Abstract The taxonomic study of brachiopods (Family Discinidae) from the upper part of the Manacapuru Formation (Lochkovian), south border of the Amazonas Basin, Brazil, allowed to recognize’ five species of Orbiculoidea: O. baini, O. bodenbenderi, O. excentrica, and two new species described herein: O. xinguensis sp. nov. and O. katzeri sp. nov. Besides, O. baini, O. bodenbenderi, and O. excentrica are recorded for the first time in the Manacapuru Formation, and in Northern Brazil, being the oldest records (Lochkovian) of these species in South America too. Their presence in the region can be explained by two reasons: the proximity of the Amazonas Basin, located in northwest Gondwana, during the Early Devonian to the continent of Laurasia (where are recorded most occurrences of Orbiculoidea during the Silurian), favoring the specific interchange between these two geographic regions; and the global sea level rise during this time, which flooded a large part of northwestern Gondwana, resulting in the presence of shallow seas in the Amazonas Basin, represented by marine sediments in the upper part of the Manacapuru Formation. These conditions promoted the colonization of inarticulate brachiopods during the Early Devonian in the north of Brazil. The discinoids identified in the strata of the Manacapuru Formation are typical of shallow marine environments, supporting previous interpretations for the upper part of this unit.

中文翻译：

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Discinoids (Brachiopoda: Lingulata) 来自巴西亚马逊盆地南部边界的上马纳卡普鲁组（早泥盆世）

摘要 巴西亚马孙盆地南部边界 Manacapuru 组 (Lochkovian) 上部腕足类 (科) 的分类学研究允许识别 5 种 Orbiculoidea: O. baini, O. bodenbenderi, O. excentrica 和这里描述的两个新物种：O. xinguensis sp. 十一月 和 O. katzeri sp。十一月 此外，O. baini、O. bodenbenderi和O. excentrica在Manacapuru组首次被记录，在巴西北部也是这些物种在南美洲最古老的记录（Lochkovian）。它们在该地区的存在可以用两个原因来解释：位于冈瓦纳西北部的亚马逊盆地在早泥盆世期间靠近劳亚大陆（在志留纪期间记录了大多数 Orbiculoidea 的出现），有利于这两个地理区域之间的特定交流；而这段时间全球海平面上升，淹没了冈瓦纳西北部的大部分地区，导致亚马逊盆地出现浅海，以马纳卡普鲁组上部的海洋沉积物为代表。在巴西北部早泥盆世期间，这些条件促进了无关节腕足类动物的定居。在 Manacapuru 组地层中确定的盘片类是典型的浅海海洋环境，支持先前对该单元上部的解释。以马纳卡普鲁组上部的海相沉积物为代表。在巴西北部早泥盆世期间，这些条件促进了无关节腕足类动物的定居。在 Manacapuru 组地层中确定的盘片类是典型的浅海海洋环境，支持先前对该单元上部的解释。以马纳卡普鲁组上部的海相沉积物为代表。在巴西北部早泥盆世期间，这些条件促进了无关节腕足类动物的定居。在 Manacapuru 组地层中确定的盘片类是典型的浅海海洋环境，支持先前对该单元上部的解释。