The Family Sigmagraptidae (Graptolithina) in the Central Andean Basin.

TORO, BLANCA A.; HERRERA SÁNCHEZ, NEXXYS C.; LO VALVO, GERARDO A.

Ciudad Autónoma de Buenos Aires

Jornada; 1er Reunión Virtual de Comunicaciones de la Asociación Paleontológica Argentina; 2020

Asociación Paleontológica Argentina

The sigmagraptids from the Central Andean Basin were scarce and poorly known until now. Based on the taxonomic classification of Graptolithina, recently published as part of the Treatise on Invertebrate Paleontology, the best-preserved specimens of the family Sigmagraptidae, coming from different regions of the Central Andean Basin, are reviewed. This study allows documenting four additional taxa as part of the Ph.D. of the former author. Single-stiped colonies of Azygograptus lapworthi Nicholson were recognized from early Dapingian levels (Middle Ordovician) at the Los Colorados and La Quiaca sections, Argentine Cordillera Oriental; Muñayoc and Huaytiquina sections, Argentine Puna; and Chaupi Uno section, Southern Bolivia. Multiramous tubaria of Sigmagraptus praecursor Ruedemann were identified for the first time in South America at Santa Rosa section, Argentine Puna. Additionally, Paradelograptus mosseboensis Erdtmann et al. and P. onubensis Erdtmann et al. are described for the first time for the Huancar section, Argentine Puna. These species are preserved as distinct stages of development, exhibiting very slender prothecae and considerably width metathecae; and can be distinguished from each other based on the sicular morphometry. In the Central Andean basin a total of 10 taxa are included in Sigmagraptidae, reaching 13% of the taxonomic diversity recorded from the middle Tremadocian (Early Ordovician) to the early Darriwilian (Middle Ordovician) times. This family was a relevant component of the graptolite fauna through this period at the basin but displayed a secondary role in the faunal composition. These quantitative results are in agreement with the global trend on graptoloids taxonomic distribution.