Cranial anatomy and stratigraphy of a new specimen of Daspletosaurus from the Judith River Formation of Central Montana
Bibliographic record
Abstract
The tyrannosaurine Daspletosaurus contains three recognized species from the Campanian of Montana and Alberta: Daspletosaurus torosus, Daspletosaurus wilsoni, and Daspletosaurus horneri. The recently named D. wilsoni has been proposed to represent a transitional anagenetic form between D. torosus and D. horneri, a hypothesis contingent on both the stratigraphic succession of these three taxa and the presence of an intermediate morphology in D. wilsoni. Adequate testing of this hypothesis is hampered by limited knowledge of the morphological variation and stratigraphic ranges of both D. wilsoni and D. torosus. We introduce a new, ontogenetically mature specimen of Daspletosaurus from the upper Campanian Coal Ridge Member of the Judith River Formation of central Montana that is well constrained to ~76.3–75.8 Ma. This specimen has a combination of features not yet reported in Daspletosaurus, increasing the known range of morphological disparity within this genus. The cranial morphology and stratigraphic position of this specimen precludes its referral to D. horneri. Although stratigraphically equivalent to D. wilsoni, this specimen lacks one of the three characters purported to distinguish that taxon from D. torosus (dorsal quadrate process of quadratojugal broadly visible laterally). We propose that this character is intraspecifically variable within Daspletosaurus and therefore not diagnostic, thus weakening the case that D. wilsoni is distinct from D. torosus. Additional specimens with stratigraphic controls are necessary to determine if D. wilsoni is a valid taxon.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".