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The development of the skull of the Egyptian cobra Naja h. haje (Squamata: Serpentes: Elapidae)

Khannoon, ER; Evans, SE; (2015) The development of the skull of the Egyptian cobra Naja h. haje (Squamata: Serpentes: Elapidae). PLoS One , 10 (4) 10.1371/journal.pone.0122185. Green open access

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Abstract

Background: The study of craniofacial development is important in understanding the ontogenetic processes behind morphological diversity. A complete morphological description of the embryonic skull development of the Egyptian cobra, Naja h. haje, is lacking and there has been little comparative discussion of skull development either among elapid snakes or between them and other snakes. Methodology/Principal Findings: We present a description of skull development through a full sequence of developmental stages of the Egyptian cobra, and compare it to other snakes. Associated soft tissues of the head are noted where relevant. The first visible ossification centres are in the supratemporal, prearticular and surangular, with slight ossification visible in parts of the maxilla, prefrontal, and dentary. Epiotic centres of ossification are present in the supraoccipital, and the body of the supraoccipital forms from the tectum posterior not the tectum synoticum. The venom glands are visible as distinct bodies as early at stage 5 and enlarge later to extend from the otic capsule to the maxilla level with the anterior margin of the eye. The gland becomes more prominent shortly before hatching, concomitant with the development of the fangs. The tongue shows incipient forking at stage 5, and becomes fully bifid at stage 6. Conclusions/significance: We present the first detailed staging series of cranial development for the Egyptian cobra, Naja h. haje. This is one of the first studies since the classical works of G. de Beer and W. Parker that provides a detailed description of cranial development in an advanced snake species. It allows us to correct errors and misinterpretations in previous accounts which were based on a small sample of specimens of uncertain age. Our results highlight potentially significant variation in supraoccipital formation among squamates and the need for further research in this area.

Type: Article
Title: The development of the skull of the Egyptian cobra Naja h. haje (Squamata: Serpentes: Elapidae)
Open access status: An open access version is available from UCL Discovery
DOI: 10.1371/journal.pone.0122185
Publisher version: http://dx.doi.org/10.1371/journal.pone.0122185
Language: English
Additional information: © 2015 Khannoon, Evans. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited http://creativecommons.org/licenses/by/4.0/
Keywords: Embryology, snake, cobra
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences > Div of Biosciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences > Div of Biosciences > Cell and Developmental Biology
URI: https://discovery.ucl.ac.uk/id/eprint/1463449
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