New remains of Nalamaeryx (Tragulidae, Mammalia) from the Ladakh Himalaya and their phylogenetical and palaeoenvironmental implications

Abstract

Nalameryx savagei is one of the rare mammals found in India during the Oligocene. Five dental remains composed the originally found material, described in 1990. The first phylogenetic hypothesis proposed Nalameryx to be closely related to the basal ruminant Lophiomerycidae. The description of new specimens from the type bed K/7b from the Kargil Formation (late Oligocene, India), led to a reinterpretation of the phylogenetic position of Nalameryx and of the early evolutionary history of the Tragulidae. Based on our phylogenetic hypothesis, Nalameryx is nested within the living Tragulidae, making it one of the oldest known tragulid. Moreover, the enigmatic late Eocene Stenomeryx from Myanmar is not recovered as a ruminant in our analysis. Tooth isotopic data indicate that Nalameryx fed on plants that have grown under xeric conditions. This is in agreement with palaeoenvironmental information observed on plants from Turkish and Pakistani localities where Nalameryx has already been found. This region of the world had a seasonal climate with an arid period during the late Oligocene.