Stelastellara baxter, axes of questionable gymnosperm affinity with unusual habit — Middle Pennsylvanian

Two specimens of Stelastellara are described from Middle Pennsylvanian age coal balls from mid-continent United States. The stellate main axis of both specimens has a solid, exarch, actinostele with elliptical to circular bordered pitting, secondary growth and a distinctive cortex with differential thickenings. One axis is assigned to S. parvula ; it divides sympodially at one end into four typical S. parvula axes. A second specimen described as a new species, S. baxteri , is 6 mm in diameter, highly stellate with primary xylem ribs extended radially up to 1.25 mm and with radially elongate and thickened cortical cells. Along the 5 cm length, seven endogenous structures are produced, mostly from one face. The axes are largely root-like and the morphological alternatives are considered. A gymnosperm affinity is suggested. The peculiar anatomy of the root-like axes and lack of in situ evidence suggest the possibility of some kind of a perched habit.