon mandible
Dolinasorex glyphodon mandible.  Photo: J. Trueba

The morphometric and phylogenetic studies of the new species reveal a close link with the species of eastern Asia, where it could have arisen and evolved before migrating to the Iberian Peninsula.

In addition, analyses of jawbones and individual teeth of Dolinasorex glyphodon, collected between 1991 and 2007 in Atapuerca, have enabled the scientists to develop paleoecological and biogeographical hypotheses, suggesting that the animal lived in an epoch characterised by a warm, wet and relatively stable climate, and that "the origin and initial dispersal of this shrew would have been in and from the Asian continent," adds Rofes.

A shrew that looks like a devil

Dolinasorex glyphodon was a shrew with red teeth that belonged to the Soricinae sub-family. By using allometric calculations (relating to changes in the size of body parts in comparison with changes in the overall size of the animal), the researchers have described it as "giant". Compared with a modern, large-sized member of the Soricidae family, such as the water shrew (Neomys fodiens), which weighs in at around 14 grams, the body mass of the extinct shrew reached 60 grams.

The study of the fossil remains of this mammal has also made it possible to discover that the shrew injected toxic saliva, in the same way that snakes do, via a "narrow and conspicuous channel" located on the inside surface of its lower incisors. "This was a mechanism very similar to that of the modern solenodons and almiquis, which are close relatives of the shrews and live on the islands of Cuba and Haiti," explains Rofes.

Although the remains of shrews are frequently found in paleontological deposits, their presence is due above all to the feeding habits of birds of prey, which "feed on micro-vertebrates and then regurgitate the skin, hair and bones in conglomerate pellets," he added.

Comparisons with faunal associations from many other European deposits have enabled the discoverers of Dolinasorex glyphodon to describe it as endemic, and it is the first genus of Soricidae to be described on the Iberian Peninsula to date. However, Rofes and his team warn that "the results of this phylogenetic study are only a first step and not at all definitive, but they could be of great interest for more complete studies in the future."