Complex Sensory Corpuscles in the Upper Jaw of Horsfield’s Tortoise (Testudo horsfieldii)

Buchtová, Marcela; Páč, Libor; Knotek, Z.; Tichý, František

doi:10.2754/avb200978020193

Cited by 7 publications

(4 citation statements)

References 21 publications

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“…However, the platypus bill is not highly keratinized compared to the beak of a turtle. The Horsfield's Tortoise is provided with sensory corpuscles probably functioning as mechanoreceptors for monitoring the movement of the keratinized ridges and the most rostral part of the upper jaw (Buchtová, Páč, Knotek, & Tichý, ) and numerous sauropsids possess sensory nerve endings in the snout region penetrating the horny scales of the skin (Düring, , ; Düring & Miller, ). In birds, the beak in innervated by a branch of the trigeminal nerve (Rehkämper, Frahm, & Mann, ).…”

Section: Discussionmentioning

confidence: 99%

Evidence for convergent evolution of a neocortex‐like structure in a late Permian therapsid

Laaß

Kaestner

2017

Journal of Morphology

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The special sensory, motor, and cognitive capabilities of mammals mainly depend upon the neocortex, which is the six-layered cover of the mammalian forebrain. The origin of the neocortex is still controversial and the current view is that larger brains with neocortex first evolved in late Triassic Mammaliaformes. Here, we report the earliest evidence of a structure analogous to the mammalian neocortex in a forerunner of mammals, the fossorial anomodont Kawingasaurus fossilis from the late Permian of Tanzania. The endocranial cavity of Kawingasaurus is almost completely ossified, which allowed a less hypothetical virtual reconstruction of the brain endocast to be generated. A parietal foramen is absent. A small pit between the cerebral hemispheres is interpreted as a pineal body. The inflated cerebral hemispheres are demarcated from each other by a median sulcus and by a possible rhinal fissure from the rest of the endocast. The encephalization quotient estimated by using the method of Eisenberg is 0.52, which is 2-3 times larger than in other nonmammalian synapsids. Another remarkable feature are the extremely ramified infraorbital canals in the snout. The shape of the brain endocast, the extremely ramified maxillary canals as well as the small frontally placed eyes suggest that special sensory adaptations to the subterranean habitat such as a well developed sense of touch and binocular vision may have driven the parallel evolution of an equivalent of the mammalian neocortex and a mammal-like lemnothalamic visual system in Kawingasaurus. The gross anatomy of the brain endocast of Kawingasaurus supports the Outgroup Hypothesis, according to which the neocortex evolved from the dorsal pallium of an amphibian-like ancestor, which receives sensory projections from the lemnothalamic pathway. The enlarged brain as well as the absence of a parietal foramen may be an indication for a higher metabolic rate of Kawingasaurus compared to other nonmammalian synapsids.

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Section: Discussionmentioning

confidence: 99%

Evidence for convergent evolution of a neocortex‐like structure in a late Permian therapsid

Laaß

Kaestner

2017

Journal of Morphology

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“…Similarly, different types of cutaneous sensory receptors have been described within scales bordering the toes of gecko lizards [68]. Less attention has been given to the integumentary sensory system of tortoises, except for the description of dermal sensory corpuscles in the facial skin of the Russian tortoise [19]. In addition, the identification of only a few thermo-sensitive nerve fibers in the reptilian skin [69] might be explained by the presence of more specialized highly sensitive thermoreceptor organs, including the pineal gland of the brain in all non-archosaurian reptiles [70], as well as the infrared-sensitive pit organs located on each side of the face between the nostril and the eye in vipers [21], and on labial scales in some pythons and boas [16,71].…”

Section: Discussionmentioning

confidence: 99%

Crocodylians evolved scattered multi-sensory micro-organs

Di‐Poï

Milinkovitch

2013

EvoDevo

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BackgroundDuring their evolution towards a complete life cycle on land, stem reptiles developed both an impermeable multi-layered keratinized epidermis and skin appendages (scales) providing mechanical, thermal, and chemical protection. Previous studies have demonstrated that, despite the presence of a particularly armored skin, crocodylians have exquisite mechanosensory abilities thanks to the presence of small integumentary sensory organs (ISOs) distributed on postcranial and/or cranial scales.ResultsHere, we analyze and compare the structure, innervation, embryonic morphogenesis and sensory functions of postcranial, cranial, and lingual sensory organs of the Nile crocodile (Crocodylus niloticus) and the spectacled caiman (Caiman crocodilus). Our molecular analyses indicate that sensory neurons of crocodylian ISOs express a large repertoire of transduction channels involved in mechano-, thermo-, and chemosensory functions, and our electrophysiological analyses confirm that each ISO exhibits a combined sensitivity to mechanical, thermal and pH stimuli (but not hyper-osmotic salinity), making them remarkable multi-sensorial micro-organs with no equivalent in the sensory systems of other vertebrate lineages. We also show that ISOs all exhibit similar morphologies and modes of development, despite forming at different stages of scale morphogenesis across the body.ConclusionsThe ancestral vertebrate diffused sensory system of the skin was transformed in the crocodylian lineages into an array of discrete multi-sensory micro-organs innervated by multiple pools of sensory neurons. This discretization of skin sensory expression sites is unique among vertebrates and allowed crocodylians to develop a highly-armored, but very sensitive, skin.

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“…In turtles and birds the osseous edentulous beak is covered by a cornified ramphotheca made of keratin. The ramphothecal tissue is a living structure supplied and innervated by numerous vessels and nerves that ramify inside the osseous beak, opening on its surface and giving a rugose texture to the external surface of maxilla, premaxilla, and palate (Witmer, ; Buchtovà, Pàč, Knotek, & Tichy, ; Hieronymus et al, ). Innervation by the somatosensory fibers of the trigeminal nerve (cranial nerve V, hereafter CNV), confers tactile sensitivity to the beak.…”

Section: Introductionmentioning

confidence: 99%

Evolution of facial innervation in anomodont therapsids (Synapsida): Insights from X‐ray computerized microtomography

Benoît

Angielczyk

Miyamae

et al. 2018

Journal of Morphology

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Anomodontia was the most successful herbivorous clade of the mammalian stem lineage (non-mammalian synapsids) during the late Permian and Early Triassic. Among anomodonts, Dicynodontia stands apart because of the presence of an osseous beak that shows evidence of the insertion of a cornified sheath, the ramphotheca. In this study, fourteen anomodont specimens were microCT-scanned and their trigeminal canals reconstructed digitally to understand the origin and evolution of trigeminal nerve innervation of the ramphotheca. We show that the pattern of innervation of the anomodont "beak" is more similar to that in chelonians (the nasopalatine branch is enlarged and innervates the premaxillary part of the ramphotheca) than in birds (where the nasopalatine and maxillary branches play minor roles). The nasopalatine branch is noticeably enlarged in the beak-less basal anomodont Patranomodon, suggesting that this could be an anomodont or chainosaur synapomorphy. Our analyses suggest that the presence or absence of tusks and postcanine teeth are often accompanied by corresponding variations of the rami innervating the caniniform process and the alveolar region, respectively. The degree of ossification of the canal for the nasal ramus of the ophthalmic branch also appears to correlate with the presence of a nasal boss. The nasopalatine canal is absent from the premaxilla in the Bidentalia as they uniquely show a large plexus formed by the internal nasal branch of the maxillary canal instead. The elongated shape of this plexus in Lystrosaurus supports the hypothesis that the rostrum evolved as an elongation of the subnarial region of the snout. Finally, the atrophied and variable aspect of the trigeminal canals in Myosaurus supports the hypothesis that this genus had a reduced upper ramphotheca.

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Complex Sensory Corpuscles in the Upper Jaw of Horsfield’s Tortoise (Testudo horsfieldii)

Cited by 7 publications

References 21 publications

Evidence for convergent evolution of a neocortex‐like structure in a late Permian therapsid

Evidence for convergent evolution of a neocortex‐like structure in a late Permian therapsid

Crocodylians evolved scattered multi-sensory micro-organs

Evolution of facial innervation in anomodont therapsids (Synapsida): Insights from X‐ray computerized microtomography

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