Astromyelon, W.C.Williamson, 1883

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 : 52-56

Astromyelon sp. ( Fig. 5F )

We will designate under this name the calamitean roots and rootlets which represent one of the most common elements of the plant assemblage, and

hiscent sporangia with folded wall) (SAR45A2L08); B -D, transverse sections of cones; B, part of one section showing the cone axis (upper right) surrounded by whorls of sporangia (S) and bracts (B) (SAR63A01); C, detail of a similar section showing the cone axis, at right, the base of one sporangiophore stalk (ST), sporangia in oblique-longitudinal section (S), two of them being attached to the sporangiophore peltate head (P) and distal lamina of bracts (B) at left (SAR01B3L13); D, distorted cone axis showing the attachement of several sporangiophore stalks (arrows) (SAR45BB04); E, detail of transverse sections of sporangia, one shows attachment to the sporangiophore peltate head (P), the two on the left contain spores (arrows) (SAR01B1BO3); F, Astromyelon sp., transverse section of a large decorticated root (SAR43CT01); G, Sphenophyllum sp., transverse section of a stem (SAR33C01). Scale bars: 1 mm.

probably the most important in terms of volume. We illustrate one rather broad but decorticated woody root ( Fig. 5F ). Smaller roots (less than 1 cm in diameter) with a little or no secondary xylem have generally a lacunose cortex preserved and are assignable to the genus Myriophylloides . Similar roots are present in the Autun material, however, A. augustodunense Renault, 1896 and A. reticulatum Renault1896 differ in detail of their cortex and correspond to rather large roots like the one illustrated here of which cortical features are missing.

Figures

FIG. 5. — Silicified plants from the Permian of Sardinia: A-E, Palaeostachya sp.: A, longitudinal section of the cone showing the central axis with pith cavity (A) and three nodes with the attachment of bracts (B) and sporangiophore stalks (ST) arising obliquely. The bracts are often displaced at their base (B with two arrows) whilst their distal part is ascending vertically (see on the left) (S), de-