Late Miocene rhinocerotids from the Balkan-Iranian province: ecological insights from dental microwear textures and enamel hypoplasia

Abstract

The late Miocene is a period of increasing aridity and habitat openness 22 in the south-eastern Mediterranean region. The impact of these changes has not 23 been fully explored regarding rhinocerotids' ecology, although rhinoceroses were 24 a major and diverse component of the Miocene mammalian faunas. Here we 25 investigate the palaeoecology of rhinocerotid specimens coming from 12 26 localities throughout the Balkan-Iranian zoogeographic province, and covering a 27 large part of the late Miocene (MN9 to MN13). Microwear textures confirmed 28 the hypothesised niche partitioning between the two main rhinocerotid species -29 Ceratotherium [Ce.] neumayri (mixed-feeder including grasses) and Dihoplus 30 pikermiensis (browser) -but highlighted dietary overlap between Ce. neumayri 31 and the co-occurring chilothere species at Maragheh, Samos and Pentalophos-1. 32 Although microwear did not reveal clear spatiotemporal differences, we found 33 obvious discrepancies regarding hypoplasia prevalence: Vallesian rhinocerotid 34 teeth displayed more defects (Xirochori and Pentalophos-1: 16.26 % of teeth 35 affected) than Turolian specimens (all other localities: 9.72 %). Similarly, 36 rhinocerotid teeth from eastern localities (Samos and Maragheh; supposedly more 37 arid), had a higher hypoplasia prevalence (13.52 %) than their western 38 counterparts (6.90 %). Insights from rhinocerotids' ecology thus challenged space 39 and time homogeneity within Balkan-Iranian province, and the associated 40 savanna habitat, at least regarding the sample studied here.

Spatio-temporal diversity of dietary preferences and stress sensibilities of early and middle Miocene Rhinocerotidae from Eurasia: impact of climate changes

“…This could mean that hypsodonty in this clade might counterbalance significant grit load induced by feeding low in open environments, thus reflecting more the habitat rather than the diet, an hypothesis that has already been proposed to explain hypsodonty evolution (Janis, 1988;Jardine et al, 2012;Semprebon et al, 2019). A lower prevalence of hypoplasia in elasmotheriines compared to other associated rhinocerotids has also been noted at Maragha (in the latest Miocene, though), where Iranotherium morgani does not present hypoplastic defects (0/16 teeth; Hullot et al, 2022). This finding could suggest an influence of diet in the stress susceptibility, with more specialized species (i.e., heavily relying on a limited number of resources) being more sensitive.…”

Spatio-temporal diversity of dietary preferences and stress sensibilities of early and middle Miocene Rhinocerotidae from Eurasia: Impact of climate changes

“…This could mean that hypsodonty in this clade might counterbalance significant grit load induced by feeding low in open environments, thus reflecting more the habitat rather than the diet, an hypothesis that has already been proposed to explain hypsodonty evolution (Janis, 1988; Jardine et al, 2012; Semprebon et al, 2019). A lower prevalence of hypoplasia in elasmotheriines compared to other associated rhinocerotids has also been noted at Maragha (in the latest Miocene, though), where Iranotherium morgani does not present hypoplastic defects (0/16 teeth; Hullot et al, 2022). This finding could suggest an influence of diet in the stress susceptibility, with more specialized species (i.e., heavily relying on a limited number of resources) being more sensitive.…”

Life in a Central European warm-temperate to subtropical open forest: paleoecology of the rhinocerotids from Ulm-Westtangente (Aquitanian, early Miocene, Germany)

“…Such events might result in increased levels of stress through vegetation damage, habitat loss or displacement and decrease of water quality (e.g., Lake et al 2006), and have already been linked to increased hypoplasia prevalence in rhinocerotids (Hullot et al 2021). Besides external stressors, an effect of the diet and/or of phylogeny on stress susceptibility has been hypothesized in Miocene rhinocerotids from other sites (Hullot et al 2023a, b). Here, both species are closely phylogenetically related (early diverging taxa of Aceratheriinae sensu lato ; Rhinocerotinae incertae sedis in Tissier et al 2020) and are similarly affected despite having different inferred diets (Table 6), suggesting that phylogeny might be the main driver.…”

“…The early Miocene is also marked by a turnover and a great endemism in rhinoceros species of Western Europe. Despite all these, the paleoecology of rhinocerotids during this important time period has rarely been studied, although it has the potential to unravel niche partioning and ecological shifts associated with climatic conditions (Hullot et al, 2023a(Hullot et al, , 2023b.…”