Locomotor reconstruction of Leptictidium from the Eocene of Messel using bone structure patterns in the postcranial skeleton of running and hopping extant mammals
Final Report Abstract
The locomotion of the fossil Leptictidium (order Leptictida), a small mammal genus from the Messel Pit (Eocene, Germany) has been debated. To date, it has been alternately suggested that Leptictidium was a bipedal hopper or runner, based on its external morphology only. In extant mammals, while the external anatomy of the skeleton is rather well-known, the distinction of the inner bone structures (i.e. cortical and trabecular components) of the limbs with different repertoires of locomotion is still to be specified. These structures record functional specialisations related to locomotion and posture. Such inner signal remains also to be explored in Leptictidium. In the present pilot study, the external and inner anatomy of arm and thigh in running and hopping modern mammals have been analysed. A new database including 29 individuals from 20 species of mammals has been created, and includes anatomical observations as well as 3D numerical images and quantifications of the inner structures based on computed tomographic scans. Our analysis indicates that the cortical shell of these bones show some clear relationships with the type of locomotion of the animal. However, a certain degree of variation is observed, which might be explained by other factors, such as inheritance and secondary behaviour (e.g. digging). The spongious bone tissue (trabeculae) seems to record an even more informative signal than the cortical one. Further analyses of this component are still required. Our combined analysis of cortical and trabecular structures extracted from the fore- and hindlimbs of extant mammals gives evidence on their locomotion, and can thus be used to reconstruct the locomotion of fossil mammals, like Leptictidium. In the course of our project, a new specimen of Leptictidium was found and detailed at high resolution by computed tomography. This is one of the first large fossil mammals from Messel to have ever been scanned and virtually reconstructed in 3D. An analysis of the inner structures of its limbs is currently ongoing. Unexpectedly, the inner ear of this animal is still preserved in 3D. Its analysis can be used to specify some details of the locomotion of this animal.
Publications
- 2010). Endostructural variations in the appendicular elements of running and hopping extant mammals - Implications for the reconstruction of Leptictidium (Eocene, Messel pit) locomotion. In: A. Hoppe, H.-G. Röhling, & C. Schüth (eds.), GeoDarmstadt 2010- Geowissenschaften sichern Zukunft. Schriftenreihe der Deutschen Gesellschaft für Geowissenschaften Heft 68: 579-580
Volpato, V., Lehmann, T.
- (2011). Endostructural morphology of the humerus and femur in placental quadrupeds and bipedal hoppers. Mammalian Biology 76S: 24
Volpato V., Kardjillov N., Hilger A., Paulke A., Lehmann T.
