Abstract
The study of a petrified twig under high-resolution optical microscopy allowed for the first formal record of the morphogenus Agathoxylon for the late Aptian Crato Member (Santana Formation, Araripe Basin, northeastern Brazil) and the description of a new species, Agathoxylon santanensis. The wood is characterized by mostly (95%) araucarian triseriate alternate bordered pits with hexagonal boundaries in a compact arrangement, and cross-field pits with araucarioid organization. In addition to Agathoxyon-type of xylem, the preservation of a belt of stone cells and axial resin ducts in the non-functional phloem, and an attached leaf with parallel venation showing longitudinally oriented stomata point to a probable Araucariaceae affinity. The presence of Agathoxylon xylem associated with phloem of Araucariaceae affinity in the Tropical-Equatorial Hot Arid belt indicate that the parent plants survived in different climatic zones in the Early Cretaceous of Western Gondwana, from periequatorial to warm and cool-temperate belts. The general growth pattern suggests that the growth interruptions zones were caused by temporary water stress, which was the limiting factor for favorable growing.
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