Stewartiopteris, Morgan & Delevoryas, 1952

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 : 56-57

Stewartiopteris sp. 1 and sp. 2

( Fig. 7C, D )

The large rachis ( Fig. 7C ), shows a broad C-shaped xylem strand (arrows, Fig. 7C ) and outer sclerenchymatous cortex; it represents the proximal region of a frond. The smaller rachis shown on Figure 7D is quite distinct in cortical organization. It certainly corresponds to a second order rachis alongside the corresponding third order rachis (R3, Fig.7D ) which is in connection with a fertile pinnule (P, Fig. 7D ). These two Stewartiopteris rachises certainly belonged to different fronds.

Foliage of these tree ferns occasionally occurs as dense accumulations of vegetative and/or fertile pinnules as shown on Figure 7E . One section of an ultimate pinna, paradermal to the pinnule surfaces ( Fig. 7F ), reveals their pecopteroid morphology. At least three different taxa occur in the assemblage as is suggested by differences in the fertile pinnae.

Figures

FIG. 7. — Silicified plants from the Permian of Sardinia:A, B, Psaronius sp.; A, part of the inner root mantle of a trunk,transverse section showing the small roots and interstitial tissue (SAR 13BB01); B, transverse section of one large free root of the outer zone; note the broad aerenchymatous cortex (SAR10A01); C, D, rachises of fronds borne by Psaronius; C, Stewartiopteris sp.1, rachis with a broad C-shaped xylem strand (arrows) and middle cortex with small lacunae (SAR59AT01); D, Stewartiopteris sp. 2., rachis with a different cortex bearing a probable third order one (R3) with fertile pinnule attached (SAR46B01); E, F, foliage of fronds borne by Psaronius; E, accumulation of fronds showing vegetative (above) and fertile pinnules (below) seen in transverse section (SAR40C1T01); F, part of a fertile pinna seen in paradermal section (SAR03A1T02). Scale bars: 2 mm.