The ferns in a new Middle Jurassic locality from the Otlaltepec Formation, Puebla, Mexico

Abstract

Mesozoic ferns from Mexico have been the subject of serious academic endeavours since the beginning of the 20th Century, to understand these plants at the time of their peak diversity. Most findings have been made in a set of Middle Jurassic Basins of the Mixtec Terrain in the Oaxaca State. However, fossil ferns are scarce in other assemblages, so further identification of this group has been infrequent. Here we describe six new and recently collected fossil plants from the Middle Jurassic Otlaltepec Formation, Puebla. Based on their fertile and vegetative fronds, we propose the new genus Paralophosoria Morales-Toledo, Mendoza-Ruiz & Cevallos-Ferriz, gen. nov. in the Dicksoniaceae, represented by Paralophosoria jurassica, Morales-Toledo, Mendoza-Ruiz & Cevallos-Ferriz, sp. nov., and identify the following genera: cf. Aspidistes, Sphenopteris, Spiropteris. A fern with uncertain affinities was also described. This work contributes to the understanding of fern diversity in low latitudes during the Middle Jurassic in Mexico.

Laurasian legacies in the Gondwanan tree fern order Cyatheales

“…The early disjunct distribution of Cyatheales is consistent with paleobotanical evidence supporting a Gondwanan–Laurasian connection during the period 3,89,90 , in the form of a biotic corridor probably extending throughout ever wet climates around the Tethys sea 89,90 . Furthermore, recent evidence from the fossils Paralophosoria 91 and Eboracia 27 , which have probable Cyathealean affinities, suggest the occupation of more meridional paleolatitudes (present-day Mexico) during this period.…”

“…have not yet been recovered). However, recent fossil evidence from the Jurassic of present-day Mexico and China expand the know paleodistribution of Cyatheales across Laurasia during the Lower Jurassic 27,91 and available evidence does not support the presence of Cyatheales in Gondwana prior to the Middle Jurassic, despite there being well studied localities in southern continents 89,90,[110][111][112] . More specifically, Cyathealean tree ferns first appear in Gondwanan landmasses towards the Middle Jurassic 88 and start to be more frequent into the Late Jurassic-Early Cretaceous [113][114][115] ; palynological records provide evidence for the presence of tree ferns in South America until the Early Cretaceous 116 .…”