Zur embryonalen Kopfentwicklung von Crocodylus cataphractus Cuv

Müller, Felix

doi:10.5962/bhl.part.75851

Cited by 35 publications

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“…In L. agilis , the acrochordal persists during ontogeny and represents the crista sellaris of the chondrocranium (Yaryhin, ), which later in ontogeny represents the dorsum sella in the ossified basisphenoid (Rieppel and Zaher, ). The same condition was reported for turtles and crocodiles (Müller, ; Kuratani, ; Tulenko and Sheil, ).…”

supporting

confidence: 71%

“…Those methodological differences would result in complicated phylogenetic interpretations, which would infer incorrect evolutionary transformations (see text for discussion). ( D ) Hypothesis after Tulenko and Sheil (), Trachemys scripta : Testudines, and Müller (), Mecistops (“ Crocodylus “) caraphractus , Crocodylia, and inferred in our study: Trabecles, parachordals, and acrochordal form separately (I); posteriorly the parachordals are fused to form the basal plate and anteriorly they fuse with the acrochordal; the trabecles are fused anteriorly and fuse with the acrochordal posteriorly (II); in that way, crista sellaris and the basicranial fenestra are formed (III). ( E ) Hypothesis after El‐Toubi and Kamal (), Chalchides ocelatus , Scincidae: Trabecles and basal plate form separately, no separate parachordals are formed (I); trabecles are fused anteriorly and fuse with the basal plate (II); the basicranial fenestra forms by degeneration in the anterior part of the basal plate (III); degeneration of the basal plate continues and basicranial fenestra growths (IV).…”

mentioning

confidence: 70%

“…C–H), one could reconstruct a complicated phylogenetic history of this skull region. The condition of turtles (Tulenko and Sheil, ) and crocodiles (Müller, ) could serve as ancestral condition (Fig. D).…”

Section: Discussionmentioning

confidence: 99%

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Chondrification and Character Identification in the Skull Exemplified for the Basicranial Anatomy of Early Squamate Embryos

Yaryhin

Werneburg

2017

J Exp Zool Pt B

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The neurocranium of vertebrates is mainly derived from early cartilaginous anlagen, the so-called chondrocranium, the base of the future skull. Two initial bar-shaped and paired chondrifications flank the notochord, the rostral trabecles and the caudal parachordals. In most reptiles, there is an additional component, the transverse acrochordal, which is placed between trabecles and parachordals. All these elements compose the base of the future chondrocranium. There are several drastically different hypotheses concerning the development and interrelationship of these elements. We reexamined the basicranial development in four squamates and found that all species show very similar conditions of early chondrocranial development. The anterior part of the notochord is not embedded into the basal plate as it was previously reported. It remains free. The medial edges of the parachordals form the lateral walls of the basicranial fenestra. Only the posterior portions of the parachordals fuse and form the basal plate. The space in-between the parachordals is filled with a thin layer of cells, which never chondrify. The anterior tips of the parachordals later fuse with the posterior edge of the acrochordal, which ultimately delimitates, as crista sellaris, the basicranial fenestra anteriorly. We consider the observed processes a common development at least in lizards and review a variety of methodological approaches and differences in data interpretation as reasons for the anatomical differences reported in the literature. Moreover, based on our data we argue that the acrochordal is of mesodermal origin, which coincides with results of fate map experimental studies.

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confidence: 71%

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confidence: 70%

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Chondrification and Character Identification in the Skull Exemplified for the Basicranial Anatomy of Early Squamate Embryos

Yaryhin

Werneburg

2017

J Exp Zool Pt B

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“…Note that the “laterosphenoidal region” of this specimen is more similar to the laterosphenoid of P. quenstedti (Figure b,d) than the latter is to that of C. porosus (see i and Figure ). (h) Chondrocranium of the crocodile Mecistops cataphractus after Müller () (also reproduced by Bellairs & Kamal, ). Note the large differences to the chondrocranial shape of C. porosus (i and Figure ).…”

Section: Introductionmentioning

confidence: 88%

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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“…There are descriptions of its appearance as a result of resorption of the basal plate (initially unpaired structure; Bäckström, ; Chekanovskaya, ; Kamal & Hammouda, , , ; El‐Toubi & Kamal, , , Kamal, ). According to some authors, it initially appears as an independent unpaired structure (Kamal & Abdeen, ; Kuratani, ; Müller, ; Tulenko & Sheil, ; Yaryhin, ). The data collected by de Beer () and Parker () stand out from many descriptions of this structure's formation in Squamata.…”

Section: Introductionmentioning

confidence: 99%

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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Zur embryonalen Kopfentwicklung von Crocodylus cataphractus Cuv

Cited by 35 publications

References 0 publications

Chondrification and Character Identification in the Skull Exemplified for the Basicranial Anatomy of Early Squamate Embryos

Chondrification and Character Identification in the Skull Exemplified for the Basicranial Anatomy of Early Squamate Embryos

Character definition and tempus optimum in comparative chondrocranial research

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

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