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

Sheverdyukova, H. V.; Kovtun, M. F.

doi:10.1002/jmor.21102

Cited by 3 publications

(2 citation statements)

References 37 publications

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“…This condition occurs in all observed specimens of A . irregularis (though see Sheverdyukova and Kovtun, 2020 for comments on the highly variable development and morphology of this region in other snakes).…”

Section: Resultsmentioning

confidence: 99%

Insights into skull evolution in fossorial snakes, as revealed by the cranial morphology of Atractaspis irregularis (Serpentes: Colubroidea)

Strong

Palci

2020

Journal of Anatomy

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Comparative osteological analyses of extant organisms provide key insight into major evolutionary transitions and phylogenetic hypotheses. This is especially true for snakes, given their unique morphology relative to other squamates and the persistent controversy regarding their evolutionary origins. However, the osteology of several major snake groups remains undescribed, thus hindering efforts to accurately reconstruct the phylogeny of snakes. One such group is the Atractaspididae, a family of fossorial colubroids. We herein present the first detailed description of the atractaspidid skull, based on fully segmented micro-computed tomography (micro-CT) scans of Atractaspis irregularis. The skull of Atractaspis presents a highly unique morphology influenced by both fossoriality and paedomorphosis. This paedomorphosis is especially evident in the jaws, palate, and suspensorium, the major elements associated with macrostomy (large-gaped feeding in snakes). Comparison to scolecophidians-a group of blind, fossorial, miniaturized snakes-in turn sheds light on current hypotheses of snake phylogeny. Features of both the naso-frontal joint and the morphofunctional system related to macrostomy refute the traditional notion that scolecophidians are fundamentally different from alethinophidians (all other extant snakes). Instead, these features support the controversial hypothesis of scolecophidians as "regressed alethinophidians," in contrast to their traditional placement as the earliest-diverging snake lineage. We propose that Atractaspis and scolecophidians fall along a morphological continuum, characterized by differing degrees of paedomorphosis. Altogether, a combination of heterochrony and miniaturization provides a mechanism for the derivation of the scolecophidian skull from an ancestral fossorial alethinophidian morphotype, exemplified by the nonminiaturized and less extreme paedomorph Atractaspis.

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Section: Resultsmentioning

confidence: 99%

Insights into skull evolution in fossorial snakes, as revealed by the cranial morphology of Atractaspis irregularis (Serpentes: Colubroidea)

Strong

Palci

2020

Journal of Anatomy

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“…The atractaspidine basisphenoid is also devoid of a dorsum sellae (Strong et al, 2020 ; present study), as well as Scolecophidia (Chretien et al, 2019 ; Rieppel et al, 2009 ) and some fossorial basal alethninophidians (Olori & Bell, 2012 ; Rieppel, 1979 ; Rieppel & Maisano, 2007 ). Nevertheless, it should be noted that this character can be somewhat variable (Sheverdyukova & Kovtun, 2020 ; Strong et al, 2020 ) and not all burrowers lack a dorsum sellae.…”

Section: Discussionmentioning

confidence: 99%

Cranial osteology of Hypoptophis (Aparallactinae: Atractaspididae: Caenophidia), with a discussion on the evolution of its fossorial adaptations

Das

Brecko

Pauwels

et al. 2022

Journal of Morphology

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Fossoriality evolved early in snakes, and has left its signature on the cranial morphology of many extinct Mesozoic and early Caenozoic forms. Knowledge of the cranial osteology of extant snakes is indispensable for associating the crania of extinct lineages with a particular mode of life; this applies to fossorial taxa as well. In the present work, we provide a detailed description of the cranium of Hypoptophis wilsonii, a member of the subfamily Aparallactinae, using micro‐computed tomography (CT). This is also the first thorough micro‐CT‐based description of any snake assigned to this African subfamily of predominantly mildly venomous, fossorial, and elusive snakes. The cranium of Hypoptophis is adapted for a fossorial lifestyle, with increased consolidation of skull bones. Aparallactines show a tendency toward reduction of maxillary length by bringing the rear fangs forward. This development attains its pinnacle in the sister subfamily Atractaspidinae, in which the rear fang has become the “front fang” by a loss of the part of the maxilla lying ahead of the fang. These dentitional changes likely reflect adaptation to subdue prey in snug burrows. An endocast of the inner ear of Hypoptophis shows that this genus has the inner ear typical of fossorial snakes, with a large, globular sacculus. A phylogenetic analysis based on morphology recovers Hypoptophis as a sister taxon to Aparallactus. We also discuss the implications of our observations on the burrowing origin hypothesis of snakes.

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Embryonic development and cranial ossification of the Japanese Aodaishō, Elaphe climacophora (Serpentes: Colubridae): with special reference to the prootic bone and auditory evolution in snakes

Nojiri,

Werneburg,

Sakai

et al. 2024

The Anatomical Record

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Snakes show remarkably deviated “body plan” from other squamate reptiles. In addition to limb loss, they have accomplished enormous anatomical specialization of the skull associated with the pit organs and the reduction of the tympanic membranes and auditory canals in the outer ears. Despite being the most diverse group of snakes, our knowledge of the embryonic staging for organogenesis and cranial ossification has been minimal for Colubridae. Therefore, in the present observation, we provide the first embryonic description of the Japanese rat snake Elaphe climacophora. We based our study on the Standard Event System (SES) for external anatomical characters and on a description of the cranial ossification during post‐ovipositional development. We further estimated the relative ossification timing of each cranial bony element and compared it with that of selected other snakes, lizards, turtles, and crocodilians. The present study shows that the relative ossification timing of the palatine and pterygoid bones is relatively early in squamates when compared to other reptiles, implying the developmental integration as the palate–pterygoid complex in this clade and functional demands for the unique feeding adaptation to swallow large prey with the help of their large palatine and pterygoid teeth. Furthermore, unlike in species with pit organs, the prootic bone of Ela. climacophora is expanded to provide articulation with the supratemporal, thereby contributing to the hearing system by detecting substrate vibration. We also demonstrate that the relative timing of the prootic ossification is significantly accelerated in colubrids compared to snakes with pit organs. Our finding suggests that the temporal changes of the prootic ossification underpin the evolution of the perception of the ground‐bourne sound signals among snakes.

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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)

Cited by 3 publications

References 37 publications

Insights into skull evolution in fossorial snakes, as revealed by the cranial morphology of Atractaspis irregularis (Serpentes: Colubroidea)

Insights into skull evolution in fossorial snakes, as revealed by the cranial morphology of Atractaspis irregularis (Serpentes: Colubroidea)

Cranial osteology of Hypoptophis (Aparallactinae: Atractaspididae: Caenophidia), with a discussion on the evolution of its fossorial adaptations

Embryonic development and cranial ossification of the Japanese Aodaishō, Elaphe climacophora (Serpentes: Colubridae): with special reference to the prootic bone and auditory evolution in snakes

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