Ancient feeding ecology and niche differentiation of Pleistocene mammalian herbivores from Tarija, Bolivia: morphological and isotopic evidence

Abstract

The exceedingly rich middle Pleistocene mammalian fauna from the classic Ensenadan Tarija basin in southern Bolivia contains a diversity of medium to large-bodied herbivores consisting of both endemic (†Toxodontia, †Litopterna, Xenarthra) and immigrant (Rodentia, Proboscidea, Perissodactyla, and Artiodactyla) taxa. In order to characterize feeding ecology and niche differences, a suite of morphological characters was measured for each of 13 species of herbivorous mammals from the Pleistocene of Tarija; these were combined with carbon isotopic results from tooth enamel. (The Xenarthra were excluded from this study because they lack tooth enamel.)Several different bivariate and multivariate combinations of characters can be used to characterize the feeding adaptations, niches, and guild composition of the Tarija mammalian herbivores. During the Pleistocene the browsing guild in the Tarija basin is interpreted to include the tapir (Tapirus tarijensis), extinct llama (Palaeolama weddelli), peccary (Tayassusp.), and deer (Hippocamelussp.). The mixed-feeding guild included two horse species (Hippidion principaleandOnohippidium devillei), litoptern (Macrauchenia patachonica), and capybara (Neochoerus tarijensis). The grazing guild included the numerically dominant horse (Equus insulatus), two lamine species (Lama angustimaxillaand cf.Vicugna, provicugna), notoungulate (Toxodon platensis), and gomphothere proboscidean (Cuvieronius hyodon). The grazing guild has the widest range of body sizes relative to the two other guilds. Closely related sympatric species within the Equidae and Camelidae differentiate their niches from one another using a combination of body size, feeding ecology, and probably local habitat. Most of the paleoecological reconstructions resulting from this combined morphological and isotopic analysis corroborate previous studies based primarily on morphology; there are, however, some notable surprises.

Hypsodonty in ungulates: an adaptation for grass consumption or for foraging in open habitat?

“…Janis & Ehrhardt, 1988;Solounias & Moelleken, 1993;MacFadden & Shockey, 1997). However, these studies do not mention that such a relationship does not hold among those species from closed habitats and some brachydont ungulates from mixed habitats.…”

Extinción de Equidae y Proboscidea en América del Sur. Un test usando datos de isótopos de carbono

“…Carbon isotopic data from Cuvieronius from Bolivia (MacFadden et al, 1994;MacFadden & Shockey, 1997) suggests an adaptation from mixed feeding to grazing. One notable exception was Cuvieronius from Chile.…”

“…Carbon isotopic data for horses from South America have been presented in several papers (MacFadden et al, 1994;MacFadden & Shockey, 1997;MacFadden, 2000b;Sánchez et al, 2006). MacFadden et al (1999) interpreted the ancient distributions and latitudinal gradients of C 3 and C 4 grasses in North and South America from the stable isotopes preserved in the teeth of Pleistocene New World horses.…”

“…MacFadden et al (1999) interpreted the ancient distributions and latitudinal gradients of C 3 and C 4 grasses in North and South America from the stable isotopes preserved in the teeth of Pleistocene New World horses. In addition, some papers investigated the application of geochemical techniques in conjunction with morphological data to characterize and reconstruct the feeding ecology and niche characterization of individual species (MacFadden & Shockey, 1997;MacFadden, 1998).…”

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“…rin, 1984; Alberdi & Bonadonna, 1988, 1990Forsten, 1988Forsten, , 1991Forsten, , 1993Forsten, , 1996Alberdi et al, 1995aAlberdi et al, , 1995cAlberdi et al, , 1998Eisenmann, 1995Eisenmann, , 1998Bernor et al, 1996;Caloi, 1997;MacFadden & Shockey, 1997;MacFadden et al, 1999). Sin embargo, apenas se habían publicado trabajos sobre los Anchitheriinae, aunque existía un consenso en considerarlos caballos ramoneadores dada la escasa altura de su dentición yugal.…”