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We describe a new genus of Leliacladus Batista & L.Kunzmann with the type species Leliacladus (Brachyphyllum) castilhoi (Duarte, 1985) Batista & L.Kunzmann gen. nov. et comb. nov., a rare fossil conifer that has been described from the Aptian (Lower Cretaceous) Romualdo Formation of the Araripe Basin, northeastern Brazil. We decided to leave this new fossil-genus unasigned to any existing family as it does not display sufficient number of anatomical characters. We re-studied the type material of the type species as well as we described additional new material from the Aptian Crato Formation of the same basin. The more recently found fossil materials include large portions of leafy shoots excavated from laminated lacustrine limestones. In contrast to the type material, the new material shows the replacement of organic matter by iron oxide, which is suitable for investigating anatomical features of the wood and leaves. The material allowed for a reappraisal of the systematic position of the fossil plant. Together, the morphological and anatomical characters revealed sufficient evidence to separate the conifer from Brachyphyllum and accommodate it in a new fossil-genus. Leliacladus gen. nov. is defined by the presence of comparatively thick and short claviform lateral branches, and the absence of thinner ultimate order branches with gradual tapering axes. The wood is characterized by dense tracheids with uniseriate pitting in the radial walls and cross-fields that possess one or two large pits. The rays are one to three cells high. The epidermises of the densely and helically arranged scale leaves show non-papillate cyclocytic stomatal complexes slightly sunken that are mostly scattered and randomly arranged across the abaxial surface. This combination of characters suggests the material belongs to the conifer families Podocarpaceae or Cheirolepidiaceae. The arrangement of the sparsely branched, but woody shoots of Leliacladus castilhoi gen. nov. et comb. nov. suggest a hypothetical candelabra-like growth habit of the plant, and the remarkable thickness of the axes suggests a hypothetical xeromorphic adaptation to the semiarid paleoenvironment. [ABSTRACT FROM AUTHOR]

Premise of research. Araucariaceae are currently disjunctively distributed over the Southern Hemisphere, dominating only some restricted habitats. In contrast, fossil representatives of this group from both hemispheres have been reported from the Mesozoic. In the Araripe Basin (northeast Brazil), fossil representatives of Araucariaceae mainly come from the Crato Formation (ca. 120 Ma). They comprise very abundant sterile leafy shoots, rare detached ovuliferous complexes, and dispersed pollen. The morphological variety of the conifer remains showing araucarioid affinities indicates more diversity in the group, which requires investigation. Methodology. Anatomical features were observed using microscopic slides under optical microscopy and with direct observation under SEM. Pivotal results. We describe vegetative shoots of Araucaria violetae sp. nov. on the basis of gross morphological and anatomical characters. The whiplike (pen)ultimate branches bear densely packed helically arranged awl-shaped leaves. Overall, the new species resembles foliage shoots of species of the extant section Eutacta. They could be interpreted either as portions of ultimate shoots of plagiotropic branches or as portions of caducous adventitious shoots. Importantly, we identify mucilage cells in the leaf parenchyma. Conclusions. The new species provides strong evidence for species diversity among Araucaria in the Araripe Basin. Mucilage cells possibly contributed to the water-use efficiency of the fossil plant in a presumed regional hot and semiarid climate. This cell type is present in extant species of the genera Araucaria and Wollemia but absent in extant species of Agathis. However, its presence in Emwadea microcarpa , a fossil stem agathioid, suggests that mucilage cells were lost in stem group agathioids. Thus, our study contributes to the understanding of mucilage cell evolution in Araucariaceae. [ABSTRACT FROM AUTHOR]