[PaleoMammalogy • 2024] Valenictus sheperdi • Tusked Walruses (Carnivora: Odobenidae) from the Miocene–Pliocene Purisima Formation of Santa Cruz, California (U.S.A.): A New Species of the Toothless Walrus Valenictus and the Oldest Records of Odobeninae and Odobenini

Valenictus sheperdi

R. Boessenecker, Poust, S. Boessenecker & Churchill. 2024

DOI: 10.1080/02724634.2023.2296567 

 coastalpaleo.blogspot.com 

 

ABSTRACT

Currently limited to cold climates near the Arctic circle, living walruses are the sole survivors of a previously much more diverse clade that occupied coastal waters throughout the northern hemisphere during the Mio–Pliocene. Though pinniped faunas have the highest diversity of walruses in the Miocene, the Purisima Formation of California records a moderately diverse assemblage of four walrus species. We report new specimens of tusked walruses (Odobeninae) including the oldest known members of Odobeninae, and Odobenini, and fossils of the specialized toothless odobenine walrus Valenictus Mitchell, 1961. Among these is the new species Valenictus sheperdi sp. nov., represented by a complete skull and referred post-crania from lower Pliocene strata within the Purisima Formation (5.33–4.89 Ma). Additionally, we report a geochronologically younger skull of Valenictus chulavistensis Deméré, 1994 from further up section (4.89–3.59 Ma). Expanded phylogenetic analysis recovers Odobeninae including Ontocetus Leidy, 1859 as the earliest diverging lineage in the Odobenini, and places a monophyletic Valenictus as the sister taxon to Pliopedia, Kellogg, 1921 which is included in a phylogeny for the first time; Odobenus is sister to the Valenictus + Pliopedia clade. Discovery of an isolated metacarpal near the base of the formation provides the oldest known well-dated evidence of odobenines. A diverse assemblage of molluskivores characterized the Neogene eastern North Pacific and their extinction around the Pliocene–Pleistocene boundary coincided with tectonically driven paleogeographic changes on the Pacific coast. The loss of temperate walruses may have provided opportunities for both new molluskivores and the otariid and phocid pinnipeds that make up present North Pacific pinniped communities.

New life restoration of the extinct "toothless" walrus Valenictus sheperdi - cruising along in an early kelp forest along the shoreline of northern California during the early Pliocene epoch.

 Illustration by Robert Boessenecker 

Robert W. Boessenecker, Ashley W. Poust, Sarah J. Boessenecker and Morgan Churchill. 2024. Tusked Walruses (Carnivora: Odobenidae) from the Miocene–Pliocene Purisima Formation of Santa Cruz, California (U.S.A.): A New Species of the Toothless Walrus Valenictus and the Oldest Records of Odobeninae and Odobenini. Journal of Vertebrate Paleontology. e2296567. DOI: 10.1080/02724634.2023.2296567

  twitter.com/CoastalPaleo/status/1751966430021767187

Valenictus sheperdi and friends: Miocene-Pliocene tusked walruses from the Purisima Formation in Santa Cruz, California

 coastalpaleo.blogspot.com/2024/02/valenictus-sheperdi-and-friends-miocene.html

[PaleoMammalogy • 2021] Phiomicetus anubis • A New Protocetid Whale offers clues to Biogeography and Feeding Ecology in early Cetacean Evolution

Phiomicetus anubis 

Gohar, Antar, Boessenecker, Sabry, El-Sayed, Seiffert, Zalmout & Sallam, 2021

DOI: 10.1098/rspb.2021.1368 

 twitter.com/HeshamSallam

  twitter.com/CoastalPaleo 

 

Abstract

Over about 10 million years, the ancestors of whales transformed from herbivorous, deer-like, terrestrial mammals into carnivorous and fully aquatic cetaceans. Protocetids are Eocene whales that represent a unique semiaquatic stage in that dramatic evolutionary transformation. Here, we report on a new medium-sized protocetid, Phiomicetus anubis gen. et sp. nov., consisting of a partial skeleton from the middle Eocene (Lutetian) of the Fayum Depression in Egypt. The new species differs from other protocetids in having large, elongated temporal fossae, anteriorly placed pterygoids, elongated parietals, an unfused mandibular symphysis that terminates at the level of P3, and a relatively enlarged I3. Unique features of the skull and mandible suggest a capacity for more efficient oral mechanical processing than the typical protocetid condition, thereby allowing for a strong raptorial feeding style. Phylogenetic analysis nests Phiomicetus within the paraphyletic Protocetidae, as the most basal protocetid known from Africa. Recovery of Phiomicetus from the same bed that yielded the remingtonocetid Rayanistes afer provides the first clear evidence for the co-occurrence of the basal cetacean families Remingtonocetidae and Protocetidae in Africa. The discovery of Phiomicetus further augments our understanding of the biogeography and feeding ecology of early whales.

Keywords: biogeography, whales, phylogeny, evolution, Fayum 

  Phiomicetus anubis gen. et sp. nov.

 

Abdullah S. Gohar, Mohammed S. Antar, Robert W. Boessenecker, Dalia A. Sabry, Sanaa El-Sayed, Erik R. Seiffert, Iyad S. Zalmout and Hesham M. Sallam. 2021. A New Protocetid Whale offers clues to Biogeography and Feeding Ecology in early Cetacean Evolution. Proc. R. Soc. B.. 288. 20211368. DOI: 10.1098/rspb.2021.1368

  twitter.com/HeshamSallam/status/1430489738918731776

  twitter.com/CoastalPaleo/status/1430508892530823174

    

[PaleoMammalogy • 2020] Ankylorhiza tiedemani • Convergent Evolution of Swimming Adaptations in Modern Whales Revealed by A Large Macrophagous Dolphin from the Oligocene of South Carolina

Ankylorhiza tiedemani 

in Boessenecker, Churchill, Buchholtz, et al., 2020. 

DOI: 10.1016/j.cub.2020.06.012  

 twitter.com/CofCNatHistory 

Highlights

• A large macroraptorial dolphin is reported from the Oligocene of South Carolina

• Well-preserved skeleton reveals stepwise evolution of locomotion in toothed whales

• Convergence in locomotor features is identified between baleen and toothed whales

Summary

Modern whales and dolphins are superbly adapted for marine life, with tail flukes being a key innovation shared by all extant species. Some dolphins can exceed speeds of 50 km/h, a feat accomplished by thrusting the flukes while adjusting attack angle with their flippers. These movements are driven by robust axial musculature anchored to a relatively rigid torso consisting of numerous short vertebrae, and controlled by hydrofoil-like flippers. Eocene skeletons of whales illustrate the transition from semiaquatic to aquatic locomotion, including development of a fusiform body and reduction of hindlimbs, but the rarity of Oligocene whale skeletons has hampered efforts to understand the evolution of fluke-powered, but forelimb-controlled, locomotion. We report a nearly complete skeleton of the extinct large dolphin Ankylorhiza tiedemani comb. n. from the Oligocene of South Carolina, previously known only from a partial rostrum. Its forelimb is intermediate in morphology between stem cetaceans and extant taxa, whereas its axial skeleton displays incipient rigidity at the base of the tail with a flexible lumbar region. The position of Ankylorhiza near the base of the odontocete radiation implies that several postcranial specializations of extant cetaceans, including a shortened humerus, narrow peduncle, and loss of radial tuberosity, evolved convergently in odontocetes and mysticetes. Craniodental morphology, tooth wear, torso vertebral morphology, and body size all suggest that Ankylorhiza was a macrophagous predator that could swim relatively fast, indicating that it was one of the few extinct cetaceans to occupy a niche similar to that of killer whales.

Keywords: Cetacea, Neocetimarine mammal, locomotion, Odontoceti, Cenozoic, apex predator, macrophagous, swimming, hydrofoil

Figure 1: Skull and Skeleton of Ankylorhiza tiedemani, CCNHM 103.
(A–M) Skull in lateral view (A); vertex in dorsal view (B); sternum in dorsal view (C); selected vertebrae in anterior view (D); skeletal reconstruction with preserved elements in white and missing elements in red (E); selected teeth in labial view (F); proximal phalanx III in lateral (top) and distal (bottom) views (G); proximal phalanx IV in proximal (top) and lateral (bottom) views (H); metacarpals in lateral view (I); ulna, pisiform, and pyramidal in lateral view (J); and humerus in medial (K), lateral (L), and anterior (M) view.
Abbreviations: c, capitulum; dpc, deltopectoral crest; fr, frontal; gt, greater tuberosity; if, infraspinatus fossa; ip, interparietal; lt, lesser tuberosity; mx, maxilla; na, nasal; nc, nuchal crest; of, olecranon facet; op, olecranon process; os, occipital shield; p, parietal; pi, pisiform; pmx, premaxilla; pop, postorbital process; py, pyramidal; rf, radial facet; tf, temporal fossa; tn, trochlear notch; uf, ulnar facet; zp, zygomatic process. 

 Systematic Paleontology

Order Cetacea; 

Suborder Odontoceti; 

Ankylorhiza gen. nov.

Etymology. Ankylorhiza. Genus is Greek for “fused roots,” referring to the advanced degree of postcanine tooth root fusion for stem Odontoceti.

Ankylorhiza tiedemani, comb. nov.

Holotype. AMNH 10445, partial rostrum, Ashley Formation, South Carolina [14].

Referred Specimens. CCNHM 103, partial skeleton (Figure 1); Chandler Bridge Formation, late Oligocene (24.7–23.5 Ma), South Carolina; CCNHM 220, partial skull and associated vertebrae; Ashley Formation, early Oligocene (29.0–26.57 Ma), South Carolina (Methods S1).

Diagnosis. Ankylorhiza tiedemani is a large (425 mm bizygomatic width; body length est. 4.8 m) stem odontocete with limited polydonty (10 postcanine teeth) and moderate heterodonty. Ankylorhiza differs from all other odontocetes in the extreme development of nuchal crests and differs from all other stem odontocetes in its larger size and combination of derived (mostly single-rooted teeth; simplified tooth crowns) and plesiomorphic characters (e.g., parietal exposed at vertex, symmetrical skull, prominent intertemporal constriction, and longer humerus with long deltopectoral crest; Methods S1: Supplemental Diagnosis of Ankylorhiza tiedemani). Ankylorhiza differs from all crown Odontoceti in possessing some double-rooted teeth, prominent intertemporal constriction, and widely open mesorostral gutter along the entire length of the rostrum.

Figure 4: Relationships of Ankylorhiza and Convergent Postcranial Evolution in Neoceti Illustrated on a Simplified Cladogram

 Robert W. Boessenecker, Morgan Churchill, Emily A. Buchholtz, Brian L. Beatty and Jonathan H. Geisler. 2020. Convergent Evolution of Swimming Adaptations in Modern Whales Revealed by A Large Macrophagous Dolphin from the Oligocene of South Carolina. Current Biology. In Press. DOI: 10.1016/j.cub.2020.06.012  

 twitter.com/CofCNatHistory/status/1281235472799404034

15-foot-long skeleton of extinct dolphin suggests parallel evolution among whales

eurekalert.org/pub_releases/2020-07/cp-1so070220.php

         

[PaleoMammalogy • 2018] The Origin and Evolutionary Biology of Pinnipeds: Seals, Sea Lions, and Walruses

The Origin and Evolutionary Biology of Pinnipeds

Berta, Churchill & Boessenecker, 2018.

DOI:  10.1146/annurev-earth-082517-010009 

@CoastalPaleo

Abstract 

The oldest definitive pinniped fossils date from approximately 30.6–23 million years ago (Ma) in the North Pacific. Pinniped monophyly is consistently supported; the group shares a common ancestry with arctoid carnivorans, either ursids or musteloids. Crown pinnipeds comprise the Otariidae (fur seals and sea lions), Odobenidae (walruses), and Phocidae (seals), with paraphyletic “enaliarctines” falling outside the crown group. The position of extinct Desmatophocidae is debated; they are considered to be closely related to both otariids and odobenids or, alternatively, to phocids. Both otariids and odobenids are known from the North Pacific, diverging approximately 19 Ma, with phocids originating in the North Atlantic or Paratethys region 19–14 Ma. Our understanding of pinniped paleobiology has been enriched by studies that incorporate anatomical and behavioral data into a phylogenetic framework. There is now evidence for sexual dimorphism in the earliest pinnipeds, heralding polygynous breeding systems, followed by increased body sizes, diving capabilities, and diverse feeding strategies in later-diverging phocid and otarioid lineages.

Keywords Pinnipedia, Otariidae, Odobenidae, Phocidae, Desmatophocidae, paleobiology 

Figure 1 Time-calibrated phylogeny of pinnipeds, showing relationships among major clades.

Figure 2 Major localities for fossil pinnipeds.

Figure 3 Life restorations of fossil pinnipeds and a close relative. 
(a) Enaliarctos mealsi (total length 1.4–1.5 m); illustrated by M. Parrish. (b) Pithanotaria starri (total length 1.26 m); illustrated by R. Boessenecker. (c) Allodesmus kernensis (total length 2.2 m); illustrated by C. Buell. (d ) Dusignathus seftoni (skull length up to 40 cm) and Valenictus chulavistensis (skull length 40 cm); illustrated by W. Stout. (e) Puijila darwini (total length just over 1 m); illustrated by C. Buell. (f) Pelagiarctos sp. (ca. 2.7 m); illustrated by R. Boessenecker.

@CoastalPaleo

Annalisa Berta, Morgan Churchill and Robert W. Boessenecker. 2018. The Origin and Evolutionary Biology of Pinnipeds: Seals, Sea Lions, and Walruses. Annual Review of Earth and Planetary Sciences. 46; 203-228. DOI:  10.1146/annurev-earth-082517-010009

 twitter.com/CoastalPaleo/status/978251979582566400

[PaleoMammalogy • 2018] Allodesmus demerei • The Last of the Desmatophocid Seals: A New Species of Allodesmus from the upper Miocene of Washington, USA, and A Revision of the Taxonomy of Desmatophocidae

Allodesmus demerei 

Boessenecker & Churchill, 2018

@CoastalPaleo   DOI:  10.1093/zoolinnean/zlx098  

Abstract

The family Desmatophocidae represents an early radiation of extinct pinnipeds that peaked in diversity during the middle Miocene. Although represented by abundant well-preserved fossils, the taxonomy and evolutionary relationships of this family remain poorly known. Late Miocene desmatophocids have been recorded, although none have been formally described, preventing a thorough appraisal of their decline and extinction. We report the discovery of a new species, Allodesmus demerei sp. nov., represented by a partial skeleton with cranium, mandibles, and axial skeleton, from the upper Miocene Montesano Formation of Washington, prompting reinterpretation of desmatophocid taxonomy, phylogeny, and extinction. Phylogenetic analysis (95 characters, 26 taxa) found strong support for monophyletic Desmatophocidae and Allodesmus. Desmatophocidae was found as sister to Phocidae with poor support. Allodesmus demerei was placed within the Allodesmus as the sister taxon to Allodesmus kernensis. The geochronologically young age (10.5–9.1 Mya) of Al. demerei establishes this species as the last of the desmatophocid seals. The middle Miocene peak in desmatophocid diversity coincides with the middle Miocene climatic optimum, suggesting that declining sea surface temperature played a role in their decline and extinction. Walruses diversified and increased in body size during the mid- to late Miocene as desmatophocids declined, suggesting some form of ecological displacement.

Robert W. Boessenecker and Morgan Churchill. 2018. The Last of the Desmatophocid Seals: A New Species of Allodesmus from the upper Miocene of Washington, USA, and a revision of the taxonomy of Desmatophocidae.  Zoological Journal of the Linnean Society. zlx098.  DOI:  10.1093/zoolinnean/zlx098 

twitter.com/CoastalPaleo/status/948605304572399616

Remains found in Grays Harbor lead to discovery of new species kxro.com/remains-found-grays-harbor-lead-discovery-new-species/

[PaleoMammalogy • 2017] Inermorostrum xenops • A Toothless Dwarf Dolphin (Odontoceti: Xenorophidae) Points to Explosive Feeding Diversification of Modern Whales (Neoceti)

Inermorostrum xenops

Boessenecker, Fraser, Churchill & Geisler, 2017

@CoastalPaleo DOI: 10.1098/rspb.2017.0531 

Abstract

Toothed whales (Odontoceti) are adapted for catching prey underwater and possess some of the most derived feeding specializations of all mammals, including the loss of milk teeth (monophyodonty), high tooth count (polydonty), and the loss of discrete tooth classes (homodonty). Many extant odontocetes possess some combination of short, broad rostra, reduced tooth counts, fleshy lips, and enlarged hyoid bones—all adaptations for suction feeding upon fishes and squid. We report a new fossil odontocete from the Oligocene (approx. 30 Ma) of South Carolina (Inermorostrum xenops, gen. et sp. nov.) that possesses adaptations for suction feeding: toothlessness and a shortened rostrum (brevirostry). Enlarged foramina on the rostrum suggest the presence of enlarged lips or perhaps vibrissae. Phylogenetic analysis firmly places Inermorostrum within the Xenorophidae, an early diverging odontocete clade typified by long-snouted, heterodont dolphins. Inermorostrum is the earliest obligate suction feeder within the Odontoceti, a feeding mode that independently evolved several times within the clade. Analysis of macroevolutionary trends in rostral shape indicate stabilizing selection around an optimum rostral shape over the course of odontocete evolution, and a post-Eocene explosion in feeding morphology, heralding the diversity of feeding behaviour among modern Odontoceti.

KEYWORDS: Xenorophidae, Odontoceti, Neoceti, suction feeding, Oligocene

Etymology. The generic name is from the Latin inermus, meaning weapon-less or defenceless, and rostrum, meaning snout, referring to the absence of teeth in the rostrum. The species name derives from Greek for strange, xeno, and face, ops, referring to the highly derived facial morphology of the holotype.

Robert W. Boessenecker, Danielle Fraser, Morgan Churchill and Jonathan H. Geisler. 2017. A Toothless Dwarf Dolphin (Odontoceti: Xenorophidae) Points to Explosive Feeding Diversification of Modern Whales (Neoceti). Proceedings of the Royal Society B. DOI: 10.1098/rspb.2017.0531

 twitter.com/CoastalPaleo/status/900366417870036992

This ancient dwarf dolphin may have slurped its food like a walrus  sciencemag.org/news/2017/08/ancient-dwarf-dolphin-may-have-slurped-its-food-walrus

   

[PaleoMammalogy • 2017] Coronodon havensteini • The Origin of Filter Feeding in Whales

Coronodon havensteini  

Geisler, Boessenecker, Brown & Beatty, 2017

Illustration: A. Gennari DOI: 10.1016/j.cub.2017.06.003 

 Highlights

• A new species of 30 million year old whale has been found near Charleston, South Carolina

• This new species is a relative of modern baleen-bearing whales but retains teeth

• Its molars are large, multi-cusped, and overlapping and were used for filter feeding

• Filter feeding evolved before baleen; early whales had teeth and baleen

Summary

As the largest known vertebrates of all time, mysticetes depend on keratinous sieves called baleen to capture enough small prey to sustain their enormous size. The origins of baleen are controversial: one hypothesis suggests that teeth were lost during a suction-feeding stage of mysticete evolution and that baleen evolved thereafter, whereas another suggests that baleen evolved before teeth were lost. Here we report a new species of toothed mysticete, Coronodon havensteini, from the Oligocene of South Carolina that is transitional between raptorial archaeocete whales and modern mysticetes. Although the morphology and wear on its anterior teeth indicate that it captured large prey, its broad, imbricated, multi-cusped lower molars frame narrow slots that were likely used for filter feeding. Coronodon havensteini is a basal, if not the most basal, mysticete, and our analysis suggests that it is representative of an initial stage of mysticete evolution in which teeth were functional analogs to baleen. In later lineages, the diastema between teeth increased—in some cases, markedly so—and may mark a stage at which the balance of the oral fissure shifted from mostly teeth to mostly baleen. When placed in a phylogenetic context, our new taxon indicates that filter feeding was preceded by raptorial feeding and that suction feeding evolved separately within a clade removed from modern baleen whales.

Keywords: Mysticeti; filter feeding; baleen; oligocene; South Carolina; toothed mysticete

Systematics

Order Cetacea 

 Suborder Mysticeti 

Coronodon havensteini gen. et sp. nov.

Holotype: CCNHM 108. Nearly complete, 1.0-m-long skull, mandibles, 14 vertebrae, and partial ribs (Figures 1, 2, and 3; Figures S1–S3; Tables S1 and S2).

Etymology: Coronodon havensteini. Genus is Greek for “crown tooth,” referring to the multi-cusped molars. The species name recognizes Mark Havenstein, who discovered the holotype.

Locality and Age: Wando River near Highway 41 Bridge, South Carolina, Berkeley County. Ashley Formation, Oligocene, uppermost Rupelian. 

Diagnosis: Coronodon has the following mysticete synapomorphies: supraoccipital level with temporal fossa (character 25: state 1), broad basioccipital crests (39: 2), all cusps of posterior teeth subequal (99: 1), upturned antorbital process of maxilla (100: 1), and splayed basal cusps on posterior teeth (206: 1). Like some archaeocetes, its rostrum is twisted counterclockwise in anterior view (Figure 3). Coronodon havensteini is unique in having anterior lower molars labially overlapping posterior lower molars.  ....

Figure 1. Cranium and Upper Dentition of Coronodon havensteini sp. et gen. nov.
(A–E) Cranium in (A) lateral and (B) dorsal views. For comparison, (C) shows a dorsal view of the archaeocete Zygorhiza kochii (USNM 11962). Also shown of Coronodon are the left P3 in (D) labial and (E) lingual views. (F and G) Left M2 in (F) labial and (G) lingual views. (H and I) Right bulla in (H) dorsal view and left petrosal in (I) ventrolateral view. Portions in gray are reconstructed.

ap, anterior process of petrosal; cp, conical apophysis; fr, fenestra rotunda; Fr, frontal; lt, ventrolateral tuberosity; mf, fossa for malleus; Mx, maxilla; Na, nasal; ol, outer lip of bulla; os, occipital shield; Pa, parietal; pc, pars cochlearis; pbf, posterior facet for bulla; pgp, postglenoid process; pp, posterior process of bulla; Px, premaxilla; sp, sigmoid process; Sq, squamosal; sc, sagittal crest; Vo, vomer; zy, zygomatic process; VII canal for facial nerve. Scale bars in (A)–(C), 10 mm. Scale bars in (D)–(I), 5 mm. Blue denotes dental wear and red denotes dental erosion.

Coronodon havensteini  Geisler, Boessenecker, Brown & Beatty, 2017 

In this reconstruction, the two main whales in the center are Coronodon havensteini, the lower two in the background are Echovenator sandersi), and the birds in the sky are Pelagornis sandersi (false toothed birds with a wingspan near 6.5 m).

Illustration: Alberto Gennari  

Jonathan H. Geisler, Robert W. Boessenecker, Mace Brown and Brian L. Beatty. 2017. The Origin of Filter Feeding in Whales. Current Biology. In Press. DOI: 10.1016/j.cub.2017.06.003

 twitter.com/CoastalPaleo/status/880455087386132480

Ancient South Carolina whale yields secrets to filter feeding's origins 

phy.so/417944795 via @physorg_com

[PaleoMammalogy • 2015] Tokarahia kauaeroa • 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

Tokarahia kauaeroa  Boessenecker & Fordyce, 2015
Life restoration of Tokarahia kauaeroa gen. et sp. nov.

Artwork by Christopher Gaskin || DOI: 10.1111/zoj.12297

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. Tokarahia kauaeroa gen. et sp. nov. 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 Mya). ‘Mauicetus’ lophocephalus is relatively similar and recombined as Tokarahia lophocephalus. Phylogenetic analysis supports the inclusion of Tokarahia within the Eomysticetidae, alongside Eomysticetus, Micromysticetus, Yamatocetus, and Tohoraata, and strongly supports the 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 used an alternative as-yet unspecified feeding strategy.

Keywords: Baleen whales; Oligocene; cetacea; Mysticeti; Eomysticetidae

Figure 2. Excavation of the Tokarahia kauaeroa gen. et sp. nov. holotype skull and skeleton:
  A, exposure of the skull and mandibles in a ventral-up position; B, removal of the large jacket containing the skull.

DOI: 10.1111/zoj.12297

Figure 4. Holotype (OU 22235) skull, mandibles, vertebrae, and sternum of Tokarahia kauaeroa gen. et sp. nov.
A, orthogonal image derived from photogrammetry. B, interpretive line drawing.

DOI: 10.1111/zoj.12297

Figure 34. Life restoration of Tokarahia kauaeroa gen. et sp. nov.

Artwork by Christopher Gaskin, ©Geology Museum, University of Otago.

  twitter.com/CoastalPaleo || DOI: 10.1111/zoj.12297 

Systematic Palaeontology

CETACEA Brisson, 1872

MYSTICETI Gray, 1864

CHAEOMYSTICETI Mitchell, 1989

Family EOMYSTICETIDAE Sanders & Barnes, 2002b

Type species: Eomysticetus whitmorei.

Included genera: Eomysticetus, Micromysticetus, Tohoraata, Tokarahia, and Yamatocetus.

TOKARAHIA new genus

Etymology: Named after the Tokarahi township, located near Island Cliff, North Otago, the type locality of T. kauaeroa gen. et sp. nov., meaning large (or panoramic) rock, referring to a mesa-like geographic feature. From the Māori ‘toka’ (rock) plus ‘rahi’ (large). Pronunciation: To-kah-rah-hi-ah, with o as in English ‘toe’, a as in ‘far’, and i as in ‘we’.

Type species: Tokarahia kauaeroa gen. et sp. nov.

Included species: Tokarahia kauaeroa gen. et sp. nov. and Tokarahia lophocephalus Marples, 1956.

TOKARAHIA KAUAEROA gen. et sp. nov.

Etymology: Kauaeroa, meaning long jaw (referring to the elongate, delicate mandibles and rostrum of the holotype), from the Māori ‘kauae’ (jaw) and ‘roa’ (long). Pronunciation: Kau-ae-roa, with au as in English ‘hoe’, ae as in ‘I’, o as in ‘toe’, and a as in ‘far’.

Figure 3. Silhouetted skeletal reconstructions of the three primary specimens of Tokarahia described in this study, with a human figure shown for scale. Skeletal reconstruction based in part on Eomysticetus whitmorei and Yamatocetus canaliculatus.

DOI: 10.1111/zoj.12297

Figure 33. Comparison of skeletal reconstructions, crania, and tympanic bullae of the protocetid Georgiacetus vogtlensis, the basilosaurid Dorudon atrox, the aetiocetid Aetiocetus weltoni, Tokarahia kauaeroa, and extant Balaenoptera edeni.

Sources for illustrations include Emlong (1966), Barnes et al. (1995), Hulbert et al. (1998), Uhen (2004), Deméré & Berta (2008), and photographs courtesy F.G. Marx and C.H. Tsai.

DOI: 10.1111/zoj.12297

Conclusion

New fossil material, including a well-preserved skull, tympanoperiotics, mandibles, and postcrania, is described as a new genus and species T. kauaeroa gen. et sp. nov. within the archaic chaeomysticete family Eomysticetidae. The problematic taxon ‘Mauicetus’ lophocephalus is transferred to this new genus and recombined as T. lophocephalus, resolving decades of uncertainty regarding the taxonomic affinities and phylogenetic significance of this historically puzzling taxon. Referred material suggests that both species existed at the same time from at least 27.3–25.2 Mya, and were perhaps sympatric. Phylogenetic analysis using a large and exhaustive data set of extant and extinct Mysticeti places both species of Tokarahia within Eomysticetidae, and robustly confirms the monophyly of Eomysticetidae. Micromysticetus is also confirmed as an eomysticetid and removed from the Cetotheriopsidae, which is not possible to diagnose and at present is restricted to the holotype of Cetotheriopsis lintianus. Incipient rostral fusion and a delicate and synovial tempromandibular joint seem to preclude lunge feeding in Tokarahia and other eomysticetids, but the uniquely elongate rostrum and comparatively enormous temporal fossae and crests for temporalis attachment suggest an uncertain but highly specialized adaptation for an as-yet unidentified feeding strategy.

Robert W. Boessenecker and R. Ewan Fordyce. 2015. 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. Zoological Journal of the Linnean Society. DOI: 10.1111/zoj.12297

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