Piscivory in a Miocene Cetotheriidae of Peru: first record of fossilized stomach content for an extinct baleen-bearing whale

Abstract

Instead of teeth, modern mysticetes bear hairfringed keratinous baleen plates that permit various bulkfiltering predation techniques (from subsurface skimming to lateral benthic suction and engulfment) devoted to various target prey (from small invertebrates to schooling fish). Current knowledge about the feeding ecology of extant cetaceans is revealed by stomach content analyses and observations of behavior. Unfortunately, no fossil stomach contents of ancient mysticetes have been described so far; the investigation of the diet of fossil baleen whales, including the Neogene family Cetotheriidae, remains thus largely speculative. We report on an aggregate of fossil fish remains found within a mysticete skeleton belonging to an undescribed late Miocene (Tortonian) cetotheriid from the Pisco Formation (Peru). Micro-computed tomography allowed us to interpret it as the fossilized content of the forestomach of the host whale and to\ud identify the prey as belonging to the extant clupeiform genus Sardinops. Our discovery represents the first direct evidence\ud of piscivory in an ancient edentulous mysticete. Since among modern mysticetes only Balaenopteridae are known to ordinarily consume fish, this fossil record may indicate that part of the cetotheriids experimented some degree of balaenopteridlike engulfment feeding. Moreover, this report corresponds to one of the geologically oldest records of Sardinops worldwide, occurring near the Tortonian peak of oceanic primary productivity and cooling phase. Therefore, our discovery evokes a link between the rise of Cetotheriidae; the setup of modern coastal upwelling systems; and the radiation of epipelagic, small-sized, schooling clupeiform fish in such highly productive environments

Decoupling Tooth Loss from the Evolution of Baleen in Whales

“…The potential decoupling of enamel loss and tooth loss as separate genetic events provides a blueprint by which this hypothesis, involving tooth loss and baleen development as separate events, may be tested. While suction feeding without the aid of a feeding apparatus would seem unlikely for a zooplankton-based diet, it is consistent with the known record of piscivory, which has been documented in Eocene basilosaurids (Uhen, 2004), Miocene mysticetes (Collareta et al, 2015), and extant mysticetes, all of which likely employ some degree of suction during the gape cycle (Werth, 2000). Thus, suction feeding as a basal feeding mode for stem mysticetes best incorporates histological and molecular datasets by proposing a fundamental decoupling between the loss of teeth and the emergence of baleen.…”

Stratigraphic framework of the late Miocene Pisco Formation at Cerro Los Quesos (Ica Desert, Peru)

“…Brand, Esperante, Chadwick, Poma Porras, & Alomía, 2004;Ehret et al, 2012;Esperante, Brand, Chadwick, & Poma, 2015;Esperante, Brand, Nick, Poma, & Urbina, 2008;Gariboldi et al, 2015;Lambert, Bianucci, & de Muizon, 2008;Lambert, Bianucci, & Post, 2009Lambert, Bianucci, Post, de Muizon, et al, 2010;Lambert, Bianucci, & Beatty, 2014;Lambert, de Muizon, & Bianucci, 2014;Lambert et al, 2015;Collareta et al, 2015). However, despite the growing significance of the vertebrate fauna of the Pisco Formation, a comprehensive stratigraphic framework for individual fossil-bearing localities and their position relative to one another has yet to be established (Brand, Urbina, Chadwick, DeVries, & Esperante, 2011;Di Celma et al, in press).…”

Description of the skeleton of the fossil beaked whale <i>Messapicetus gregarius</i>: searching potential proxies for deep-diving abilities

“…Acrophyseter sp. ), Ziphiidae (M. gregarius, Chimuziphius coloradensis), Inioidea (Brachydelphis mazeasi and an undescribed taxon), two undescribed kentriodontid-like Delphinida, Balaenopteroidea, and Cetotheriidae (Bianucci et al, 2010(Bianucci et al, , 2016bCollareta et al, 2015;Gioncada et al, 2016;Lambert et al, 2010a). The geological age of the lower allomember is estimated as 9.9-8.9 Ma (Tortonian, Late Miocene) based on the presence of the diatom species Lithodesmium reynoldsii and radiometric dating of a local ash layer .…”