Articles | Volume 2, issue 1
Primate Biol., 2, 89–110, 2015

Special issue: Hans-Jürg Kuhn and the German Primate Center

Primate Biol., 2, 89–110, 2015

Research article 25 Sep 2015

Research article | 25 Sep 2015

The ethmoidal region of the skull of Ptilocercus lowii (Ptilocercidae, Scandentia, Mammalia) – a contribution to the reconstruction of the cranial morphotype of primates

I. Ruf1, S. Janßen2, and U. Zeller2 I. Ruf et al.
  • 1Senckenberg Forschungsinstitut und Naturmuseum Frankfurt, Abteilung Paläoanthropologie und Messelforschung, Senckenberganlage 25, 60325 Frankfurt am Main, Germany
  • 2FG Spezielle Zoologie, Lebenswissenschaftliche Fakultät, Albrecht Daniel Thaer-Institut für Agrar- und Gartenbauwissenschaften, Humboldt-Universität zu Berlin, Ziegelstrasse 5–9, 10117 Berlin, Germany

Abstract. The ethmoidal region of the skull houses one of the most important sense organs of mammals, the sense of smell. Investigation of the ontogeny and comparative anatomy of internal nasal structures of the macrosmatic order Scandentia is a significant contribution to the understanding of the morphotype of Scandentia with potential implications for our understanding of the primate nasal morphological pattern. For the first time perinatal and adult stages of Ptilocercus lowii and selected Tupaia species were investigated by serial histological sections and high-resolution computed tomography (μCT), respectively. Scandentia show a very common olfactory turbinal pattern of small mammals in having two frontoturbinals, three ethmoturbinals, and one interturbinal between the first and second ethmoturbinal. This indicates a moderately developed sense of smell (moderately macrosmatic). The observed septoturbinal is probably an apomorphic character of Scandentia. A general growth in length occurs during postnatal ontogeny; thus the adult ethmoidal region is proportionally longer compared to the rest of the skull. Throughout ontogeny Ptilocercus has a proportionally longer nasal cavity than Tupaia. Major differences exist between Ptilocercus and Tupaia in regard to the proportions of the nasal cavity which correlate with the position of the orbits. Compared to Tupaia, Ptilocercus shows more anteriorly oriented orbits and has a proportionally longer nasal capsule than Tupaia and based on anatomy probably a higher level of olfactory discrimination. Furthermore, Ptilocercus has a platybasic skull base that resembles a derived feature of Ptilocercidae. In contrast, Tupaia has a distinct septum interorbitale leading to a tropibasic skull, a pattern that is a plesiomorphic character of Tupaiidae and Scandentia in general. This finding helps us to understand the septum interorbitale pattern in Primates. Our results indicate that differences among the investigated Scandentia species are correlated with adaptations to foraging and behavioural biology.

Short summary
For the first time internal structures of the nasal region were studied in different ontogenetic stages of selected species of tree shrews (Scandentia) based on histology and µCT. The observed morphology of the turbinal skeleton reveals important characters for future systematic analyses. The pattern of the interorbital septum, a bony plate that separates the orbits, and its relevance for the closely related Primates are discussed in terms of ontogeny and functional morphology.