New discoveries on the giant hedgehog Deinogalerix from the Miocene of Gargano (Apulia, Italy)

Abstract

During the Miocene, the Abruzzo/Apulia region (Italy), isolated from the continent, was the theatre of the evolution of a vertebrate ecosystem in insular context. During the Late Miocene, the protagonists of this ecosystem called “Mikrotia fauna” show a high endemic speciation level, presenting spectacular giant and dwarf species of mammals and birds. Deinogalerix is one of the most uncommon forms of this peculiar fauna. It is the largest Galericinae that ever lived. From Gargano (Apulia, Italy) deposits (also called “Terre Rosse”), Deinogalerix has been, since its discovery in the 1970s’, the subject of two publications in which various morphotypes were described. Its presence is also attested at Scontrone (Abruzzo, Italy). In 2005, the new Miocene fissure “Mikrotia 013” (M013) was found in the Gargano area at Cava Dell’Erba by a team of the Università degli studi di Torino. The study of the micromammals, and in particular the presence of an archaic form of Mikrotia, attests that M013 is the oldest fissure known to date. All the Deinogalerix remains come from the smallest morphotype ever found. The morphological features (other than size) allow us to describe the new species Deinogalerix masinii. It presents a large variability of dental and mandibular features expressed in mosaic patterns within the material: the robustness of the upper and lower P3 and P4, and the characteristic trigonid of m1 of the genus; the archaic morphology of the maxilla and the mandible; the abrading pattern of the teeth are unique for Deinogalerix. These new remains allow us to update the knowledge of Deinogalerix. The suit of characters testified that D. masinii nov. sp. is an archaic form on the evolutionary trend toward the most derived representatives of the genus. The affinities of Deinogalerix with the Parasorex group are confirmed, but the time of immigration in Gargano remains debated.

Introduction

Among the most spectacular insular adaptations of terrestrial fauna, the dwarfism of large continental species (large mammals, dinosaurs; Sander et al., 2006) and gigantism of the small ones (micromammals, birds, reptiles) are probably the most characteristic (Sondaar, 1977). This phenomenon is known as the “Island Rule” (Van Valen, 1973, Lomolino, 1985, Lomolino, 2005). Today, most of the species with extreme insular features are extinct. The most spectacular cases are observed in the fossil record (Van Der Geer et al., 2010, Sondaar, 1991). The insular extinct genus we are interested in here is the giant gymnure Deinogalerix, the largest galericine ever (Fig. 1).

Deinogalerix is part of an endemic ecosystem of the Late Miocene in the Abruzzo-Apulia palaeobioprovince, now part of the east coast of southern Italy. This bioprovince was isolated from the continent during the Miocene and formed a large palaeo-island (Rook et al., 2006). Deinogalerix has been mostly recovered among the Late Miocene “Terre Rosse” faunal complex (also known as the Mikrotia fauna) in the Gargano area (Freudenthal, 1971, Masini et al., 2010), but it is also present in the Tortonian limestone deposits of Scontrone in Abruzzo, Southern Italy (Mazza and Rustioni, 2008).

We report in the present paper new discoveries of the genus Deinogalerix from the “Terre Rosse” sediments of a karstic fissure named “Mikrotia 013” (M013), with special emphasis on the cranial remains.