Fig. 7: Predicting telencephalon neuron number from brain mass for Tyrannosaurus rex.
From: Phylogenetically informed predictions outperform predictive equations in real and simulated data
The relationship between telencephalon neuron number and brain mass (both logged) was estimated across a sample of 202 sauropsid species using both ordinary least squares (OLS, green) and phylogenetic generalised least squares (PGLS, orange) regression models. We then predicted the neuron count for T. rex using both model equations (see text, green and orange triangles) as well as phylogenetic inference (blue triangles), assuming the relationship in T. rex aligns with non-avian sauropsids. This was done using two alternative brain size measurements: firstly, if the brain takes up 42% of the braincase (triangle pointing upwards) and secondly, if the brain takes up 31% of the braincase (triangle pointing downwards). Altering the ratio obtains qualitatively similar conclusions, but the inferred values simply ‘slide’ up or down the regression line. The two measures were calculated as an average across 3 different specimens, but results are qualitatively identical when each specimen is considered separately. A separate slope was estimated for avian taxa (grey points, dashed lines).
