Foliar Morphology and Anatomy of the Gigantopterid Plant Delnortea Abbottiae, From the Lower Permian of West Texas

Abstract

Delnortea is a monotypic genus (type‐species: D. abbottiae) of Lower Permian gymnosperms based on leaves from uppermost Leonardian deltaic sediments exposed in the Del Norte Mountains, West Texas. The leaves are simple, symmetrical, mostly oblong or elliptical, and vary in length from 1.2 to about 35 cm. The petioles are short and stout, with a basally enlarged abscission zone. The margins are crenate, with a narrow, indurated border. Venation is in 4 orders: the secondaries and tertiaries are robust, unbranched, and pinnately arranged in a precise “herringbone” pattern, with the secondaries ending in the marginal sinuses; the quaternaries divide sparingly and fuse with others to form a dense reticulum of small meshes. Permineralized petiole and midrib material reflects a bifacial cambium, shown by a semicircular vascular arc, irregularly divided into several collateral bundles with secondary xylem and phloem. Delnortea is referable to the Gigantopteridaceae, a probably artificial family of gymnosperms incertae sedis with important venation features in common, but without known diagnostic reproductive organs. With Delnortea, the North American gigantopterids now include 5 genera, but Gigantopteris itself is lacking. Delnortea holds a relatively advanced evolutionary position among the American gigantopterids; its leaf morphology and gymnospermous anatomy entail intriguing points of comparison with Gnetum. The limited geographic and stratigraphic ranges and morphological distinctiveness of the American gigantopterids and associated taxa attest to rapid evolution and dispersal from a small area of origin in the southwestern United States during Leonardian time.

A physiologically explicit morphospace for tracheid-based water transport in modern and extinct seed plants

“…The Permian gigantopterids, largely found as compression fossils in China and the central United States, are well-known for their angiosperm-like vegetative organs, including large, entire-margined leaves and putative vessel elements (Beck and Labandeira 1998, Glasspool et al 2004a, Glasspool et al 2004b, Li and Taylor 1998, Li et al 1996, Mamay et al 1988. Although permineralized specimens are rare, and reproductive organs have never been found-preventing any taxonomic link with other seed plant groups-gigantopterid vegetative features suggest that they may resemble medullosans and angiosperms in functional space, rather than conifers.…”

An Early Permian Coastal Flora from the Central Basin Platform of Gaines County, West Texas

“…1). The report of this fossil by Mamay et al (1988), in the Road Canyon Formation (type Roadian Stage) of the Del Norte Mountains, may be coeval with the youngest plant-bearing beds at NRU. A gigantopterid that Adams (1933) collected and illustrated, as a probably fragment of Gigantopteris americana, from a drill core in Glasscock County, Texas, is D. abbottiae (Sergius Mamay, oral communication, 1999; this specimen resides in the collections of the National Museum of Natural History as specimen number USNM 41167).…”

“…1), southwestern Texas (Mamay et al, 1988). At present, this is the youngest reported occurrence of a gigantopterid in North America.…”

“…1). Material from the Del Norte Mountains (Mamay et al, 1988) was recovered from surface outcrops of Roadian age (early Guadalupian, Middle Permian; Glenister et al, 1999). Another surface deposit was discovered recently in Tom Green County, in the Choza Formation, Clear Fork Group, of late Leonardian age.…”

Reevaluation and taxonomic clarification ofGigantopteridiumandCathaysiopterisof western equatorial Pangea and their biogeographical significance

“…Gigantopterids as discussed here include the taxa commonly recovered from western equatorial Pangea. Eight North American genera have been recognized; Gigantopteridium Koidzumi, Cathaysiopteris Koidzumi, Zeilleropteris Koidzumi, Gigantonoclea Koidzumi, Evolsonia Mamay, Delnortea Mamay, Euparyphoselis DiMichele, Looy, and Chaney, and Lonesomia Weber, each represented in North America by a single species (Mamay, 1960(Mamay, , 1967(Mamay, , 1986(Mamay, , 1988(Mamay, , 1989Mamay et al, 1986Mamay et al, , 1988Weber, 1997;Glasspool et al, 2004;DiMichele et al, 2011). Additional species of some genera also have been described from eastern Asia (Halle, 1927;Koidzumi, 1934Koidzumi, , 1936Gu and Zhi, 1974;Li and Yao, 1983;Shen, 1995;Yao and Liu, 2004;DiMichele et al, 2011).…”