Palmoxylon hebbertii, from the Lower Oligocene Goldens Ranch Formation of central Utah, U.S.A., with an analysis of some characteristics previously used in the classification of Palmoxylon

Abstract

The new species, Palmoxylon hebbertii, described here was collected from the Lower Oligocene Goldens Ranch Formation southwest of Nephi, Utah, U.S.A. In cross section, the collateral vascular bundles are generally reniform in shape with a well-developed fibrous bundle sheath and a median sinus that is very shallow or absent. They are bivascular and, in the subdermal zone, surrounded by radiating parenchyma. The phloem is well differentiated into protophloem and metaphloem elements with oblique sieve plates. The metaxylem and protoxylem vessel elements show a gradual change in the morphology of their end plates as well as in their wall thickenings. An analysis of 41 well preserved Palmoxylon species from India suggests that Stenzel's grouping of the species based on the nature of the bundle sheath is artificial and that several characteristics including the nature of the vascular tissues, used in classification of extant species, should be used.Key words: palm, Goldens Ranch Formation, Utah, Oligocene, Stenzel's grouping, Jaccard's method.