New biogeochemical insights into Mesozoic terrestrial paleoecology and evidence for omnivory in troodontid dinosaurs
Bibliographic record
Abstract
Abstract The Cretaceous paleocommunities of North America preserve a rich record of biodiversity that suggests many species occupied narrow biogeographic ranges in comparison to their ecological equivalents in extant systems. How taxa in these systems partitioned their niches and structured their communities can be difficult to determine from fossils alone, which has led to a variety of hypotheses concerning diets and habitat use. Here, we examine element ratios (Sr/Ca, Ba/Ca) in the enamel of a suite of co-occurring vertebrate taxa sampled from a spatiotemporally constrained interval in the Oldman Formation of Alberta, Canada, to reconstruct trophic structure, and use δ13C, δ18O, and 87Sr/86Sr compositions to test for niche partitioning and habitat use among hadrosaurids, ceratopsids, and ankylosaurs. We also test previously proposed dietary hypotheses of troodontid theropods. In large ornithischians, we find Ba/Ca and Sr/Ca ratios that are consistent with herbivory, with hadrosaurs distinct from ceratopsids and ankylosaurids in their 87Sr/86Sr ranges, a pattern that is indicative of differences in habitat use/breadth, dietary plant sources, and feeding height. The sampled mammals, varanoid lizards, dromaeosaurids, and tyrannosaurids preserve a gradient of lower Sr/Ca and Ba/Ca ratios that is consistent with animal-dominant omnivorous to faunivorous diets. Troodontids, which have been variably hypothesized as either faunivorous, omnivorous, or herbivorous due to their distinct and unusual dentition, preserve Sr/Ca and Ba/Ca ratios that fall between those of the ornithischians and the dromaeosaurids. From these multi-proxy data, we interpret troodontids as mixed-feeding to plant-dominant omnivores. These proxies represent a valuable tool for understanding the trophic and community ecology of Cretaceous ecosystems and hold enormous potential for future research in paleobiology.
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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 | 0.000 | 0.000 |
| 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".