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Abstract. EOGUPTIOXYLON ANTIQUA NOV. GEN. ET SP. (PTERIDOSPERMAE) FROM THE UPPER PERMIAN (LA ANTIGUAEOGUPTIOXYLON ANTIQUA NOV. GEN. ET SP. (PTERIDOSPERMAE) FROM THE UPPER PERMIAN (LA ANTIGUA FORMATION), LA RIOJA PROVINCE, ARGENTINA. A polystelic pteridosperm wood with steles irregularly disposed in ground parenchyma from the Upper Permian La Antigua Formation (La Rioja province) is described. Each stele has preserved a central diaphragm pith with lacunes, primary and secondary xylem surrounded by sclerenchymatic tissue. The new geners confered with different taxa anatomical with similar characters observed in Carboniferous-Permian Medullosales (Medullosa) and Jurassic ones such as Pentoxylales (Pentoxylon, Nipanioxylon) and the incertae sedis genus Guptioxylon. Other anatomical characters, like picnoxylic secondary wood with uni- to biseriate pits, araucarioid cross-fields and the type of rays are shared with Coniferales. Guptioxylon from the Rajmahal Hills (India) correspond to the genus with most affinities with the herein described. However, the studied specimens can not be adscribed to this taxon because of marked differences in the pith and the secondary xylem, departure and conformation traces, and the absence of the X-shaped peculiar periderm, all of them characteristics present in the pith of Guptioxylon. Consequently a new genus and species is proposed to include this new Pteridosperm from the Upper Permian of Argentina. from the Upper Permian of Argentina. with most affinities with the herein described. However, the studied specimens can not be adscribed to this taxon because of marked differences in the pith and the secondary xylem, departure and conformation traces, and the absence of the X-shaped peculiar periderm, all of them characteristics present in the pith of Guptioxylon. Consequently a new genus and species is proposed to include this new Pteridosperm from the Upper Permian of Argentina. from the Upper Permian of Argentina. like picnoxylic secondary wood with uni- to biseriate pits, araucarioid cross-fields and the type of rays are shared with Coniferales. Guptioxylon from the Rajmahal Hills (India) correspond to the genus with most affinities with the herein described. However, the studied specimens can not be adscribed to this taxon because of marked differences in the pith and the secondary xylem, departure and conformation traces, and the absence of the X-shaped peculiar periderm, all of them characteristics present in the pith of Guptioxylon. Consequently a new genus and species is proposed to include this new Pteridosperm from the Upper Permian of Argentina. from the Upper Permian of Argentina. with most affinities with the herein described. However, the studied specimens can not be adscribed to this taxon because of marked differences in the pith and the secondary xylem, departure and conformation traces, and the absence of the X-shaped peculiar periderm, all of them characteristics present in the pith of Guptioxylon. Consequently a new genus and species is proposed to include this new Pteridosperm from the Upper Permian of Argentina. from the Upper Permian of Argentina. Pentoxylales (Pentoxylon, Nipanioxylon) and the incertae sedis genus Guptioxylon. Other anatomical characters, like picnoxylic secondary wood with uni- to biseriate pits, araucarioid cross-fields and the type of rays are shared with Coniferales. Guptioxylon from the Rajmahal Hills (India) correspond to the genus with most affinities with the herein described. However, the studied specimens can not be adscribed to this taxon because of marked differences in the pith and the secondary xylem, departure and conformation traces, and the absence of the X-shaped peculiar periderm, all of them characteristics present in the pith of Guptioxylon. Consequently a new genus and species is proposed to include this new Pteridosperm from the Upper Permian of Argentina. from the Upper Permian of Argentina. with most affinities with the herein described. However, the studied specimens can not be adscribed to this taxon because of marked differences in the pith and the secondary xylem, departure and conformation traces, and the absence of the X-shaped peculiar periderm, all of them characteristics present in the pith of Guptioxylon. Consequently a new genus and species is proposed to include this new Pteridosperm from the Upper Permian of Argentina. from the Upper Permian of Argentina. like picnoxylic secondary wood with uni- to biseriate pits, araucarioid cross-fields and the type of rays are shared with Coniferales. Guptioxylon from the Rajmahal Hills (India) correspond to the genus with most affinities with the herein described. However, the studied specimens can not be adscribed to this taxon because of marked differences in the pith and the secondary xylem, departure and conformation traces, and the absence of the X-shaped peculiar periderm, all of them characteristics present in the pith of Guptioxylon. Consequently a new genus and species is proposed to include this new Pteridosperm from the Upper Permian of Argentina. from the Upper Permian of Argentina. with most affinities with the herein described. However, the studied specimens can not be adscribed to this taxon because of marked differences in the pith and the secondary xylem, departure and conformation traces, and the absence of the X-shaped peculiar periderm, all of them characteristics present in the pith of Guptioxylon. Consequently a new genus and species is proposed to include this new Pteridosperm from the Upper Permian of Argentina. from the Upper Permian of Argentina. in ground parenchyma from the Upper Permian La Antigua Formation (La Rioja province) is described. Each stele has preserved a central diaphragm pith with lacunes, primary and secondary xylem surrounded by sclerenchymatic tissue. The new geners confered with different taxa anatomical with similar characters observed in Carboniferous-Permian Medullosales (Medullosa) and Jurassic ones such as Pentoxylales (Pentoxylon, Nipanioxylon) and the incertae sedis genus Guptioxylon. Other anatomical characters, like picnoxylic secondary wood with uni- to biseriate pits, araucarioid cross-fields and the type of rays are shared with Coniferales. Guptioxylon from the Rajmahal Hills (India) correspond to the genus with most affinities with the herein described. However, the studied specimens can not be adscribed to this taxon because of marked differences in the pith and the secondary xylem, departure and conformation traces, and the absence of the X-shaped peculiar periderm, all of them characteristics present in the pith of Guptioxylon. Consequently a new genus and species is proposed to include this new Pteridosperm from the Upper Permian of Argentina. from the Upper Permian of Argentina. with most affinities with the herein described. However, the studied specimens can not be adscribed to this taxon because of marked differences in the pith and the secondary xylem, departure and conformation traces, and the absence of the X-shaped peculiar periderm, all of them characteristics present in the pith of Guptioxylon. Consequently a new genus and species is proposed to include this new Pteridosperm from the Upper Permian of Argentina. from the Upper Permian of Argentina. like picnoxylic secondary wood with uni- to biseriate pits, araucarioid cross-fields and the type of rays are shared with Coniferales. Guptioxylon from the Rajmahal Hills (India) correspond to the genus with most affinities with the herein described. However, the studied specimens can not be adscribed to this taxon because of marked differences in the pith and the secondary xylem, departure and conformation traces, and the absence of the X-shaped peculiar periderm, all of them characteristics present in the pith of Guptioxylon. Consequently a new genus and species is proposed to include this new Pteridosperm from the Upper Permian of Argentina. from the Upper Permian of Argentina. with most affinities with the herein described. However, the studied specimens can not be adscribed to this taxon because of marked differences in the pith and the secondary xylem, departure and conformation traces, and the absence of the X-shaped peculiar periderm, all of them characteristics present in the pith of Guptioxylon. Consequently a new genus and species is proposed to include this new Pteridosperm from the Upper Permian of Argentina. from the Upper Permian of Argentina. Pentoxylales (Pentoxylon, Nipanioxylon) and the incertae sedis genus Guptioxylon. Other anatomical characters, like picnoxylic secondary wood with uni- to biseriate pits, araucarioid cross-fields and the type of rays are shared with Coniferales. Guptioxylon from the Rajmahal Hills (India) correspond to the genus with most affinities with the herein described. However, the studied specimens can not be adscribed to this taxon because of marked differences in the pith and the secondary xylem, departure and conformation traces, and the absence of the X-shaped peculiar periderm, all of them characteristics present in the pith of Guptioxylon. Consequently a new genus and species is proposed to include this new Pteridosperm from the Upper Permian of Argentina. from the Upper Permian of Argentina. with most affinities with the herein described. However, the studied specimens can not be adscribed to this taxon because of marked differences in the pith and the secondary xylem, departure and conformation traces, and the absence of the X-shaped peculiar periderm, all of them characteristics present in the pith of Guptioxylon. Consequently a new genus and species is proposed to include this new Pteridosperm from the Upper Permian of Argentina. from the Upper Permian of Argentina. like picnoxylic secondary wood with uni- to biseriate pits, araucarioid cross-fields and the type of rays are shared with Coniferales. Guptioxylon from the Rajmahal Hills (India) correspond to the genus with most affinities with the herein described. However, the studied specimens can not be adscribed to this taxon because of marked differences in the pith and the secondary xylem, departure and conformation traces, and the absence of the X-shaped peculiar periderm, all of them characteristics present in the pith of Guptioxylon. Consequently a new genus and species is proposed to include this new Pteridosperm from the Upper Permian of Argentina. from the Upper Permian of Argentina. with most affinities with the herein described. However, the studied specimens can not be adscribed to this taxon because of marked differences in the pith and the secondary xylem, departure and conformation traces, and the absence of the X-shaped peculiar periderm, all of them characteristics present in the pith of Guptioxylon. Consequently a new genus and species is proposed to include this new Pteridosperm from the Upper Permian of Argentina. from the Upper Permian of Argentina. ORMATION), LA RIOJA PROVINCE, ARGENTINA. A polystelic pteridosperm wood with steles irregularly disposed in ground parenchyma from the Upper Permian La Antigua Formation (La Rioja province) is described. Each stele has preserved a central diaphragm pith with lacunes, primary and secondary xylem surrounded by sclerenchymatic tissue. The new geners confered with different taxa anatomical with similar characters observed in Carboniferous-Permian Medullosales (Medullosa) and Jurassic ones such as Pentoxylales (Pentoxylon, Nipanioxylon) and the incertae sedis genus Guptioxylon. Other anatomical characters, like picnoxylic secondary wood with uni- to biseriate pits, araucarioid cross-fields and the type of rays are shared with Coniferales. Guptioxylon from the Rajmahal Hills (India) correspond to the genus with most affinities with the herein described. However, the studied specimens can not be adscribed to this taxon because of marked differences in the pith and the secondary xylem, departure and conformation traces, and the absence of the X-shaped peculiar periderm, all of them characteristics present in the pith of Guptioxylon. Consequently a new genus and species is proposed to include this new Pteridosperm from the Upper Permian of Argentina. from the Upper Permian of Argentina. with most affinities with the herein described. However, the studied specimens can not be adscribed to this taxon because of marked differences in the pith and the secondary xylem, departure and conformation traces, and the absence of the X-shaped peculiar periderm, all of them characteristics present in the pith of Guptioxylon. Consequently a new genus and species is proposed to include this new Pteridosperm from the Upper Permian of Argentina. from the Upper Permian of Argentina. like picnoxylic secondary wood with uni- to biseriate pits, araucarioid cross-fields and the type of rays are shared with Coniferales. Guptioxylon from the Rajmahal Hills (India) correspond to the genus with most affinities with the herein described. However, the studied specimens can not be adscribed to this taxon because of marked differences in the pith and the secondary xylem, departure and conformation traces, and the absence of the X-shaped peculiar periderm, all of them characteristics present in the pith of Guptioxylon. Consequently a new genus and species is proposed to include this new Pteridosperm from the Upper Permian of Argentina. from the Upper Permian of Argentina. with most affinities with the herein described. However, the studied specimens can not be adscribed to this taxon because of marked differences in the pith and the secondary xylem, departure and conformation traces, and the absence of the X-shaped peculiar periderm, all of them characteristics present in the pith of Guptioxylon. Consequently a new genus and species is proposed to include this new Pteridosperm from the Upper Permian of Argentina. from the Upper Permian of Argentina. Pentoxylales (Pentoxylon, Nipanioxylon) and the incertae sedis genus Guptioxylon. Other anatomical characters, like picnoxylic secondary wood with uni- to biseriate pits, araucarioid cross-fields and the type of rays are shared with Coniferales. Guptioxylon from the Rajmahal Hills (India) correspond to the genus with most affinities with the herein described. However, the studied specimens can not be adscribed to this taxon because of marked differences in the pith and the secondary xylem, departure and conformation traces, and the absence of the X-shaped peculiar periderm, all of them characteristics present in the pith of Guptioxylon. Consequently a new genus and species is proposed to include this new Pteridosperm from the Upper Permian of Argentina. from the Upper Permian of Argentina. with most affinities with the herein described. However, the studied specimens can not be adscribed to this taxon because of marked differences in the pith and the secondary xylem, departure and conformation traces, and the absence of the X-shaped peculiar periderm, all of them characteristics present in the pith of Guptioxylon. Consequently a new genus and species is proposed to include this new Pteridosperm from the Upper Permian of Argentina. from the Upper Permian of Argentina. like picnoxylic secondary wood with uni- to biseriate pits, araucarioid cross-fields and the type of rays are shared with Coniferales. Guptioxylon from the Rajmahal Hills (India) correspond to the genus with most affinities with the herein described. However, the studied specimens can not be adscribed to this taxon because of marked differences in the pith and the secondary xylem, departure and conformation traces, and the absence of the X-shaped peculiar periderm, all of them characteristics present in the pith of Guptioxylon. Consequently a new genus and species is proposed to include this new Pteridosperm from the Upper Permian of Argentina. from the Upper Permian of Argentina. with most affinities with the herein described. However, the studied specimens can not be adscribed to this taxon because of marked differences in the pith and the secondary xylem, departure and conformation traces, and the absence of the X-shaped peculiar periderm, all of them characteristics present in the pith of Guptioxylon. Consequently a new genus and species is proposed to include this new Pteridosperm from the Upper Permian of Argentina. from the Upper Permian of Argentina. Medullosa) and Jurassic ones such as Pentoxylales (Pentoxylon, Nipanioxylon) and the incertae sedis genus Guptioxylon. Other anatomical characters, like picnoxylic secondary wood with uni- to biseriate pits, araucarioid cross-fields and the type of rays are shared with Coniferales. Guptioxylon from the Rajmahal Hills (India) correspond to the genus with most affinities with the herein described. However, the studied specimens can not be adscribed to this taxon because of marked differences in the pith and the secondary xylem, departure and conformation traces, and the absence of the X-shaped peculiar periderm, all of them characteristics present in the pith of Guptioxylon. Consequently a new genus and species is proposed to include this new Pteridosperm from the Upper Permian of Argentina. from the Upper Permian of Argentina. with most affinities with the herein described. However, the studied specimens can not be adscribed to this taxon because of marked differences in the pith and the secondary xylem, departure and conformation traces, and the absence of the X-shaped peculiar periderm, all of them characteristics present in the pith of Guptioxylon. Consequently a new genus and species is proposed to include this new Pteridosperm from the Upper Permian of Argentina. from the Upper Permian of Argentina. like picnoxylic secondary wood with uni- to biseriate pits, araucarioid cross-fields and the type of rays are shared with Coniferales. Guptioxylon from the Rajmahal Hills (India) correspond to the genus with most affinities with the herein described. However, the studied specimens can not be adscribed to this taxon because of marked differences in the pith and the secondary xylem, departure and conformation traces, and the absence of the X-shaped peculiar periderm, all of them characteristics present in the pith of Guptioxylon. Consequently a new genus and species is proposed to include this new Pteridosperm from the Upper Permian of Argentina. from the Upper Permian of Argentina. with most affinities with the herein described. However, the studied specimens can not be adscribed to this taxon because of marked differences in the pith and the secondary xylem, departure and conformation traces, and the absence of the X-shaped peculiar periderm, all of them characteristics present in the pith of Guptioxylon. Consequently a new genus and species is proposed to include this new Pteridosperm from the Upper Permian of Argentina. from the Upper Permian of Argentina. Pentoxylon, Nipanioxylon) and the incertae sedis genus Guptioxylon. Other anatomical characters, like picnoxylic secondary wood with uni- to biseriate pits, araucarioid cross-fields and the type of rays are shared with Coniferales. Guptioxylon from the Rajmahal Hills (India) correspond to the genus with most affinities with the herein described. However, the studied specimens can not be adscribed to this taxon because of marked differences in the pith and the secondary xylem, departure and conformation traces, and the absence of the X-shaped peculiar periderm, all of them characteristics present in the pith of Guptioxylon. Consequently a new genus and species is proposed to include this new Pteridosperm from the Upper Permian of Argentina. from the Upper Permian of Argentina. with most affinities with the herein described. However, the studied specimens can not be adscribed to this taxon because of marked differences in the pith and the secondary xylem, departure and conformation traces, and the absence of the X-shaped peculiar periderm, all of them characteristics present in the pith of Guptioxylon. Consequently a new genus and species is proposed to include this new Pteridosperm from the Upper Permian of Argentina. from the Upper Permian of Argentina. Guptioxylon from the Rajmahal Hills (India) correspond to the genus with most affinities with the herein described. However, the studied specimens can not be adscribed to this taxon because of marked differences in the pith and the secondary xylem, departure and conformation traces, and the absence of the X-shaped peculiar periderm, all of them characteristics present in the pith of Guptioxylon. Consequently a new genus and species is proposed to include this new Pteridosperm from the Upper Permian of Argentina. from the Upper Permian of Argentina. Guptioxylon. Consequently a new genus and species is proposed to include this new Pteridosperm from the Upper Permian of Argentina.