The oldest ‘Lingulellotreta’ (Lingulata, Brachiopoda) from China and its phylogenetic significance: integrating new material from the Cambrian Stage 3–4 Lagerstätten in eastern Yunnan, South China

Abstract

The origin of Cambrian brachiopods and their phylogenetic relationship with other lophotrochozoans is far from clear. Lingulellotretidae, the oldest family of lingulate brachiopods, is typified by possessing a pouch-like coelomic extension beyond the hinge line, subtended in a triangular pseudointerarea. The early Cambrian (Stage 4) linguloid brachiopod – originally described as ‘Lingulepis’ malongensis Rong, and later referred to Lingulellotreta within the Family Lingulellotretidae – is here redescribed and assigned to Eoobolus within the Family Eoobolidae, based on new exceptionally preserved topotype material from the type locality, part of the Guanshan Lagerstätte (Wulongqing Formation), Kunming–Malong area, eastern Yunnan, South China. For the first time, we provide a record of the soft anatomy, including a pedicle for the cosmopolitan genus Eoobolus. Due to loss of the type specimen, a neotype of E. malongensis is selected. Differing from the Guanshan E. malongensis, the Chengjiang species is slightly bigger in shell size, and possesses an elongated ventral pseudointerarea. In addition, new flattened specimens of ‘Lingulellotreta malongensis’ from the Chengjiang (Stage 3) biota, preserved in lateral and dorsoventral views, demonstrate an interior lophophore organization and a well-developed pedicle foramen, typical of the genus Lingulellotreta. When compared to the type species – Lingulellotreta ergalievi Koneva – from the Shabakty Group (Cambrian Stage 4), Malyi Karatau Range, Kazakhstan, the Chengjiang species possessed a more elongated ventral pseudointerarea, accommodating an extended body cavity, deepening posteriorly, with a recurved digestive tract. Accordingly, the Chengjiang specimens are thus referred to a new species, Lingulellotreta yuanshanensis sp. nov. The elongated, tubular extended body cavity of Lingulellotreta, which is not present in the slightly younger Guanshan Eoobolus, has recently gained further phylogenetic significance, as support continues to emerge for the view that a ‘tubular’ body plan may be primitive within the lophotrochozoans, notably brachiopods.http://zoobank.org/urn:lsid:zoobank.org.pub:B3212125-F671-4B88-82C5-40C37B5C1631: