Browsing by Autor "Richard F. Kay"

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New palaeothentid marsupial from the Middle Miocene of Bolivia
(Wiley, 2003) Francisco J. Goin; Marcelo R. Sánchez‐Villagra; Richard F. Kay; Federico Anaya‐Daza; Masanaru Takai
The new species Acdestis maddeni is described based on the most complete skull of a palaeothentid marsupial known so far. The skull preserves most of the upper dentition and of the ear region, the latter an anatomical region previously unknown in this extinct family. A right maxillary fragment including C–M2 also belongs to the new species. The specimens come from the middle Miocene localities of Rosario and Quebrada Honda in southernmost Bolivia. The generic allocation of the new species is somewhat problematic, given that most of the taxonomy of fossil palaeothentids is based on lower dentitions. Compared to that of caenolestids, the skull of A. maddeni is much larger, with a shorter and broader snout, a proportionally narrower interorbital constriction, and a less globular, more triangular–shaped braincase in dorsal view.
Revised age of the Salla beds, Bolivia, and its bearing on the age of the Deseadan South American Land Mammal “Age”
(Taylor & Francis, 1998) Richard F. Kay; Bruce J. MacFadden; Richard H. Madden; H A Sandeman; Federico Anaya
ABSTRACT The Salla beds of Bolivia contain a mammalian faunal assemblage assigned to the Deseadan South American Land Mammal “Age” (SALMA), known elsewhere principally in Patagonia. The earliest platyrrhine monkey Branisella comes from a single stratigraphie level in these beds. The age of the Salla beds is debated; new radiometrie dates constrain the age of the Deseadan SALMA in Bolivia and clarify the timing of the first record of platyrrhines in South America. The oldest vertebrate fossils from the Salla beds are contained within the magnetic polarity interval ClOr, between 28.8 and 29.4 Ma. The youngest fossils occur above the 275 m ash in Chron C7Ar, between 25.65 to 25.82 Ma. The best known faunas, including those of the Branisella level, come from several localities within Chron C8 (25.82 to 27.02 Ma). If the recent suggestion by Flynn and S wisher (1995) that redating indicates that the Deseadan in Patagonia spans only about 27 to 29 Ma, then the bulk of the Salla fauna is younger than that of Patagonia.
The Adaptations of Branisella boliviana, the Earliest South American Monkey
(2002) Richard F. Kay; Blythe A. Williams; Federico Anaya