A new Encephalarteae trunk (Cycadales) from the Cretaceous of Patagonia (Mata Amarilla Formation, Austral Basin), Argentina

MARTÍNEZ, LEANDRO C.A.; IGLESIAS, ARI; ARTABE, ANALÌA E.; VARELA, AUGUSTO N.

CRETACEOUS RESEARCH (PRINT)

ACADEMIC PRESS LTD-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2017 vol. 72 p. 81 - 94

0195-6671

The cycads are remnants of a flora that dominated the ecosystems across Mesozoic. However, floristic and climate changes from Cretaceous to Paleogene (e.g. diversification of the Magnoliophyta, temperature diminution, etc.) constrained the cycad populations. This scenario is documented by the fossil record, showing a peak of diversity in the Cretaceous of Patagonia with several taxa of trunks, leaves and reproductive structures. On the other hand, the fossil stem record of cycads is scanty, with seventeen genera described around the world. Eight come from Argentina (Triassic to Paleogene strata), and six of them come from Cretaceous of Patagonia. In this research, we erect a new genus of fossil cycad come from Upper Cretaceous of Austral Basin, Patagonia (Argentina). The good preservation of the permineralized stem allows profuse descriptions and comparisons, allows assigning the Zamunercycas nov gen. to the Encephalarteae. This new taxa has a great development of parenchyma tissues with a marked amount of specialized cells (idioblasts), probably related with some protection function. The probable climatic conditions of the Mata Amarilla Formation were inferred, from the new genus described, and correlated with hot and humid to xeric climate the southern of South America during the early Upper Cretaceous. Zamunercycas reinforce the existence of a greater diversity of Encephalarteae in South America during the mid-Cretaceous.