Functional cranial morphology of archaeocete and mysticete whales, and the potential loss of cranial asymmetry in relation with the evolution of low-frequency hearing in baleen whales
Final Report Abstract
In order to understand the evolution and functional morphology of cranial asymmetry in whales in relation to the frequencies they hear or heard, 3D surface models of mysticete, odontocete, archaeocete, and terrestrial artiodactyl crania were generated using photogrammetry, CT scanning, and laser scanning, and cranial asymmetry was quantitatively analyzed using 3D geometric morphometrics. The relationship of cranial and cochlear shape with hearing frequencies was investigated by correlating cranial shape data with cochlear shape data derived from CT scans, and with known hearing frequencies as well as cochlear and cranial measurements. Finally, the suitability of photogrammetry and CT scanning for 3D surface reconstruction of paleontological specimens was tested. Results of the asymmetry analysis indicate that archaeocete cranial asymmetry is not significant when the cranial shape is analyzed in 3D and the rostrum is taken out of the equation, that there was no conspicuous directional cranial asymmetry in mysticetes at any time during the evolution of this clade, and that directional cranial asymmetry in cetaceans is restricted to odontocetes. Therefore, the original working hypothesis (cranial symmetry in extant mysticetes is secondary, asymmetry was reduced during mysticete evolution) is not supported. Results of the comparison of digitization methods for paleontological application generally recommend manual photogrammetry for external surface reconstruction, because it has a high degree of reproducibility and is the most efficient and least costly method of those tested. Their technical provide valuable advice for the application of 3D digitization techniques in paleontology. Results of the correlation of cranial and cochlear shape find that asymmetric and symmetric components of cranial shape correlate with cochlear shape and hearing frequencies in that the symmetric, broad mysticete cranial shape is linked to lower hearing frequencies and the asymmetric, “telescoped” odontocete cranial shape to higher hearing frequencies. Fahlke, J.M. 2015. Virtueller Schädel, echte Beule. Pages 258-259 in: Hermannstädter, A., Heumann, I. & Pannhorst, K. (eds.) Wissensdinge – Geschichten aus dem Naturkundemuseum. Nicolai-Verlag, Berlin. Also online together with Hampe, O.: http://www.mfn-wissensdinge.de/3d-kopf-mit-beule/
Publications
- (2018) Relationships of cochlear coiling shape and hearing frequencies in cetaceans, and the occurrence of infrasonic hearing in Miocene Mysticeti. Foss. Rec. (Fossil Record) 21 (1) 33–45
Ritsche, Indira S.; Fahlke, Julia M.; Wieder, Frank; Hilger, André; Manke, Ingo; Hampe, Oliver
(See online at https://doi.org/10.5194/fr-21-33-2018) - 2013. One fits all: using photogrammetry to solve diverse problems with large-sized paleontological objects. – 73rd Annual Meeting of the Society of Vertebrate Paleontology, Los Angeles, CA, USA, October 30-November 2, 2013. SVP 2013 Program and Abstract Book (Supplement to the online Journal of Vertebrate Paleontology, October 2013): 124
Fahlke, J.M., Mallison, H., Wings, O. & Schwarz-Wings, D.
- 2013. Whale ears inside and out: are low-frequency hearing and cranial shape related in early baleen whales (Cetacea, Mysticeti)? – A Joint Conference of the “Paläontologische Gesellschaft” and the “Palaeontological Society of China”, Göttingen, Germany, September 23-27, 2013. Pages 43-44 in: Reitner, J., Yang, Q., Wang, Y. & Reich, M. (eds.) Palaeobiology and Geobiology of Fossil Lagerstätten through Earth History, Universitätsverlag Göttingen
Fahlke, J.M., Ritsche, I.S. & Hampe, O.
- 2014. Did whales straighten up to hear better? Potential connection between cranial symmetry and low-frequency hearing in mysticetes (Cetacea). – 7th Triennial Conference on Secondary Adaptations of Tetrapods to Life in Water, Fairfax, VA, and Washington, D.C., USA, June 2-4, 2014
Fahlke, J.M., Ritsche, I.S. & Hampe, O.
- 2014. Generation of three-dimensional (3D) surface models of baleen whale skulls (Cetacea: Mysticeti) for morphometric analyses: possibilities and limits of photogrammetry. – 10th North American Paleontological Convention, Gainesville, FL, USA, February 15-18, 2014. NAPC Abstracts. Paleontological Society Special Publication, 13: 171
Fahlke, J.M.
(See online at https://doi.org/10.1017/S2475262200013654) - 2015. Cranial symmetry in baleen whales (Cetacea, Mysticeti) and the occurrence of cranial asymmetry throughout cetacean evolution. – The Science of Nature / Naturwissenschaften, 102(58): 1-16
Fahlke, J.M. & Hampe, O.
(See online at https://doi.org/10.1007/s00114-015-1309-0) - 2016. Photogrammetry vs. micro-CT scanning for 3D surface generation of a typical vertebrate fossil - a case study. – Journal of Paleontological Techniques 14: 1-18
Fahlke, J.M. & Autenrieth, M.
