Three dimensional digital reconstruction of the jaw adductor musculature of the extinct marsupial giant<i>Diprotodon optatum</i>

Sharp, Alana C.

doi:10.7717/peerj.514

Cited by 29 publications

(34 citation statements)

References 21 publications

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“…3). The sinuses of the extinct species studied here are located in the frontal bone and extend caudally into the parietals and interparietals, laterally into the squamosal section of the zygomatic arch, dorsally over the endocranial cavity and into the occipitals (Sharp, 2014). The braincase is surrounded by epitympanic sinuses, squamosal sinuses and parietal sinuses separating it from the external surface of the skull.…”

Section: Morphology Of the Endocranial Sinusesmentioning

confidence: 99%

“…The frontal sinuses in Diprotodon are bilaterally symmetrical and relatively simple, divided by two bony septa, one lying in the sagittal plane (dividing the area into left and right parts) and another in the frontal plane (dividing the area into anterior and posterior parts) (Sharp, 2014). These partitions align with the coronal suture between the frontal and parietal bones and the sutural contact between the frontals along the midsagittal plane.…”

Section: Morphology Of the Endocranial Sinusesmentioning

confidence: 99%

“…The extent of the endocranial sinuses in large marsupial crania is truly remarkable, resulting in crania composed of little more than air cells surrounded by thin cranial bone. The most impressive example can be found in the extinct Diprotodon optatum, the largest marsupial known (Sharp, 2014). The sinuses extend throughout the cranium from the frontals into the parietals, dorsally over the brain and into the occipitals.…”

Section: Introductionmentioning

confidence: 99%

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A quantitative comparative analysis of the size of the frontoparietal sinuses and brain in vombatiform marsupials

Sharp¹

2016

MMV

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Sharp, A.C. 2016. A quantitative comparative analysis of the size of the frontoparietal sinuses and brain in vombatiform marsupials. Memoirs of Museum Victoria 74: 331-342.Cranial sinuses result from the resorption and deposition of bone in response to biomechanical stress during a process known as pneumatisation. The morphology of a pneumatic bone represents an optimisation between strength and being light weight. The presence of very large sinuses has been described in a number of extinct marsupial megafauna, the size of which no longer exist in extant marsupials. With advances in digital visualisation, and the discovery of a number of exceptionally preserved fossil crania, a unique opportunity exists to investigate hypotheses regarding the structure and evolution of the atypically voluminous sinuses. Sinus function is difficult to test without first obtaining data on sinus variation within and between species. Therefore, the crania of seven species of extinct and extant vombatiform marsupials were studied using CT scans to provide a volumetric assessment of the endocast and cranial sinuses. Sinus volume strongly correlates with skull size and brain size. In the extinct, large bodied palorchestids and diprotodontids the sinuses expand around the dorsal and lateral parts of the braincase. Brain size scales negatively with skull size in vombatiform marsupials. In large species the brain typically fills less than one quarter of the total volume of the endocranial space, and in very large species, it can be less than 10%. Sinus expansion may have developed in order to increase the surface area for attachment of the temporalis muscle and to lighten the skull. The braincase itself would have provided insufficient surface area for the predicted muscle masses.

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Section: Morphology Of the Endocranial Sinusesmentioning

confidence: 99%

Section: Morphology Of the Endocranial Sinusesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A quantitative comparative analysis of the size of the frontoparietal sinuses and brain in vombatiform marsupials

Sharp¹

2016

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“…; Crompton et al. ; Warburton, ; Sharp, ; Sharp & Trusler, ). The muscles included are masseter superficialis, masseter profundus, zygomaticomandibularis, temporalis superficialis, temporalis profundus, pterygoideus medialis and pterygoideus lateralis.…”

Section: Methodsmentioning

confidence: 99%

“…In the case of Diprotodon , the convex frontoparietal region of the cranium and the associated large sinuses may be a more optimal way to increase the attachment area of the temporalis muscle than would a plate‐like sagittal crest for an animal of such size with a proportionally small braincase (Sharp, ; Sharp, in press). A plate‐like sagittal crest is a common feature among mammals for attachment of the temporalis muscle.…”

Section: Introductionmentioning

confidence: 99%

Cranial biomechanics, bite force and function of the endocranial sinuses in Diprotodon optatum, the largest known marsupial

Sharp

Rich

2016

Journal of Anatomy

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The giant extinct marsupial Diprotodon optatum has unusual skull morphology for an animal of its size, consisting of very thin bone and large cranial sinuses that occupy most of the internal cranial space. The function of these sinuses is unknown as there are no living marsupial analogues. The finite element method was applied to identify areas of high and low stress, and estimate the bite force of Diprotodon to test hypotheses on the function of the extensive cranial sinuses. Detailed three-dimensional models of the cranium, mandible and jaw adductor muscles were produced. In addition, manipulations to the Diprotodon cranial model were performed to investigate changes in skull and sinus structure, including a model with no sinuses (sinuses 'filled' with bone) and a model with a midsagittal crest. Results indicate that the cranial sinuses in Diprotodon significantly lighten the skull while still providing structural support, a high bite force and low stress, indicating the cranium may have been able to withstand higher loads than those generated during feeding. Data from this study support the hypothesis that pneumatisation is driven by biomechanical loads and occurs in areas of low stress. The presence of sinuses is likely to be a byproduct of the separation of the outer surface of the skull from the braincase due to the demands of soft tissue including the brain and the large jaw adductor musculature, especially the temporalis. In very large species, such as Diprotodon, this separation is more pronounced, resulting in extensive cranial sinuses due to a relatively small brain compared with the size of the skull.

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Craniomandibular Variation in Phalangeriform Marsupials: Functional Comparisons with Primates

Clair

Reback

Perry

2018

The Anatomical Record

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Phalangeriform marsupials have often been compared with primates because of similarity in the range of external morphology, ecological niches, and body size between the two radiations. We explore morphological convergence in the masticatory anatomy of strepsirrhine primates and phalangeriforms, through osteological measurements of the mandible and facial skeleton, and through dissection of the masticatory musculature, presenting new data on the arrangement and proportions of jaw adductors in phalangeriforms. Phalangeriforms and primates have a large number of shape differences in mandibular morphology. Despite these differences in shape on phylogenetic lines, dietary groups used to pool species of phalangeriforms and strepsirrhines also differed from each other in a range of shape variables. Notably, the striped possum (Dactylopsila), previously described as convergent with the aye-aye (Daubentonia), shares a number of features of mandibular shape with Daubentonia, and the exudate-feeding sugar-glider, Petaurus, shares shape features with gummivorous strepsirrhines. Petaurus also has long-fibered jaw adductors for its body mass, as would be expected for a species with a requirement for large gape. Phalangeriform species on the frugivore-folivore continuum were less clearly comparable to strepsirrhine species with similar diets. There are a number of significant dietary contrasts in osteological measurements, but in the masticatory muscles phalangeriforms did not meet all expectations based on available dietary data, highlighting the possible complexity of dietary adaptation in phalangeriform folivores. Anat Rec, 301:227-255, 2018. © 2018 Wiley Periodicals, Inc.

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Three dimensional digital reconstruction of the jaw adductor musculature of the extinct marsupial giantDiprotodon optatum

Cited by 29 publications

References 21 publications

A quantitative comparative analysis of the size of the frontoparietal sinuses and brain in vombatiform marsupials

A quantitative comparative analysis of the size of the frontoparietal sinuses and brain in vombatiform marsupials

Cranial biomechanics, bite force and function of the endocranial sinuses in Diprotodon optatum, the largest known marsupial

Craniomandibular Variation in Phalangeriform Marsupials: Functional Comparisons with Primates

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