IMBECU   20882
INSTITUTO DE MEDICINA Y BIOLOGIA EXPERIMENTAL DE CUYO
Unidad Ejecutora - UE
artículos
Título:
Pink fairy armadillo meniscate burrows and ichnofabrics from Miocene and Holocene interdune deposits of Argentina: Palaeoenvironmental and palaeoecological significance
Autor/es:
MELCHOR, R.; GENISE, J.F.; UMAZANO, A.M.; SUPERINA, M.
Revista:
PALAEOGEOGRAPHY PALAEOCLIMATOLOGY PALAEOECOLOGY
Editorial:
ELSEVIER SCIENCE BV
Referencias:
Lugar: Amsterdam; Año: 2012 vol. 350 p. 149 - 170
ISSN:
0031-0182
Resumen:
The possible producer and environmental setting of large meniscate burrows (Nagtuichnus meuleni igen. andisp. nov.) occurring in late Miocene and Holocene aeolian deposits from Argentina are discussed. These areunbranched burrows with an uniform meniscate filling that range in width from 46 to 78 mm. N. meulenidistinguishing features are a filling composed of a discontinuous, outer massive layer between a centralmeniscate core and the excavation boundary, sets of parallel ridges in the external wall, and a particular outlineplus the presence of paired pits in the concave surface of menisci (or hollows in the convex surface). Thelate Miocene lower member of the Río Negro Formation at La Lobería (Río Negro province) is interpreted asaeolian dune, damp interdune and dry interdune deposits. The Holocene sediments from Gran Salitral(southwestern La Pampa province) represent aeolian dune, wet interdune and dry interdune deposits.N. meuleni occurs only in damp and dry interdune deposits. The composite ichnofabric produced byN. meuleni in the Holocene of the Gran Salitral is composed of two suites of trace fossils. A former Skolithossuite includes Skolithos linearis, Taenidium barretti, Polykladichnus aragonensis and root traces developed inlacustrine calcareous mudstone deposits (wet interdune). This suite is overprinted by N. meuleni, with subordinateparticipation of S. linearis and root traces, composing the Nagtuichnus suite. The later suite is developed inbrown silt and sand of dry interdune areas. The Nagtuichnus ichnofabric is considered indicative of damp todry interdune facies of lateMiocene to Holocene age. The burrowsystems of the likely producers of the HoloceneN. meuleni structures were studied in the field and in the laboratory. The candidates were selected from theextant local fauna of the Gran Salitral, including southern cavies (Microcavia australis, Rodentia), tuco-tucos(Ctenomys azarae, Rodentia), and pink fairy armadillos or pichiciegos (Chlamyphorus truncatus, Xenarthra).The most likely producer of N. meuleni are pichiciegos because they have fully subterranean habits and insectivorousdiet involving the production of long, unbranched, horizontal burrows excavated in sand,which aremostlybackfilled. In contrast to this, tuco-tucos and southern cavies, which are herbivores that forage aboveground, usetheir more permanent burrows for dwelling and reproduction. As observed in a live, captive-kept C. truncatus,the meniscate structure of the fill can be explained by the animal packing the excavated sand with its rumpplate. This mechanism also results in a massive layer of sediment in the burrow fill. Other significant bioglyphsthat are a sort of fingerprint of pichiciegos are the outline of menisci in cross-section (mimicking their rumpplate) and pairs of rounded pits in the concave surface of menisci (probably tail traces.