The structure and development of the chondrocranium of <i>Varanus</i>. II. The development of the orbito‐temporal region

Shrivastava, R. K.

doi:10.1002/jmor.1051150107

Cited by 8 publications

(11 citation statements)

References 12 publications

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“…Whereas a detailed description of the chondrocranial development in V. bengalensis was presented by Shrivastava (1963Shrivastava ( , 1964a, dermatocranial development and particularly the progress of ossification were hardly mentioned. Our paper primarily aims to present a source of embryological information which might be useful for future studies with a comparable comprehensive anatomical approach (Polachowski and Werneburg, 2013).…”

Section: G Modelmentioning

confidence: 99%

Bony skull development in the Argus monitor (Squamata, Varanidae, Varanus panoptes) with comments on developmental timing and adult anatomy

Werneburg

Polachowski

Hutchinson

2015

Zoology

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Section: G Modelmentioning

confidence: 99%

Bony skull development in the Argus monitor (Squamata, Varanidae, Varanus panoptes) with comments on developmental timing and adult anatomy

Werneburg

Polachowski

Hutchinson

2015

Zoology

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“…The platybasic condition of the skull of reptile embryos does not indicate that the reptile skull is primitively platybasic, as it was suggested by SHRIVASTAVA (1964). It only suggests that the reptile skull goes through an initial platybasic condition because an ancestral skull (at an undetermined level) also went through an initial platybasic condition during ontogeny (which is different from having a platybasic adult skull): Following the criteria ofoutgroup comparison (KLUGE 1976), early ontogenetic stages of various groups of organisms are compared, and this has no impact on the evaluation of character-states in the adult stages of the same groups of organisms.…”

Section: The Significance Of Successive Ontogenetic Stagesmentioning

confidence: 81%

“…The platybasic condition is observed during the earliest developmental stages of some turtles (Emys: KUNKEL 1912; Chrysemis: SHANER 1926), of crocodiles (Crocodybs: MUEL-LER 1967), of Sphenodon (HOWES and SWINNERTON 1901) and of a few lizards such as Varanus (SHRIVASTAVA, 1964), Ptyodactylus (EL-TOUBI and KAMAL 1961) and Lacerta vivipara (BELLAIRS 1949).…”

Section: The Significance Of Successive Ontogenetic Stagesmentioning

confidence: 99%

Ontogeny and the recognition of primitive character states

Rieppel¹

2009

Journal of Zoological Systematics and Evolutionary Research

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Summary The use of ontogeny has recently been proposed for the evaluation of character‐states in adult organisms as an alternative or an addition to outgroup comparison (Bonde 1977; Nelson 1970). Such a methodology is here rejected on the following grounds: 1. The comparison of ontogenetic stages follows the criteria of outgroup comparison. 2. While similarity of early ontogenetic stages does indicate common ancestry, it does so at an undetermined level. Character analysis among adult organisms has to proceed with respect to the most recent common ancestor, however. 3. The status of ontogenetic features of early developmental stages, whether primitive or advanced, has no impact on the status of adult features derived from these ontogenetic stages. 4. Ontogeny may serve as a test for hypothesized homologies, adding further topological criteria to these features. It does not provide the clue to primitive character‐states on an a priori basis. Zusammenfassung Ontogenetische Entwicklung und die Bestimmung primitiver Merkmalszustände Bonde (1977) und Nelson (1970) schlugen vor, ontogenetische Frühstadien zur Bestimmung von primitiven Zuständen adulter Merkmale innerhalb einer Transformationsserie zu verwenden. Ein Vergleich ontogenetischer Friihstadien mit einem solchen Zweck wird hier abgelehnt. 1. Der Vergleich ontogenetischer Frühstadien erfolgt nach denselben Kriterien wie der Vergleich adulter Merkmale. 2. ähnlichkeiten ontogenetischer Frühstadien verraten den Ursprung der Merkmalsträger von einem gemeinsamen Vorfahren. Doch wird dabei keine Aussage möglich, wie weit dieser gemeinsame Vorfahre in der Genealogie der Merkmalsträger zurückliegt. Beim Merkmalsvergleich innerhalb einer Gruppe von adulten Organismen müssen jedoch primitive oder abgeleitete Merkmale stets im Hinblick auf den letzten gemeinsamen Vorfahren postuliert werden. 3. Wenn ein ontogenetisches Frühstadium eines Merkmales als primitiv oder abgeleitet zu betrachten ist, so bedeutet das nicht, daβ das sich daraus ableitende adulte Merkmal entsprechend zu bewerten ist. 4. Die Ontogenie von Merkmalen kann als Test von postulierten Homologien dienen, indem ontogenetische Stadien weitere Lagekriterien liefern können. Die Ontogenie liefert jedoch nicht a priori den Schlüssel zu primitiven Merkmalen. Résumé Le développement embryologique et la déterminution des caractères primitifs

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“…Both pilae are present in P. apodus in early ontogeny; however, the pila antotica never completely chondrifies, and late in embryogenesis it undergoes reduction. The ontogenetic regression of the pila antotica which takes place in P. apodus, is well documented for other clades of lizards, like gymnophthalmids, 40 skinks, 17,19,41,42 varanids, 43 agamids, 39,44,45 and chamaeleonids, 46,47 too. By extrapolating the developmental traits of the pila accessoria of lacertid lizards [23][24][25][26]48,49 to A. fragilis, the absence of the pila accessoria in the fully formed chondrocranium suggests a complete absence of the pila antotica in this species early in ontogeny.…”

Section: Evolution Of Anguid Chondrocranial Anatomymentioning

confidence: 82%

Limb reduction in squamate reptiles correlates with the reduction of the chondrocranium: A case study on serpentiform anguids

Yaryhin

Klembara

Pichugin

et al. 2021

Developmental Dynamics

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Background: In vertebrates, the skull evolves from a complex network of dermal bones and cartilage-the latter forming the pharyngeal apparatus and the chondrocranium. Squamates are particularly important in this regard as they maintain at least part of the chondrocranium throughout their whole ontogeny until adulthood. Anguid lizards represent a unique group of squamates, which contains limbed and limbless forms and show conspicuous variation of the adult skull. Results: Based on several emboadryonic stages of the limbless lizards Pseudopus apodus and Anguis fragilis, and by comparing with other squamates, we identified and interpreted major differences in chondrocranial anatomy. Among others, the most important differences are in the orbitotemporal region. P. apodus shows a strikingly similar development of this region to other squamates. Unexpectedly, however, A. fragilis differs considerably in the composition of the orbitotemporal region. In addition, A. fragilis retains a paedomorphic state of the nasal region.Conclusions: Taxonomic comparisons indicate that even closely related species with reduced limbs show significant differences in chondrocranial anatomy. The Pearson correlation coefficient suggests strong correlation between chondrocranial reduction and limb reduction. We pose the hypothesis that limb reduction could be associated with the reduction in chondrocrania by means of genetic mechanisms.

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The structure and development of the chondrocranium of Varanus. II. The development of the orbito‐temporal region

Cited by 8 publications

References 12 publications

Bony skull development in the Argus monitor (Squamata, Varanidae, Varanus panoptes) with comments on developmental timing and adult anatomy

Bony skull development in the Argus monitor (Squamata, Varanidae, Varanus panoptes) with comments on developmental timing and adult anatomy

Ontogeny and the recognition of primitive character states

Limb reduction in squamate reptiles correlates with the reduction of the chondrocranium: A case study on serpentiform anguids

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