New Paratethyan dwarf baleen whales mark the origin of cetotheres

Abstract

BackgroundFamily Cetotheriidae sensu stricto and several closely related taxa comprise the Cetotherioidea and represent a lineage of Neogene baleen whales that includes the smallest edentulous baleen whales in Earth history. Most of known cetotheriids came from the Late Miocene to Quaternary, and the earliest records from the latest Middle Miocene. The Paratethys region shows a great diversity of Middle to Late Miocene cetotheriids. That includes nominative taxon of the family, Cetotherium rathkii, and this suggests that the earliest cetotheriids may have lived in that region.Materials and methodsHere, Ciuciulea davidi, a new genus and species from the Middle Miocene of southeastern Europe, is described as the chronologically earliest and earliest diverging member of Cetotheriidae. Also, a new specimen of Otradnocetus, a basal Cetotherioidea sensu Gol’din & Steeman, 2015 is identified from the Late Miocene deposits of Caucasus and compared with Otradnocetus virodovi from the Middle Miocene of the same region.Results and discussionCiuciulea davidi is a dwarf whale displaying primitive traits: posterior ends of facial bones forming a single transverse line, a narrow occipital shield, and a relatively long interparietal region. Meanwhile, it shares some cetotheriid apomorphies: posteriorly telescoped wedge-shaped facial bones and an ovoid tympanic bulla with shallow lateral and medial furrows, a short anterior lobe and a short sigmoid process. Phylogenetic analysis suggests that Parietobalaena and Otradnocetus are branches diverging before the clade Cetotheriidae + Neobalaenidae. This is confirmed by the stepwise evolution of the anatomy of the squamosal, mandible, and ear bones across these groups. The re-described juvenile specimen of Otradnocetus differs from O. virodovi in the more primitive anatomy of the mandible and the autapomorphic anatomy of the humerus. Records of the earliest cetotheriids and related taxa in the Paratethys support the idea that this could be the region where Cetotheriidae evolved before their worldwide dispersal and radiation.

A large Late Miocene cetotheriid (Cetacea, Mysticeti) from the Netherlands clarifies the status of Tranatocetidae

“…The latter is thought to be more closely related to balaenopterids than to cetotheriids, and comprises the eponymous Tranatocetus , as well as Mesocetus longirostris , Mixocetus elysius , ‘ Aulocetus latus ’, ‘ Cetotherium ’ megalophysum , and ‘ Metopocetus ’ vandelli (Gol’din & Steeman, 2015). Of these, the last three frequently cluster in phylogenetic analyses, and may represent the same genus or even species (El Adli, Deméré & Boessenecker, 2014; Gol’din, 2018; Marx, Bosselaers & Louwye, 2016).…”

“…Total body length was estimated based on bizygomatic width, using the stem balaenopteroid equation of Pyenson & Sponberg (2011), and the general mysticete equation of Lambert et al (2010). To establish evolutionary relationships, we coded our new material, as well as Tranatocetus argillarius and the recently described Middle Miocene cetotheriid Ciuciulea davidi (Gol’din & Steeman, 2015; Gol’din, 2018), into a slightly modified version of the phylogenetic matrix of Fordyce & Marx (2018). The analysis was run in MrBayes 3.2.6, on the Cyberinfrastructure for Phylogenetic Research (CIPRES) Science Gateway (Miller, Pfeiffer & Schwartz, 2010), using the same settings as in Fordyce & Marx (2018).…”

“…Cetotheriids are one of three major branches of modern baleen whales, alongside right whales (Balaenidae) and rorquals (Balaenopteridae). The family is first recorded during the Middle Miocene (Gol’din, 2018), but its roots likely stretch further back in time (Marx & Fordyce, 2015). Late Miocene cetotheriids were speciose and attained a nearly global distribution, with records from the North Atlantic (Bisconti, 2015; Marx, Bosselaers & Louwye, 2016; Whitmore Jr & Barnes, 2008), the Paratethys (Gol’din & Startsev, 2017), and both the North (El Adli, Deméré & Boessenecker, 2014; Kellogg, 1929; Saita, Komukai & Oishi, 2011; Tanaka, Furusawa & Barnes, 2018b; Tanaka & Watanabe, 2018) and eastern South Pacific (Bouetel & de Muizon, 2006; Marx, Lambert & Muizon, 2017).…”

Peer Review #2 of "A large Late Miocene cetotheriid (Cetacea, Mysticeti) from the Netherlands clarifies the status of Tranatocetidae (v0.1)"

“…The angular process of the mandible tends to be enlarged in Cetotheriidae, either dorsoventrally as in cetotheriines (Gol'din et al 2014;Gol'din 2018), or anteroposteriorly as in Piscobalaena and herpetocetines (Bouetel & de Muizon 2006;El Adli et al 2014). In the latter two, the process notably projects beyond the level of the mandibular condyle, and bears a well-developed fossa for the medial pterygoid muscle.…”

“…Bouetel & de Muizon 2006;El Adli et al 2014;Gol'din & Startsev 2017; Marx & Fordyce 2015; Steeman 2007; Whitmore & Barnes 2008). Nevertheless, the scope of the family has been thrown in doubt by the inclusion of the pygmy right whale, Caperea marginata (Fordyce & Marx 2013; Marx & Fordyce 2016; Park et al 2017), and the proposed grouping of several species usually regarded as cetotheriids into the separate family Tranatocetidae (Gol'din & PeerJ reviewing PDF | (2018:11:33024:1:1:CHECK 26 Dec 2018)…”