Deflexed Baltograptus species in the early to mid Arenig graptolite biostratigraphy of Northwestern Argentina.

TORO, B.A.; MALETZ, J.

Acta Palaeontologica Sinica

Science Press

Lugar: Beijing; Año: 2007 vol. 46 p. 489 - 496

0001-6616

Abstract. Deflexed didymograptids of the genus Baltograptus are common in strata of the Acoite Formation of Northwestern Argentina. A number of distinct species can be used as biostratigraphic indices for the early to mid Arenig. They mainly differ in their proximal end development and stipe width. Early forms in the Tetragraptus akzharensis to "Baltograptus deflexus" Biozones present an isograptid proximal development type. Slender-stiped Baltograptus deflexus and Baltograptus sp. nov. occur together with wide-stiped forms of the B. turgidus group. Another slender species with an artus type development, here identified as B. deflexus s. str is restricted to younger levels corresponding to the Didymograptellus bifidus Biozone.