Occipital condyle width (OCW) is a highly accurate predictor of body mass in therian mammals

Engelman, Russell K.

doi:10.1186/s12915-021-01224-9

Cited by 14 publications

(27 citation statements)

References 427 publications

(311 reference statements)

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“…Notably, this study also found that although there is a very strong correlation between OCW and body mass, this correlation is not strictly linear even after log transformation; instead showing a log-allometric relationship. The study also found a similar relationship between skull length and body mass in mammals [23]. More specifically, there are several aspects of OCW which make it a strong candidate for estimating body mass in extinct caviomorphs.…”

Section: Introductionsupporting

confidence: 69%

“…Open Sci. 9: 220370 extrapolation as in previous studies [8] and because the residuals of the rodent-specific regressions in Engelman [23] were non-normally distributed.…”

Section: Methodsmentioning

confidence: 85%

“…However, Phoberomys and Josephoartigasia exhibit a condition similar to Dinomys and Hydrochoerus in which the condyles are tall but narrow (similar to rabbits and dipodomyines, though more robust) [23]. Taxa with this kind of condylar morphology form a line parallel to the least fit line for the entire sample, suggesting the error in the body mass estimate is due to differences in condylar shape, rather than differences in allometry, and therefore OCW can still be used to estimate body mass in these taxa if differences in condylar shape are corrected for [23]. Correcting for differences in shape using a correction factor derived from Dinomys and Hydrochoerus produces body mass estimates of 108-127 kg royalsocietypublishing.org/journal/rsos R. Soc.…”

Section: Resultsmentioning

confidence: 99%

“…One of these specimens of D. branickii (CMNH 22121) had an associated body mass of 9.525 kg, helping to constrain mass estimates. The only change to the dataset of Engelman [23] was the values for D. branickii were updated based on remeasurement of CMNH 22121. In Engelman [23], 96 taxa are rodents, a much larger sample than previous studies that attempted to calculate body mass for Phoberomys and Josephoartigasia [8,11,17,18].…”

Section: Methodsmentioning

confidence: 99%

“…ungulates, carnivorans) and thus the model can make predictions of body mass without the need for extrapolation. Here, I use the OCW dataset of Engelman [23] to estimate the body mass of Phoberomys , Josephoartigasia, and several other closely related extinct giant rodents and discuss these estimates within the context of the debate over these animals' body size.…”

Section: Introductionmentioning

confidence: 99%

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Resizing the largest known extinct rodents (Caviomorpha: Dinomyidae, Neoepiblemidae) using occipital condyle width

Engelman

2022

R. Soc. open sci.

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Several extinct chinchilloid rodents in the clades Dinomyidae and Neoepiblemidae grew to sizes much larger than any living rodent species. However, the exact size of these rodents is a matter of controversy, with authors disagreeing due to issues over extrapolation and model selection. Prior estimates for the two largest extinct rodents, Phoberomys pattersoni and Josephoartigasia monesi , range from 230 to 700 kg for P. pattersoni and 350 to 2600 kg for J. monesi . Here, I estimate body mass in large, extinct rodents using occipital condyle width (OCW), a strong predictor of body size in mammals, using a dataset that circumvents many of the issues faced by previous studies of species. Body masses under shape-corrected OCW are much lower than previous studies: 108–200 kg for P. pattersoni and 480 kg for J. monesi . Mass estimates for other rodent taxa ( Neoepiblema , Telicomys , Dinomys ) agree with previous studies. Estimates using skull length, corrected condyle width and head-body length are similar, suggesting estimates of 150 kg for Phoberomys and 480 kg for Josephoartigasia , and that larger estimates of 700 and 1200 kg are unlikely. High estimates in previous studies appear to be due to the unrecognized, nonlinear relationship between certain skeletal measurements (skull size) and body mass.

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Section: Introductionsupporting

confidence: 69%

“…Open Sci. 9: 220370 extrapolation as in previous studies [8] and because the residuals of the rodent-specific regressions in Engelman [23] were non-normally distributed.…”

Section: Methodsmentioning

confidence: 85%

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Resizing the largest known extinct rodents (Caviomorpha: Dinomyidae, Neoepiblemidae) using occipital condyle width

Engelman

2022

R. Soc. open sci.

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Weighing in on miniaturization: New body mass estimates for Triassic eucynodonts and analyses of body size evolution during the cynodont‐mammal transition

Kaiuca,

Martinelli,

Schultz

et al. 2024

The Anatomical Record

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Body size influences most aspects of an animal's biology, consequently, evolutionary diversification is often accompanied by differentiation of body sizes within a lineage. It is accepted that miniaturization, or the evolution of extremely small body sizes, played a key role in the origin and early evolution of different mammalian characters in non‐mammaliaform cynodonts. However, while there are multiple studies on the biomechanical, behavioral, and physiological consequences of smaller sizes, few explore the evolutionary processes that lead to them. Here, we use body mass as a universal size measurement in phylogenetic comparative analyses to explore aspects of body size evolution in Cynodontia, focusing on the cynodont‐mammal transition, and test the miniaturization hypothesis for the origin of Mammaliaformes. We estimated the body masses of 29 species, ranging from Theriocephalia to Mammaliaformes, providing the largest collection of Triassic cynodont body mass estimates that we know of, and used these estimates in analyses of disparity through time and RRphylo. Unexpectedly, our results did not support the miniaturization hypothesis. Even though cynodont body size disparity fell during the Late Triassic, and remained lower than expected under a purely Brownian motion model of evolution up until the Early Jurassic, we found that rates of body size evolution were significantly lower in prozostrodontians leading to the first Mammaliaformes than in other lineages. Evolution rates were higher in medium and large‐sized taxa, indicating that size was changing more rapidly in those lineages and that small sizes were probably a persistent plesiomorphic character‐state in Cynodontia.

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Covariation in the Craniocervical Junction of Carnivora

Böhmer,

Ocak

2024

Journal of Morphology

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The craniocervical junction is the transition between the skull and the vertebral column that provides mobility while maintaining sufficient stability (i.e., protection of the brainstem and the spinal cord). The key elements involved are the occiput, the first cervical vertebra (CV1, atlas) and the second cervical vertebra (CV2, axis). The two vertebrae forming the atlas‐axis complex are distinct in their morphology and differences in form have been linked to differences in ecological function in mammals. Here, we quantified the morphological diversity of the cranium, CV1 and CV2 in a sample of Carnivora using 3D geometric morphometrics to reveal phylogenetic and ecological patterns. Our results indicate that the observed variation in CV2 is related to the taxonomic diversity (i.e., strong phylogenetic signal), whereas variation in CV1 appears to be decoupled from species diversity in Carnivora and, thus, is likely to reflect a functional signal. The phylogenetically informed correlation analyses showed an association between the CV1 morphology and diet. Taxa that primarily feed on large prey tend to have larger transverse processes on CV1 which provides larger muscle attachment areas and may correlate with stronger muscles. The latter needs to be verified by future quantitative covariation analyses between bone and muscle data. Morphological peculiarities within Pinnipedia and Mustelidae could be explained by differences in terrestrial locomotion between Phocidae and Otariidae and the exceptional defensive behavior (i.e., handstanding) in Mephitidae. Despite differences in the degree of morphological diversity, covariation between cranium, CV1 and CV2 morphology is consistently high (≥ 0.82) highlighting that overall, the craniocervical junction is an integrated structure, but there are traits that are not constrained.

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Occipital condyle width (OCW) is a highly accurate predictor of body mass in therian mammals

Cited by 14 publications

References 427 publications

Resizing the largest known extinct rodents (Caviomorpha: Dinomyidae, Neoepiblemidae) using occipital condyle width

Resizing the largest known extinct rodents (Caviomorpha: Dinomyidae, Neoepiblemidae) using occipital condyle width

Weighing in on miniaturization: New body mass estimates for Triassic eucynodonts and analyses of body size evolution during the cynodont‐mammal transition

Covariation in the Craniocervical Junction of Carnivora

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