首页|Middle Miocene paleoenvironmental reconstruction in the central Great Plains, USA, from stable carbon isotopes in ungulates
Middle Miocene paleoenvironmental reconstruction in the central Great Plains, USA, from stable carbon isotopes in ungulates
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NSTL
Elsevier
Middle Miocene (-18-12 Ma) mammalian faunas of the North American Great Plains contained a higher diversity of presumed browsers than any modern biome. This has been attributed to greater primary productivity, which commonly corresponds with densely vegetated, forested habitats today. However, several lines of evidence suggest that open biomes, which support low browser diversity today, dominated the middle Miocene. To gain a better understanding of middle Miocene habitats on the northern Great Plains, we generated a large dataset of stable carbon isotope values (delta C-13) from a wide variety of fossil ungulates. Tooth enamel was sampled from four local faunas in Nebraska of late Barstovian age (14.8-12.5 Ma). Paleoenvironmental interpretations were made using a predictive model based on delta C-13 values in vegetation and mammalian herbivores in modern biomes. Resulting mean delta C-13 fossil values for local faunas plot in the upper range expected for C-3 vegetation, indicating open biomes. Most mean values for genera plot in the range expected for open canopy habitats with only two genera in the closed canopy range. Of all the taxa, only the grazing horse, Neohipparion, plots in the range for likely C-4 consumption. Neohipparion has the highest mean delta C-13 value of any taxon, with one individual plotting in the range for unequivocal C-4 consumption and others in the mixed C-4/C-3 or C-3 water-stressed range. Neohipparion appears to be the earliest known taxon that included C-4 vegetation in its dietary niche. The range in carbon isotope values suggests browsers, mixed-feeders, and grazers all consumed vegetation in mostly open areas. Our model implies a fairly dry, open biome with limited riparian habitat. This interpretation is generally consistent with previous interpretations of an open savanna-like biome. A high diversity of middle Miocene browsers and other taxa appear to have lived in an open biome with no modern analog.
NSTL
Elsevier
