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A new Miocene penguin from Patagonia and its phylogenetic relationships

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Acosta H. C., Tambussi C., Donato M., Cozzuol M.
Acta Palaeontologica Polonica
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2007
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tom 52
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nr 2
We describe a new medium−sized penguin, Madrynornis mirandus gen. et sp. nov., from the early late Miocene Puerto Madryn Formation, Chubut Province, Argentina. Although it is evident that extant and fossil penguins form a remarkably homogeneous family of birds, Spheniscidae, their within−group phylogenetic relationships are less obvious. In order to identify the phylogenetic position of the new taxon, we conducted a phylogenetic analysis using 44 osteological characters sampled from 14 representative species of all living genera and five fossil species of Spheniscidae. The family is clearly monophyletic and Madrynornis mirandus is closely related to living taxa. Our phylogenetic interpretation is congruent with biostratigraphic data, with Paraptenodytes from the early Miocene (about 20 Ma) located at the base of the Spheniscidae. Classically, two basic tarsometatarsal types were recognized (one for pre−Miocene and the other for the post−Miocene penguins) based on the pattern of the proximal foramina and the hypotarsus. Madrynornis mirandus exhibits an arrangement of the proximal foramina and a degree of metatarsals fusion similar to that in the living forms, although its elongation index (total length/proximal width) is reminiscent of the extinct Paraptenodytes(a penguin historically recognized as a pre−Miocene form, coming from the early Miocene of Argentina). Madrynornis reveals that the two basic tarsometatarsal types co−existed among Miocene penguins.
2
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First record of an extinct marabou stork in the Neogene of South America

80%
Noriega J. I., Cladera G.
Acta Palaeontologica Polonica
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2008
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tom 53
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nr 4
We describe a new large species of marabou stork, Leptoptilus patagonicus(Ciconiiformes, Ciconiidae, Leptoptilini), from the late Miocene Puerto Madryn Formation, Chubut Province, Argentina. The specimen consists mainly of wing and leg bones, pelvis, sternum, cervical vertebrae, and a few fragments of the skull. We provisionally adopt the traditional systematic scheme of ciconiid tribes. The specimen is referred to the Leptoptilini on the basis of similarities in morphology and intramembral proportions with the extant genera Ephippiorhynchus, Jabiru, and Leptoptilos. The fossil specimen resembles in overall morphology and size the species of Leptoptilos, but also exhibits several exclusive characters of the sternum, humerus, carpometacarpus, tibiotarsus, and pelvis. Additionally, its wing proportions differ from those of any living taxon, providing support to erect a new species. This is the first record of the tribe Leptoptilini in the Tertiary of South America.
3
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Capybaras, size, shape, and time: A model kit

80%
Vucetich M. G., Deschamps C. M., Olivares A. I., Dozo M. T.
Acta Palaeontologica Polonica
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2005
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tom 50
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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.
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