Abstract
AbstractRhinoceroses are among the most endangered mammalian species today. Their past diversity is well documented from the Eocene onward, although their evolutionary history is far from being fully understood. Here, we elucidate the systematic affinities of a Pleistocene rhinoceros species represented by a partial skeleton from 709 ± 68 kya archaeological deposits in Luzon Island, Philippines. We perform a comprehensive phylogenetic analysis, including all living species and a wide array of extinct rhinocerotid species. We confirm the early split between Elasmotheriinae and Rhinocerotinae at c. 35.5 Mya and constrain the divergence between recent Asian and African rhinoceroses at c. 24 Mya, with contrasting phenotypic evolutionary rates in Diceroti and Rhinoceroti. Dental features reveal the existence of an unsuspected Asian Pleistocene clade, referred to as Nesorhinus gen. nov.. It includes the rhinoceros from the Philippines and another extinct species from Taiwan, N. hayasakai. Nesorhinus is the sister-group to a cluster comprising Dicerorhinus and Rhinoceros. Our phylogenetic results strongly suggest an island-hopping dispersal for Nesorhinus, from the Asian mainland towards Luzon via Taiwan by the Late Miocene or later, and Pleistocene dispersals for representatives of Rhinoceros. Nesorhinus philippinensis would be the first perissodactyl species supporting the island-rule hypothesis, with decreased body weight and limb-bone robustness.
Highlights
Past dispersal patterns of terrestrial vertebrates towards and within the Philippine archipelago remain a widely debated topic
Three major Pleistocene dispersal routes to the islands of Southeast Asia have been considered: one along the exposed Sunda Shelf from the Siwaliks during the Early–Middle Pleistocene with extinct genera like Stegodon, a second from China via Thailand to Indonesia with extant genera like Pongo in the Late Pleistocene and the third across sea barriers from Taiwan to the Philippines and elsewhere to the South and to the West. This latter hypothesis was favoured as the main route to the Wallacean islands by von Koenigswald (1956) while other scholars preferred the Sino-Malayan route with Palawan Island as the main gate to the Philippines
Stone tools were recovered together with the skeleton and several skeletal elements exhibited evidence of butchery (Ingicco et al, 2018, 2020). This early Middle Pleistocene individual considerably adds to the knowledge of Philippine rhinocerotid species, as its hypodigm was restricted to a few fossil teeth without any clear stratigraphic context, recovered from different islands in the archipelago
Summary
Past dispersal patterns of terrestrial vertebrates towards and within the Philippine archipelago remain a widely debated topic. Three major Pleistocene dispersal routes to the islands of Southeast Asia have been considered: one along the exposed Sunda Shelf from the Siwaliks during the Early–Middle Pleistocene with extinct genera like Stegodon (the Siva-Malayan route), a second from China via Thailand to Indonesia with extant genera like Pongo in the Late Pleistocene (the Sino-Malayan route) and the third across sea barriers from Taiwan to the Philippines and elsewhere to the South and to the West. Stone tools were recovered together with the skeleton and several skeletal elements exhibited evidence of butchery (Ingicco et al, 2018, 2020) This early Middle Pleistocene individual considerably adds to the knowledge of Philippine rhinocerotid species, as its hypodigm was restricted to a few fossil teeth without any clear stratigraphic context, recovered from different islands in the archipelago (von Koenigswald, 1956; Bautista, 1995). The completeness of the specimen allows us to test the different phylogenetic and subsequently palaeobiogeographical scenarios at hand
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