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

Resumen

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.