In this contribution, four species of Agathoxylon are described from the La Matilde Formation, Gran Bajo de San Julián and central and south-western sectors of Santa Cruz Province, Argentina. Agathoxylon agathioides (Kräusel and Jain) n. comb., Agathoxylon santalense (Sah and Jain) n. comb., Agathoxylon termieri (Attims) Gnaedinger and Herbst, and the new species Agathoxylon santacruzense n. sp. are described based on a detailed description of the secondary xylem. In this work, it was possible to construct scatter plots to elucidate the anatomical differences between the fossil species described on quantitative anatomical data. Comparisons are made with other Agathoxylon species from Gondwana. These parameters can be used to discriminate genera and species of wood found in the same formation, as well as to establish differences/similarities between other taxa described in other formations. Some localities contain innumerable “in situ” petrified trees, which allowed us to infer that these taxa formed small forests, or local forests, or small forests within a dense forest, which is a habitat coincident with the extant Araucariaceae.
-NEW WOOD RECORDS OF THE MIOCENE OF THE SOLIMÕES FORMATION, ACRE BASIN, AMAZONIA, BRAZIL.New fossil wood records associated to the families Lecythidaceae, Calophyllaceae, Combretaceae and Arecaceae for the Miocene of the Solimões Formation, Acre Basin, Brazil, are described. The specimens have been collected on the banks of the Juruá and Envira rivers. The main anatomical characters that allowed relating the specimens to these families are tangential diameter and distribution of vessels per mm 2 , parenchyma type, intravascular pits and types and sizes of rays. It is the first record of Carinianoxylon brasiliense Selmeier, Calophyloxylon eoionophyllum Prakash and Awasthi, Terminalioxylon erichensii Mussa and Palmoxylon Schenk for formation; in addition, a new species for the genus Lecythioxylon Milanez is described. Systematic comparisons have been made with the other fossil records of these families in other Gondwana formations. The paleoflora of the Solimões Formation analyzed here shows a great richness of taxonomic groups, reason why this work provides new and important data for the knowledge of the paleoflora of the Amazon region.Key words: Angiosperms, Miocene, Solimões Formation, Amazon.RESUMO -Novos registros de lenhos fósseis atribuídos às famílias Lecythidaceae, Calophyllaceae, Combretaceae e Arecaceae são descritos para o Mioceno da Formação Solimões, Bacia do Acre, Brasil. Os exemplares foram coletados as margens dos rios Juruá e Envira. As principais características anatômicas que permitiram relacionar os exemplares a estas famílias são: diâmetro tangencial e distribuição dos vasos por mm 2 , tipo de parênquima, pontuações intervaculares, tipos e tamanhos de raios. Se registra pela primeira vez Carinianoxylon brasiliense Selmeier, Calophyloxylon eoionophyllum Prakash & Awasthi, Terminalioxylon erichensii Mussa e Palmoxylon Schenk, para a Formação Solimões. Além disso, é proposta uma nova espécie para o gênero Lecythioxylon Milanez para a formação. As comparações sistemáticas foram realizadas com outros registros fósseis destas famílias para outras formações do Gondwana. A paleoflora da Formação Solimões analisada até o momento mostra uma grande riqueza de grupos taxonômicos, pelos quais este trabalho contribui com novos e importantes dados para o conhecimento da paleoflora da região Amazônica.
-Detailed descriptions are provided for specimens of a new genus and species of Mimosoideae and Swartzioxylon naraense Delteil-Desneux emended (Papilionoideae) from the Solimões Formation, Miocene, Acre Basin, Brazil. Anatomical characteristics of the woods show a resemblance with the extant genera Zygia P. Browne and Swartzia Schreb, respectively. These genera currently have a wide distribution in Brazil and throughout the Amazon region; their presence in the outcrops of the Solimões Formation supports the idea that these genera might have been important components and indicates their importance in the fossil record, both to establish its distribution and evolution from the past to present of Amazon fl ora.Key words: wood anatomy, Mimosoideae, Papilionoideae, Neogene.RESUMO -Descrições detalhadas são fornecidas para os espécimes de um novo gênero e espécie de Mimosoideae e Swartzioxylon naraense Delteil-Desneux emend. (Papilionoideae) da Formação Solimões, Mioceno, bacia do Acre, Brasil. Características anatômicas das madeiras mostram uma semelhança com os gêneros viventes Zygia P. Browne e Swartzia Schreb, respectivamente. Esses gêneros têm atualmente uma ampla distribuição no Brasil e em toda a região amazônica, sua presença nos afl oramentos da Formação Solimões suporta a ideia de que poderiam ter sido importantes componentes e indica a sua importância no registro fóssil, tanto para estabelecer sua distribuição e evolução do passado ao presente da fl ora amazônica.Palavras-chave: anatomia da madeira, Mimosoideae, Papilionoideae, Neógeno.
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