New Data on Miocene Neotropical Provinciality from Cerdas, Bolivia

We provide the first faunal report for the early/middle Miocene fauna of Cerdas, Bolivia (16.5–15.3 Ma; 20° 52′ S, 66° 19′ W), based primarily on new specimens collected in 2007. As many as twelve species of mammals in nine families are represented. Notoungulates include Palyeidodon obtusum (Toxodontidae), Protypotherium cf. attenuatum and Protypotherium sp. nov. (Interatheriidae), ‘Plesiotypotherium’ minus and possibly Microtypotherium choquecotense (Mesotheriidae), and Hegetotherium? sp. nov. (Hegetotheriidae). Xenarthrans include Stenotatus planus and Prozaedyus sp. (Cingulata: Dasypodidae), Peltephilidae gen. et sp. nov. (Cingulata), and Xyophorus cf. bondesioi (Pilosa: Nothrotheriidae). A new species of litoptern is also present (Macraucheniidae) as well as an unidentified rodent (Chinchillidae: Lagostominae). Two of these Cerdas species occur in Friasian sensu stricto/Colloncuran SALMA faunas of Patagonia, and perhaps one in Santacrucian SALMA faunas. Among middle latitude localities, Cerdas resembles Chucal, Chile (late early Miocene, Santacrucian SALMA) in community composition (e.g., abundant mesotheriids, few rodent species), but has no species in common; it shares one species with Quebrada Honda, Bolivia (middle Miocene, Laventan SALMA), and perhaps as many as three more. These observations indicate that Cerdas is not referable to the Santacrucian, and that the upper limit of this SALMA in the middle latitudes falls somewhere between 17.5 Ma (the top of Chucal) and 16.5 Ma (the base of Cerdas). Based on the range of dates proposed for the youngest Santacrucian intervals in Patagonia, a diachronous offset of up to 2.1 Ma may exist at this point in the SALMA sequence between middle and high latitude faunas.     

Macrauchenia patachonica Owen, 1838: Limb bones morphology,locomotory biomechanics,and paleobiological inferences

Macrauchenia patachonica Owen, 1838 was among the last and largest litopterns, an extinct order of South American native ungulates. Macrauchenia patachonica had anatomical peculiarities as extremely retracted nasals, enlarged cervical vertebrae, and limb bones proportions without good living analogs that lead to asking about its paleobiology. To quantitatively assess the strange combination of limb bone features in M. patachonica, we constructed an indicator of differences in anatomical adaptations for efficient running between forelimb and hind limb (IDFH). We also made a multivariate analysis using data on osteological ratios of living mammals and two other litopterns. We discuss several biomechanical and paleobiological implications of the striking differences between hind limb and forelimb design in M. patachonica. Our main suggestion is that M. patachonica, during fast locomotion, probably used a posture with the neck in a horizontal position.     

Macrauchenia patachonica Owen (Mammalia, Litopterna) de la région de São Raimundo Nonato (Piauí, Nordeste brésilien) et la diversité des Macraucheniidae pléistocènes

The São Raimundo Nonato (Piauí, Northeastern Brazil) area yielded about 50 Macraucheniidae remains. The study of this material and of other fossils from Northeastern Brazil (Paraíba, Pernambuco, Rio Grande do Norte) shows a great similarity to Macrauchenia patachonica as it was defined in Argentina, which is the most abundant of the three species pertaining to the genus. Thus the taxon Xenorhinotherium bahiense created in 1988 by Cartelle et Lessa for a material discovered in the Bahia State and assigned to use for all the Quaternary Litopterns from tropical Brazil appears to be no more than a junior synonym of it. M. patachonica seems to have occupied very varied biotopes from sea level up to a high of 4000 m, and from the cold Southern Patagonia to the Equatorial Venezuela. The species lived from the Middle Pleistocene up to the beginning of the Holocene.