TY - JOUR
T1 - Evaluating extinct pseudosuchian body mass estimates using a femur volume-based model
AU - Woodward, Holly N.
AU - Aubier, Paul
AU - de Sena, Mariana Valéria Araújo
AU - Cubo, Jorge
N1 - Publisher Copyright:
© 2024 American Association for Anatomy.
PY - 2025/2
Y1 - 2025/2
N2 - The clade Pseudosuchia appeared 250 million years ago. The exclusively semi-aquatic Crocodylia, which includes crocodiles, alligators, caimans, and gharials is the only surviving subgroup. Investigating Crocodylia biology is pivotal for inferring traits of extinct pseudosuchians. Alligator femur length is widely used for modeling pseudosuchian body mass, but the regression is influenced by sex and captivity status, leading to potential accuracy problems. An alternative model results from the correlation between alligator femur volume and body mass, which is unaffected by those covariates. Here, an alligator femur volume-based regression is applied to estimate the masses of non-crocodylian pseudosuchians, encompassing goniopholids, dyrosaurs, notosuchians, and thalattosuchians. For each, femur volume as the predictor yields lower body masses than does femur length. Morphological resemblances to existing crocodylians support the inference that extinct goniopholids and dyrosaurs were semi-aquatic. Therefore, body masses predicted from femur length and volume should be reasonable, although larger body masses obtained from femur length may reflect sensitivity to sex or environmental factors. Fully terrestrial notosuchians had proportionately longer femora for their body sizes compared to semi-aquatic crocodylians, suggesting that the higher body masses predicted from alligator femur length are overestimates. Fully aquatic thalattosuchians, skeletally adapted for buoyancy and with reduced reliance on the femur for locomotion, pose challenges for both femur length and volume-based models. The results of this study advocate for the use of femur volume to predict body mass, particularly for semi-aquatic and terrestrial pseudosuchians, and encourage further exploration of volumetric models as body size predictors for extinct vertebrates.
AB - The clade Pseudosuchia appeared 250 million years ago. The exclusively semi-aquatic Crocodylia, which includes crocodiles, alligators, caimans, and gharials is the only surviving subgroup. Investigating Crocodylia biology is pivotal for inferring traits of extinct pseudosuchians. Alligator femur length is widely used for modeling pseudosuchian body mass, but the regression is influenced by sex and captivity status, leading to potential accuracy problems. An alternative model results from the correlation between alligator femur volume and body mass, which is unaffected by those covariates. Here, an alligator femur volume-based regression is applied to estimate the masses of non-crocodylian pseudosuchians, encompassing goniopholids, dyrosaurs, notosuchians, and thalattosuchians. For each, femur volume as the predictor yields lower body masses than does femur length. Morphological resemblances to existing crocodylians support the inference that extinct goniopholids and dyrosaurs were semi-aquatic. Therefore, body masses predicted from femur length and volume should be reasonable, although larger body masses obtained from femur length may reflect sensitivity to sex or environmental factors. Fully terrestrial notosuchians had proportionately longer femora for their body sizes compared to semi-aquatic crocodylians, suggesting that the higher body masses predicted from alligator femur length are overestimates. Fully aquatic thalattosuchians, skeletally adapted for buoyancy and with reduced reliance on the femur for locomotion, pose challenges for both femur length and volume-based models. The results of this study advocate for the use of femur volume to predict body mass, particularly for semi-aquatic and terrestrial pseudosuchians, and encourage further exploration of volumetric models as body size predictors for extinct vertebrates.
KW - Pseudosuchia
KW - alligator
KW - body mass
KW - crocodylian
KW - femur
UR - http://www.scopus.com/inward/record.url?scp=85191006868&partnerID=8YFLogxK
U2 - 10.1002/ar.25452
DO - 10.1002/ar.25452
M3 - Article
C2 - 38634509
AN - SCOPUS:85191006868
SN - 1932-8486
VL - 308
SP - 257
EP - 265
JO - Anatomical Record
JF - Anatomical Record
IS - 2
ER -