Abstract
Niche partitioning has long been considered to be a fundamental part of speciation and difference in body size is a straightforward proxy for ecology and niche partitioning. Here we report a new aetiocetid specimen from the upper part of Morawan Formation (Oligocene; late Chattian, ~26–24 Ma), Ashoro, Hokkaido, Japan. This specimen comprises an isolated left squamosal and an isolated left periotic; the morphology of the squamosal is distinguishable from all aetiocetids, but shows a close match with the aetiocetid Morawanocetus yabukii in that: the dorsal margin of the zygomatic process of the squamosal is twisted dorsomedially; the zygomatic process expands dorsoventrally; the zygomatic process is transversely thin; and the anterior tip of the zygomatic process is acutely tapered. The estimated body size of this Morawanocetus-like specimen is ca. 8 m, almost twice the size of all known aetiocetids (3–4 m). Moreover, the preserved periotic reveals structures that are otherwise poorly known in aetiocetids. This large Morawanocetus-like aetiocetid sheds new light on niche partitioning of Oligocene toothed mysticetes and evolution of body size in Mysticeti.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
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
Damuth JD, MacFadden BJ (1990) Body Size in Mammalian Paleobiology: Estimation and Biological Implications. Cambridge University Press, Cambridge
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
Emlong D (1966) A new archaic cetacean from the Oligocene of northwest Oregon. Bulletin of the Museum of Natural History, University of Oregon 3:1–51
Fitzgerald EMG (2006) A bizarre new toothed mysticete (Cetacea) from Australia and the early evolution of baleen whales. Proc R Soc B: Biol Sci 273:2955–2963. doi:10.1098/Rspb.2006.3664
Fitzgerald EMG (2010) The morphology and systematics of Mammalodon colliveri (Cetacea: Mysticeti), a toothed mysticete from the Oligocene of Australia. Zool J Linn Soc 158:367–476. doi:10.1111/J.1096-3642.2009.00572.X
Fitzgerald EMG (2012) Archaeocete-like jaws in a baleen whale. Biol Lett 8:94–96. doi:10.1098/rsbl.2011.0690
Gause G (1934) The Struggle for Existence. Williams and Wilkins, Baltimore
Gavrilchuk K, Lesage V, Ramp C, Sears R, Bérubé M, Bearhop S, Beauplet G (2014) Trophic niche partitioning among sympatric baleen whale species following the collapse of groundfish stocks in the northwest Atlantic. Mar Ecol Progr Ser 497:285–301
Gingerich PD, Ul-Haq M, von Koenigswald W, Sanders WJ, Smith BH, Zalmout IS (2009) New protocetid whale from the middle Eocene of Pakistan: birth on land, precocial development, and sexual dimorphism. PLoS ONE 4:e4366 doi:10.1371/journal.pone.0004366
Hutchinson GE (1957) Concluding remarks. In: Cold Spring Harbor Symposia on Quantitative Biology. Cold Spring Harbor Laboratory Press, pp 415–427
Lambert O, Giovanni B, Post K, Muizon C de, Salas-Gismondi R, Urbina M, Reumer J (2010) The giant bite of a new raptorial sperm whale from the Miocene epoch of Peru. Nature 466:105–108. doi: 10.1038/nature09067
Mead JG, Fordyce RE (2009) The therian skull: a lexicon with emphasis on the odontocetes Smithsonian Contrib Zool 627:1–248
Morita R, Titova LV, Akiba F (1996) Oligocene-early Miocene molluscs and diatoms from the Kitami-Tsubetsu area, eastern Hokkaido, Japan. Science Reports of the Tohoku University (Geology) 63:53–213
Pyenson ND, Sponberg SN (2011) Reconstructing body size in extinct crown Cetacea (Neoceti) using allometry, phylogenetic methods and tests from the fossil record. J Mammal Evol 18:269–288. doi: 10.1007/S10914-011-9170-1
Pyenson ND, Goldbogen JA, Shadwick RE (2013) Mandible allometry in extant and fossil Balaenopteridae (Cetacea: Mammalia): the largest vertebrate skeletal element and its role in rorqual lunge feeding. Biol J Linn Soc 108:586–599. doi: 10.1111/J.1095-8312.2012.02032.X
Ralls K, Mesnick S (2009) Sexual dimorphism. In: Perrin WF, Wursig B, Thewissen JGM (eds) Encyclopedia of Marine Mammals. 2nd edn. Academic Press, San Diego, pp 1005–1011
Risting S (1922) Av hvalfangstens historie. vol 2. J. Petlitz Boktrykkeri, Kristiania, Norway
Russell LS (1968) A new cetacean from the Oligocene Sooke Formation of Vancouver Island, British Columbia. Canadian J Earth Sci 5:929–933
Sanders AE, Barnes LG (2002) Paleontology of the late Oligocene Ashley and Chandler Bridge formations of South Carolina, 3: Eomysticetidae, a new family of primitive mysticetes (Mammalia: Cetacea). Smithsonian Contrib Paleobiol 93:313–356
Smith FA, Lyons SK (2011) How big should a mammal be? A macroecological look at mammalian body size over space and time. Phil Trans R Soc B: Biol Sci 366:2364–2378
Stewart BS, Leatherwood S (1985) Minke whale, Balaenoptera acutorostrata (Lacepede, 1804). In: Ridgway SH, Harrison R (eds) Handbook of Marine Mammals. Volume 3: The Sirenians and Baleen Whales. Academic Press, London, pp 91–136
Tsai CH, Fordyce RE (2014) Disparate heterochronic processes in baleen whale evolution. Evol Biol 41:299–307. doi:10.1007/s11692-014-9269-4
Acknowledgments
We thank Katsuie Yabuki for collecting and donating AMP 9 to the Ashoro Museum of Paleontology; Tatsuya Shinmura for life reconstruction of AMP 9; John R. Wible (Editor-in-chief), Erich Fitzgerald, and an anonymous reviewer for constructive comments; Robert Boessenecker for pre-submission review. For access to collections and allowing photography during CHT and/or TA’s visits, we thank Nicholas Pyenson and David Bohaska (National Museum of Natural History, Smithsonian Institution, USA); Patricia Holroyd (University of California Museum of Paleontology); Lawrence Barnes and Samuel McLeod (Natural History Museum of Los Angeles County, USA). CHT thanks the Ashoro Museum of Paleontology (Hiroshi Sawamura, TA, and Tatsuya Shinmura) for hosting research visits. James Mead (Washington, DC) and Robert Boessenecker (California) kindly accommodated Tsai during various visits. CHT is supported by a University of Otago Doctoral Scholarship.
Ethical Statement
This manuscript has not been published previously and not been submitted to more than one journal simultaneously for consideration.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Tsai, CH., Ando, T. Niche Partitioning in Oligocene Toothed Mysticetes (Mysticeti: Aetiocetidae). J Mammal Evol 23, 33–41 (2016). https://doi.org/10.1007/s10914-015-9292-y
Published:
Issue Date:
DOI: https://doi.org/10.1007/s10914-015-9292-y