Lagenochitina sp. A. measurements.

Chitinozoans recovered from one section of the Middle Devonian Los Monos Formation in the TCB X-1001-Tacobo borehole, sub-Andean basin of Bolivia, have been analysed. Eleven from the eighteen processed cutting samples yielded specimens that allowed taxonomic study. Eleven genera and thirty-five chitinozoan species were identified from the Los Monos Formation with four of them recorded for the first time in Western Gondwana. Ancyrochitina biconstricta, Ancyrochitina parisi, Angochitina galarzae and Ramochitina boliviensis are among the most relevant taxa restricted to Western Gondwana that support the affinity with this paleocontinent. One new species, Lagenochitina tacobensis sp. nov. is described, and Ramochitina candelariaensis sp. nov. (n. n.) is formally erected. The chitinozoan assemblage reinforces the late Eifelian–middle Givetian age previously proposed by organic-walled phytoplankton and miospores for this section of the TCB X-1001-Tacobo borehole. A new local chitinozoan biozonation based on the chitinozoan assemblages is proposed and a revision of the current chitinozoan biozonation for Western Gondwana and Bolivia is recommended.对采自玻利维亚亚安第斯盆地TCB X-1001-Tacobo钻孔中泥盆统洛斯莫诺斯组（Los Monos Formation）单个剖面的几丁虫（Chitinozoans）样品开展了分析研究。本次处理的18块岩屑样品中，11块获取了可用于分类学研究的几丁虫标本。从洛斯莫诺斯组中共鉴定出11属35种几丁虫，其中4种为西冈瓦纳大陆（Western Gondwana）首次报道的类群。双缩安氏几丁虫（Ancyrochitina biconstricta）、帕里安氏几丁虫（Ancyrochitina parisi）、加拉尔萨安吉几丁虫（Angochitina galarzae）以及玻利维亚分枝几丁虫（Ramochitina boliviensis）均为西冈瓦纳大陆特有的代表性分类单元，印证了该地层与该古大陆的生物亲缘关系。本文记述了1个新种——塔科博瓶形几丁虫（Lagenochitina tacobensis sp. nov.），并正式建立了坎德拉里亚分枝几丁虫（Ramochitina candelariaensis sp. nov. (n. n.)）新组合。该几丁虫组合进一步支持了此前通过有机壁浮游植物和微孢子所提出的TCB X-1001-Tacobo钻孔该剖面的时代为艾菲尔阶晚期—吉维特阶中期的结论。本文基于该几丁虫组合提出了一套全新的区域几丁虫生物地层分带方案，并建议对当前西冈瓦纳大陆及玻利维亚地区的几丁虫生物地层分带体系进行修订。