ScienceDaily (Dec. 23, 2009) — Museum Victoria palaeobiologist Dr Erich Fitzgerald has made groundbreaking discoveries into the origin of baleen whales, based on a 25-million-year-old fossil found near Torquay in Victoria, Australia.
Dr Fitzgerald's study, which is published in the Zoological Journal of the Linnean Society, is centred on Mammalodon colliveri, a primitive toothed baleen whale, one of a group of whales that includes the largest animal ever to have lived, the blue whale. Although Mammalodon was discovered in 1932 and named in 1939, it has remained relatively unknown until now.
Fossil skull of the whale Mammalodon colliveri. Length of skull about 45 cm. (Credit: Image: Rodney Start / Source: Museum Victoria)
"Through study of Mammalodon, I hypothesise that it was a bottom-feeding mud-sucker that may have used its tongue and short, blunt snout to suck small prey from sand and mud on the seafloor. This indicates early and varied experimentation in the evolution of baleen whales," explained Dr Fitzgerald.
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The morphology and systematics of Mammalodon colliveri (Cetacea: Mysticeti), a toothed mysticete from the Oligocene of Australia
ERICH M. G. FITZGERALD 1,2,3 *
1 School of Geosciences, Monash University, Victoria 3800, Australia
2 Museum Victoria, GPO Box 666, Melbourne, Victoria 3001, Australia
3 Division of Mammals, National Museum of Natural History, Smithsonian Institution, NHB MRC 108, PO Box 37012, Washington, DC 20013-7012, USA
Correspondence to *E-mail: efitzgerald@museum.vic.gov.au
KEYWORDS
evolution • Mammalodontidae • phylogeny • whale
ABSTRACT
Mammalodon colliveri is an unusual toothed archaic mysticete (Cetacea) from the Upper Oligocene Jan Juc Formation of south-east Australia. The morphology of the holotype skull and postcrania are described in detail. Superimposed on the generally plesiomorphic archaeocete-like morphology of Mammalodon are subtle mysticete synapomorphies. Derived features of Mammalodon include a short and bluntly rounded rostrum, reduced premaxillae, and anterodorsally directed orbits. Within Mysticeti, this suite of features is unique. The aberrant rostral morphology of Mammalodon suggests specialization for suction feeding. Janjucetus hunderi is placed in an expanded family Mammalodontidae. Phylogenetic analysis corroborates the monophyly of Basilosauridae, Neoceti, Odontoceti, and Mysticeti, and yields a novel hypothesis of toothed mysticete relationships: a basal clade of undescribed toothed mysticetes from South Carolina, a Llanocetidae + Mammalodontidae clade, and monophyletic Aetiocetidae are posited as successive sister taxa to edentulous baleen whales (Chaeomysticeti). Toothed archaic mysticetes clearly employed diverse prey capture strategies, with exaptations for filter feeding evolving sequentially in stem group Mysticeti. A stratigraphically calibrated phylogeny implies that the initial diversification of Mysticeti occurred during the Late Eocene.
© 2009 The Linnean Society of London, Zoological Journal of the Linnean Society, 2009.
Received 25 January 2009; accepted for publication 6 February 2009
DIGITAL OBJECT IDENTIFIER (DOI)
10.1111/j.1096-3642.2009.00572.x About DOI
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