Boletín de la Sociedad Geológica Mexicana Volumen 66, núm. 1, 2014, p. 85-96 http://dx.doi.org/10.18268/BSGM2014v66n1a7

Early Permian conifer remains from Central Mexico and reevaluation of Paleozoic conifer morphotaxa

Genaro R. Hernández-Castillo^1,*, Silvia A. Silva-Pineda², Sergio R.S. Cevallos²

¹ Paleoconifer Consulting Ltd., Edmonton, AB, T6X 0X7, Canada.
² Departamento de Paleontología, Instituto de Geología, UNAM, Ciudad Universitaria, Del. Coyoacán, México D.F., 04510, México.

^* This email address is being protected from spambots. You need JavaScript enabled to view it.

Abstract

This paper describes the first Permian walchian conifer from Mexico based on several specimens preserved as compressions/impressions. The material comes from the Tuzancoa Formation in the state of Hidalgo, Central Mexico. It is described as Calnalia hidalguensis gen. nov. et sp. nov. a new conifer morphotaxon based on isolated lateral branches with leaves. This new conifer has some of the smallest branches and leaves found among previously described walchians. Calnalia hidalguensis has two types of branches (ovoid and deltoid) with simple and helically arranged leaves. Leaves are narrowly triangular to linear in front view, slightly concave and spreading (penultimate shoots) to slightly concave to slightly S-shaped (ultimate shoots), in side view. Leaves range from 3.2 mm long by 0.5 mm wide on penultimate shoots, to 1.3 - 2.9 mm long by 0.4 - 0.9 mm wide on ultimate shoots, with angles of leaf insertion ranging from 16º to 39º. The new species is most similar to Emporia lockardii Mapes and Rothwell, Walchia goeppertiana Florin, Walchia mucronata Florin, and Otovicia hypnoides Kerp, Poort, Swinkels & Verwer. However, none of these have the same ranges of morphological variation found in the leaves of Mexican species. The new taxon expands the diversity of walchian conifers at the end of the Paleozoic in America, and marks the beginning of new research of Permian floras in Mexico. The presence of C. hidalguensis and other gymnosperms, to be described, reinforces the presence of an arc along the Oaxaquia block that connected Mexico to the North American craton during the late Paleozoic. These new data also allow us to test hypotheses about the origin and evolution of Paleozoic floras in Euramerica.

Keywords: conifer, Mexico, morphotaxa, Permian, Walchia.