Skull ontogenetic variation of the coastal developmental stage of the loggerhead turtle (Caretta caretta) in the western South Atlantic Ocean

Lunardon, Eduardo Araujo; Costa-Schmidt, Luiz Ernesto; Lenz, Ana Júlia; Martins, Márcio Borges; Oliveira, Larissa Rosa de

doi:10.1007/s10750-020-04204-2

Cited by 3 publications

(7 citation statements)

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“…Specimens were divided into three age classes that broadly reflect ontogenetic differences: hatchling, intermediate, and adult (Table 1). Individuals were categorised as hatchlings (n = 14) if they exhibited fontanelles and lacked ossified basicranial elements, individuals were categorised as adults (n = 24) if they had a skull length within two standard deviations of the average reported adult skull size for the species (Pritchard and Trebbau 1984;Dodd 1988;Zangerl et al 1988;Nishizawa et al 2010;Lunardon et al 2020). The remaining individuals were categorised as intermediates (n = 25), as they had closed fontanelles and ossified basicranial elements but were two standard deviations smaller than the skull size reported for an adult of that species.…”

Section: Specimensmentioning

confidence: 99%

“…Given the functional roles of the vertebrate skull in food acquisition and processing (Pritchard and Trebbau 1984;Claude et al 2004;Parham and Pyenson 2010;Jones et al 2012), the relationship between turtle skull structure and diet has been previously investigated in sea turtles but generally with a focus on one or two species. Examinations of skull development of Chelonia mydas (green) and Caretta caretta (loggerhead) indicate that dietary shifts are associated with morphological differences between ontogenetic stages (Nishizawa et al 2010;Coelho et al 2018;Lunardon et al 2020). However, the relationship between skull shape and size among extant turtles remains poorly known, which limits our ability to distinguish ontogenetic and phylogenetic shape differences (Jones et al 2012) which could inhibit interpretations of turtle evolution.…”

Section: Introductionmentioning

confidence: 99%

“…aqua. org/ blog/ 2015/ April/ oceans-seven) Matsui 1995, 1997;Kamezaki et al 2003), landmarks (Nishizawa et al 2010;Coelho et al 2018), or both (Lunardon et al 2020). However, most of these studies focused on variation within one species: Ca.…”

Section: Introductionmentioning

confidence: 99%

“…However, most of these studies focused on variation within one species: Ca. caretta (Kamezaki and Matsui 1997;Lunardon et al 2020) or Ch. mydas (Kamezaki and Matsui 1995;Nishizawa et al 2010;Coelho et al 2018).…”

Section: Introductionmentioning

confidence: 99%

“…Although some of these studies use large sample sizes they do not include all stages of ontogeny: a study of Ca. caretta used 80 individuals but none were younger than 10 years old (Lunardon et al 2020), whereas the study of Ch. mydas used 145 individuals all between 3 and 5 years old (Kamezaki and Matsui 1995).…”

Section: Introductionmentioning

confidence: 99%

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Ontogenetic allometry underlies trophic diversity in sea turtles (Chelonioidea)

et al. 2022

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Despite only comprising seven species, extant sea turtles (Cheloniidae and Dermochelyidae) display great ecological diversity, with most species inhabiting a unique dietary niche as adults. This adult diversity is remarkable given that all species share the same dietary niche as juveniles. These ontogenetic shifts in diet, as well as a dramatic increase in body size, make sea turtles an excellent group to examine how morphological diversity arises by allometric processes and life habit specialisation. Using three-dimensional geometric morphometrics, we characterise ontogenetic allometry in the skulls of all seven species and evaluate variation in the context of phylogenetic history and diet. Among the sample, the olive ridley (Lepidochelys olivacea) has a seemingly average sea turtle skull shape and generalised diet, whereas the green (Chelonia mydas) and hawksbill (Eretmochelys imbricata) show different extremes of snout shape associated with their modes of food gathering (grazing vs. grasping, respectively). Our ontogenetic findings corroborate previous suggestions that the skull of the leatherback (Dermochelys coriacea) is paedomorphic, having similar skull proportions to hatchlings of other sea turtle species and retaining a hatchling-like diet of relatively soft bodied organisms. The flatback sea turtle (Natator depressus) shows a similar but less extreme pattern. By contrast, the loggerhead sea turtle (Caretta caretta) shows a peramorphic signal associated with increased jaw muscle volumes that allow predation on hard shelled prey. The Kemp’s ridley (Lepidochelys kempii) has a peramorphic skull shape compared to its sister species the olive ridley, and a diet that includes harder prey items such as crabs. We suggest that diet may be a significant factor in driving skull shape differences among species. Although the small number of species limits statistical power, differences among skull shape, size, and diet are consistent with the hypothesis that shifts in allometric trajectory facilitated diversification in skull shape as observed in an increasing number of vertebrate groups.

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Section: Specimensmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Ontogenetic allometry underlies trophic diversity in sea turtles (Chelonioidea)

et al. 2022

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The topological organization of the turtle cranium is constrained and conserved over long evolutionary timescales

Miller,

Lee,

Abzhanov

et al. 2023

The Anatomical Record

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The cranium of turtles (Testudines) is characterized by the secondary reduction of temporal fenestrae and loss of cranial joints (i.e., characteristics of anapsid, akinetic skulls). Evolution and ontogeny of the turtle cranium are associated with shape changes. Cranial shape variation among Testudines can partially be explained by dietary and functional adaptations (neck retraction), but it is unclear if cranial topology shows similar ecomorphological signal, or if it is decoupled from shape evolution. We assess the topological arrangement of cranial bones (i.e., number, relative positioning, connections), using anatomical network analysis. Non‐shelled stem turtles have similar cranial arrangements to archosauromorph outgroups. Shelled turtles (Testudinata) evolve a unique cranial organization that is associated with bone losses (e.g., supratemporal, lacrimal, ectopterygoid) and an increase in complexity (i.e., densely and highly interconnected skulls with low path lengths between bones), resulting from the closure of skull openings and establishment of unusual connections such as a parietal–pterygoid contact in the secondary braincase. Topological changes evolutionarily predate many shape changes. Topological variation and taxonomic morphospace discrimination among crown turtles are low, indicating that cranial topology may be constrained. Observed variation results from repeated losses of nonintegral bones (i.e., premaxilla, nasal, epipterygoid, quadratojugal), and changes in temporal emarginations and palate construction. We observe only minor ontogenetic changes. Topology is not influenced by diet and habitat, contrasting cranial shape. Our results indicate that turtles have a unique cranial topology among reptiles that is conserved after its initial establishment, and shows that cranial topology and shape have different evolutionary histories.

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A comparative study of cranial osteogenesis in turtles: implications for the diversification of skull morphology

Tokita

Sato

et al. 2021

Zoomorphology

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Skull ontogenetic variation of the coastal developmental stage of the loggerhead turtle (Caretta caretta) in the western South Atlantic Ocean

Cited by 3 publications

References 42 publications

Ontogenetic allometry underlies trophic diversity in sea turtles (Chelonioidea)

Ontogenetic allometry underlies trophic diversity in sea turtles (Chelonioidea)

The topological organization of the turtle cranium is constrained and conserved over long evolutionary timescales

A comparative study of cranial osteogenesis in turtles: implications for the diversification of skull morphology

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