Table 1.
Fossil cetaceans analyzed.
Figure 1.
Cross and longitudinal sectioning planes in fossil cetacean teeth.
Figure 2.
Specimens examined in lingual view.
All fossils other than Prosqualodon australis have been coated with sublimed ammonium chloride. a) Unnamed Kekenodontidae (OU 22023). b) Prosqualodon australis (MPEF-PV 1868). c) Unnamed Squalodontidae (OU 22257). d) Unnamed Squalodontidae (OU 22457). e) Otekaikea sp. (cf. Squalodelphinidae) (OU 22306). f) Unnamed Delphinoidea (OU 22108). g) Unnamed Delphinoidea (SGO-PV-754). Scale bars = 1 cm. Images of Fig. 2A and 2C–F used with permission of Geology Museum, University of Otago.
Table 2.
Enamel thickness in the fossil cetaceans analyzed.
Figure 3.
Enamel ultrastructure in Kekenodontidae and Platanistoidea.
a) Inner layer of HSB and outer layer of radial enamel in the Kekenodontidae (OU 22023) in longitudinal section, magnification 270X. b) Inner layer of HSB and outer layer of radial enamel in Prosqualodon (MPEF-PV 1868) in longitudinal section, magnification 180X. c) Inner layer of HSB and outer layer of radial enamel in the Squalodontidae (OU 22457) in longitudinal section, magnification 230X. d) Radial enamel with thin prismless outer surface in Otekaikea sp. (OU 22306) in longitudinal section, magnification 750X. Note tubules near the EDJ (arrow). (EDJ = enamel-dentine junction; HSB = Hunter-Schreger bands; PL = prismless; R = radial).
Figure 4.
Enamel ultrastructure in Delphinoidea and dentine structure.
a) Radial enamel with prismless outer surface in the Delphinoidea (OU 22108) in longitudinal section, magnification 430X. Note heavily altered dentine underneath the EDJ, possibly due to secondary carbonates. b) Detail of the prismless outer layer in the Delphinoidea (OU 22108) in longitudinal section, magnification 2200X. c) Radial enamel with prismless outer surface in the Delphinoidea (SGO-PV-754) in cross section, magnification 210X. Note the diagenetic alteration in the OES and near the EDJ. d) Dentinal surface of Prosqualodon australis (MPEF-PV 1868) in longitudinal section, magnification 1200X. Note the mineral crystallization inside dentine tubules. (EDJ = enamel-dentine junction; PL = prismless; OES = outer enamel surface; R = radial).
Figure 5.
Generalized phylogeny of the fossil cetaceans analyzed in this study, based on Murakami et al. 2012 [39], and the Schmelzmuster of fossil cetacean enamel (HSB + R indicates Hunter-Schreger bands + radial; R+PL indicates radial + prismless).
The phylogenetic position for Kekenodontidae followed Fordyce (2004) [40].