Hernandez-Castillo, Genaro R. , Silva-Pineda, Alicia .
Walchian conifer remains from the early Permian of Mexico.
Walchian conifers are common floristic elements in late Pennsylvanian and early Permian localities of Euramerica. However, little information is known about walchian conifers at the end of the Paleozoic in Mexico. Our goal is to describe a new early Permian walchian conifer from central Mexico. Material was collected from the upper section of the Tuzancoa Formation near Calnali, Hidalgo. Specimens are preserved as compressions/impressions of lateral branches with leaves. Fossil conifers are characterized by ovoid and deltoid lateral plagiotropic branches covered by helically arranged simple leaves. Leaves on penultimate shoots are 3.2 mm long by 0.5 mm wide, narrowly triangular to linear (face view) and slightly concave and spreading (side view). Leaves on ultimate shoots range 1.3-2.9 mm in length and 0.4-0.9 mm in width, narrowly triangular to linear (face view) and slightly concave to slightly S-shaped (side view). All leaves have angles of insertion that range from 16° to 39°. The new conifer has some of the smallest branches and leaves found among previously described walchian conifers. Traditional morphological characters of branches and leaves allow us to recognize a new conifer morphotaxon that is similar to lateral branches of Emporia lockardii Mapes and Rothwell, Otovicia hypnoides Kerp, Poort, Swinkels & Verwer, and Walchia goeppertiana (Florin) Clement-Westerhof and Walchia mucronata (Florin) Clement-Westerhof. Unequivocal species recognition using small amounts of conifer specimens remains problematical, as many walchians display overlapping ranges of variation. Multivariate numerical analyses of morphological characters of these species suggest a more complicated scenario. Showing that conifer morphology, plant architecture and depositional bias play an important role in understanding fossil conifer diversity. This species expands known geographical boundaries for North American walchian conifers and serves a starting point to study Permian plants in Mexico
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1 - Universidad del Mar, Instituto de Recursos, Carr. a Oaxaca via Sola de Vega Km 1.5, Puerto Escondido, Oaxaca, 71980, Mexico
2 - Universidad Nacional Autonoma de Mexico, Paleontologia, Instituto de Geologia, Cto. Investigacion Cientifica, Ciudad Universitaria, Mexico City, Mexico D.F., 04510, Mexico
Presentation Type: Oral Paper:Papers for BSA Sections
Location: Superior A/Cliff Lodge - Level C
Date: Monday, July 27th, 2009
Time: 3:15 PM