Polar cartilages and formation of Crista sellaris in grass snake, natrix natrix (Ophidia, Colubridae), chondrocranium at the early stages of embryogenesis

Sheverdyukova, H. V.

doi:10.2478/v10058-012-0038-5

Cited by 2 publications

(4 citation statements)

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“…In contrast to other authors, Parker () observed the formation of the transverse bar (crista sellaris) in N. natrix as a result of the fusion of processes extending from the confluence of the trabeculae and parachordals (which is analogous to the description of de Beer in L. agilis ). According to our data (Sheverdyukova, ), the crista sellaris in N. natrix is formed in a way similar to that described by Parker (). The only difference is that the merging processes would derive not from the place where the parachordials and cranial trabeculae confluence, but from the polar cartilages.…”

Section: Discussionsupporting

confidence: 84%

“…Sheverdyukova () described the formation of the transverse bar (crista sellaris) at successive developmental stages in N. natrix (Linnaeus, 1758) (Colubridae) embryogenesis in detail. Its formation is similar to that described by Parker () in N. natrix and de Beer () in L. agilis .…”

Section: Introductionmentioning

confidence: 99%

“…Despite the long history of studying the formation of the basic structures of the reptilian chondrocranium, the contrasting descriptions of the formation of the transverse bar (acrochordal cartilage or crista sellaris) cause doubts and continued interest (Yaryhin & Werneburg, 2017) and therefore research on the development of the transverse bar does not lose its relevance. Sheverdyukova (2012) described the formation of the transverse bar (crista sellaris) at successive developmental stages in N. natrix (Linnaeus, 1758) (Colubridae) embryogenesis in detail. Its formation is similar to that described by Parker (1878) in N. natrix and de Beer (1930) in L. agilis.…”

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confidence: 99%

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Variation in the formation of crista sellaris and basisphenoid in the skull of the grass snake Natrix natrix embryos (Serpentes, Colubridae)

Sheverdyukova

Kovtun

2020

Journal of Morphology

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The crista sellaris is one of the basic structures of the snake chondrocranium. In embryogenesis it ossifies, forming the basisphenoid. This article describes variations of the crista sellaris, which, in turn, leads to variation in the formation of the basisphenoid in the skull of grass snake Natrix natrix (Serpentes, Colubridae) embryos. Several embryos at different developmental stages are investigated. Embryos from one developmental stage are taken simultaneously from one clutch. Thus, variation of the crista sellaris and basisphenoid in the skull of embryos is discovered, including those from one clutch. In several embryos, the crista sellaris is absent or partially formed. The absence of the crista sellaris does not preclude the formation of the basisphenoid. Based on the observed variations of the crista sellaris, the basisphenoid may have a different origin. In embryos with formed crista sellaris, the basisphenoid develops as a complex endochondral bone from three ossification centers (paired—in the polar cartilages and unpaired in the crista sellaris). In embryos without fully formed crista sellaris the basisphenoid develops as a paired bone of mixed origin: endochondral ossification appears in the polar cartilages, but where the crista sellaris is absent, it is formed by dermal ossification. In general, we observed the absence of the crista sellaris in 15% of studied embryos. We assume that it may be due to a reduction of the orbital‐temporal region of the chondrocranium in N. natrix embryos. Research highlights The variation of the crista sellaris and basisphenoid formation in grass snake embryos is revealed. Depending on the presence or absence of the crista sellaris, basisphenoid is formed as a complex chondral bone or as a paired bone of mixed origin.

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Section: Discussionsupporting

confidence: 84%

Section: Introductionmentioning

confidence: 99%

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confidence: 99%

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Variation in the formation of crista sellaris and basisphenoid in the skull of the grass snake Natrix natrix embryos (Serpentes, Colubridae)

Sheverdyukova

Kovtun

2020

Journal of Morphology

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“…For reptiles, some descriptions exist on phylogenetic “key species” such as the tuatara Sphenodon punctatus (Figure f,g) (Howes & Swinnerton, ; Schauinsland, ; Werner, ) or easily available species such as Grass snake Natrix natrix (Bäckström, ; Chekanovskaya, ; Kovtun & Sheverdyukova, ; Parker, ; Sheverdyukova, ,b) and the Sand lizard Lacerta agilis (de Beer, ; Gaupp, ; Kovtun & Yaryhin, ; Yaryhin, , ; Yaryhin & Klembara, ; Yaryhin & Werneburg, , ). A detailed observation on the variation of basitrabecular process chondrification, for example, resulted in the finding of a unique pattern.…”

Section: Intra‐ and Interspecific Variabilitymentioning

confidence: 99%

Character definition and tempus optimum in comparative chondrocranial research

Werneburg

Yaryhin

2018

Acta Zoologica

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Here, we define a research program using primordial skull characters for broad scale phylogenetic comparisons, particularly for amniotes. There are many chondrocranium descriptions in the literature, encompassing many clades of vertebrates. The definition of a comparable “tempus optimum” for fully formed chondrocrania, as developed herein, will enable discrete character definition in the sense of phylogenetic systematics. The “tempus optimum” is a time period in which the nose region shows full chondrification and the basicranium has not yet changed in its anatomy by ossification processes. For studies on heterochrony, changes in the developmental timing through evolution, the available data in the literature are insufficient. Anatomical standardizations, traceable methodological approaches and clear definitions of comparable developmental stages are needed. Moreover, for profound homology assertions of chondrocranial structures, ontogeny needs to be traced from early mesenchymal condensation, through several stages of cartilage development, up to postnatal stages, in which ossifications are already present. A holistic observation, including hard and soft tissue anatomy, is of paramount importance to generate hypotheses of homology with much explanatory power and to derive conclusions on functional morphology. For that, traditional histological methodology is needed. We exemplify the suggested approach in two case studies on the disputed laterosphenoid in turtles and crocodiles and on the homology of pila antotica in a pleurodire turtle, and, using here defined criteria, we formulate hypotheses on their homology.

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Polar cartilages and formation of Crista sellaris in grass snake, natrix natrix (Ophidia, Colubridae), chondrocranium at the early stages of embryogenesis

Cited by 2 publications

References 3 publications

Variation in the formation of crista sellaris and basisphenoid in the skull of the grass snake Natrix natrix embryos (Serpentes, Colubridae)

Variation in the formation of crista sellaris and basisphenoid in the skull of the grass snake Natrix natrix embryos (Serpentes, Colubridae)

Character definition and tempus optimum in comparative chondrocranial research

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