Large and Mainly Unnoticed: The First Lower Tithonian Record of a Suspension-Feeding Pachycormid from Southern Gondwana

Abstract

Abstract. A large fossil specimen could easily go unnoticed, especially when the specimen osteology is not well known, is usually represented by fragmentary material and has a sparsely ossified skeleton resulting in low preservation potential. This is particularly true for the suspensionfeeding Pachycormiformes, a clade of actinopterygians. This work provides the description of a complete gill raker recovered from the Upper Jurassic (lower Tithonian) levels of the Vaca Muerta Formation at Cerro Lotena, Neuquen Province, southwestern Argentina. The specimen is referred to the suspension-feeding pachycormid, Leedsichthys, based on similarities in size and shape morphology of the gill raker stalk, the shape of the gill raker base and for having similar morphology of the fimbriae (growing tongue-like distally). Although suspension-feeding pachycormids are known mainly from Laurasia, some remains were also recovered from Gondwana. The lower Tithonian Leedsichthys record extends the geographic and stratigraphic...