A new species of Pityostrobus from the lower Cretaceous of California and its bearing on the evolution of Pinaceae

A single cylindrical, abraded cone specimen has been found associated with ammonites of the Lower Cretaceous Budden Canyon Formation near Ono, Califor nia. The specimen was embedded in bioplastic and sectioned using the cellul ose acetate peel technique. The pith is composed of parenchyma and scattere d sclereids and is bounded by a ring of resin canals. The secondary xylem o f the cone axis, with a ring of small-diameter resin canals, is continuous. The cortex is composed primarily of parenchyma with an outer sclerotic zon e 10-16 cells thick and has 27-30 dilating resin canals. Vascular traces to the ovuliferous scale and bract diverge separately from the vascular cylin der and are accompanied by a single resin canal from the pith that is posit ioned between the arms of the horseshoe-shaped ovuliferous scale trace. The bract trace is terete, accompanied by two lateral resin canals from the co rtical axial system, and enters the free part of the bract. The ovuliferous scale is almost completely sclerotic, with resin canals both abaxial and a daxial to the vascular strands. A large interseminal ridge is present betwe en the two winged seeds on each scale. This cone represents a new species o f Pityostrobus and is described as Pityostrobus californiensis sp. nov. A p hylogenetic analysis using morphological data from the ovulate cones of all the extant and fossil taxa of Pinaceae, as well as those of Cryptomeria ja ponica, Sciadopitys verticillata, and Pararaucaria patagonica, was done. Re lationships of the fossil species of Pityostrobus, Obirastrobus, and Pseudo araucaria to the living taxa of Pinaceae were assessed. The idea that Pityo strobus represents an artificial assemblage of pinaceous taxa is supported by the analyses. The genus Obirastrobus cannot be distinguished from Pityos trobus species, while Pseudoaraucaria species appear as a clade. The diffic ulty of basing fossil taxa purely on cone characteristics is discussed in l ight of the analyses.