A new odontocete (toothed cetacean) from the Early Miocene of Peru expands the morphological disparity of extinct heterodont dolphins

Abstract

A key step in the evolutionary history of Odontoceti (echolocating toothed cetaceans) is the transition from the ancestral heterodont condition â\u80\u93 characterized by the presence of double-rooted cheek teeth bearing accessory denticles â\u80\u93 to the homodont dentition displayed by most extant odontocete species. During the last few decades, new finds and the reassessment of specimens in collections revealed an increased morphological disparity amongst the Oligoâ\u80\u93Miocene heterodont odontocetes. Based on a partly articulated skeleton from late Early Miocene (Burdigalian, 18.8â\u80\u9318.0 Ma) beds of the Chilcatay Formation (Pisco Basin, Peru), we describe a new genus and species of heterodont odontocete, Inticetus vertizi, in the new family Inticetidae. This large dolphin is characterized by, amongst other things, a long and robust rostrum bearing at least 18 teeth per quadrant; the absence of procumbent anterior teeth; many large, broad-based accessory denticles in double-rooted posterior cheek teeth; a reduced ornament of dental crowns; the styliform process of the jugal being markedly robust; a large fovea epitubaria on the periotic, with a correspondingly voluminous accessory ossicle of the tympanic bulla; and a shortened tuberculum of the malleus. Phylogenetic analyses (with and without molecular constraint; with and without down-weighting of homoplastic characters) yielded contrasting results, with Inticetus falling either as a stem Odontoceti or as an early branching member of a large Platanistoidea clade. With its large size, robust rostrum and unusual dental morphology, and the absence of conspicuous tooth wear, Inticetus increases the morphological and ecological disparity of Late Oligoceneâ\u80\u93Early Miocene heterodont odontocetes. Finally, this new taxon calls for caution when attempting to identify isolated cetacean cheek teeth, even at the suborder level. http://zoobank.org/urn:lsid:zoobank.org:pub:5B306B49-EB1B-42F9-B755-B0B05B4F938

Increased pliosaurid dental disparity across the Jurassic–Cretaceous transition

“…Fahlke ; Lambert et al . ). All examples above support the idea that tetrapods bearing sufficiently large conical teeth can colonize macropredatatory niches in marine ecosystems.…”

Facies analysis, stratigraphy and marine vertebrate assemblage of the lower Miocene Chilcatay Formation at Ullujaya (Pisco basin, Peru)

“…The Chilcatay Formation, southern Peru, has received wide attention in the past few years due to numerous significant discoveries of fossil cetaceans (Bianucci, Urbina, & Lambert, 2015;Lambert et al, 2017;Lambert, Bianucci, & Urbina, 2014;Lambert, de Muizon, & Bianucci, 2015). By contrast, published sedimentological and stratigraphical interpretations on this unit are sparse and mostly limited to preliminary studies based on selected outcrops (DeVries & Schrader, 1997;León, Aleman, Torres, Rosell, & De La Cruz, 2008;Wright, Dunbar, Allen, & Baker, 1988).…”

An Inticetus-like (Cetacea, Odontoceti) cheek tooth from the Pietra Leccese (Miocene, Southern Italy)

“…Furthermore, in both the holotype of I.vertizi and the specimen from Pietra leccese, slight subvertical grooves are present on the enamel. The only morphological difference between MCSNC 4457 and the cheek teeth of I. vertizi is the smaller number of denticles in the postcanine teeth of the latter (Lambert et al, 2018). I. vertizi is dated to the early Miocene (Burdigalian) (Lambert et al, 2017), a time span that is compatible with the stratigraphic range of Pietra leccese.…”

“…From a palaeobiogeographical point of view, the presence of forms close to Inticetus Lambert et al, 2018 in both the southeastern Pacific Ocean and the Medi-terranean Sea could be due to a faunistic interchange between the Indo-Pacific Ocean and the Mediterranean Sea through the Tethyan Seaway, the latter passage being still active in early Miocene times (Reuter et al, 2009). More probably, inticetids dispersed via the Central America Seaway: indeed, the Panama Isthmus did not exist until latest Miocene times (Jacobs et al, 2004), so it is plausible that inticetids dispersed through the Atlantic Ocean, thus recalling what has been proposed by Bianucci et al (2016) for the beaked whale genus Messapicetus in late Miocene times.…”