Dinosaur intra- & inter-specific variation and growth models
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Ben Creisler
May 12, 2026, 11:23:37 AM (5 days ago) May 12
to DinosaurMa...@googlegroups.com
Ben Creisler
A new paper:
Evan Thomas Saitta (2026)
Are we underfitting dinosaur growth models? Accounting for intra- & inter-specific variation
Cretaceous Research 106426
doi: https://doi.org/10.1016/j.cretres.2026.106426
https://www.sciencedirect.com/science/article/abs/pii/S0195667126001151
Highlights
Dinosaur growth models can underfit observed variation by excluding key factors
Ontogeny-only bias may appear in the analysis and presentation of data itself
Recent work shows growth models can contradict evidence of interspecific variation
Sexual variation is an underappreciated form of dinosaur intraspecific variation
ABSTRACT
Some recent growth models of dinosaurs may be underfit, deemphasizing key sources of biological variation (e.g., sexual or interspecific). This bias can be reflected in methodological approaches (e.g., using line graphs instead of regression, discarding residuals, or relying on ‘cladistic ontograms’). Studying the ontogeny of long-extinct animals is challenging. The fossil record is highly incomplete, and many biological phenomena are driven by multiple factors, such as an organism’s size being influenced by growth/development, sex, nutrition, and normal genetic variation between individuals of a population. Still, fundamentals of data analysis and statistics should be followed so as not to exacerbate these limitations. Beyond uncertainty inherent in fossil datasets (e.g., uncertainty of mass and age estimates), individuals with different idealized growth trajectories in vivo due to sexual and non-sexual variation will die at different points within their lifespan. We should model this data with growth dynamics that are a priori likely, while appreciating uncertainty and natural variation by calculating measures such as confidence and prediction intervals. I discuss several recent case studies of dinosaur growth. These studies might inappropriately model the data, biasing our understanding of dinosaur paleobiology (e.g., overlooking differences between individuals of a population, sexes, or species). Such attempts unrealistically model universally acknowledged biological variation. Conclusions therefore become biased toward predominantly ontogenetic explanations for observed variation between specimens, as in some studies of sauropods, tyrannosaurs, ceratopsians, and pachycephalosaurs. Indeed, dinosaurs such as Centrosaurus likely require additional explanatory variables beyond ontogeny to fully explain differences in horn morphology, likely sexual variation. Failure to account for sexual variation may be a major cause of underfitting growth models in dinosaur paleobiology, in addition to underestimating species richness.
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Evan Thomas Saitta (2026)
Are we underfitting dinosaur growth models? Accounting for intra- & inter-specific variation
Cretaceous Research 106426
doi: https://doi.org/10.1016/j.cretres.2026.106426
https://www.sciencedirect.com/science/article/abs/pii/S0195667126001151
Highlights
Dinosaur growth models can underfit observed variation by excluding key factors
Ontogeny-only bias may appear in the analysis and presentation of data itself
Recent work shows growth models can contradict evidence of interspecific variation
Sexual variation is an underappreciated form of dinosaur intraspecific variation
ABSTRACT
Some recent growth models of dinosaurs may be underfit, deemphasizing key sources of biological variation (e.g., sexual or interspecific). This bias can be reflected in methodological approaches (e.g., using line graphs instead of regression, discarding residuals, or relying on ‘cladistic ontograms’). Studying the ontogeny of long-extinct animals is challenging. The fossil record is highly incomplete, and many biological phenomena are driven by multiple factors, such as an organism’s size being influenced by growth/development, sex, nutrition, and normal genetic variation between individuals of a population. Still, fundamentals of data analysis and statistics should be followed so as not to exacerbate these limitations. Beyond uncertainty inherent in fossil datasets (e.g., uncertainty of mass and age estimates), individuals with different idealized growth trajectories in vivo due to sexual and non-sexual variation will die at different points within their lifespan. We should model this data with growth dynamics that are a priori likely, while appreciating uncertainty and natural variation by calculating measures such as confidence and prediction intervals. I discuss several recent case studies of dinosaur growth. These studies might inappropriately model the data, biasing our understanding of dinosaur paleobiology (e.g., overlooking differences between individuals of a population, sexes, or species). Such attempts unrealistically model universally acknowledged biological variation. Conclusions therefore become biased toward predominantly ontogenetic explanations for observed variation between specimens, as in some studies of sauropods, tyrannosaurs, ceratopsians, and pachycephalosaurs. Indeed, dinosaurs such as Centrosaurus likely require additional explanatory variables beyond ontogeny to fully explain differences in horn morphology, likely sexual variation. Failure to account for sexual variation may be a major cause of underfitting growth models in dinosaur paleobiology, in addition to underestimating species richness.
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