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Phylogeny and evolutionary patterns of South American octodontoid rodents

100%

Verzi D. H., Olivares A. I., Morgan C. C.

Acta Palaeontologica Polonica

2014

tom 59

nr 4

Octodontoidea is the most diverse clade of hystricognath rodents, and is richly recorded in South America since at least the Oligocene. A parsimony-based morphological phylogenetic analysis of a wide range of extant and extinct octodontoids recovered three major clades, here recognised as Echimyidae, Octodontidae, and Abrocomidae. Taxa previously assigned to Echimyidae or Octodontoidea incertae sedis are here interpreted for the first time as early representatives of Ctenomyinae (Octodontidae), Octodontinae or Abrocomidae. Based on our results, we estimate the divergence of octodontoid families and subfamilies to have occurred during the Late Oligocene, which is consistent with molecular estimates, but older than previous inferences based on the fossil record. Contrary to previous suggestions, we show the first appearances of modern members of Abrocomidae, Octodontinae and Ctenomyinae to be distinctly decoupled from the origin of these clades, with different stages in the evolutionary history of octodontoids seemingly following distinct phases of palaeoenvironmental change. Depending on the phylogenetic pattern, fossils from the stage of differentiation bear evolutionary information that may not be provided by crown groups, thus highlighting the unique and important contribution of fossils to our understanding of macroevolutionary patterns.

Capybaras, size, shape, and time: A model kit

100%

Vucetich M. G., Deschamps C. M., Olivares A. I., Dozo M. T.

Acta Palaeontologica Polonica

2005

tom 50

nr 2

The capybaras (Hydrochoeridae) are outstanding rodents for their large size and euhypsodont and multilaminated cheek teeth. Although today they are represented by a single species, it was generally thought that their past diversity was much higher, especially during the late Miocene–early Pliocene. Such diversity is here analyzed taking into account the ontogenetic variation of the p4–m3 in different populations. Numerous isolated teeth of different size found in the upper levels of the Puerto Madryn Formation (late Miocene, Peninsula Valdés, Argentina) were interpreted as members of an ontogenetic series of a new species here described, Cardiatherium patagonicum. They provided clues to evaluate ontogenetic variation and a new framework to analyze the family diversity. In this context, it is proposed that multiple species described from the Ituzaingó Formation (late Miocene, Entre Ríos, Argentina) based on lower teeth, may actually represent specimens of different stages of the ontogenetic trajectory of a single species. Likewise, we found that several nominal taxa from other localities were based on juvenile specimens. According to these results, the diversity of the Hydrochoeridae during the late Miocene and early Pliocene was drastically reduced. The validity of the subfamily Cardiatheriinae is debated. Finally, it is suggested that the whole family should be revised taking into account the ontogenetic variation.

Ograniczanie wyników

2 Acta Palaeontologica Polonica

2 Olivares A. I.

1 Deschamps C. M.

1 Dozo M. T.

1 Morgan C. C.

1 Verzi D. H.

1 Vucetich M. G.

1 2014

1 2005

Wyniki wyszukiwania

Phylogeny and evolutionary patterns of South American octodontoid rodents

Capybaras, size, shape, and time: A model kit