Convergent evolution of skim feeding in baleen whales

Abstract

The evolutionary relationships of the pygmy right whale Caperea marginata, the smallest and most enigmatic of the living baleen whales (mysticetes), remain contentious. For 150 years, morphological analyses have allied Caperea with right whales based on their similar skim filter feeding strategies and shared cranial features like a tall braincase, highly arched rostrum, and elongate baleen plates (Beddard, 1901;Bisconti, 2012;Gray, 1871;McLeod et al., 1993). By contrast, molecular and some anatomical evidence-e.g., presence of a squamosal cleft, tympanic recess, and four-fingered flipper-suggest a closer relationship with rorquals and gray whales, Eschrichtius robustus

The tympanoperiotic complex of the blue whale, Balaenoptera musculus

“…Ekdale et al's (2011) and our own works show that tympanoperiotic morphology is compatible with the mysticete taxonomic subdivisions adopted by a number of students (Bisconti et al, 2023;Boessenecker & Fordyce, 2016;El Adli et al, 2014;Churchill et al, 2011;Deméré et al, 2005). This taxonomic interpretation contrasts with most molecular results and some morphological and total evidence studies that support a close relationship of Caperea marginata and Balaenopteroidea, as well as a paraphyletic status for Eschrichtiidae, Balaenopteridae, and Balaenoptera ( Árnason et al, 2018;Dutoit et al, 2023;Lammers et al, 2019).…”

“…Such a result finds corroboration in several morphologybased studies like those of Bisconti et al (2023Bisconti et al ( , 2017; Bisconti, Damarco, Mao, et al (2021), Boessenecker andEl Adli et al (2014). However, this result, again, contrasts with molecular phylogenies in which Caperea is not related to Balaenidae (Dutoit et al, 2023;Wolf et al, 2023). Moreover, earbone morphology supports the monophyly of Balaenomorpha (including Balaenoidea and Balaenopteroidea).…”

“…The cladograms are 124 steps in length, have consistency index of 0.581, and retention index of 0.626. In the strict consensus tree, IRSNB 1540 is the sister group of a monophyletic clade formed by B. physalus and B. musculus USNM 239280 as coded by Ekdale et al (2011), the latter being considered here as most likely corresponding to Árnason et al, 2018;Dutoit et al, 2023;Lammers et al, 2019;Wolf et al, 2023). Megaptera novaeangliae is the sister group of Balaenoptera thus confirming the monophyly of Balaenopteridae as including Balaenoptera and Megaptera and excluding Eschrichtius robustus.…”