DOI: 10.5061/dryad.0zpc866vd
title: Morphologic-phylogenetic analysis of the late Cenozoic Chlamydini von Teppner (Bivalvia: Pectinidae) of southern South America

description: The tribe Chlamydini was highly diversified in the marine Neogene of
 southern South America, reaching its maximum taxonomic diversity during
 the Miocene. However, the evolutionary relationships of South American
 taxa remain uncertain. This is the first phylogenetic analysis based on a
 large morphological matrix on Pectinidae, which is focusing on South
 American taxa and species related to Chlamys s. The phylogenetic analysis
 is based on a matrix composed of 145 shell characters scored for 48
 species and multiple searches were conducted using equal and implied
 weighting. Two new monophyletic clades are defined, Multiplicata and
 Pauciplicata. The first includes Dietotenhosen, Ckaraosippur, Zygochlamys,
 Moirechlamys (South America), the Northwest Pacific Azumapecten, and the
 Northeast Pacific Chlamys hastata. Pauciplicata is represented by
 Chokekenia (Patagonia Argentina), Laevichlamys (tropical Atlantic and
 Indo-Pacific), Semipallium (Indo-Pacific), Swiftopecten (South America and
 North Pacific), and Jorgechlamys +Reticulochlamys (Patagonia, Argentina).
 All these genera are monophyletic except for the paraphyletic
 Jorgechlamys. The oldest documented occurrence of the tribe is Semipallium
 foulcheri from the early Oligocene, which is a derived taxon that pushes
 the divergence time of basal genera to the Eocene–Oligocene boundary,
 generating ghost lineages in several clades, except for
 Jorgechlamys+Reticulochlamys. Pauciplicata and Multiplicata diverge in the
 early history of the tribe, at the Eocene–Oligocene boundary. Future
 analyses are necessary to gain a better understanding of the taxonomic
 arrangement of this poorly understood tribe to discover the relationships
 on its deepest nodes, which probably allow to resolve many ghost lineages.
description: The present contribution is focused on 17 species of Chlamydini
 from the late Cenozoic of Argentina, Chile, and Peru and it comprises 48
 species of pectinids in total. Two South American species of
 <i>Psychrochlamys</i> are also included. Most of those taxa
 were studied from specimens in hand and some through high-quality images
 after being compared with proper systematic descriptions.
 <i>Phylogenetic searches, branch supports, and tree
 calibration. </i> The software TNT v1.5 (Goloboff
 & Catalano 2016) was used to conduct heuristic tree searches
 because the high number of herein included taxa. Space was configured for
 20000 trees in memory and the searches were conducted applying maximum
 parsimony criterion, starting from 100 replicates of Wagner trees with
 random addition sequence (RAS) of taxa, which is followed by Tree
 Bisection and Reconnection (TBR) branch-swapping algorithm saving 10 trees
 per replication. To minimize the effect of the homoplasy, characters were
 weighted (as suggested by Goloboff <i>et al.</i> 2003;
 Goloboff <i>et al.</i> 2008), which allows obtaining more
 reliable and stable results when a complex matrix that includes a high
 number of homoplastic characters is analysed. Search
 strategies involve two weighting arrangements: equal weights and implied
 weighting (Goloboff 1993), the latter using concavity (k) values from 1
 to100 by increments of 1, and both strategies under traditional
 searches. Clades recovered in different search
 strategies were illustrated through sensitive grids (Wheeler 1995; Pérez,
 2019). To measure branch support, the resampling method was used by means
 of frequency differences (GC), and the Jackknife (jk) index (Farris
 <i>et al.</i> 1996) was computed with a p=0.14 (equivalent to
 remove 10% of the characters) (Goloboff <i>et al.</i> 2003)
 for1000 pseudo-replicates. The consistency (CI) and retention (RI) indices
 were computed (Farris 1989). Common synapomorphies of the selected
 topology (k=48–68) are described and listed below in the results
 section. <i>Phylogenetic
 time-scaling</i> One of the most frequent
 topologies (implied weighting, k=48–68, recovered for twenty values of
 concavity) was selected to be temporally calibrated using R (R Core Team
 2019 3.6.0). The packages ‘paleotree’ (Bapst 2012), ‘ape’ (Paradis
 <i>et al.</i> 2004; Popescu <i>et al.</i> 2012)
 and ‘strap’ (Bell & Lloyd 2014) were loaded to read the matrix and
 tree topology, and implement different functions in R. The functions
 ‘timePaleoPhy’ and ‘geoscalePhylo’ were applied by means of the minimum
 branch length (mbl) method of calibration with a mbl of 0.1 My, in which a
 minimum branch duration is setting <i>a priori</i>.