The Sedimentary Basin of Abunã is located near the channel of the Madeira River, in
the state of Rondônia - Brazil, and is characterized by a flat relief, resulting from
accumulation processes of fluvial sediments along the Quaternary. Within this context, there
has been an increase in published works in recent years, reporting the paleoenvironmental and
paleoclimatic characteristics of this region. The present study aims to describe the leaf
morphology and taxonomic recognition of four fossils leaves collected in the outcrop Stake
93 (09 ° 16'25.05 "S; 64 ° 38'16.87" W) at the construction site of the Hydroelectric Power
Plant Jirau (UHE). The samples were submitted to a previous curatorial preparation and were
numbered and packed with PVC film and placed in paraffin molds. The date for the layer
from which the material analyzed here has been presented, has already been presented in
previous works, presenting an age of ± 43,500 A.P. The specimens were photographed and
the venation patterns redesigned. The taxonomic recognition was made based on the key of
identification of angiosperms following the detail proposed by the Manual of Leaf
Architecture, being also that were compared with representatives of the current Amazonian
flora through consultation the specific bibliography. From the presence of typical elements it
was possible to record the occurrence of two families: Chrysobalanaceae, primary vein of
pinnate and secondary semicraspedodromous, opposite venation and alternating in the same
leaf, determining the registration of a new morphogen and morphospecies, Temporarily
referred to as of Morphotype 02; Calophyllaceae, with numerous secondary venations, parallel
to each other, filling the entire foliar field, defining the description of a new morphospecies
for the genus Calophyllum, here temporarily termed Calophyllum sp1. The presence of these
families indicates similarity with the flora currently established in the region, making possible
the inference of a paleoclimate very similar to the existing one. Thus, this finding
corroborates previous studies that postulate the presence of a typically tropical forest already
established since at least ± 43,500 years, corresponding to the Late Pleistocene.
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