The Asymmetry and Modularity of the Hyoid Bone

Abstract

SUMMARY:Morphological variation is a result of interplay among multiple intervening factors. For hyoid bones, the shape and size differences have been scarcely covered in the literature and in majority limited to studies of sexual dimorphism or age dependency. To our knowledge, the human hyoid bone, in complete opposite to other cranial bones, has not been fully utilized to address development questions in terms of asymmetry or modularity. In the present paper, we used landmark-based methods of geometric morphometrics and multivariate statistical approach to study human hyoid morphology represented by the hyoid body and greater horns in a sample of 211 fused and non-fused bones. Within a sample variation analysis, we showed that the hyoid bone is, by nature, asymmetrical bone which exhibits both directional and fluctuating types of asymmetry and is composed of well-integrated anatomical elements for which the biomechanical load of attached muscles is the most determining factor of variation. Yet, the covariance and evidence of unequal amount of fluctuating asymmetry among modules suggests a certain degree of independence during early stages of development.

Evaluating modularity in morphometric data: challenges with the RV coefficient and a new test measure

“…; Tsuboi, Gonzalez‐Voyer & Kolm ; Urbanova et al . ). Unfortunately, while RV‐based procedures are intuitive and conceptually straightforward, they suffer several mathematical deficiencies that limit their ability to accurately assess the degree of modularity or integrated structure in phenotypic data sets.…”

“…Permutation tests may then be used to evaluate these patterns (Klingenberg 2009). For morphometric data, use of the RV coefficient is appealing, as the same analytical tool may be utilized to evaluate either hypotheses of modular structure or hypotheses of integration among modules (for examples see: Jojic, Blagojevic & Vujosevic 2012;Santanta & Lofgren 2013;Goswami et al 2014;Sorenson et al 2014;Tsuboi, Gonzalez-Voyer & Kolm 2014;Urbanova et al 2014). Unfortunately, while RV-based procedures are intuitive and conceptually straightforward, they suffer several mathematical deficiencies that limit their ability to accurately assess the degree of modularity or integrated structure in phenotypic data sets.…”

Analyzing Fluctuating Asymmetry with Geometric Morphometrics: Concepts, Methods, and Applications

“…Therefore, the test can be conducted by obtaining the distribution of RV coefficients for a large number of alternative partitions of the landmarks into subsets of the same sizes as the modules in the hypothesis [170]. This method of comparing a measure of association among alternative partitions can be used for fluctuating asymmetry as well as for individual variation, and a growing number of studies have applied it to both levels [67,72,74,75,82,97,101,106,170,172,174].…”

Post Natal Cranial Areas of Evolution in the Small African Pangolin (Phataginus Tricuspis) Ontogeny From Three Geo-Ecologies – A First Report: Asymmetry, Elliptical Fourier Analyses and Modularity

“…The present investigation is to the better of our knowledge a first post natal developmental investigation on the skull of the small African Pangolin. Calvarias development aims at achieving a symmetric paired structure (Elliot, 2010), deviations from this 'target' morphology could result from individual or population developmental stress/noise (ecologic input) (Urbanova et al, 2014) and can be useful in making inferences about such biological processes since morphological asymmetry may provide information on a variety of biological mechanisms (Polak, 2003). There is lack of documented evidence on the development of the skull in this species, thus making accurate taxonomic classification and discrimination among similar extant species conjectural especially for trafficked Pangolin.…”