Killer sperm whale: a new basal physeteroid (Mammalia, Cetacea) from the Late Miocene of Italy

Abstract

Zygophyseter varolai , a new genus and species of Physeteroidea (Cetacea, Odontoceti), is based on an almost complete skeleton from the Late Miocene (Tortonian) in southern Italy. The extreme elongation of the zygomatic process of the squamosal and the circular supracranial basin (probably for housing the spermaceti organ) delimited by a peculiar anterior projection of the supraorbital process of the right maxilla are the most distinctive features of this bizarre sperm whale. Large body size, large teeth present in both lower and upper jaw, and anteroposteriorly elongated temporal fossa and zygomatic process of the squamosal indicate that this cetacean (for which we suggest the English common name killer sperm whale) was an active predator adapted to feeding on large prey, similarly to the extant killer whale ( Orcinus orca ). A phylogenetic analysis reveals that Zygophyseter belongs to a Middle-Late Miocene clade of basal physeteroids, together with Naganocetus (new genus for the type of ' Scaldicetus ' shigensis ). Moreover, the phylogenetic analysis shows evidence of a wide physeteroid radiation during the Miocene and that the extant Physeter and Kogia belong to two distinct families that form a clade representing the crown-group Physeteroidea.

Pseudogenization of the tooth gene enamelysin (MMP20) in the common ancestor of extant baleen whales

“…We also discovered an opal stop codon ('TGA') in the propeptide-coding region of MMP20 exon 2 in a single individual of the pygmy sperm whale, Kogia breviceps (electronic supplementary material, alignment 1). This species and its congener, Kogia sima (dwarf sperm whale), have enamel-less teeth [47]. Previously, three frameshift mutations were reported in the enamelin (ENAM) genes of Kogia, two in the common ancestor of the two extant species, and the other in K. sima [16].…”

“…The MMP20 SINE insertion in the common ancestor of extant baleen whales is indicated with a red arrow, and may have occurred on the branch before or after the indicated node. Phylogenetic relationships and divergence times among extant lineages (grey branches) are according to McGowen et al [38]; the placements of extinct lineages (dotted lines) are as in Bianucci & Landini [47] for the physeteroid, Zygophyseter and as in Fitzgerald [9] for stem mysticetes (Eomysticetus, Aetiocetus, Mammalodon, Janjucetus) and the archaeocete outgroup, Basilosaurus.…”

Miocene Toothed Whales (Cetacea, Odontoceti) from the Dniester Valley: The First Record of Sperm Whales (Physeteroidea) from The Eastern Europe

“…The root strongly widens proximally, and it is likely to have been banana-shaped. No constriction basal to the crown, neither a neck nor a "gingival collar" (see Bianucci and Landini, 2006), is observed. There is a groove at the posterior surface of the external portion of the tooth, similar to those reported by Bianucci and …”

<i>Koristocetus pescei</i> gen. et sp. nov., a diminutive sperm whale (Cetacea: Odontoceti: Kogiidae) from the late Miocene of Peru

“…All the phylogenetic analyses of Physeteroidea including all extant and fossil kogiids published to date (Bianucci and Landini, 2006;Lambert, 2008;Lambert et al, 2008Lambert et al, , 2010Lambert et al, , 2017Boersma and Pyenson, 2015;Velez-Juarbe et al, 2015) agreed on the existence of three groups among Kogiidae: (i) a paraphyletic group including early branching forms such as Aprixokogia and Thalassocetus; (ii) a lineage (subfamily Scaphokogiinae) consisting of the sole bizarre genus Scaphokogia; (iii) a clade (subfamily Kogiinae), sister group to Scaphokogia, whose members are Kogia spp., Nanokogia, and Praekogia. Our cladistic analysis confirms this phylogenetic structure for Kogiidae but identifies a sister group to Scaphokogia in MUSM 3291 and MUSM 3405, which are thus recognized as representatives of a new form of Scaphokogiinae.…”

“…We used the phylogenetic definitions proposed by Bianucci and Landini (2006) and Lambert (2008) for Physeteroidea, Physeteridae, and Kogiidae. Embracing the subdivision of Kogiidae in subfamilies proposed by de Muizon (1988) and then reappraised by Bianucci and Landini (1999), Lambert (2008), and Whitmore and Kaltenbach (2008), here we redefine Kogiinae Gill, 1871 as the most inclusive clade including Kogia but not Scaphokogia, whereas we redefine Scaphokogiinae de Muizon, 1988 as the most inclusive clade including Scaphokogia but not Kogia.…”