New insights into Middle Devonian chitinozoans from Bolivia

GARCÍA MURO, VICTORIA J.; CAMINA, SONIA C.; CLAUDIA VIVIANA RUBINSTEIN

Oxford

Congreso; The Palaeontological Association 64th Annual Meeting Virtual meeting; 2020

Oxford University Museum of Natural History

The TCB X-1001 ? Tacobo borehole, located in the foothills of Bolivia, eastern sub-Andean ranges, was palynologically analysed. It comprises the Middle Devonian shallow marine sedimentary succession of the Los Monos Formation. A late Eifelian? to middleGivetian age was already interpreted, based on organic-walled phytoplankton and miospores from the same samples. In total 669 chitinozoan specimens were examined under SEM. A moderately well preserved chitinozoan assemblage was recognized from the middle levels of the formation, allowing for the identification of five genera and 33species. The lower and upper levels produced scarce and poorly preserved specimens. The formation yielded a typical late Eifelian to early Givetian chitinozoan fauna of western Gondwana. The assemblage is dominated by the genus Ancyrochitina, which constitutes43 %, with representatives of Ancyrochitina biconstricta and Ancyrochitina multibrachiata, among others. It reveals strong similarities to assemblages previously recorded from the Middle Devonian of Bolivia. The presence of Ramochitina stiphrospinata, which is the index species of the eponymous early Givetian chitinozoan zone of western Gondwana,supports the age assignment based on other palynomorph groups. Other early Givetiancharacteristic species are Ancyrochitina flexuosa, Ancyrochitina frankeli, Ancyrochitinamorzadeci and Ramochitina boliviensis, the latter being very abundant in the studied assemblage.