The evolution of the meatal chamber in crocodyliforms

Montefeltro, Felipe C.; Andrade, Denis V.; Larsson, Hans C. E.

doi:10.1111/joa.12439

Cited by 61 publications

(79 citation statements)

References 149 publications

(449 reference statements)

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“…Upon entering the middle-ear space, the stapedial artery bifurcates into a dorsal branch, the temporoorbital artery, and a medial branch, the caudal auricular artery (Figs 4 and 6). The caudal auricular artery supplies a mass of erectile tissue and a plexus that ramifies across the ventral aspect of the squamosal (Sedlmayr, 2002;Montefeltro et al 2016), often leaving a series of grooves and foramina in the squamosal (Figs 2,4,(6)(7)(8).…”

Section: Stapedial Arterymentioning

confidence: 99%

Vascular patterns in the heads of crocodilians: blood vessels and sites of thermal exchange

2016

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Extant crocodilians are a highly apomorphic archosaur clade that is ectothermic, yet often achieve large body sizes that can be subject to higher heat loads. Therefore, the anatomical and physiological roles that blood vessels play in crocodilian thermoregulation need further investigation to better understand how crocodilians establish and maintain cephalic temperatures and regulate neurosensory tissue temperatures during basking and normal activities. The cephalic vascular anatomy of extant crocodilians, particularly American alligator (Alligator mississippiensis) was investigated using a differential-contrast, dual-vascular injection technique and high resolution X-ray micro-computed tomography (μCT). Blood vessels were digitally isolated to create representations of vascular pathways. The specimens were then dissected to confirm CT results. Sites of thermal exchange, consisting of the oral, nasal, and orbital regions, were given special attention due to their role in evaporative cooling and cephalic thermoregulation in other diapsids. Blood vessels to and from sites of thermal exchange were studied to detect conserved vascular patterns and to assess their ability to deliver cooled blood to neurosensory tissues. Within the orbital region, both the arteries and veins demonstrated consistent branching patterns, with the supraorbital, infraorbital, and ophthalmotemporal vessels supplying and draining the orbit. The venous drainage of the orbital region showed connections to the dural sinuses via the orbital veins and cavernous sinus. The palatal region demonstrated a vast plexus that comprised both arteries and veins. The most direct route of venous drainage of the palatal plexus was through the palatomaxillary veins, essentially bypassing neurosensory tissues. Anastomotic connections with the nasal region, however, may provide an alternative route for palatal venous blood to reach neurosensory tissues. The nasal region in crocodilians is probably the most prominent site of thermal exchange, as it offers a substantial surface area and is completely surrounded by blood vessels. The venous drainage routes from the nasal region offer routes directly to the dural venous sinuses and the orbit, offering evidence of the potential to directly affect neurosensory tissue temperatures. The evolutionary history of crocodilians is complex, with large-bodied, terrestrial, and possibly endothermic taxa that may have had to deal with thermal loads that likely provided the anatomical building-blocks for such an extensive vascularization of sites of thermal exchange. A clear understanding of the physiological abilities and the role of blood vessels in the thermoregulation of crocodilians neurosensory tissues is not available but vascular anatomical patterns of crocodilian sites of thermal exchange indicate possible physiological abilities that may be more sophisticated than in other extant diapsids.

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Section: Stapedial Arterymentioning

confidence: 99%

Vascular patterns in the heads of crocodilians: blood vessels and sites of thermal exchange

2016

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“…): a longitudinal depression on the rostral portion of frontal; frontal longitudinal ridge extending rostrally beyond the frontal midlength; supratemporal fenestra with equally developed medial and rostral rims; lacrimal duct positioned at the angular junction between the dorsal and lateral surfaces of the lacrimal; well‐developed rounded foramen between the anterior and posterior palpebrals; quadratojugal and jugal do not form a continuous ventral border (a notch is present due to the ventral displacement of the quadratojugal); four subtympanic foramina ( sensu Montefeltro et al . ) visible laterally; a single ventral parachoanal fenestra and one ventral parachoanal fossa (divided into medial and lateral parachoanal subfossae); lateral Eustachian foramina larger than the medial one; a deep depression on the caudodorsal surface of the pterygoid wings; complete absence of postcranial osteoderms.…”

Section: Systematic Palaeontologymentioning

confidence: 99%

Evidence for heterochrony in the cranial evolution of fossil crocodyliforms

et al. 2018

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The southern supercontinent of Gondwana was home to an extraordinary diversity of stem-crocodylians (Crocodyliformes) during the Late Cretaceous. The remarkable morphological disparity of notosuchian crocodyliforms indicates that this group filled a wide range of ecological roles more frequently occupied by other vertebrates. Among notosuchians, the distinctive cranial morphology and large body sizes of Baurusuchidae suggest a role as apex predators in ecosystems in which the otherwise dominant predatory theropod dinosaurs were scarce. Large-bodied crocodyliforms, modern and extinct, are known to have reached large sizes by extending their growth period. In a similar way, peramorphic heterochronic processes may have driven the evolution of the similarly large baurusuchids. To assess the presence of peramorphic processes in the cranial evolution of baurusuchids, we applied a geometric morphometric approach to investigate ontogenetic cranial shape variation in a comprehensive sample of notosuchians. Our results provide quantitative morphological evidence that peramorphic processes influenced the cranial evolution of baurusuchids. After applying size and ancestral ontogenetic allometry corrections to our data, we found no support for the action of either hypermorphosis or acceleration, indicating that these two processes alone cannot explain the shape variation observed in Notosuchia. Nevertheless, the strong link between cranial shape variation and size increase in baurusuchids suggests that peramorphic processes were involved in the emergence of hypercarnivory in these animals. Our findings illustrate the role of heterochrony as a macroevolutionary driver, and stress, once more, the usefulness of geometric morphometric techniques for identifying heterochronic processes behind evolutionary trends.

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“…Terrestrisuchus, Dibothrosuchus, Junggarsuchus, Almadasuchus, Macelognathus), and in some of them the connection with the middle ear cavity was confirmed (Leardi, Pol & Clark, 2017). As it was observed with the peculiar shape of the otic aperture, the lack of a subtympanic foramen (sensu Montefeltro, Andrade & Larsson, 2016) and an associated infundibular diverticulum is common to most thalattosuchians (e.g. S.…”

Section: Manuscript To Be Reviewedmentioning

confidence: 85%

Peer Review #1 of "Braincase and endocranial anatomy of two thalattosuchian crocodylomorphs and their relevance in understanding their adaptations to the marine environment (v0.1)"

Walsh¹

2018

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Thalattosuchians are a group of Mesozoic crocodylomorphs known from aquatic deposits of the Early Jurassic-Early Cretaceous that comprises two main lineages of almost exclusively marine forms, Teleosauridae and Metriorhynchoidea. Teleosaurids were found in shallow marine, brackish and freshwater deposits, and have been characterized as semiaquatic near-shore forms, whereas metriorhynchids are a lineage of fully pelagic forms, supported by a large set of morphological characters of the skull and postcranial anatomy. Recent contributions on Thalattosuchia have been focused on the study of the endocranial anatomy. This newly available information provides novel evidence to suggest adaptations on the neuroanatomy, senses organs, vasculature, and behavioral evolution of these crocodylomorphs. However, is still not clear if the major morphological differences between teleosaurids and metriorhynchids were also mirrored by changes in the braincase and endocranial anatomy. Based on X-ray CT scanning and digital endocast reconstructions we describe the braincase and endocranial anatomy of two well-preserved specimens of Thalattosuchia, the semiaquatic teleosaurid Steneosaurus bollensis and the pelagic metriorhynchid Cricosaurus araucanensis. We propose that some morphological traits, such as: an enlarged foramen for the internal carotid artery, a carotid foramen ventral to the occipital condyle, a single CN XII foramen, absence of brain flexures, welldeveloped cephalic vascular system, lack of subtympanic foramina and the reduction of the paratympanic sinus system, are distinctive features of Thalattosuchia. It has been previously suggested that the enlarged foramen for the internal carotid artery, the absence of brain flexures, and the hypertrophied cephalic vascular system were synapomorphies of Metriorhynchidae; however, new information revealed that all of these features were already established at the base of Thalattosuchia and might have been exapted later on their evolutionary history. Also, we recognized some differences within

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The evolution of the meatal chamber in crocodyliforms

Cited by 61 publications

References 149 publications

Vascular patterns in the heads of crocodilians: blood vessels and sites of thermal exchange

Vascular patterns in the heads of crocodilians: blood vessels and sites of thermal exchange

Evidence for heterochrony in the cranial evolution of fossil crocodyliforms

Peer Review #1 of "Braincase and endocranial anatomy of two thalattosuchian crocodylomorphs and their relevance in understanding their adaptations to the marine environment (v0.1)"

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