Data and code from: A new Mongolian tyrannosauroid and the evolution of Eutyrannosauria
Bibliographic record
Abstract
Eutyrannosauria were the large apex predators that dominated Asian and North American terrestrial faunas in the latest Cretaceous. These predators arose from smaller-bodied tyrannosauroid ancestors during the “middle” Cretaceous, which are poorly known due to the paucity of fossil material. Here we report on a new tyrannosauroid, Khankhuuluu mongoliensis gen. et sp. nov., from lower Upper Cretaceous deposits of Mongolia that provides a new perspective on eutyrannosaurian origins and evolution. A phylogenetic analysis recovers Khankhuuluu as the species closest to Eutyrannosauria and uniquely recovers the massive, deep-snouted Tyrannosaurini and the smaller, gracile, shallow-snouted Alioramini as highly derived sister clades. Khankhuuluu and Alioramini independently share features related to a shallow skull and gracile build with juvenile eutyrannosaurians, reinforcing the key role heterochrony played in eutyrannosaurian evolution. Within a Eutyrannosauria influenced by peramorphosis or accelerated growth, Alioramini is revealed as a derived lineage that retained immature features via paedomorphosis and is not a more basal lineage as long and widely accepted. Our analyses novelly reveal Eutyrannosauria originated and remained exclusively in North America until their first and only dispersal to Asia in the latest Cretaceous, where the lineage of Alioramini + Tyrannosaurini evolved. Stark morphological differences between Alioramini and Tyrannosaurini likely evolved due to divergent heterochronic trends, paedomorphosis vs. peramorphosis, respectively, allowing these sister clades to coexist in Asia and occupy different ecological niches.
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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 | 0.004 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.003 | 0.003 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.002 | 0.001 |
| Open science | 0.001 | 0.002 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.245 | 0.118 |
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".