Centrum growth patterns provide evidence for two small taxa of Hiodontidae in the Cretaceous Dinosaur Park Formation
Bibliographic record
Abstract
Disarticulated centra recovered from the Campanian Dinosaur Park Formation (Cretaceous) are used to describe hiodontid age, growth, and longevity. Previous studies of Cretaceous centrum morphology have shown only one morphotype. However, growth characteristics can be used to test the one-taxon hypothesis. Age and growth characteristics indicate that Cretaceous hiodontids were shorter-lived (i.e., 7 years) and significantly smaller than extant Hiodon. The fossil centra also exhibit two significantly different growth patterns. Initially it was predicted that two factors could explain the presence of the two growth patterns: (1) sexual size dimorphism, and (2) variation in centrum size from multiple species. Sexual size dimorphism did not produce the two growth patterns because (1) H. alosoides maximum total length is significantly correlated with temperature, and (2) the paleotemperature in the depositional environment fluctuated approximately 6 °C mean annual temperature resulting in continuous growth variation. Concerning the second factor, the coefficient of variation (CV) observed in the Cretaceous centrum size data (0.23 CV) is 22% greater than that of the two extant species of Hiodon combined (0.18 CV) suggesting that at least two species of hiodontids were present in the Dinosaur Park Formation. The distribution of sizes of the smaller Cretaceous centra is not different from one extant species but is significantly different from two species suggesting that three taxa were not present.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".