Sommerxylon spiralosus from Upper Triassic in southernmost Paraná Basin (Brazil): a new taxon with taxacean affinity

Abstract

The anatomical description of silicified Gymnospermae woods from Upper Triassic sequences of southernmost Paraná Basin (Brazil) has allowed the identification of a new taxon: Sommerxylon spiralosus n.gen. et n.sp. Diagnostic parameters, such as heterocellular medulla composed of parenchymatous and sclerenchymatous cells, primary xylem endarch, secondary xylem with dominant uniseriate bordered pits, spiral thickenings in the radial walls of tracheids, medullar rays homocellular, absence of resiniferous canals and axial parenchyma, indicate its relationship with the family Taxaceae, reporting on the first recognition of this group in the Triassic on Southern Pangea. This evidence supports the hypothesis that the Taxaceae at the Mesozoic were not confined to the Northern Hemisphere.

Phylogenetic relationships and divergence times of the family Araucariaceae based on the DNA sequences of eight genes

“…In this study, the divergence time of the family Araucariaceae, estimated by MCMCTREE, was calculated to be (308 ± 53) Ma (Late Carboniferous) [30][31][32] , but most of the Araucariaceae fossil records were in Triassic (205-250 Ma). One reason for this mismatch is that the fossil records usually lag behind the divergence time.…”

Late Triassic climate in southernmost Parana Basin (Brazil): evidence from dendrochronological data

“…However, diagnostic parameters of the wood indicate its relationship with the family Taxaceae (Pires and Guerra-Sommer, 2004). Currently, this family occurs within the Northern Hemisphere's subtropical to temperate climate regions.…”

“…The anatomical description of silicified gymnosperm woods from the Linha São Luiz outcrop, Faxinal do Soturno, Rio Grande do Sul, has enabled the identification of Sommerxylon spiralosus Pires et Guerra- Sommer (2004). Diagnostic parameters of the wood, such as heterocellular medulla composed of parenchymatic, secretory, and sclerenchymatic cells; primary xylem endarch; secondary xylem with dominant uniseriate pits; spiral thickenings in the radial walls of tracheids; an absence of resiniferous channels; and axial parenchyma indicate its relationship with the family Taxaceae and its first recognition in the Triassic of southern Pangea.…”

New gymnosperm wood fossils, a seed-ovule structure, and a new generic affinity to Cedroxylon canoasense Rau from the Permian and Triassic–Jurassic of Southern Brazil

“…On other side, in the more southern Água Boa and Chiniquá expositions (Figure 1), they are exclusive by the conjunct occurrence of conifers (mainly related with the Araucariaceae) and Ginkgophyta (Bardola et al, 2010), and thus support the older ages proposed by the stratigraphic models. In spite of the wealth of specimens in the whole region and the studies made (Pires & Guerra-Sommer, 2004;Bardola et al, 2009Bardola et al, , 2010Crisafulli et al, , 2016, their description is still far from providing a complete understanding of its diversity.…”