Sommerxylon

Name

Sommerxylon

Rank

Genus

Authors (Pub.)

Pires E. F. Guerra-Sommer M.  

Publication

Sommerxylon spiralosus from Upper Triassic in southernmost Paraná Basin (Brazil): a new taxon with taxacean affinity [2004/9]

Journal

Anais da Academia Brasileira de Ciências

Volume

76

Issue

3

Page number

596

Year

2004

Parent Taxon

[Class] Taxopsida

Fossil Status

stems (wood)

Type

Sommerxylon spiralosum

Diagnosis

Gymnospermous wood consisting of pith, primary xylem, secondary xylem, phloem and cortex. Pith solid, circular to sub-circular, with occasional large gaps, irregularly shaped heterocellular. Thin walled parenchymatous cells of the pith, rounded or polygonal in cross section, grouped in solid nests. Thick walled sclerenchymatous cells, polygonal, walls heavily pitted, single and isolated or in small nests, not oriented. Protoxylem endarch, centrifugal, wedge shaped. Growth rings distinct, large, with a gradual transition from early to late wood; early wood wide. Bordered pits in radial walls of secondary xylem uniseriate (99%), isolated or contiguous, locally biseriate (1%) alternate or opposite. Medullary ray homocellular, uniseriate. Cross-field pits single, small, 1–4 pits per cross-field, irregularly disposed. Radial spiral thickenings single in radial walls, inclination against the wall of tracheids 40– 45◦. Wood parenchyma and resinous canals absent. Phloem not differentiated in primary and secondary phloem, showing parenchymatous cells with dark contents and phloematic rays; resinous canals absent. Cortex with parenchymatous cells and canals.