Ecomorphology of the cervid calcaneus as a proxy for paleoenvironmental reconstruction

Abstract

This study presents new ecomorphological models for the cervid calcaneus that can be used to make predictions about the nature of ancient environments. Using geometric morphometrics to quantitatively assess the length of the articular surface supporting the malleolus, the length and orientation of the tuber calcanei, and the position of the articular facets, we aimed to establish correlations between morphological traits, locomotor behavior, and environmental parameters in extant cervids. The morphology of the calcaneus was found to primarily vary with locomotor strategy and habitat, along a continuum from habitats with an open vegetation structure to habitats with a closed vegetation structure. Confounding factors, including sexual dimorphism, allometry, and phylogeny were accounted for using Principal Component Analysis, regressions and phylogenetic comparative methods. The results of our analyses suggested that these factors did not substantially obscure habitat predictions. As such, the calcaneus provides a valuable proxy for paleoenvironmental reconstruction that is broadly applicable to Quaternary fossil assemblages with a sufficiently large sample of cervids.

Ecomorphology of the cervid intermediate phalanx and its implications for palaeoenvironmental reconstruction

“…If Pagel's λ is close to 0, this indicates a weak phylogenetic signal. If the value is close to 1, a strong phylogenetic signal can be inferred (Gruwier & Kovarovic, 2021; Molina‐Venegas & Rodríguez, 2017).…”

“…In this weighed regression, phylogeny was included as an error term as part of the regression of shape on the habitat variables (Gruwier & Kovarovic, 2021; Martins & Hansen, 1997; Walmsley et al, 2012). Using phylogenetic tree branch lengths to estimate phylogenetic covariance, the covariance for two species was proportional to the sum of the branch lengths from the root to the last common ancestor (Gruwier & Kovarovic, 2021; Monteiro, 2013). Tree branch lengths for the cervid family were taken from the 10KTrees website (Arnold et al, 2010) and their accuracy checked against a recently published cervid phylogenetic framework by Heckeberg (2020).…”

“…To estimate the effect of phylogeny in the dataset, we conducted a phylogenetic generalized least squares (PGLS) regression (Martins & Hansen, 1997) in Caper 1.0 in R (Orme et al, 2018). This approach consisted of regressing the mean shape coordinates for each species on the habitat groups transformed into dummy variables (Barr, 2014a, 2014b; Curran, 2015; Gruwier & Kovarovic, 2021; Meloro et al, 2007, 2008; Walmsley et al, 2012). In this weighed regression, phylogeny was included as an error term as part of the regression of shape on the habitat variables (Gruwier & Kovarovic, 2021; Martins & Hansen, 1997; Walmsley et al, 2012).…”

“…Although other escape behaviors, such as galloping and trotting, exist (Blank, 2018), there are generally five main locomotor strategies used by artiodactyls to escape predators: leaping (vertical jump), bounding (long horizontal jump), tacking or zig-zag running (sharp turn that suddenly changes course), stotting (a bouncing gait) and prancing (type of pronounced and exaggerated high step; Caro et al, 2004;Caro, 1986Caro, , 1994. The latter two behaviors are presumably intended to wrongfoot the predator (Caro et al, 2004;Caro, 1994), but tacking is more common when evading predators in dry, open habitat (Caro et al, 2004), while leaping is preferred when animals flee in environments with a dense vegetation and complex terrain (Caro, 1994;Gruwier & Kovarovic, 2021).…”

“…In this ecomorphological approach, morphological patterns in extant species are compared with those observed in extinct taxa, which allows for inferences to be made about probable adaptations in fossils (Andrews & Hixson, 2014;DeGusta & Vrba, 2003;Gruwier & Kovarovic, 2021). This approach has the advantage that it directly considers how animals functioned in their ecosystem (Curran, 2012), independent of their taxonomic affinity (although see Klein et al, 2010).…”