Cranial variation in <i>Gryposaurus</i> and biostratigraphy of hadrosaurines (Ornithischia: Hadrosauridae) from the Dinosaur Park Formation of Alberta, Canada
Bibliographic record
Abstract
The Dinosaur Park Formation (Campanian) of Alberta documents one of the most diverse assemblages of hadrosaurine dinosaurs. Historically, two species of the genus Gryposaurus Lambe, 1914 have been recognized in the Dinosaur Park Formation, Gryposaurus notabilis Lambe, 1914 and Gryposaurus incurvimanus Parks, 1919, which are differentiated primarily on their nasal arch morphology. These two species have recently been suggested to represent either variable morphs within G. notabilis (e.g., ontogeny) or two distinct taxa within an evolving Gryposaurus lineage (e.g., anagenesis). These alternative hypotheses have never been adequately tested via detailed morphological comparisons, morphometrics, or biostratigraphy. A geometric morphometric analysis of hadrosaurine skulls from the Dinosaur Park Formation was performed to assess the influence of ontogeny on skull morphology. Gryposaurus incurvimanus skulls were found to be distinctly smaller, and morphologically divergent from those of G. notabilis, with larger G. notabilis skulls having higher nasal arches set farther back on the skull, a size-correlated pattern consistent with ontogenetic nasal retraction documented in other hadrosaurids. Stratigraphic data were used to map this morphology through time, to evaluate the anagenesis hypothesis. The stratigraphic distributions of the two species showed considerable overlap, rejecting anagensis and indicating that the sampled individuals lived over a short period of time (<0.5 Myr). Overall, our results suggest that the hypothesis that G. incurvimanus and G. notabilis represent different ontogenetic stages within a single species cannot be rejected. This study improves our understanding of the extent of potential individual variation within a single Gryposaurus species, which will be useful in assessing the validity of other hadrosaurines.
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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 | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.002 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
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".