A new mammal fauna at the top of the Gran Barranca sequence and its biochronological significance

KRAMARZ, A.; VUCETICH, M.G.; CARLINI, A.; CIANCIO, M; ABELLO, A.; DESCHAMPS, C.; GELFO, G.

The Paleontology of Gran Barranca: Evolution and Environmental Change through the Middle Cenozoic

Cambridge University Press

Lugar: Cambridge; Año: 2010; p. 264 - 277

<!-- /* Font Definitions */ @font-face {font-family:AdvP6975; panose-1:0 0 0 0 0 0 0 0 0 0; mso-font-charset:0; mso-generic-font-family:roman; mso-font-format:other; mso-font-pitch:auto; mso-font-signature:3 0 0 0 1 0;} @font-face {font-family:AdvP4C4E74; panose-1:0 0 0 0 0 0 0 0 0 0; mso-font-charset:0; mso-generic-font-family:auto; mso-font-format:other; mso-font-pitch:auto; mso-font-signature:3 0 0 0 1 0;} /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman";} @page Section1 {size:612.0pt 792.0pt; margin:70.85pt 3.0cm 70.85pt 3.0cm; mso-header-margin:36.0pt; mso-footer-margin:36.0pt; mso-paper-source:0;} div.Section1 {page:Section1;} --> The top of the stratigraphic sequence of the fossil-bearing Sarmiento Formation at Gran Barranca has yielded a distinctive assemblage of mammalian taxa. Fossils occur in strata located 25m above the uppermost level bearing typical Colhuehuapian mammals. This association is represented by fragmentary remains of small to middle-sized mammals belonging to paucituberculatan marsupials, dasypodids, glyptodonts, tardigrades, hegetotheres, interatheres, proterotheriids, and hystricognath rodents. Although this fauna contains at least two new rodent species not recorded in other faunas, it is more similar to that recorded at the lower and middle sections of the Pinturas Formation in northwest Santa Cruz Province (the Ameghinos’ Astrapothericulan fauna) than to any other known fossil mammal assemblage. The strata yielding this fauna (Upper Fossil Zone, UFZ) is estimated to be in Chron C6n (19.7 to 18.7Ma), but the taxic similarity with the younger Astrapothericulan fauna (dated between 17.5 and 16.5 Ma) suggests that the UFZ is placed at the youngest extreme of the Chron C6n. The Astrapothericulan and the UFZ assemblages would correspond to a single post-Colhuehuapian – pre-Santacrucian biochronological unit (the “Pinturan”) which would span from _18.75 to _16.5Ma. This is the youngest faunal unit within the standard sequence of the middle Cenozoic SALMAs at Gran Barranca. The assignment to this unit of other earlyMiocene faunas elsewhere in South America (at present poorly o partially known) depends on further descriptions and future findings.