Cenozoic evolution of Muricidae (Mollusca, Neogastropoda) in the Southern Ocean, with the description of a new subfamily

Abstract

Gastropods are among the most studied group in Antarctica, and taxa with an advanced status of systematic knowledge can be used as a model to study how oceanographic and climatic patterns shaped Recent faunal assemblages. Within the ongoing study of the muricid phylogeny, we have analysed molecular and morphological data from species traditionally ascribed to the muricid subfamily Trophoninae. Particularly, the availability of specimens collected in the Southern Ocean and surrounding basins allowed to demonstrate as the genera Pagodula, Xymenopsis, Xymene and Trophonella, which are traditionally classified in the Trophoninae, actually belong to a distinct lineage, for which the new subfamily Pagodulinae is herein introduced. We propose and discuss a possible framework for the origin and radiation of Antarctic muricids.

A molecular phylogenetic framework for the subfamily Ocenebrinae (Gastropoda, Muricidae)

“…These two subfamilies have similar radulae, a structure considered useful in delimiting muricid subfamilies (Vokes ; Radwin & D'Attilio ; Barco et al . ). Both Ocenebrinae and Trophoninae have a so‐called 3D rachidian tooth (Vokes ), while two marginal cusps (bifid condition), previously thought to be a synapomorphy of the Ocenebrinae, also occur briefly during the early juvenile stage of trophonines (Herbert et al .…”

“…The occurrence of basal polytomies has been observed in previous phylogenetic studies of the Muricidae (Barco et al . , ), which probably reflects rapid diversification early in the family's evolutionary history. High rates of lineage diversification can produce low molecular variation, limiting resolution even with higher gene coverage (e.g.…”

Key stages in the evolution of the Antarctic marine fauna

“…Mid‐Miocene phases of Antarctic diversification have been identified in both a deep‐sea octopus clade (Strugnell, Rogers, Prodöhl, Collins, & Allcock, ) and primnoid bottlebrush octocorals (Dueñas et al., ). Limpet gastropods of the genus Nacella show a distinct radiation at 7.0–8.5 Ma (González‐Wevar et al., ), and predatory muricid gastropods of the subfamily Pagodulinae have a postulated Late Eocene origin ( c. 40 Ma) but did not diversify in the Southern Ocean until the latest Miocene–Pliocene (Barco, Schiaparelli, Houart, & Olivero, ). Molecular phylogenetic evidence also suggests that the amphipod genus Epimeria , which forms a species flock at the present day in the Southern Ocean, can be traced back to an initial Middle or Late Eocene Antarctic radiation (Verheye, Backeljau, & d'Udetem d'Acoz, ).…”

The varix: evolution, distribution, and phylogenetic clumping of a repeated gastropod innovation

“…They are currently divided into eleven subfamilies (Barco et al, 2010(Barco et al, , 2012, five of which we consider to be completely lacking varices: Rapaninae, Coralliophilinae, Trophoninae, Haustrinae, and Pagodulinae. All the other subfamilies have at least a few members with varices ( Fig.…”

“…The earliest varicate muricid is the Early Paleocene genus Timbellus (Merle, Garrigues & Pointier, 2011) with three or four synchronized varices on each whorl. Although the subfamily to which Timbellus belongs is unclear, Barco et al (2012) suggests it may fit with the typhines. We estimate seven origins of varices in the Muricidae, but the lack of subfamilial trees makes this a broad estimate at best, with clear evidence of phylogenetic clumping.…”