Nestling-sized hadrosaurine cranial material from the Hell Creek Formation of northeastern Montana, USA, with an analysis of cranial ontogeny in Edmontosaurus annectens
Bibliographic record
Abstract
Despite over a century of intense collecting, the Hell Creek Formation has produced exceedingly few specimens of small juveniles and nestling-sized dinosaurs. Here, we report on the first cranial material of nestling-sized hadrosaurid dinosaurs from the formation. The specimens were recovered from the Sandstone Basin locality in Garfield County, northeastern Montana. The material consists of two dentaries, a surangular, and a quadrate from disassociated individuals, which through ontogenetically independent characters allows assignment of the surangular (UCMP 235857) and quadrate (UCMP 235859) to Hadrosaurinae and the dentary (UCMP 235860) to Edmontosaurus . Since Edmontosaurus annectens is the only known hadrosaurid in the formation, we hypothesize that these specimens represent the earliest ontogenetic growth stage of E. annectens providing a significant ontogenetic extension when assessing aspects of cranial ontogeny in this taxon. Using the newly identified nestling cranial material as end members of ontogenetic series for each element in E. annectens , we evaluated ontogenetic variability in phylogenetic characters associated with these elements that are used in assessing phylogenetic relationships among hadrosaurids. Although the quadrate and surangular generally develop isometrically and show minimal ontogenetic variation in morphology, the dentary undergoes significant ontogenetic changes. In particular, the dental battery exhibits a high degree of intraspecific variability through ontogeny. Ontogenetic variability in the dentary should reflect a commensurate degree of variation in the jaws and facial skeleton, suggesting caution should be used when taxonomically identifying small edmontosaur material, such as that known from Alaska. Taxonomic identification of new taxa should be restricted to adult individuals until enough specimens are available to adequately assess taxonomic variation in ontogenetically equivalent semaphorants/ontogimorphs for a large range of complementing taxa.
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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 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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 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".