Fossils used for calibration
The oldest reported cetacean, Himalayacetus subathuensis, is a basal archaeocete (stem-Cetacea) represented by a partial jaw from India dated at 54-53 Ma using biostratigraphy and sequence stratigraphy (Bajpai and Gingerich, 1998). The phylogenetic position of H. subathuensis has not been seriously questioned. The oldest reported species of Neoceti is Llanocetus denticrenatus, known from a partial jaw from Seymour Island, Antarctica, named by Mitchell (1989). The rest of the specimen, comprising a nearly-complete skull and jaw fragments that fit onto the piece named by Mitchell, was collected and prepared by one of us (R.E. Fordyce, hereafter REF), and it suffices to identify L. denticrenatus as a toothed stem Mysticeti (for phylogenetic position see Fordyce, 2003a; Fordyce, 2003b; Fitzgerald, 2006; Steeman, 2007). Direct biostratigraphic and isotopic dates are not available for the nearly-complete skull, which is from a concretionary bed near the top of the La Meseta Formation (Sadler, 1988: Geologic Map) of Seymour Island, but a horizon 1.1 km northwest of the L. denticrenatus locality is dated using Sr/Sr to 34.2 +/-0.87 Ma or latest Eocene for the upper La Meseta Formation (Dingle and Lavelle, 1998). The oldest reported species of crown Mysticeti is a putative archaic right whale, stem Balaenidae (not formally described), represented by a partial skull, earbones, and vertebrae recovered by REF from the lower Kokoamu Greensand near Duntroon, New Zealand (Fordyce, 2002). The age is lower (local) Duntroonian stage to upper Whaingaroan stage, based on benthic foraminifera, close to an interstage boundary reportedly 27.3+/-0.1 Ma (Cooper, 2004); here we use an age of 28 Ma. The oldest crown Balaenopteridae for which phylogenetic position is reasonably established (Deméré et al., 2005) is “Megaptera” miocaena of (Kellogg, 1922), which is from diatomite at Lompoc, California. The reported age for this sequence is 8.2-7.3 Ma, based on diatom biostratigraphy (Chang et al., 1998); here we use an age of 7.3 Ma.
Of the Odontoceti, Delphinida, the oldest reported and reliably identified stem Delphinoidea, is a skull and associated skeleton of cf. Kentriodon (Kentriodon sp. of Ichishima et al., 1995) from near the top of the Carter Siltstone Member of the Te Akatea Formation near Port Waikato, New Zealand. (White and Waterhouse, 1993: Fig. 2) indicated a minimum age of about 23.5 Ma for the top of the unit, consistent with a planktic foraminiferal date (personal communication from the late N. de B. Hornibrook, to REF) of middle Waitakian stage; this approximates the Oligocene/Miocene boundary (Cooper, 2004). Within the Inioidea, the oldest reported species of stem Pontoporiidae is Brachydelphis mazeasi (Muizon, 1988) from the Cerro La Bruja (or CLB) horizon of the Pisco Formation. Because of a lack of microfossil or macroinvertebrate dates, some ages within the Pisco Formation are base don less-conventional grades of evolution of shark teeth, giving these ages cited for CLB: early late or more likely late middle Miocene (Muizon and De Vries, 1985), 13-11 Ma (Muizon, 1988) and 14-12 Ma (Marocco and Muizon, 1988). Here we use an age of 12 Ma, being a rounded age for late middle Miocene. Finally, the oldest reported age of the crown Delphinoidea appears to be Salumiphocaena stocktoni of (Wilson, 1973) (genus follows Barnes 1985), placed in the stem Phocoenidae (Fajardo-Mellor et al., 2006). The age of the source horizon in the upper part of the Valmonte Diatomite of the Monterey Formation (Wilson, 1973) has been variously cited as 11-7 Ma (Fajardo-Mellor et al., 2006 who used earlier cited dates), 12.6-9.0 Ma (Uhen et al., 2008), and 13-8 Ma (Rowell, 1981 based on diatom biostratigraphy). Here we use an age of 10 Ma.
Bajpai, S., and P. D. Gingerich. 1998. A new Eocene archaeocete (Mammalia, Cetacea) from India and the time of origin of whales. Proceedings of the National Academy of Sciences 95:15464-15468.
Barnes, L. G. 1985. Evolution, taxonomy and antitropical distribution of the porpoises (Phocoenidae, Mammalia). Marine Mammal Science 1:149–165.
Chang, A. S., K. A. Grimm, and L. D. White. 1998. Diatomaceous sediments from the Miocene Monterey Formation California: A lamina-scale investigation of biological, ecological, and sedimentary processes. Palaios 13:439-458.
Cooper, R. A. (ed) 2004. The New Zealand geological timescale. Institute of Geological and Nuclear Sciences monograph.
Deméré, T., A. Berta, and M. McGowen. 2005. The taxonomic and evolutionary history of fossil and modern balaenopteroid mysticetes. Journal of Mammalian Evolution 12:99-143.
Dingle, R. V., and M. Lavelle. 1998. Antarctic Peninsular cryosphere: Early Oligocene (c. 30 Ma) initiation and a revised glacial chronology. Journal of the Geological Society 155:433-437.
Fajardo-Mellor, L., A. Berta, R. L. J. Brownell, C. C. Boy, and R. N. P. Goodall. 2006. The phylogenetic relationships and biogeography of true porpoises (Mammalia: Phocoenidae) based on morphological data. Marine Mammal Science 22:910-932.
Fitzgerald, E. M. 2006. A bizarre new toothed mysticete (Cetacea) from Australia and the early evolution of baleen whales. Proceedings of the Royal Society B: Biological Sciences 273:2955-63.
Fordyce, R. E. 2002. Oligocene origin of skim-feeding right whales: a small archaic balaenid from New Zealand. Journal of Vertebrate Paleontology 22:54A.
Fordyce, R. E. 2003a. Cetacea evolution and Eocene-Oligocene oceans revisited. Pages 154-170 in From greenhouse to icehouse. The marine Eocene-Oligocene transition (D. R. Prothero, L. C. Ivany, and E. Nesbitt, eds.). Columbia University Press, New York.
Fordyce, R. E. 2003b. The toothed stem-mysticete Llanocetus in the Latest Eocene of the southern Ocean. Journal of Vertebrate Paleontology 23:50a-51a.
Ichishima, H., L. G. Barnes , R. E. Fordyce, M. Kimura, and D. J. Bohaska. 1995. A review of kentriodontine dolphins (Cetacea; Delphinoidea; Kentriodontidae): Systematics and biogeography. The Island Arc 3:486-492.
Kellogg, A. R. 1922. Description of the skull of Megaptera miocaena, a fossil humpback whale from the Miocene diatomaceous earth of Lompoc, California. Proceedings of the United States National Museum 61:1-18.
Marocco, R., and C. d. Muizon. 1988. Los vertebrados del Néogeno de la costa Sur del Péru: ambiente sedimentario y condiciones de fosilización. Bulletin de l'Institut Francais d'Etudes Andines 17:105-117.
Mitchell, E. D. 1989. A new cetacean from the late Eocene La Mesta Formation, Seymore Island, Antarctic Peninsula. Canadian Journal of Fisheries and Aquatic Sciences 46:2219-2235.
Muizon, C. d. 1988. Les Vertébrés fossiles de la Formation Pisco (Pérou). III. Les odontocètes du Miocène. Editions Recherche sur les Civilisations. Mémoire 78:1-244.
Muizon, C. d., and T. J. De Vries. 1985. Geology and paleontology of late Cenozoic marine deposits in the Sacaco area (Peru). Geologische Rundschau 74:547-563.
Rowell, H. C. 1981. Biostratigraphy of Monterey Formation, Palos Verde Hills, Southern California. AAPG Bulletin 65:982.
Sadler, P. M. 1988. Geography and stratification of uppermost Cretaceous and Paleogene units on Seymour Island, northern Antarctic Peninsula. Geological Society of America Memoir 169:303-320 + separate geologic map.
Steeman, M. E. 2007. Cladistic analysis and a revised classification of fossil and recent mysticetes. Zoological Journal of the Linnean Society 150:875-894.
Uhen, M. D., R. E. Fordyce, and L. G. Barnes 2008. Odontoceti. Pages 566-606 in Evolution of Tertiary mammals of North America, 2 (C. M. Janis, G. F. Gunnell, and M. D. Uhen, eds.). Cambridge University Press, Cambridge.
White, P. J., and B. C. Waterhouse. 1993. Lithostratigraphy of the Te Kuiti Group; a revision. New Zealand Journal of Geology and Geophysics 36:255-266.
Wilson, L. E. 1973. A dephinid Mammalia, Cetacea, from the Miocene of Palos Verdes Hills, California. University of California Publications in Geological Sciences 103:1-34.