Legume fossil woods from the Arroyo Feliciano Formation (late Pleistocene, Northeastern Argentina ): Palaeobiogeographic implications

MOYA, E.; BREA, M,

AMEGHINIANA

ASOCIACION PALEONTOLOGICA ARGENTINA

Lugar: Buenos Aires; Año: 2015 vol. 52 p. 558 - 573

0002-7014

This paper describes two new genera of the Mimosoideae from the Upper Pleistocene of Argentina. The fossil specimens were recovered from the Consorcio Paso Sociedad Locality of the Arroyo Feliciano Formation, located in the upper Gualeguay River Basin, eastern Argentina. The anatomical features of these specimens suggest a relationship with Cylicodiscus Harms 1897 for the first one and Abarema Pittier 1927 and Hydrochorea Barneby and J.W. Grimes 1996 for the second. Cylicodiscuxylon paragabunensis gen. nov. and sp. nov. is characterised by diffuse-porous wood, solitary vessels, in radial multiples and in clusters; alternate and vestured intervessel pits; vasicentric, aliform, lozenge-aliform and confluent axial parenchyma, strands of 5?11 cells, prismatic crystals in chains in chambered axial parenchyma cells; 1?3 (4) seriate rays and homocellular, vessel-ray parenchyma pits similar in size and shape to intervessel pits, and non-septate fibres. Abaremaxylon hydrochorea gen. nov. and sp. nov. has the following diagnostic features: diffuse-porous wood, solitary vessels, in radial multiples and in clusters; alternate and vestured intervessel pits; vasicentric, aliform and unilateral aliform, confluent axial parenchyma, strands of 4?16 cells; prismatic crystals in chains in chambered axial parenchyma cells; exclusively uniseriate and homocellular rays, and non-septate fibres. The fossils described herein represent the first report of legume woods from the Gualeguay River Basin. The record of Cylicodiscuxylon in southern South America supports the existence of an old relationship with the African flora and Abaremaxylon reinforces the idea that Neotropical flora was widespread in the past. The analysis of fossil plants suggests that they grew under warm and humid to semi-arid climatic conditions.