Supporting CT data for: Ontogenetic changes in endocranial anatomy in <em>Gorgosaurus libratus</em> (Theropoda: Tyrannosauridae) provide insight into the evolution of the tyrannosauroid endocranium
Bibliographic record
Abstract
Over the past two decades, increased accessibility to computed tomographic (CT) scanners has allowed researchers to document the endocranium of numerous extinct theropod taxa. However, most of these studies have focused on the morphology of mature individuals. How endocranial morphology might vary through ontogeny in theropods remains largely unknown. Based on CT scans of braincases, we virtually reconstruct the endocranial morphology for a growth series of the tyrannosaurid Gorgosaurus libratus, including two recently discovered juvenile individuals, and compare it to that of other tyrannosauroids. This study sheds light not only on the ontogenetic changes in endocranial anatomy in a tyrannosaurid but also on the variation in brain morphology among basal coelurosaurs. The endocasts of the smallest Gorgosaurus specimens (~50% adult skull length) exhibit more distinct cerebral hemispheres, optic lobes, and cerebella than do those of larger, more mature specimens. This suggests greater congruence between endocast-to-brain shape among juvenile tyrannosaurids and that their endocasts provide a more accurate representation of the brain than those of adult individuals. The brain morphology of Gorgosaurus is revealed to be intermediate between that of more basal sauropsids (e.g., crocodilians) and derived coelurosaurs (e.g., birds). Plesiomorphic features include large olfactory bulbs and tracts, posteroventrally long axis of the cerebrum, and posterior position optic lobes, whereas derived features include a highly angular brain, somewhat enlarged cerebrum, and a cerebellum that at least partially separates the left and right optic lobes. Future research aiming to establish brain morphology in more basal theropods, such as tyrannosauroids, should consult endocasts of juvenile individuals, as these may more closely reflect the actual brain morphology and could better clarify the nature and timing of changes that led to the evolution of the avian brain.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.007 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.003 | 0.005 |
| Science and technology studies | 0.002 | 0.001 |
| Scholarly communication | 0.002 | 0.002 |
| Open science | 0.002 | 0.002 |
| Research integrity | 0.004 | 0.002 |
| Insufficient payload (model declined to judge) | 0.751 | 0.191 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".