Lutra 61(2)_de Vriend et al_2018

3D bone analysis for improving species identification: a case study on scapulae of selected small toothed whales occurring along the Dutch coast

Carcasses are sometimes difficult to identify to species level when the head is lacking. The shoulder blade, or scapula, is often still well preserved in degraded carcasses though, and it can also be found in the archaeological and fossil record. Without any context, identification of these bones to the correct species can be cumbersome. In this pilot study, we investigated whether scapulae of small toothed whales (Odontoceti) possess sufficient unique features to discriminate between similar looking species. There is a clear need for this as illustrations of extinct and extant species occurring along the Dutch coast are available in outdated literature only. Photographs were taken from scapulae of 16 harbour porpoises (Phocoena phocoena), three common dolphins (Delphinus delphis) and three white-beaked dolphins (Lagenorhynchus albirostris). These were subsequently edited manually or semi-automatically. Overlapping pictures were aligned with specific software into a three-dimensional (3D) model. To compare the 3D models, 60 (semi-)landmarks were placed on each scapula. These landmarks were subsequently analysed with a newly created online bioinformatics pipeline (github.com/naturalis/3d-cetaceanscapulae). This pipeline produces a wireframe plot that visualises the differences between the bones investigated. The most discriminative components of the scapulae analysed could be identified. These components were the acromion, coracoid and glenoid cavity. An on-line interactive identification key was built (cetaceanscapulae.linnaeus.naturalis.nl/) with these characters. With the underlying bioinformatics pipeline, many more bones of fossil and extant animal species found on the beach and in museum depots can now be analysed to improve their
identification.