Abstract:The limbless skink Ophiomorus punctatissimus is a cryptozoic species found in the Peloponnese region of Greece and on the Greek island Kythira. To provide the first thorough description of the cranial and postcranial osteology of this species, both disarticulated specimens and X‐ray computed tomographies of wet‐preserved specimens were examined in detail. Resulting from this, an anatomical atlas of this species is provided. Two separate considerations, an evolutionary and an ecomorphological one, are made base… Show more
“…These conclusions have been validated by recent studies (e.g. Da Silva et al, 2018;Camaiti et al, 2019;Macaluso et al, 2019) linking the evolution of limb loss to the adaptation to complex three-dimensional environments such as underground burrows and crevices. Whereas these studies have been instrumental in incorporating ecological and functional constraints as main factors in the acquisition of serpentiform body shapes, they have been disproportionately focused on their implications with regard to the evolution of limbless squamates instead of intermediate limb-reduced body shapes.…”
Section: (C) Hox Genes Shh and Fgfsupporting
confidence: 57%
“…For instance, species that appear externally convergent in body shape might prove quite different in their internal anatomies. Furthermore, even for limbless or severely limb-reduced species, reduced or vestigial structures of limb bones and girdles can inform on how limbs and associated parts have regressed through evolution (see Miralles et al, 2015;Camaiti et al, 2019). These internal patterns, primarily represented by differential degrees of development of modules of limbs and girdles, can prove an invaluable tool to reconstruct the evolutionary pathways that led to independent events of body-shape transformation.…”
Elongated snake-like bodies associated with limb reduction have evolved multiple times throughout vertebrate history. Limb-reduced squamates (lizards and snakes) account for the vast majority of these morphological transformations, and thus have great potential for revealing macroevolutionary transitions and modes of body-shape transformation. Here we present a comprehensive review on limb reduction, in which we examine and discuss research on these dramatic morphological transitions. Historically, there have been several approaches to the study of squamate limb reduction: (i) definitions of general anatomical principles of snake-like body shapes, expressed as varying relationships between body parts and morphometric measurements; (ii) framing of limb reduction from an evolutionary perspective using morphological comparisons; (iii) defining developmental mechanisms involved in the ontogeny of limb-reduced forms, and their genetic basis; (iv) reconstructions of the evolutionary history of limb-reduced lineages using phylogenetic comparative methods; (v) studies of functional and biomechanical aspects of limb-reduced body shapes; and (vi) studies of ecological and biogeographical correlates of limb reduction. For each of these approaches, we highlight their importance in advancing our understanding, as well as their weaknesses and limitations. Lastly, we provide suggestions to stimulate further studies, in which we underscore the necessity of widening the scope of analyses, and of bringing together different perspectives in order to understand better these morphological transitions and their evolution. In particular, we emphasise the importance of investigating and comparing the internal morphology of limb-reduced lizards in contrast to external morphology, which will be the first step in gaining a deeper insight into body-shape variation.
“…These conclusions have been validated by recent studies (e.g. Da Silva et al, 2018;Camaiti et al, 2019;Macaluso et al, 2019) linking the evolution of limb loss to the adaptation to complex three-dimensional environments such as underground burrows and crevices. Whereas these studies have been instrumental in incorporating ecological and functional constraints as main factors in the acquisition of serpentiform body shapes, they have been disproportionately focused on their implications with regard to the evolution of limbless squamates instead of intermediate limb-reduced body shapes.…”
Section: (C) Hox Genes Shh and Fgfsupporting
confidence: 57%
“…For instance, species that appear externally convergent in body shape might prove quite different in their internal anatomies. Furthermore, even for limbless or severely limb-reduced species, reduced or vestigial structures of limb bones and girdles can inform on how limbs and associated parts have regressed through evolution (see Miralles et al, 2015;Camaiti et al, 2019). These internal patterns, primarily represented by differential degrees of development of modules of limbs and girdles, can prove an invaluable tool to reconstruct the evolutionary pathways that led to independent events of body-shape transformation.…”
Elongated snake-like bodies associated with limb reduction have evolved multiple times throughout vertebrate history. Limb-reduced squamates (lizards and snakes) account for the vast majority of these morphological transformations, and thus have great potential for revealing macroevolutionary transitions and modes of body-shape transformation. Here we present a comprehensive review on limb reduction, in which we examine and discuss research on these dramatic morphological transitions. Historically, there have been several approaches to the study of squamate limb reduction: (i) definitions of general anatomical principles of snake-like body shapes, expressed as varying relationships between body parts and morphometric measurements; (ii) framing of limb reduction from an evolutionary perspective using morphological comparisons; (iii) defining developmental mechanisms involved in the ontogeny of limb-reduced forms, and their genetic basis; (iv) reconstructions of the evolutionary history of limb-reduced lineages using phylogenetic comparative methods; (v) studies of functional and biomechanical aspects of limb-reduced body shapes; and (vi) studies of ecological and biogeographical correlates of limb reduction. For each of these approaches, we highlight their importance in advancing our understanding, as well as their weaknesses and limitations. Lastly, we provide suggestions to stimulate further studies, in which we underscore the necessity of widening the scope of analyses, and of bringing together different perspectives in order to understand better these morphological transitions and their evolution. In particular, we emphasise the importance of investigating and comparing the internal morphology of limb-reduced lizards in contrast to external morphology, which will be the first step in gaining a deeper insight into body-shape variation.
“…In order to obtain limb measurements for limb‐reduced pygopodid species, we used micro‐CT (Computed Tomography) scanning and VG Studio Max software v3.3 (https://www.volumegraphics.com/en/products/vgstudio-max.html) to visualize the internal morphology of these species and infer fore and hind limb positioning. The locations of the pectoral and pelvic girdles were identified and used to locate the vertebrae associated with the fore limb and hind limb (Camaiti et al., 2019; Stanley et al., 2016). Snout–axilla length (SAL) and inter‐limb length (ILL) were measured using the polyline digital measuring tool.…”
Aim
Climatic variation has long been regarded as a primary source of morphological variation. However, there is mixed support for the adherence of reptiles to ecogeographical hypotheses, such as Bergmann’s rule (body size decreases with temperature) and Allen’s rule (limb length increases with temperature). We quantified body and limb morphology among the diverse Australian gecko fauna (4 families, 30 genera, 226 of the 231 described species) to investigate environmental correlates of morphological variation in this radiation.
Location
Australia.
Major taxa studied
Geckos (Squamata: Gekkota; the families Gekkonidae, Carphodactylidae, Diplodactylidae and Pygopodidae).
Methods
We measured 20 external features of ethanol‐preserved museum specimens. We investigated whether principal component axes of morphology were correlated with three key environmental variables, and the microhabitat occupied by each species.
Results
Morphology varied greatly among Australian gecko families and genera, although there was a strong phylogenetic signal in morphology. After accounting for phylogeny, morphology was correlated with a species’ microhabitat use. Saxicolous species and species with variable microhabitat requirements (i.e., generalists) had larger body dimensions than terrestrial species. Saxicolous species also had longer proportional forelimbs and hindlimbs than terrestrial species.
Main conclusions
Our results highlight the importance of phylogeny and microhabitat use in shaping the morphology of Australian geckos. We find little evidence that Australian geckos adhere to Bergmann’s rule or Allen’s rule, suggesting that these ecogeographical hypotheses provide limited insight into the adaptive potential of lizard species to altered environmental conditions.
“…Whereas the typical skink has four well-developed limbs, limb reduction and loss are common, with numerous independent events of limb reduction estimated in the group [ 34 , 35 ], including multiple times within some genera [ 36 , 37 ]. Limb reduction is typically correlated with a fossorial lifestyle and accompanied by a suite of other adaptations [ 38 , 39 ]. Despite this diversity, cranial descriptions of the group are few, with only ~ 250 species (~ 16% of the family) having osteological descriptions for complete skulls and/or individual disarticulated bones [ 11 ].…”
Section: Introductionmentioning
confidence: 99%
“… Fig. 1 A Multi-locus squamate phylogeny [ 39 ] trimmed to show species in this study. Species names are colored by substrate.…”
Background
Skulls serve many functions and as a result, are subject to many different evolutionary pressures. In squamates, many fossorial species occupy a unique region of skull morphospace, showing convergence across families, due to modifications related to head-first burrowing. As different substrates have variable physical properties, particular skull shapes may offer selective advantages in certain substrates. Despite this, studies of variation within burrowers have been limited and are typically focused on a single origin of fossoriality. We focused on seven skink genera (Acontias, Typhlosaurus, Scelotes, Sepsina, Feylinia, Typhlacontias, and Mochlus; 39 sp.) from southern Africa, encompassing at least three independent evolutions of semi-fossoriality/fossoriality. We used microCT scans and geometric morphometrics to test how cranial and mandibular shape were influenced by phylogenetic history, size, and ecology. We also qualitatively described the skulls of four species to look at variation across phylogenetic and functional levels, and assess the degree of convergence.
Results
We found a strong effect of phylogenetic history on cranial and mandibular shape, with size and substrate playing secondary roles. There was a clear gradient in morphospace from less specialized to more specialized burrowers and burrowers in sand were significantly different from those in other substrates. We also created an anatomical atlas for four species with each element described in isolation. Every bone showed some variation in shape and relative scaling of features, with the skull roofing bones, septomaxilla, vomer, and palatine showing the most variation. We showed how broad-scale convergence in traits related to fossoriality can be the result of different anatomical changes.
Conclusions
Our study used geometric morphometrics and comparative anatomy to examine how skull morphology changes for a highly specialized and demanding lifestyle. Although there was broad convergence in both shape and qualitative traits, phylogenetic history played a large role and much of this convergence was produced by different anatomical changes, implying different developmental pathways or lineage-specific constraints. Even within a single family, adaptation for a specialized ecology does not follow a singular deterministic path.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
