Abstract

Anourosoricini are among the most specialized shrews in terms of dentition and mandibular structure, showing carnivore-like specializations such as carnassial function and reduction and disappearance of third molars. The tribe is documented from the Upper Neogene of Europe, Asia, and North America, and from the Quaternary of Asia, where a single relict species has survived until the present day.

The Mediterranean area functioned as a sink area for the Anourosoricini. Their source area was a northern, more humid, and more forested zone extending from France to the Ukraine. Southward-directed range shifts resulted in the intermittent presence of the tribe in the Mediterranean region during more humid intervals. The dense Upper Miocene micromammal succession from the Teruel and Calatayud-Daroca basins, central Spain, shows that Crusafontina endemica was present in the area around 10.2 and between 9.7–9.5 Ma. It is succeeded by the dentally more gracile C. fastigata n. sp. at 9.0–8.8 Ma. The larger and more robust C. vandeweerdi n. sp., a form sharing features with Paranourosorex, peaks at ∼7 Ma. The last major acme occurs around 6.3 Ma and is represented by Amblycoptus jessiae. The final disappearance of the tribe from the area takes place at 5–4.5 Ma.

The Anourosoricini provide a well-documented pre-Quaternary example of recurrent climate-controlled north-south range expansion. The proposed paleobiogeographic model presumes that southward mammal migrations are driven by changes in the precipitation regime rather than the temperature regime of the Mediterranean region. A comparison to paleoecological interpretations based on the independent rodent record shows that Anourosoricini avoid areas with low levels of precipitation and low soil humidity. A mean annual precipitation minimum of 600 mm/yr is about the threshold value for populations of the tribe to survive locally.

The available evidence suggests eastward dispersal of a primitive Crusafontina species from Eurasia into North America at about the same time when Hipparion crossed the Bering Strait in a westward direction.

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