Stable isotope analysis of middle Miocene mammals from the Siwalik sub-Group of Pakistan

Abstract

Stable isotope analysis is pivotal for investigating the paleodiet and paleoecology of past mammals. In this paper, we analyzed thirty fossil enamel samples belonging to the families Suidae, Rhinocerotidae, and Deinotheriidae for δ13Cenamel and δ18Oenamel composition to investigate paleodiet and paleoecology of middle Miocene mammals of the Siwalik sub-Group of Pakistan. The three mammalian groups, when combined together, yielded an average δ13Cenamel value of -12.2 ± 2‰, indicating a pure to nearly pure C3 diet. Suids show slightly higher δ13Cenamel values of -11.2 ± 1.4‰ when compared to rhinocerotids and deinotheres (-12.3 ± 0.8‰ and -12.5 ± 1.3‰, respectively), which could be explained by selective foraging on new leaf shoots or feeding from open spaces. Alternatively, the differences in δ13Cenamel could be due to different digestive physiologies and different enamel-diet enrichment factors. Members of all three families showed significant differences in δ18Oenamel values, where suids yielded higher δ18O values of -8.2 ± 1.2‰ compared to rhinocerotids and deinotheres (-11.4 ± 1.8‰ and -10.4 ± 1.7‰, respectively). Based upon these results, we assume that these mammals inhabited subtropical forests similar that of mid-Miocene of the Siwalik Group, India and Nepal. The modern analogues of such vegetation system are present in East and South of Myanmar, Nepal, and Malaya where precipitation is enough to support evergreen C3 forests. By contrast, today's floodplain environments in Pakistan are dominated by C4 grasses, and C3 vegetation is only present in non-floodplain settings.

Tectonically Controlled Establishment of Modern‐Like Precipitation Patterns in East and Central Asia During the Early Late Miocene

“…This species was a forest resident that favored soft and less gritty vegetation, preferentially leaves of plants and trees, and preferred to live in forest land near swamps (Biasatti et al., 2018). The paleoenvironmental reconstruction of this mammal's habitat in the middle Miocene deposits in the Siwaliks of Pakistan (Waseem et al., 2021) indicates precipitation supporting an evergreen ecology similar to the modern‐day vegetation of central Myanmar (which has a MAP range of 500–1,000 mm). This also supports the calculated MAP interpretations of the MJZ section.…”

Dietary Traits of Late Miocene Hipparions From Maragheh Revealed Through Dental Wear

“…On the other hand, this difference might indicate a different paleoenvironment of fossil taxa. For example, it is evident that floodplain environments today in Pakistan are dominated by C 4 grasses, and C 3 vegetation is only present in non-floodplain (Waseem et al 2021). So, animals living/feeding in different paleoenvironmental settings demonstrate different diets.…”