Morphologic-phylogenetic approach of the late Cenozoic Chlamydini von Teppner, 1922 (Bivalvia: Pectinidae) of southern South America

SANTELLI, MARÍA BELÉN; ALVAREZ, MAXIMILIANO; DEL RÍO CLAUDIA JULIA

SPECIAL PAPERS IN PALAEONTOLOGY SERIES

PALAEONTOLOGICAL ASSOC

Lugar: Londres; Año: 2021 p. 1825 - 1846

0038-6804

The tribe Chlamydini constitutes a highly diversified group in the Neogene marine rocks of southern South America, reaching its maximum taxonomic diversity during Miocene times but its relationships remain completely uncertain. This contribution is the first phylogenetic analysis based on a large morphological matrix of characters of Pectinidae, performed within a partial phylogenetic framework of the tribe Chlamydini to discover its hypothetical evolutionary relationships in the region. The phylogenetic analysis was performed from a matrix composed by 145 shell-characters scored for species and multiple searches were conducted using equal and implied weighting. Two new monophyletic clades are defined, Multiplicata and Pauciplicata. The first includes to the southern hemisphere Dietotenhosen, Ckaraosippur, Zygochlamys, Moirechlamys,and the north-east Pacific Azumapecten, and Chlamys hastata. Pauciplicata is represented by Chokekenia (Patagonia Argentina), Laevichlamys (tropical Atlantic Ocean and Indo-Pacific Ocean), Semipallium (Indo-Pacific Ocean), Swiftopecten (southern South America and North Pacific), and the nested Jorgechlamys and Reticulochlamys (Patagonia, Argentina). All these Chlamydini genera are monophyletic except for the paraphyletic Jorgechlamys. The oldest proved occurrence of the tribe is early Oligocene age (Semipallium foulcheri), a derivate taxon that would push the divergence time of the basal genera to the Eocene?Oligocene boundary in the time-calibrated tree, generating ghost lineages in several clades, except for Jorgechlamys+Reticulochlamys. Pauciplicata and Multiplicata also would diverge in the early history of the tribe, at the Eocene?Oligocene boundary. Future analyses are necessary to understand the composition of this complex tribe to discover its origin.