Influence of Sequence Heterochrony on Hadrosaurid Dinosaur Postcranial Development
Bibliographic record
Abstract
A goal of modern dinosaur paleobiology is to synthesize the understanding of dinosaurian development and phylogeny. This study explores the Iguanodontia, one clade that includes several taxa for which growth series are preserved. It is hypothesized that analysis of growth series of iguanodontian taxa will reveal important developmental differences at play during the evolution of the clade. Such differences can reflect the impact of sequence heterochrony on iguanodontian evolution. Data were collected on the growth stages of the postcranial skeleton of a basal iguanodontian, Tenontosaurus; a lambeosaurine hadrosaurid, Hypacrosaurus; and two hadrosaurine hadrosaurids, Brachylophosaurus and Maiasaura to test the hypothesis. The event-pairing method provides a framework for the comparison of ontogenetic sequences among related taxa to detect significant evolutionary changes in developmental sequence. Significant developmental events are identified for the group and then the relative timings of those events in the developmental sequence are compared among the different species. Synapomorphic characters of Hadrosauridae, including the development of a prominent biceps tubercle on the coracoid, appear to be the result of changes in the developmental sequences of hadrosaurid taxa compared to basal iguanodontian taxa. This analysis also recognizes the developmental sequence differences that result in the development of the robust appendicular elements that characterize Lambeosaurinae. This comparative methodology shows that the development of characters such as the well developed supraacetabular process of the ilium results from the early onset of the development of those characters in the lambeosaurine hadrosaurid Hypacrosaurus compared to the hadrosaurines Brachylophosaurus and Maiasaura.
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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) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 0.001 |
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".