Life History and Skeletal Adaptations in the Galapagos Marine Iguana (<i>Amblyrhynchus cristatus</i>) as Reconstructed with Bone Histological Data—A Comparative Study of Iguanines

Hugi, Jasmina; Sánchez‐Villagra, Marcelo R.

doi:10.1670/11-071

Cited by 43 publications

(39 citation statements)

References 43 publications

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“…As already mentioned by Muizon et al [15], marine iguanas may be considered as featuring an ecology putatively close to that of Thalassocnus. Such claim is now also supported by bone microstructural data, as marine iguanas also display bones that are relatively more compact than those of their terrestrial close relatives [35]. Because none of the Thalassocnus bones examined contained any remnant of calcified cartilage, endochondral osteogenesis is interpreted as normal: the hypertrophic cartilage produced by the growth plates at the epiphyseal level was entirely eroded by chondroclasts in the metaphysis and replaced by endosteal trabeculae made of lamellar bone tissue.…”

Section: Resultsmentioning

confidence: 81%

Gradual adaptation of bone structure to aquatic lifestyle in extinct sloths from Peru

et al. 2014

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Non-pathological densification (osteosclerosis) and swelling ( pachyostosis) of bones are the main modifications affecting the skeleton of land vertebrates (tetrapods) that returned to water. However, a precise temporal calibration of the acquisition of such adaptations is still wanting. Here, we assess the timing of such acquisition using the aquatic sloth Thalassocnus, from the Neogene of the Pisco Formation, Peru. This genus is represented by five species occurring in successive vertebrate-bearing horizons of distinct ages. It yields the most detailed data about the gradual acquisition of aquatic adaptations among tetrapods, in displaying increasing osteosclerosis and pachyostosis through time. Such modifications, reflecting a shift in the habitat from terrestrial to aquatic, occurred over a short geological time span (ca 4 Myr). Otherwise, the bones of terrestrial pilosans (sloths and anteaters) are much more compact than the mean mammalian condition, which suggests that the osteosclerosis of Thalassocnus may represent an exaptation.

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Section: Resultsmentioning

confidence: 81%

Gradual adaptation of bone structure to aquatic lifestyle in extinct sloths from Peru

et al. 2014

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“…The sampled specimen of Heloderma has the highest BV/TV value and both sprawling postures seem to be used depending on the individuals. Amblyrhynchus has a high BV/TV value (0.27), which might be associated with the high compactness values especially found in its fore limb (Hugi & Sánchez‐Villagra, ). A higher compactness in fore limb bones counteracts lung buoyancy and facilitates diving and long‐lasting underwater stays (de Ricqlès & de Buffrénil, ; Hugi & Sánchez‐Villagra, ).…”

Section: Discussionmentioning

confidence: 99%

Trabecular architecture in the humeral metaphyses of non‐avian reptiles (Crocodylia, Squamata and Testudines): Lifestyle, allometry and phylogeny

Plasse

Amson

Bardin

et al. 2019

Journal of Morphology

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The lifestyle of extinct tetrapods is often difficult to assess when clear morphological adaptations such as swimming paddles are absent. According to the hypothesis of bone functional adaptation, the architecture of trabecular bone adapts sensitively to physiological loadings. Previous studies have already shown a clear relation between trabecular architecture and locomotor behavior, mainly in mammals and birds. However, a link between trabecular architecture and lifestyle has rarely been examined. Here, we analyzed trabecular architecture of different clades of reptiles characterized by a wide range of lifestyles (aquatic, amphibious, generalist terrestrial, fossorial, and climbing). Humeri of squamates, turtles, and crocodylians have been scanned with microcomputed tomography. We selected spherical volumes of interest centered in the proximal metaphyses and measured trabecular spacing, thickness and number, degree of anisotropy, average branch length, bone volume fraction, bone surface density, and connectivity density. Only bone volume fraction showed a significant phylogenetic signal and its significant difference between squamates and other reptiles could be linked to their physiologies. We found negative allometric relationships for trabecular thickness and spacing, positive allometries for connectivity density and trabecular number and no dependence with size for degree of anisotropy and bone volume fraction. The different lifestyles are well separated in the morphological space using linear discriminant analyses, but a cross‐validation procedure indicated a limited predictive ability of the model. The trabecular bone anisotropy has shown a gradient in turtles and in squamates: higher values in amphibious than terrestrial taxa. These allometric scalings, previously emphasized in mammals and birds, seem to be valid for all amniotes. Discriminant analysis has offered, to some extent, a distinction of lifestyles, which however remains difficult to strictly discriminate. Trabecular architecture seems to be a promising tool to infer lifestyle of extinct tetrapods, especially those involved in the terrestrialization.

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“…Among modern vertebrates, once sexual maturity is reached, animals experience a distinctive change in their growth dynamics, which is reflected in the slower/changed rate at which bone deposition occurs. This phenomenon has been well studied in many extant lizards (e.g., Castanet et al, 1993;Hugi and Sánchez-Villagra, 2012), in the primate, Microcebus murinus, , as well as in the extant kiwi (Bourdon et al, 2009). In most birds, however, the situation appears to be more complex: Castanet et al (1996) found that the switch to the more slowly formed bone tissue that makes up the OCL begins to be deposited in juvenile ducks well before sexual maturity.…”

Section: Methodsmentioning

confidence: 96%

Osteohistology and Life History of the Basal Pygostylian, Confuciusornis sanctus

Chinsamy

Marugán‐Lobón

Serrano

et al. 2019

The Anatomical Record

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More than a thousand specimens of Confuciusornis sanctus have been recovered from the Early Cretaceous Jehol Group of Northeastern China. Here, we investigate the bone microstructure of 33 long bones sampled from 14 C. sanctus specimens in an attempt to assess the life history patterns of this basal pygostylian bird. Analysis of the histology of various skeletal elements (femur, humerus, tibia, radius, and ulna) revealed differences in the histology of their bone walls. Based on the osteohistology, we coded the examined specimens into five histology age classes. We found that histological age was not strictly correlated with body size. The variability in the histology of multiple bones from single skeletons suggests differences in the growth rate of the skeleton in response to allometry, functional demands, and pathology. We show that although fibrolamellar bone is widespread across birds, the extent and duration of this rapid phase of bone deposition is highly variable. Comparisons among Mesozoic birds confirm that early ontogenetic growth was rapid, but that later post‐hatching growth was strongly influenced by the ontogenetic age of the individual, body size, and local environment, as well as taxonomy. Our findings indicate that C. sanctus experienced rapid growth from early ontogeny until almost fully grown, and thereafter transitioned to slow, episodic growth (for at least 3–4 years) to reach skeletal maturity. Anat Rec, 303:949–962, 2020. © 2019 American Association for Anatomy

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Life History and Skeletal Adaptations in the Galapagos Marine Iguana (Amblyrhynchus cristatus) as Reconstructed with Bone Histological Data—A Comparative Study of Iguanines

Cited by 43 publications

References 43 publications

Gradual adaptation of bone structure to aquatic lifestyle in extinct sloths from Peru

Gradual adaptation of bone structure to aquatic lifestyle in extinct sloths from Peru

Trabecular architecture in the humeral metaphyses of non‐avian reptiles (Crocodylia, Squamata and Testudines): Lifestyle, allometry and phylogeny

Osteohistology and Life History of the Basal Pygostylian, Confuciusornis sanctus

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