GILBOAPHYTON ARGENTINUM SP. NOV.: A HERBACEOUS LYCOPOD FROM THE EARLY CARBONIFEROUS OF ARGENTINA

A new species of a herbaceous lycophyte with tripartite leaves is attributed to Gilboaphyton Arnold on the basis of the leaf morphology and the hexagonal shape of its leaf bases on the stem surface. The new species includes specimens previously classified as Archaeosigillaria conferta (Frenguelli) Menendez,a primitive lycophyte which has been considered of biostratigraphic value in the Lower Carboniferous of Argentina. The excellent preservation of its delicate leaves adpressed to the stem has allowed to recognize its tripartite shape.. The fossil remains are from lower strata of the Jaramillo Formation, in the Tepuel - Genoa Basin in NW Patagonia, Argentina. Gilboaphyton argentinum Carrizo & Azcuy sp. nov. is compared with the two species of Gilboaphyton Arnold, G. goldringiae Arnold from New York and G. griersonii Berry & Edwards from Venezuela. Its age is discussed and it is concludes that the biocron of the genus Gilboaphyton has to be extended into the Early Carboniferous. RESUMO - Uma nova especie de licofita herbacea e proposta com base na morfologia de suas folhas e no modelo hexagonal de suas bases folilares na superficie do talo. A nova especie inclui especimens anteriormente referidos a Archaeosigillaria conferta (Frenguelli) Menendez, uma primitiva licofita, a qual e atribuido um importante valor estratigrafico em formacoes do Carbonifero Inferior da Argentina. A excelente preservacao do material, com delicadas folhas adpresas sobre o talo permitiu reconhecer seu caracter tripartido. Os restos fosseis aqui descritos sao provenientes dos estratos basais da Formacao Jaramillo, bacia Tepuel-Genoa, na regiao noroeste da Patagonia. Gilboaphyton argentinum sp. nov. e comparada a outras especies de Gilboaphyton Arnold, tais como G. goldringiae Arnold de New York e G. griersonii Berry & Edwards da Venezuela. Sua idade e discutida e se conclui que o biocron do genero Gilboaphyton deve ser extendido ao inicio do Carbonifero.