Conifer wood from the Upper Jurassic of Utah, USA-Part II: Araucarioxylon hoodii sp. nov.

Abstract

The new species, Araucarioxylon hoodii, collected from the Brushy Basin member of the Upper Jurassic Morrison Formation in South central Utah, USA is compared to other species of Araucarioxylon and Dadoxylon, Dadoxylon (Araucarimylon) japonicum Shimakura from Japan being the closest. They differ by the round to elliptical crossfield pits in A. hoodia having round apertures, lacking oppositely arranged tracheary pitting and having larger tangential pits of A. hoodia whereas Dadoxylon (A.) japonicum has circular pits with obliquely elongated lenticular, included apertures. Opposite tracheary pits are often present in the latter species, and its tangential pits are smaller than A. hoodia. Araucarioxylon hoodia is the first member of the genus to be described with assurance from the Jurassic of the Colorado Plateau, USA. Associated fossil plants and the anatomical structure of A. hoodia suggest that it grew under a fairly equable damp climate in which its growth rings were not well developed.