Evaluating extinct pseudosuchian body mass estimates using a femur volume-based model

Area of Science:

• Paleontology
• Comparative Anatomy
• Vertebrate Biology

Background:

• Pseudosuchia, an ancient reptile group, includes the only surviving subgroup, Crocodylia.
• Studying Crocodylia biology aids in understanding extinct pseudosuchian traits.
• Alligator femur length is a common but potentially inaccurate proxy for pseudosuchian body mass due to sex and captivity influences.

Purpose of the Study:

• To investigate the efficacy of alligator femur volume as a predictor of body mass for extinct pseudosuchians.
• To compare body mass estimations derived from femur length versus femur volume for various pseudosuchian subgroups.
• To refine methods for reconstructing the biology and ecology of extinct reptiles.

Main Methods:

• Developed a regression model correlating alligator femur volume with body mass, independent of sex and captivity.
• Applied this volume-based regression to estimate body masses of extinct pseudosuchians (goniopholids, dyrosaurs, notosuchians, thalattosuchians).
• Compared results with estimations derived from traditional femur length-based regressions.

Main Results:

• Femur volume consistently yielded lower body mass estimates than femur length across studied pseudosuchian groups.
• Semi-aquatic goniopholids and dyrosaurs showed reasonable mass estimates from both methods, with volume potentially more accurate.
• Terrestrial notosuchians' longer femora suggested femur length overestimates their mass, supporting the volume-based model.
• Fully aquatic thalattosuchians presented challenges for both models due to adaptations for buoyancy.

Conclusions:

• Femur volume is a more reliable predictor of body mass for semi-aquatic and terrestrial extinct pseudosuchians.
• Volumetric models offer improved accuracy by mitigating biases associated with sex and environmental factors.
• Further research into volumetric approaches is recommended for reconstructing body size in extinct vertebrates.