A NEW CYNEPTERIS FROM THE UPPER TRIASSIC OF ARIZONA: POTENTIAL IMPLICATIONS FOR THE EARLY DIVERSIFICATION OF SCHIZAEALEAN FERNS Brian J. Axsmith 1 Biology Department, LSCB 124, University of South Alabama, Mobile, Alabama 36688, U.S.A. Cynepteris bolichii is proposed as a new species of the monogeneric fern family Cynepteridaceae on the basis of a single, well-articulated specimen from the Upper Triassic Chinle Formation in Petrified Forest National Park, Arizona. The specimen consists of an erect rhizome with at least eight attached fronds. As for the other three known Cynepteris species, C. bolichii pinnae exhibit reticulate venation and scattered, solitary, exindusiate sporangia on their abaxial surfaces. Each sporangium is ovoid to pyriform with a short, thick stalk and a complete, apical, caplike annulus consisting of a single row of cells surrounding a multicellular distal plate. These sporangial features are similar to those of several fossil and extant schizaealean ferns. Cynepteris bolichii differs from other Cynepteris species mainly in having once-pinnate fronds with abundant, elongate hairs on the rachises and veins. Most recent estimates of fern phylogeny consider the Jurassic fossils Stachypteris, Klukiopsis, and Klukia as the oldest fossil representatives of the Schizaeales. It is here proposed that Cynepteris should be considered as a probable Late Triassic record of the order. Features such as reticulate venation, scattered sporangia, and lack of fertile/sterile frond dimorphism are rare and scattered among other fossil and extant ferns currently attributed to the Schizaeales, underscoring the importance of fossils for understanding the early divergence, ancestral morphology, and biogeography of ancient plants groups like the ferns. Keywords: Chinle Formation, Cynepteris bolichii sp. nov., ferns, Schizaeales, Triassic. Introduction The striking similarity between the sporangia of the Late Triassic fern Cynepteris lasiophora and those of several repre- sentatives of the Schizaeales was noted in the original generic description (Ash 1970). However, unlike most schizaealean ferns, the sporangia of Cynepteris are scattered over the abaxial frond surface, there is no fertile/sterile frond dimorphism, the spores are relatively unornamented, and the venation is strongly re- ticulate. On the basis of these features, Ash (1970) erected the new family Cynepteridaceae to accommodate the fern. It has become increasingly clear that members of the Cyn- epteridaceae were a widespread if not common component of the North American Late Triassic flora. Cynepteris lasio- phora is now known from numerous localities in the Chinle Formation in the Colorado Plateau region (Ash 1980) as well as the Newark Supergroup of eastern North America (Dele- voryas and Hope 1973). Two additional species, Cynepteris intranscendentalis and Cynepteris sonorensis, have been de- scribed from the Santa Clara Formation of Mexico (Weber 1985). In addition, Bock’s (1969) figures of lost fertile speci- mens assigned to Lonchopteris virginiana from the Triassic flora of Winterpock Virginia indicate that these fossils repre- sent yet another species of Cynepteris (Ash 1970). Recent collecting from the lower part of the Chinle Forma- tion of Late Triassic age in Petrified Forest National Park, Arizona (PEFO), has produced several new ferns, including the well-articulated specimen proposed here as the new species Cynepteris bolichii. In addition to providing a description of this fern, this article considers the potential role of the Cyn- epteridaceae for understanding the early diversification of the schizaealean ferns relative to recent phylogenies based mainly on molecular approaches. Material and Methods The new Cynepteris specimen described here was collected from Petrified Forest National Park plant fossil locality PFP 101 (locality 1 of this report) in the mudstone facies of the Newspaper Rock Bed in the Blue Mesa Member of the Chinle Formation (fig. 1). This locality is about 600 m west of local- ity PFP 001, which contained most of the plant fossils de- scribed from the park by L. Daugherty in 1941. These fossils included many ferns including some fine specimens of Cynep- teris lasiophora that were mistakenly assigned to Lonchopteris virginiensis by that author (see Ash 1970). Both localities are in the overbank deposits of the stream that deposited the Newspaper Sandstone Bed (fig. 2). The holotype and only specimen of the new species is pre- served as an impression/compression fossil on a large (;40 cm diameter) slab of mudstone (fig. 3A). Exposed portions of the fern were first examined directly on the slab surface. Additional regions that were obscured by overlying sediments were exposed with fine needles. Small pieces of matrix bearing fertile pinnae compressions removed by this process were transferred by coat- ing the surfaces with clear nail polish, dissolving the matrix in 1 E-mail: baxsmith@jaguar1.usouthal.edu. Manuscript received June 2008; revised manuscript received January 2009. 657 Int. J. Plant Sci. 170(5):657–665. 2009. Ó 2009 by The University of Chicago. All rights reserved. 1058-5893/2009/17005-0008$15.00 DOI: 10.1086/597782