Cones, Seeds, and Foliage ofTetraclinis Salicornioides(Cupressaceae) from the Oligocene and Miocene of Western North America: A Geographic Extension of the European Tertiary Species

Abstract

The cupressaceous genus Tetraclinis is recognized from the Oligocene and Miocene of western North America on the basis of co‐occurring seed cones, seeds, and foliage branches. Morphological and anatomical comparisons with the two previously recognized European Tertiary species indicate that the North American specimens are morphologically inseparable from Tetraclinis salicornioides (Unger) Kvaček. The North American taxon is treated as a new variety, T. salicornioides (Unger) Kvaček var. praedecurrens (Knowlton) comb. et stat. nov., and is distinguished from the European representatives, T. salicornioides (Unger) Kvaček var. salicornioides, by slight anatomical differences in the leaf epidermis. Although cones and seeds of the fossil species are closely similar to those of extant Tetraclinis articulata, the foliage is more “spreading,” composed of flattened segments with fused facial and lateral leaves that are apparently adaptive for a more mesic climate. The recognition of T. salicornioides in western North America along with the absence of Tetraclinis in the fossil and recent flora of eastern Asia provide evidence for communication of the species across the North Atlantic during the early or middle Tertiary.