Wednesday, April 18, 2018

[PaleoMammalogy • 2018] Toipahautea waitaki • A New Archaic Baleen Whale (early-Late Oligocene, New Zealand) and the Origins of Crown Mysticeti

Toipahautea waitaki   Tsai & Fordyce, 2018

Burial in the ancient sea of Zealandia: a Toipahautea whale skeleton is slowly covered by sand 27-28 million years ago, on its path to becoming a fossil 

 Reconstruction by Chris Gaskin, Geology Museum, University of Otago 

A new genus and species of extinct baleen whale, †Toipahautea waitaki (Late Oligocene, New Zealand) is based on a skull and associated bones, from the lower Kokoamu Greensand, about 27.5 Ma (local upper Whaingaroan Stage, early Chattian). The upper jaw includes a thin, elongate and apparently toothless maxilla, with evidence of arterial supply for baleen. Open sutures with the premaxilla suggest a flexible (kinetic) upper jaw. The blowhole is well forward. The mandible is bowed laterally and slightly dorsally; unlike the Eomysticetidae, there are no mandibular alveoli, and the coronoid process is tapered and curved laterally. Jaw structure is consistent with baleen-assisted gulp-feeding. The age of early Chattian makes †Toipahautea a very early, if not the oldest named, toothless and baleen-bearing mysticete, suggesting that the full transition from toothed to baleen-bearing probably occurred in the Early Oligocene. Late Oligocene mysticetes vary considerably in jaw form and kinesis, tooth form and function, and development of baleen, implying a wide range of raptorial, suctorial and filter-feeding behaviour. More study may elucidate the function of jaws, teeth and baleen in terms of opportunist/generalist feeding, as in modern gray whales, versus specialized feeding. We here propose that early mysticetes, when transitioned from toothed to baleen-bearing, were generalists and opportunists instead of specializing in any forms of feeding strategies. In addition, two different phylogenetic analyses placed †Toipahautea either in a polytomy including crown Mysticeti, or immediately basal to the crown, and above †Eomysticetidae in both cases. Because the †Toipahautea waitaki holotype is an immature individual, it may plot more basally in phylogeny than its true position.

Keywords: Cetacea, mysticete, feeding strategy, filter-feeding, specialist/generalist, opportunist

  initial preparation of †Toipahautea waitaki OU 21981 by A. Grebneff
 (photo: R.E. Fordyce)

Burial in the ancient sea of Zealandia: a Toipahautea whale skeleton is slowly covered by sand 27-28 million years ago, on its path to becoming a fossil

 Reconstruction by Chris Gaskin, Geology Museum, University of Otago 

Cetacea Brisson, 1762
Mysticeti Gray, 1864

Incertae familiae

Toipahautea waitaki gen. et. sp. nov 

Etymology. Toi means origin and pahautea refers to whalebone/baleen in Maori, alluding to the origin of the early toothless and baleen-bearing mysticetes. Waitaki is a name for the wider region, including the Waitaki River (wai, water or river; taki, tears) into which the smaller Hakataramea River drains.

 Holotype. Toipahautea waitaki is known only from the holotype, OU 21981: a disarticulated partial skull (parts of the maxillae and premaxillae, left nasal, frontals, squamosals, exoccipitals, basioccipital and supraoccipital), incomplete mandibles, left tympanic bulla and periotic, hyoid(?), atlas, axis, two thoracic vertebrae, two scapulae, a partial humerus, two radii and ribs. Most of the elements were disarticulated but associated when excavated.

Diagnosis. Toipahautea waitaki is interpreted as a chaeomysticete based on the presence of ‘baleen’ sulci on the ventral surface of the maxilla and lack of mandibular alveoli. †Toipahautea waitaki has a unique combination of: massive size of periotic; well-developed superior process of the periotic; prominent elongation of dorsomedial margin of the internal acoustic meatus; prominent fissure between the fenestra rotunda and the aperture for the cochlear aqueduct; small medial posterior sulcus; the presence of the anteroexternal foramen; the presence of the sigmoidal cavity; the presence of the elliptical foramen; horizontal sigmoidal cleft far anterior than the anterior margin of the sigmoidal process; posteromedial margin of the bulla orienting slightly anteromedially.

Locality and horizon. OU 21981 (field number REF- was recovered from the Hakataramea Valley, South Canterbury, South Island, New Zealand (figure 1). ....


Cheng-Hsiu Tsai and R. Ewan Fordyce. 2018. A New Archaic Baleen Whale,Toipahautea waitaki (early-Late Oligocene, New Zealand) and the Origins of Crown Mysticeti.   R. Soc. Open Sci. 5: 172453.  DOI: 10.1098/rsos.172453

Whale of a discovery: NZ's ancient (and extinct) ocean mammal, via @nzherald

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