The awkward record of fossil whales

Abstract

The habitat, actuopalaeontology and global fossil record of crown cetaceans, today occupying apex positions in the marine ecosystem, is reviewed. A large Neogene-Quaternary dataset is built, covering the time span of the evolutionary radiation of crown Odontoceti and Mysticeti and including updated information on whale taxonomy, chronostratigraphy, geography, paleoenvironment, taphonomy and size. We outline an uneven chronostratigraphic and geographic distribution of fossils, which influences our understanding of global diversity trends. Despite the vast majority of whale carcasses sink to bathyal depths, the fossil record is mainly associated with shelf paleoenvironments. The evolution of gigantic whales triggered the radiation of whale-fall communities, including a global bone-eating fauna that hampers the preservation of carcasses at bathyal depths. This "Osedax" effect may explain the unexpected distribution of the fossil record, particularly in the Pleistocene, when baleen whales became gigantic and the ecosystem engineers they are today. A review of the relative thickness of Pleistocene marine strata rules out artefacts of the rock record. The distribution of taphonomic grades suggests that the average skeletal completeness decreases during the Neogene and Quaternary, consistently with an increased efficiency of bioeroders. The frequency of complete and articulated skeletons is time-independent, suggesting a control by sedimentation rates. Quality of the record is expected to improve particularly from taxonomic studies dedicated to the rich, but unexplored South american record, documenting the record of little known productive regions, such as Africa, the Arctic and Antarctica, and the taphonomy and stratigraphic paleobiology of old and new findings.

A skyline birth-death process for inferring the population size from a reconstructed tree with occurrences

“…Fig. S10) resulting from oversampling of some species and localities, possibly due to greater abundance or spatiotemporal biases (Dominici et al 2020). This observation violates our assumption of identical fossil sampling rates among taxa during a given interval.…”

“…Occurrences come from the PBDB (data archive 9, M. D. Uhen) on May 11, 2020. The dataset initially consisted of all 4678 cetacean occurrences, but the cetacean fossil record is known to be subject to several biases (Uhen and Pyenson 2007; Marx et al 2016;Dominici et al 2020). A detailed exploration (see Supp.…”

“…D) of this occurrence dataset revealed several notable biases. First, an artefactual cluster of occurrences in very recent times, combined with other expected Pleistocene biases (Dominici et al 2020), led us to remove all Late Pleistocene and Holocene occurrences. Second, we detected substantial variations in fossil recovery per time unit across lineages (see Supp.…”

Evaluating the Existence of Vertebrate Deadfall Communities from the Early Jurassic Posidonienschiefer Formation

“…This may explain the well-developed reef stage in the Jurassic deadfall communities documented here and in Table 1 relative recent deadfall associations. The magnitude of this effect appears to be correlated with depth, such that this carcass persistence bias between Jurassic and recent assemblages is less severe for shallow water deadfalls [86,87]. No Jurassic deep-water deadfalls have been described (Table 1).…”

First records of extinct kentriodontid and squalodelphinid dolphins from the Upper Marine Molasse (Burdigalian age) of Switzerland and a reappraisal of the Swiss cetacean fauna

“…The Miocene fossil record of cetaceans (whales and dolphins) in the circum-Mediterranean region (Mediterranean and Paratethys) is known from localities in Egypt, southern France, southern Germany, Italy, Malta, Spain and Switzerland ( Bianucci et al, 2011 ; Dominici et al, 2020 ). Revisions of several neighbouring faunas prompted this reappraisal of Swiss specimens.…”