A new genus and species of eomysticetid (Cetacea: Mysticeti) and a reinterpretation of ‘Mauicetus’ lophocephalus Marples, 1956: transitional baleen whales from the upper Oligocene of New Zealand

Abstract

The early evolution of toothless baleen whales (Chaeomysticeti) remains elusive despite a robust record of Eocene-Oligocene archaeocetes and toothed mysticetes. Eomysticetids, a group of archaic longirostrine and putatively toothless baleen whales fill in a crucial morphological gap between well-known toothed mysticetes and more crownward Neogene Mysticeti. A historically important but perplexing cetacean is “Mauicetus” lophocephalus (upper Oligocene South Island, New Zealand). The discovery of new skulls and skeletons of eomysticetids from the Oligocene Kokoamu Greensand and Otekaike Limestone permit a redescription and modern reinterpretation of “Mauicetus” lophocephalus, and indicating that this species may have retained adult teeth. A new genus and species, Tokarahia kauaeroa, is erected on the basis of a well-preserved subadult to adult skull with mandibles, tympanoperiotics, and cervical and thoracic vertebrae, ribs, sternum, and forelimbs from the Otekaike Limestone (>25.2 Ma). “Mauicetus” lophocephalus is relatively similar and recombined as Tokarahia lophocephalus. Phylogenetic analysis supports inclusion of Tokarahia within the Eomysticetidae alongside Eomysticetus, Micromysticetus, Yamatocetus, and Tohoraata, and strongly supports monophyly of Eomysticetidae. Tokarahia lacked extreme rostral kinesis of extant Mysticeti and primitively retained a delicate archaeocete-like posterior mandible and synovial temporomandibular joint, suggesting that Tokarahia was capable of at most, limited lunge feeding in contrast to extant Balaenopteridae, and utilized an alternative as-yet unspecified feeding strategy.

A new eomysticetid from the Oligocene Kokoamu Greensand of New Zealand and a review of the Eomysticetidae (Mammalia, Cetacea)

“…However, in light of the numerous differences that make it less similar to the holotype than other specimens (OU 22742; OU 22743), AUGD 6646 is conservatively identified as Matapa sp. The differences might reflect marked intraspecific variation in the periotic of Matapa waihao or, alternatively, interspecific variation indicating the presence of two closely related sympatric and coeval species of Matapa, as is the case for Tokarahia (Boessenecker & Fordyce 2015c). New discoveries may elucidate the matter.…”

“…Regardless of the identification, similar braincase and periotic morphology indicates that the holotype specimen of Matapa waihao is readily diagnosable despite being a juvenile. The large size of OU 22742 (Supplemental Table 1) suggests a body length of 5À6 metres for adult Matapa, based on comparing exoccipital width with Tokarahia kauaeroa (Boessenecker & Fordyce 2015c). In contrast, the juvenile holotype of Matapa waihao (OU 12918) is much smaller, and perhaps measured only 3.5À4.5 metres at death.…”

“…These alveoli medially arise from a longitudinal, dorsoventrally shallow cavity, presumably the infraorbital canal, between the dorsal and ventral laminae of the maxilla, as in Tokarahia sp., cf. T. lophocephalus (OU 22081;Boessenecker & Fordyce 2015c). No obvious lateral nutrient sulci are preserved on the palatal surface of the maxilla.…”

Relationships of cochlear coiling shape and hearing frequencies in cetaceans, and the occurrence of infrasonic hearing in Miocene Mysticeti

“…Skull length is condylobasal length measured from cranial models used by Fahlke and Hampe (2015). For family attribution and relationships, see Steeman (2007Steeman ( , 2010, Boessenecker and Fordyce (2015), and Marx et al (2016 connected to form a continuous line and exported as volume data (image stacks).…”

“…Nevertheless, we decided not to perform a phylogenetic analysis, because several specimens included here, especially those from the Neogene of Belgium and Germany, are described on isolated periotic bones only. Phylogenetic relationships for part of the taxa are either not resolved or currently under debate (see Steeman, 2007;Hampe and Ritsche, 2011;Boessenecker and Fordyce, 2015;Marx and Fordyce, 2015).…”