Is biodiversity promoted in rift-associated basins? Evidence from Middle Jurassic conifers from the Otlaltepec Formation in Puebla, Mexico

Abstract

The Jurassic Period is an important moment in the origin and evolution of modern conifer lineages. They dominated most of the land plant communities, as reported in different high latitude floras worldwide. However, there have been few reports of Middle Jurassic conifers from low latitude regions of Western Laurasia, such as Mexico. Most data on the composition of these Jurassic Mexican floras come from other plant lineages that thrived in different rift-associated basins, like the Tlaxiaco Basin and the Ayuquila Basin. Here we describe six new fossil conifers from the Middle Jurassic Otlaltepec Formation, Puebla, Mexico. Based on morphological features, we identify the following genera: Brachyphyllum, Platycladium, Podocarpites, and Masculostrobus and propose two new species (Brachyphyllum dimorpha Morales-Toledo & Cevallos-Ferriz, sp. nov. and Platycladium mexicanum Morales-Toledo & Cevallos-Feriz, sp. nov.). The description of the first ovulate cone for the Middle Jurassic of Mexico is provided, as well as a conifer foliage of uncertain affinities. Based on the available data we discuss the implications of the fossil record from the Otlaltepec Formation in context of the break-up of Pangea and how the conifer diversity seems to be increased by the rifting process through separating plant communities in different basins. Finally, this work contributes to the knowledge of conifer diversity at low latitude floras from Western Laurasia during the Middle Jurassic.