Early Permian Flora, Doña Ana Mountains, Southern New Mexico, with Special Consideration of Taxonomic Issues and Arthropod Damage

Abstract

Plant fossils were collected from nine sites, and noted at several others, in Lucero Arroyo and its immediate tributaries in the Doña Ana Mountains, north of Las Cruces, in southern New Mexico. The strata hosting the plant fossils are assigned to the Robledo Mountains Formation and are of early Permian (Leonardian/Artinskian) age. The succession comprises, primarily, siltstones and sandstones deposited in active or abandoned stream channels. The plant-fossil material is allochthonous at each collecting site. Most of the collections are small, consisting of <10 specimens; three are larger, consisting of between 19 and 98 specimens. The flora is heavily dominated by coriaceous, xeromorphic seed-plant foliage; based on the number of sample-site occurrences, conifers and cordaitaleans were the most widespread plants, and likely dominated the landscape. In the larger collections, however, greater diversity was found, and peltaspermous, or presumed peltaspermous, genera were found, including Rhachiphyllum, Supaia (and/or possibly Glenopteris), Auritifolia, cf. Zeilleropteris, and possibly Gigantopteridium. A lectotype for Supaia anomala is formally designated herein, and the species is transferred to the genus Auritifolia, based on its gross morphology and, particularly, its venation. The flora also contains rare examples of calamitaleans, small ferns, and the noeggerathialean cf. Yuania. Arthropod damage was found to be rare and includes several examples of galling and margin feeding on the lamina, primarily of Auritifolia and gigantopterids. The flora likely occupied a seasonally arid landscape, but one with one or more intervals of substantial rainfall.