Braincase anatomy of extant Crocodylia, with new insights into the development and evolution of the neurocranium in crocodylomorphs

Kuzmin, Ivan T.; Boitsova, Elizaveta A.; Gombolevskiy, Victor A.; Mazur, Evgeniia V.; Морозов, С. П.; Сенников, А. Г.; Skutschas, Pavel P.; Sues, Hans‐Dieter

doi:10.1111/joa.13490

Cited by 25 publications

(172 citation statements)

References 97 publications

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“…Sensory systems, however, also undergo significant changes during ontogenetic growth although these have received far less study. In crocodylians, the brain (and thus the brain endocast) becomes anteroposteriorly more elongated from juvenile to more mature individuals (Hu et al, 2020; Jirak & Janacek, 2017), the tubes for the pharyngotympanic and median pharyngeal sinus structures become vertically longer (Dufeau & Witmer, 2015), and the semicircular canals have recently been shown to undergo negative allometric growth in relation to the bony otic capsule (Kuzmin et al, 2021). Thus, it can be hypothesized that most endocranial systems are affected by ontogeny, but much work remains to document and interpret these changes.…”

Section: Introductionmentioning

confidence: 99%

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: Introductionmentioning

confidence: 99%

Ontogenetic variation in the crocodylian vestibular system

et al. 2021

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“…obs. of FMNH 98396; see also Kuzmin et al, 2021) which contrasts with T. rackhami where the quadrates, although highly pneumatic, are not as hollow as those in the aforementioned.…”

Section: Cranial Pneumaticitymentioning

confidence: 85%

“…The term diverticulum (plural, diverticula) is not used in referral to the skeletal pneumatic recess. Like Dufeau & Witmer (2015) and Kuzmin et al (2021), I accept the definition of a pneumatic diverticulum as an air-filled epithelial extension that occupies a recess.…”

Section: Anatomical Terminologymentioning

confidence: 99%

“…Reliable reconstruction for the optic nerves endocast (cranial nerves II) was not possible, however. In crocodylians, the osteological boundaries/ rims for the optic nerve endocast/canal are located anteromedially on the braincase, or more specifically, they are bounded by the anterior processes of the laterosphenoids (Iordansky, 1973;Kuzmin et al, 2021;Lessner & Holliday, 2020;. Cope, 1861, (q) Tomistoma schlegelii (Müller, 1838), and (r) Trilophosuchus rackhami Willis, 1993.…”

Section: Cranial Nerve and Vasculature Endocasts/ Canalsmentioning

confidence: 99%

“…Interspecific variation is another factor in the development of pneumaticity, not only within Crocodylia but Crocodylomorpha in general (Dufeau, 2011;Kuzmin et al, 2021). At present, the palaeoneurology of most extinct crocodylomorphs, including their paratympanic pneumaticity, is understudied.…”

Section: Cranial Pneumaticitymentioning

confidence: 99%

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Neuroanatomy of the mekosuchine crocodylianTrilophosuchus rackhamiWillis, 1993

Ristevski

2022

Journal of Anatomy

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Although our knowledge on crocodylomorph palaeoneurology has experienced considerable growth in recent years, the neuroanatomy of many crocodylomorph taxa has yet to be studied. This is true for Australian taxa, where thus far only two crocodylian crocodylomorphs have had aspects of their neuroanatomy explored. Here, the neuroanatomy of the Australian mekosuchine crocodylian Trilophosuchus rackhami is described for the first time, which significantly increases our understanding on the palaeoneurology of Australian crocodylians. The palaeoneurological description is based on the taxon's holotype specimen (QMF16856), which was subjected to a μCT scan. Because of the exceptional preservation of QMF16856, most neuroanatomical elements could be digitally reconstructed and described in detail. Therefore, the palaeoneurological assessment presented here is hitherto the most in‐depth study of this kind for an extinct Australian crocodylomorph. Trilophosuchus rackhami has a brain endocast with a distinctive morphology that is characterized by an acute dural peak over the hindbrain region. While the overall morphology of the brain endocast is unique to T. rackhami, it does share certain similarities with the notosuchian crocodyliforms Araripesuchus wegeneri and Sebecus icaeorhinus. The endosseous labyrinth displays a morphology that is typical for crocodylians, although a stand‐out feature is the unusually tall common crus. Indeed, the common crus of T. rackhami has one of the greatest height ratios among crocodylomorphs with currently known endosseous labyrinths. The paratympanic pneumatic system of T. rackhami is greatly developed and most similar to those of the extant crocodylians Osteolaemus tetraspis and Paleosuchus palpebrosus. The observations on the neuroanatomy of T. rackhami are also discussed in the context of Crocodylomorpha. The comparative palaeoneurology reinforces previous evaluations that the neuroanatomy of crocodylomorphs is complex and diverse among species, and T. rackhami has a peculiar neuromorphology, particularly among eusuchian crocodyliforms.

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Anatomy and relationships of the early diverging Crocodylomorphs Junggarsuchus sloani and Dibothrosuchus elaphros

Ruebenstahl

Klein²,

et al. 2022

The Anatomical Record

162

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The holotype of Junggarsuchus sloani, from the Shishugou Formation (early Late Jurassic) of Xinjiang, China, consists of a nearly complete skull and the anterior half of an articulated skeleton, including the pectoral girdles, nearly complete forelimbs, vertebral column, and ribs. Here, we describe its anatomy and compare it to other early diverging crocodylomorphs, based in part on CT scans of its skull and that of Dibothrosuchus elaphros from the Early Jurassic of China. Junggarsuchus shares many features with a cursorial assemblage of crocodylomorphs, informally known as "sphenosuchians," whose relationships are poorly understood. However, it also displays several derived crocodyliform features that are not found among most "sphenosuchians." Our phylogenetic analysis corroborates the hypothesis that Junggarsuchus is closer to Crocodyliformes, including living crocodylians, than are Dibothrosuchus and Sphenosuchus, but not as close to crocodyliforms as Almadasuchus and Macelognathus, and that the "Sphenosuchia" are a paraphyletic assemblage. D. elaphros and Sphenosuchus acutus are hypothesized to be more closely related to Crocodyliformes than are the remaining non-crocodyliform crocodylomorphs, which form several smaller groups but are largely unresolved.

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Braincase anatomy of extant Crocodylia, with new insights into the development and evolution of the neurocranium in crocodylomorphs

Cited by 25 publications

References 97 publications

Ontogenetic variation in the crocodylian vestibular system

Ontogenetic variation in the crocodylian vestibular system

Neuroanatomy of the mekosuchine crocodylianTrilophosuchus rackhamiWillis, 1993

Anatomy and relationships of the early diverging Crocodylomorphs Junggarsuchus sloani and Dibothrosuchus elaphros

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