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. 2015 Dec 2;2(12):150476.
doi: 10.1098/rsos.150476. eCollection 2015 Dec.

A new Early Oligocene toothed 'baleen' whale (Mysticeti: Aetiocetidae) from western North America: one of the oldest and the smallest

Felix G Marx  1 , Cheng-Hsiu Tsai  2 , R Ewan Fordyce  3
Affiliations

A new Early Oligocene toothed 'baleen' whale (Mysticeti: Aetiocetidae) from western North America: one of the oldest and the smallest

Felix G Marx et al. R Soc Open Sci. .

Abstract

Archaic toothed mysticetes represent the evolutionary transition from raptorial to bulk filter feeding in baleen whales. Aetiocetids, in particular, preserve an intermediate morphological stage in which teeth functioned alongside a precursor of baleen, the hallmark of all modern mysticetes. To date, however, aetiocetids are almost exclusively Late Oligocene and coeval with both other toothed mysticetes and fully fledged filter feeders. By contrast, reports of cetaceans from the Early Oligocene remain rare, leaving the origins of aetiocetids, and thus of baleen, largely in the dark. Here, we report a new aetiocetid, Fucaia buelli, from the earliest Oligocene (ca 33-31 Ma) of western North America. The new material narrows the temporal gap between aetiocetids and the oldest known mysticete, Llanocetus (ca 34 Ma). The specimen preserves abundant morphological detail relating to the phylogenetically informative ear bones (otherwise poorly documented in this family), the hyoid apparatus and much of the (heterodont) dentition. Fucaia comprises some of the smallest known mysticetes, comparable in size with the smallest odontocetes. Based on their phylogenetic relationships and dental and mandibular morphology, including tooth wear patterns, we propose that aetiocetids were suction-assisted raptorial feeders and interpret this strategy as a crucial, intermediary step, enabling the transition from raptorial to filter feeding. Following this line of argument, a combination of raptorial and suction feeding would have been ancestral to all toothed mysticetes, and possibly even baleen whales as a whole.

Keywords: Aetiocetidae; Mysticeti; baleen; baleen whale; filter feeding; suction feeding.

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Figures

Figure 1.
Figure 1.
Type locality and horizon of Fucaia buelli. (a) Locality map, (b) age and provenance of Fucaia and Chonecetus. Details as to the exact location and horizon are available directly from UWBM. O., Olympic Peninsula; Van., Vancouver Island.
Figure 2.
Figure 2.
Cranium of Fucaia buelli in dorsal view: (a) photograph and (b) line drawing.
Figure 3.
Figure 3.
Cranium of Fucaia buelli in (a) posterior and (b) anterolateral view. (a,b) photographs and (a′,b′) line drawings.
Figure 4.
Figure 4.
Cranium of Fucaia buelli in lateral view. (a) Photograph and (b) line drawing.
Figure 5.
Figure 5.
Details of the cranium of Fucaia buelli. (a) Apex of supraoccipital shield in dorsal view, showing the possible interparietal; (b) displaced right exoccipital revealing an unfused planar elongate surface of the supra-exoccipital suture immediately anterior to the eroded upper margin of the right occipital condyle.
Figure 6.
Figure 6.
Right periotic of Fucaia buelli. Specimen shown in (a) dorsal, (b) posteromedial, (c) medial, (d) lateral and (e) ventral view. (a–e) Photographs and (a′–e′) line drawings.
Figure 7.
Figure 7.
Right tympanic bulla of Fucaia buelli. Specimen shown in (a) dorsal, (b) anteromedial, (c) medial, (d) lateral, (e) ventral and (f) posterior view. (a–f) Photographs and (a′–f′) line drawings.
Figure 8.
Figure 8.
Fragment of right mandible of Fucaia buelli.
Figure 9.
Figure 9.
Anterior teeth of Fucaia buelli in labial (left) and lingual (right) view. (a–e) Presumed incisors; specimen shown in (c) preserves only the root; (f) potential first premolar; (g) presumed left P1; (h) presumed left p1.
Figure 10.
Figure 10.
Postcanine teeth of Fucaia buelli. (a,b) Presumed P2/p2; (c) presumed posterior left upper molar in labial view; (d) presumed left P3; (e) presumed right P3; (f) presumed left M1; (g) presumed main denticle of postcanine, position unknown—possibly a first premolar; (h,i) isolated roots presumed to represent postcanines (post-P2/p2). All teeth except (c) are shown in labial (left) and lingual (right) view; the orientations of the root fragments (h,i) are uncertain.
Figure 11.
Figure 11.
Details of attritional and abrasive tooth wear. (a) Left P3; (b) right P3, (c) left M1, all in lingual view.
Figure 12.
Figure 12.
Hyoid apparatus of Fucaia buelli. (a) Basihyal, with the partial left thyrohyal (top right) and other bone fragments still attached; (b) right thyrohyal; (c) right stylohyal. All in dorsal view.
Figure 13.
Figure 13.
Atlas and axis of Fucaia buelli. Axis in (a) anterior and (b) posterior view; atlas in (c) anterior and (d) posterior view.
Figure 14.
Figure 14.
Posterior cervical vertebrae of Fucaia buelli. (a) C3, (b) C4, (c) C5, (d) C6, (e) C7. All in anterior view.
Figure 15.
Figure 15.
Thoracic vertebrae of Fucaia buelli. (a–e) T1–T5, (f) T6, (g–j) posterior thoracic vertebrae of uncertain identity. All in anterior view.
Figure 16.
Figure 16.
Lumbar vertebrae of Fucaia buelli. All in anterior view.
Figure 17.
Figure 17.
Forelimb of Fucaia buelli. Left scapula in (a) lateral and (b) medial view.
Figure 18.
Figure 18.
Phylogenetic relationships of archaic mysticetes. Individual families are labelled. For details of the analysis, see Marx and Fordyce [13]. Abbreviations: Pli, Pliocene, Pls., Pleistocene.
Figure 19.
Figure 19.
Position of the lacrimal relative to the ascending process of the maxilla in F. goedertorum and Janjucetus hunderi. C. goedertorum (left) is represented by LACM 131146, J. hunderi (right) by NMV P216929.
Figure 20.
Figure 20.
Proposed evolution of mysticete feeding strategies. Phylogeny is the same as in figure 18. Boxes above the branches indicate the type of dentition, with black denoting heterodonty, white homodonty and grey the transition between. Roman numerals refer to the three stages of aetiocetid tooth simplification explained in the text. Stippled lines indicate uncertainty about when a particular feeding strategy first appeared.
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References

    1. Barnes LG, Kimura M, Furusawa H, Sawamura H. 1995. Classification and distribution of Oligocene Aetiocetidae (Mammalia; Cetacea; Mysticeti) from western North America and Japan. Island Arc 3, 392–431. (doi:10.1111/j.1440-1738.1994.tb00122.x) - DOI
    1. Rivin MA. 2010. Early Miocene cetacean diversity in the Vaqueros Formation, Laguna Canyon, Orange County, California. MSc thesis, California State University Fullerton.
    1. Emlong D. 1966. A new archaic Cetacean from the Oligocene of Northwest Oregon. Bull. Mus. Nat. Hist. Univ. Oreg. 3, 1–51.
    1. Van Valen L. 1968. Monophyly or diphyly in the origin of whales. Evolution 22, 37–41. (doi:10.2307/2406647) - DOI - PubMed
    1. Deméré TA, McGowen MR, Berta A, Gatesy J. 2008. Morphological and molecular evidence for a stepwise evolutionary transition from teeth to baleen in mysticete whales. Syst. Biol. 57, 15–37. (doi:10.1080/10635150701884632) - DOI - PubMed

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