Cordaixylon, F.C.Grand'Eury, 1877

Galtier, Jean, Ronchi, Ausonio & Broutin, Jean, 2011, Early Permian silicified floras from the Perdasdefogu Basin (SE Sardinia): comparison and bio-chronostratigraphic correlation with the floras of the Autun Basin (Massif central, France), Geodiversitas 33 (1), pp. 43-69 : 60-62

Cordaixylon sp. ( Fig. 9A )

We illustrate a small, partly decorticated stem, about 6 mm in diameter. The cylinder of secondary xylem averages 4 mm and the pith 1.5 mm in diameter.The wood tracheids are small, ranging from 12-15 µm in diameter for the innermost ones to 20-30 µm in diameter at the periphery.The endarch maturation of the primary xylem conforms to the genus Cordaixylon Grand’Eury. On the surfaces studied the pith is solid and consists of a parenchyma of small cells (around 30 µm in diameter).One incomplete rachis, crescentshaped in cross section (P, Fig.9A ), is closely associated with the stem; it certainly represents one petiole of this plant, as suggested by its vascular anatomy consisting of more than six bundles as it should be expected in the petiole of such a young cordaitean stem. Associated in the same chert block we found fragments of leaves with a thin lamina ( Fig. 9F , see below).

E

doxylon cf. rollei Unger , isolated wood fragment; A, transverse

section showing the distorted files of tracheids (SAR07BB03);

B, detail of the same showing rows of tracheids separated by narrow rays; C, radial longitudinal section showing poorly preserved uni-to biseriate circular pits of tracheids between two rays (SAR07BLR01); D, tangential longitudinal section showing the narrow (uniseriate) rays of variable height (SAR07AL07); E, isolated wood of pteridosperm affinities, radial longitudinal section showing the broad tracheids with multi (4 to 5)-seriate pitting (SARBB02). Scale bars: A, 1 mm; B, 0.5 mm; C-E, 100 μm.

Cordaites leaves

Some rock specimens contain diverse cordaitean leaves interspersed among leaves of other plants ( Fig. 9B ). These leaves, of different thickness and anatomy,are illustrated at the same magnification on Figure 9 C-F.

Figures

FIG. 9. — Silicified plants from the Permian of Sardinia: A, Cordaixylon sp., transverse section of a partly decorticated small stem with a solid parenchymatous pith; on the left the closely associated rachis (P) with several xylem bundles may represent a petiole of the same plant (SAR24B4L13);B, Cordaites leaves associated with Pecopteris pinnules;the broadest leaf (CC) with interfascicular scleren-