Convex-hull mass estimates of the dodo (Raphus cucullatus): application of a CT-based mass estimation technique

Abstract

The external appearance of the dodo (Raphus cucullatus, Linnaeus, 1758) has been a source of considerable intrigue, as contemporaneous accounts or depictions are rare. The body mass of the dodo has been particularly contentious, with the flightless pigeon alternatively reconstructed as slim or fat depending upon the skeletal metric used as the basis for mass prediction. Resolving this dichotomy and obtaining a reliable estimate for mass is essential before future analyses regarding dodo life history, physiology or biomechanics can be conducted. Previous mass estimates of the dodo have relied upon predictive equations based upon hind limb dimensions of extant pigeons. Yet the hind limb proportions of dodo have been found to differ considerably from those of their modern relatives, particularly with regards to midshaft diameter. Therefore, application of predictive equations to unusually robust fossil skeletal elements may bias mass estimates. We present a whole-body computed tomography (CT) -based mass estimation technique for application to the dodo. We generate 3D volumetric renders of the articulated skeletons of 20 species of extant pigeons, and wrap minimum-fit ‘convex hulls’ around their bony extremities. Convex hull volume is subsequently regressed against mass to generate predictive models based upon whole skeletons. Our best-performing predictive model is characterized by high correlation coefficients and low mean squared error (a = − 2.31, b = 0.90, r2 = 0.97, MSE = 0.0046). When applied to articulated composite skeletons of the dodo (National Museums Scotland, NMS.Z.1993.13; Natural History Museum, NHMUK A.9040 and S/1988.50.1), we estimate eviscerated body masses of 8–10.8 kg. When accounting for missing soft tissues, this may equate to live masses of 10.6–14.3 kg. Mass predictions presented here overlap at the lower end of those previously published, and support recent suggestions of a relatively slim dodo. CT-based reconstructions provide a means of objectively estimating mass and body segment properties of extinct species using whole articulated skeletons.

“A Era do Gelo – O Filme”: uma análise de seu potencial para o ensino de paleontologia

“…Na região da Reserva de Volta Velha foi identificado que a vegetação tropical foi substituída por vegetações de clima frio e que depois reestabeleceu-se após o evento glacial (PILLAR et al, 2009 Teve sua extinção 100 anos após sua descoberta em 1598 (HUME, 2006). Essa ave apresenta, além do grande tamanho corporal, asas pequenas que impossibilitavam o vôo (HUME, 2006); (BRASSEY et al, 2016); (BERGAMAN, 2005).…”

Reconstruction of the musculoskeletal system in an extinct lion

“…15 -16% (Pitts and Bullard, 1968)). Convex hull models have been used recently to reconstruct body segmental shapes and estimate body masses for skeletons with no preserved soft tissues (e.g., Sellers et al, 2012;Basu et al, 2016;Bates et al, 2016;Brassey et al, 2016). The convex hull model for the entire skeleton of P. atrox produced a volume of 0.185 m 3 (Figure 4).…”

Body-Mass Estimation in Paleontology: A Review of Volumetric Techniques

“…Finally, all previous applications of convex hulling have relied on a dataset of modern 3-D skeletal models derived from LiDAR-scanned museum mounts. For the first time, Brassey et al (2016) produced an extant calibration dataset generated entirely from CT-based 3-D models, in this case, a large interspecific sample of modern pigeons on which to base body-mass estimates of the dodo, Raphus cucullatus (Linnaeus, 1758). By restricting the modern dataset to CT-scanned carcasses, any uncertainty in skeletal articulation is negated (assuming that the cadavers are intact) and body mass is directly obtainable from weighing the specimen.…”

“…The thoracic ribs of Stegosaurus stenops (NHMUK R36730) were found to be straightened due to post mortem damage, resulting in a broadened, flaring ribcage and requiring further sensitivity analyses to quantify the impact of taphonomy on predicted body mass . Likewise, one side of the Edinburgh dodo (NMS.Z.1993.13) ribcage required mirroring before convex hulling could be conducted to account for missing ribs (Brassey et al, 2016), and the entire torso of Sivatherium giganteum was replaced with that of a modern specimen of Giraffa prior to volumetric mass estimation (Basu et al, 2016). A consensus is currently lacking with regard to how to approach ribcage reconstructions.…”

“…In the past, this has necessarily resulted in literature values being assigned to modern specimens prior to their inclusion in predictive models (e.g., Sellers et al, 2012;Brassey and Sellers, 2014). However, carcass masses have been found to deviate considerably from published literature mean values (Brassey et al, 2016, and see online peer-review history), and restricting analyses to individuals with associated body masses can severely limit sample sizes. Fortunately, some museums are still engaged in active collection of cadavers, with emphasis on those with associated data.…”