Deep evolutionary diversification of semicircular canals in archosaurs

Bronzati, Mario; Benson, Roger; Evers, Serjoscha; Ezcurra, Martín D.; Cabreira, Sérgio Furtado; Choiniere, Jonah N.; Dollman, Kathleen N.; Paulina‐Carabajal, Ariana; Radermacher, Viktor; Roberto-da-Silva, Lúcio; Sobral, Gabriela; Stocker, Michelle R.; Witmer, Lawrence M.; Langer, Max C.; Nesbitt, Sterling J.

doi:10.1016/j.cub.2021.03.086

Cited by 39 publications

(66 citation statements)

References 80 publications

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“…It is still under debate if, in reptiles, skull dimensions generally have more impact on inner ear size and shape than lifestyle and locomotion or phylogeny, and how all of these factors might interact to shape inner ear evolution across phylogeny and evolutionary time (e.g. Benson et al, 2017;Bronzati et al, 2021;Hanson et al, 2021).…”

Section: Discussionmentioning

confidence: 99%

“…Semicircular canal morphology has previously been associated with habitat, behaviour and locomotion in various vertebrate groups (e.g. Hanson et al, 2021; Neenan et al, 2017; Schwab et al, 2019, 2020; Spoor et al, 2002; see also Bronzati et al, 2021). More limited study has assessed labyrinth changes in an ontogenetic context, but only in a small sample of species, with most focus on mammals.…”

Section: Introductionmentioning

confidence: 97%

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confidence: 99%

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Ontogenetic variation in the crocodylian vestibular system

et al. 2021

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Crocodylians today live in tropical to subtropical environments, occupying mostly shallow waters. Their body size changes drastically during ontogeny, as do their skull dimensions and bite forces, which are associated with changes in prey preferences. Endocranial neurosensory structures have also shown to change ontogenetically, but less is known about the vestibular system of the inner ear. Here we use 30 high‐resolution computed tomography (CT) scans and three‐dimensional geometric morphometrics to investigate the size and shape changes of crocodylian endosseous labyrinths throughout ontogeny, across four stages (hatchling, juvenile, subadult and adult). We find two major patterns of ontogenetic change. First, the labyrinth increases in size during ontogeny, with negative allometry in relation to skull size. Second, labyrinth shape changes significantly, with hatchlings having shorter semicircular canal radii, with thicker diameters and an overall dorsoventrally shorter labyrinth than those of more mature individuals. We argue that the modification of the labyrinth during crocodylian ontogeny is related to constraints imposed by skull growth, due to fundamental changes in the crocodylian braincase during ontogeny (e.g. verticalisation of the basicranium), rather than changes in locomotion, diet, or other biological functions or behaviours.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 97%

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Ontogenetic variation in the crocodylian vestibular system

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“…The elongate but low morphology results in a low aspect ratio of the labyrinth, which could be related to the relatively flat nature of the cranium. This suggests that labyrinth shape in turtles may in part be influenced by spatial constraints imposed by braincase shape (see also [58,59]). Despite their lengths, the ASC and PSC are near straight along most of their extent, and most of the canal curvature is concentrated near the ampullae and the common crus (figure 6c).…”

Section: Craniummentioning

confidence: 99%

A new pelomedusoid turtle,Sahonachelys mailakavava, from the Late Cretaceous of Madagascar provides evidence for convergent evolution of specialized suction feeding among pleurodires

et al. 2021

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The Maevarano Formation in northwestern Madagascar has yielded a series of exceptional fossils over the course of the last three decades that provide important insights into the evolution of insular ecosystems during the latest Cretaceous (Maastrichtian). We here describe a new genus and species of pelomedusoid turtle from this formation, Sahonachelys mailakavava , based on a nearly complete skeleton. A phylogenetic analysis suggests close affinities of Sahonachelys mailakavava with the coeval Madagascan Sokatra antitra . These two taxa are the only known representatives of the newly recognized clade Sahonachelyidae , which is sister to the speciose clade formed by Bothremydidae and Podocnemidoidae . A close relationship with coeval Indian turtles of the clade Kurmademydini is notably absent. A functional assessment suggests that Sahonachelys mailakavava was a specialized suction feeder that preyed upon small-bodied invertebrates and vertebrates. This is a unique feeding strategy among crown pelomedusoids that is convergent upon that documented in numerous other clades of turtles and that highlights the distinct evolutionary pathways taken by Madagascan vertebrates.

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“… 36 ). Currently, it is a matter of debate to what extent the morphology of the semicircular canals is a proxy for certain ecological affinities within Archosauromorpha 37 , 38 . Few endosseous labyrinths of ankylosaur taxa are known, of which all possess relatively short and thick semicircular canals, as seen in the early-diverging ankylosaur Kunbarrasaurus ieversi 14 , the ankylosaurids B. archibaldi 13 , Euoplocephalus tutus 39 (and probably T. teresae 15 ), and the nodosaurid Pawpawsaurus campbelli 40 .…”

Section: Discussionmentioning

confidence: 99%

Neuroanatomy of the nodosaurid Struthiosaurus austriacus (Dinosauria: Thyreophora) supports potential ecological differentiations within Ankylosauria

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Stumpf

Kriwet

et al. 2022

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Nodosauridae is a group of thyreophoran dinosaurs characterized by a collar of prominent osteoderms. In comparison to its sister group, the often club-tailed ankylosaurids, a different lifestyle of nodosaurids could be assumed based on their neuroanatomy and weaponry, e.g., regarding applied defensive strategies. The holotype of the nodosaurid Struthiosaurus austriacus consists of a single partial braincase from the Late Cretaceous of Austria. Since neuroanatomy is considered to be associated with ecological tendencies, we created digital models of the braincase based on micro-CT data. The cranial endocast of S. austriacus generally resembles those of its relatives. A network of vascular canals surrounding the brain cavity further supports special thermoregulatory adaptations within Ankylosauria. The horizontal orientation of the lateral semicircular canal independently confirms previous appraisals of head posture for S. austriacus and, hence, strengthens the usage of the LSC as proxy for habitual head posture in fossil tetrapods. The short anterior and angular lateral semicircular canals, combined with the relatively shortest dinosaurian cochlear duct known so far and the lack of a floccular recess suggest a rather inert lifestyle without the necessity of sophisticated senses for equilibrium and hearing in S. austriacus. These observations agree with an animal that adapted to a comparatively inactive lifestyle with limited social interactions.

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Deep evolutionary diversification of semicircular canals in archosaurs

Cited by 39 publications

References 80 publications

Ontogenetic variation in the crocodylian vestibular system

Ontogenetic variation in the crocodylian vestibular system

A new pelomedusoid turtle,Sahonachelys mailakavava, from the Late Cretaceous of Madagascar provides evidence for convergent evolution of specialized suction feeding among pleurodires

Neuroanatomy of the nodosaurid Struthiosaurus austriacus (Dinosauria: Thyreophora) supports potential ecological differentiations within Ankylosauria

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