Redescription of three fossil baleen whale skulls from the Miocene of Portugal reveals new cetotheriid phylogenetic insights

Abstract

Cetotheriidae is a family of baleen whales that went nearly extinct during the Pleistocene (excluding Caperea marginata). For a long time, the Cetotheriidae family has been seen as a problematic clade, but in the past two decades there have been various studies trying to resolve the phylogeny of this group. In 1831, Alexandre Vandelli described three cetotheriid skulls, found during a gold exploration at Adiça beach (Portugal). These specimens constituted the first Portuguese vertebrate fossils ever published in the literature. Another skull was added to the “Vandelli skulls” by Jacinto Pedro Gomes, in 1914, during a survey of the Museu Nacional de História Natural collections without giving information on the origin of this skull. In 1941, Remington Kellogg states that one of the original “Vandelli skulls” is no longer present in the Museu Nacional de História Natural collections. Until today, there is no information on how, or exactly when, the fourth skull and one of the original three “Vandelli skulls” appeared and disappeared, respectively. Since their discovery, all the attempts to describe these specimens were not based on direct observations and no comprehensive phylogenetic analysis have included the three skulls. Here we provide a detailed anatomic description, a new phylogenetic analysis and a palaeoecological reconstruction of these specimens, clarifying their relationships within the Cetotheriidae family and fostering the importance of these historical specimens to the modern comprehension of fossil whale evolution. In addition, our results support that Cephalotropis nectus is a valid species with an emended diagnosis. We also concluded that two specimens belong to a new genus, forming two new fossil species (new combinations).