Ichnological evidence for small quadrupedal ornithischians from the basal Cretaceous of SE Asia and North America: implications for a global radiation
Bibliographic record
Abstract
Abstract Tracks of small quadrupedal ornithischians with five manual and four pedal digits have been recorded from sedimentary rocks near the Late Jurassic–Early Cretaceous (Tithonian–Berriasian) boundary in NE Thailand and British Columbia. These are compared with larger tracks of gracile, quadrupedal ornithopods from the earliest Cretaceous of Spain and smaller tracks of a quadruped of unknown age from Zimbabwe. The Thai and Canadian tracks are similar to the Early Jurassic (Liassic) ichnogenus Anomoepus and the small ornithopod tracks from the Late Jurassic of Spain. They are the only known post-Liassic ornithischian tracks in which up to five discrete manus digit impressions are clearly visible. Based on strong heteropody (manus much smaller than pes) in all cases we infer an ornithopod trackmaker rather than another ornithischian. The scattered, but widespread earliest Cretaceous occurrence of this ichnotaxon, herein assigned to Neoanomoepus perigrinatus ichnogen. and ichnosp. nov., on the basis of type material from Canada, suggests that these hitherto unknown earliest Cretaceous ichnofaunas may represent a radiation of small basal ornithopods (pes length less than 15 cm), appearing before the widespread radiation of large ornithopods (pes length up to 60 cm or more) later in the Neocomian (Valanginian–Barremian), Aptian–Albian and Late Cretaceous. The primitive condition of the trackmaker is indicated by the pedal and manual morphology, which consists of four and five digits respectively that are not enclosed by well-developed fleshy padding or integument. In contrast, all larger Cretaceous ornithopod tracks, mostly from post-Berriasian strata, have only three pedal digits enclosed in fleshy pads and a manus in which all functional digits are reduced and enclosed by substantial flesh.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 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".