El registro fósil de Ephedra en el Cretácico Temprano (Aptiano) de la Formación La Cantera, Provincia de San Luis, Argentina

GABRIELA G. PUEBLA; IGLESIAS ARI; GÓMEZ M.A.

AMEGHINIANA

ASOCIACION PALEONTOLOGICA ARGENTINA

Lugar: Buenos Aires; Año: 2012 vol. 49 p. 155 - 155

0002-7014

Although the current diversity of the Order Gnetales is limited, in the fossil record, it was widespread and highly diverse during the Early Cretaceous. Most Cretaceous macrofossil records assigned to Gnetales are related to the genus Ephedra Linnaeus, 1753 and usually come from sediments of China, Central Asia and Australia. The polyplicate pollen grains related to the genera Ephedra and Welwitschia Hooker, 1863 are recorded since the Triassic with an increment in abundance during the mid-Cretaceous, and represent one of the most characteristic components of xeric environments of Gondwana. Ephedra verticillata Cladera et al., 2007 is the only known macrofossil of this family in South America, however, polyplicate pollen grains are reported in several Cretaceous basins of Argentina. In the La Cantera Formation (San Luis Basin) the palynological assemblage is dominated by pollen grains of Ephedripites Bolkhovitina, 1953 /Steevesipollenites Stover, 1964. In this paper we describe the first Ephedraceae macroremains that include stems, leaves, cones and seeds found at the type locality of the La Cantera Formation. The fossil remains have an excellent preservation allowing recognition of cuticular and seminal features that identify new Ephedra species. These records correspond to new xeromorphic elements that provide information about paleoenvironments that characterized the subtropical seasonal dry biome in mid-latitudes of South America.