Absolute and relative ages of fossil localities in the Santa Cruz and Pinturas Formations

Caviomorphs (South American hystricognaths) are recorded in the continent since the middle Eocene. The middle Eocene-early Oligocene is considered a key moment for their evolutionary history because by the early Oligocene they were differentiated into four superfamilies: Octodontoidea, Cavioidea, Chinchilloidea and Erethizontoidea. Due to their generalized dental patterns and abundance in the fossil record, Octodontoidea are interesting for analysing the origin and early history of caviomorphs. The phylogenetic relationships of the earliest octodontoids are studied herein. Results confirmed a basal caviomorph diversification in the middle Eocene (c. 45 Mya), with one lineage leading to Pan-Octodontoidea, and another leading to Erethizontoidea, Cavioidea and Chinchilloidea, which is not in accordance with analyses based on molecular data. Three major radiations were identified: the first one (late Eocene?/early Oligocene?) occurred in low latitudes with the differentiation of Pan-Octodontoidea and the earliest crown-Octodontoidea. The second radiation (late Oligocene) was a large-scale South American event; in the southernmost part of the continent it is recognized as the first Patagonian octodontoid radiation, which provided the characteristic high morphological disparity of the superfamily. The third radiation (late Miocene) is characterized by the replacement of 'old' by 'modern' octodontoids; the nature of this third event needs to be study in a broader taxonomic context.

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“…For the age calibration we followed Fleagle et al . () and Dunn et al . () for the Oligocene – early Miocene, Deschamps et al .…”

Section: Methodsmentioning

confidence: 87%

Main radiation events in Pan-Octodontoidea (Rodentia, Caviomorpha)

Arnal

Vucetich

2015

Zool J Linn Soc

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“…In particular, we analysed the taxa recorded by Kay et al (2012) in the Fossiliferous Levels 1-7 of Tauber (1997); excluding Homalodotherium, for which there are no mandibles recovered from those levels. These taxa represent a narrow temporal window (P17.4-17.5 Ma; Fleagle et al 2012;Perkins et al 2012), which allows palaeoecological integration. See Vizcaíno et al (2012) for a detailed description of the localities mentioned.…”

Section: Specimensmentioning

confidence: 99%

Teeth complexity, hypsodonty and body mass in Santacrucian (Early Miocene) notoungulates (Mammalia)

Cassini

Pino

Muñoz

et al. 2015

Earth and Environmental Science Transactions of the Royal Socie

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Notoungulates, native South American fossil mammals, have been recently objective of several palaeoecological studies. Ecomorphology and biomechanics of the masticatory apparatus, together with micro and mesowear analyses on tooth enamel, were applied in order to understand their palaeobiology. In particular, the relationship between some dental traits (hypsodonty, occlusal surface area and complexity) and body mass is still poorly understood. These features were measured by means of the hypsodonty index (HI), occlusal surface area (OSA) and tooth area (OTA), enamel crest complexity (ECC) and length (OEL). The relationships between these indices were evaluated in five pan-contemporaneous Santacrucian Notoungulata genera from Patagonia: Adinotherium and Nesodon (Toxodontia), Interatherium, Protypotherium and Hegetotherium (Typotheria). While OSA, OTA and OEL were size dependent and strongly correlated, HI and ECC were size independent. All notoungulates analysed have very hypsodont teeth, indicating high rates of tooth wear in response to an increase of abrasives consumed with the food; their tooth occlusal area and complexity could be related to chewing efforts associated with the toughness of the plants consumed. HI, OSA and ECC were considered useful for palaeoecological reconstructions, but the results presented here show that these three features are integrated as a complex, so should not be evaluated separately.

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“…First defined as the 'piso Santacruceño' by F. Ameghino based on the extensive collections made by his brother Carlos in the Santa Cruz Province (Ameghino, 1887(Ameghino, , 1889(Ameghino, , 1906, its classic localities within the Santa Cruz Formation stretch along the Atlantic coastal cliffs from Monte León National Park to Río Gallegos (Ameghino, 1906;Marshall, 1976;Tauber, 1997;Kay et al, 2008;Fleagle et al, 2012;Fig. 1).…”

Section: An Overview Of the Pansantacrucian Fossil Faunasmentioning

confidence: 99%

“…However, different scholars have pointed out that typical Santacrucian mammals do occur in slightly older inland horizons, indicating that the Santacrucian SALMA probably extends to somewhat earlier ages. These include Andean and central Patagonian outcrops, as for example the upper succession of the eolian-volcaniclastic Pinturas Formation in the valley of the Pinturas River (Kramarz and Bellosi, 2005), and exposures at Lake Posadas/Puyrredón (Hatcher, 1903;Blisniuk et al, 2006), Río Chalia/Sehuén (Hatcher, 1903), Estancia El Carmen, Lake Cardiel, and Gobernador Gregores (Bown and Fleagle, 1993;De Barrio et al, 1994;Kramarz and Bellosi, 2005;Fleagle et al, 2012). Other localities with potential Santacrucian fossils are El Trébol and Camerón (Bordas, 1939), Meseta Latorre (Brandmayr, 1945), and the Cerro Boleadoras Formation in the valley of the Jeinimeni and Zeballos Rivers, south of Lake General Carrera/Buenos Aires (Ugarte, 1956;Vucetich, 1994;Scillato-Yané and Carlini, 1998.…”

Section: An Overview Of the Pansantacrucian Fossil Faunasmentioning

confidence: 99%