Snakes as a model for measuring skull preparation errors in geometric morphometrics

Abstract

Researchers often use skulls prepared by different techniques in geometric morphometrics (GM). The main goal of this paper was to compare and measure errors in GM analyses using snake skulls prepared with two of these techniques (microCT Scan and chemical maceration). We evaluate if analyses employing skulls with both types of preparation may generate biased results or if this parameter is negligible. Thirty‐four heads of Liophis miliaris merremi were first scanned and subsequently prepared following the techniques of chemical maceration. We used 37 and 18 landmarks for dorsal and ventral views of skulls respectively. To evaluate shape differences between the same skull assessed by microCT Scan and chemical maceration, we performed discriminant analyses, Hotelling's T2 and cross‐validation tests. Discriminant analyses showed significant differences between preparation techniques for both views. However, all the differences between dried and microCT scanned skulls were smaller than those between individuals of the same taxon, which means that such differences are within the range of intraspecific variation. The results support the use of specimens prepared according to both techniques in studies of GM.

Morphological integration and modularity in the hyperkinetic feeding system of aquatic‐foraging snakes

“…2019; Souto et al. 2019; Murta‐Fonseca et al. 2019) and additional studies have superimposed nonrigid structures together in other organisms when taking appropriate precautions (Adams 1999, 2004; Rohlf and Corti 2000; Adams and Rohlf 2000; further discussed below).…”

Can morphotaxa be assessed with photographs? Estimating the accuracy of two‐dimensional cranial geometric morphometrics for the study of threatened populations of African monkeys

“…This interpretation is consistent with the finding (see Section 3 ) that individual shape variance is 14 times larger than 2D digitizing error (and on average more than 10 times larger using 3D skulls of guenons; Cardini & Elton, 2008a ), whereas in the TTD comparison it was only four to five times bigger. Thus, if the digitizing error in the TTD comparison is only slightly larger than in 2D, with the orientation error typically about as large as digitization error (smaller sometimes: Evin et al, 2020 ; Fox et al, 2020 ; Jojić et al, 2011 ; Souto et al, 2019 ; Jojic, pers. comm.…”

Morphological Integration and Modularity in the Hyperkinetic Feeding System of Aquatic-foraging Snakes

“…2). Other authors have adopted a similar strategy for analyzing the shape of the entire feeding apparatus (e.g., Watanabe et al 2019;Palci et al 2016;Klaczko et al 2016;Souto et al 2019;Silva et al 2018;Murta-Fonseca et al 2019;dos Santos et al 2017) and additional studies have superimposed non-rigid structures together in other organisms when taking appropriate precautions (Adams 1999;Rohlf & Corti 2000;Adams & Rohlf 2000;Adams 2004).…”