Ontogeny and evolution of Lambeosaurine dinosaurs (Ornithischia: Hadrosauridae)
Bibliographic record
Abstract
Lambeosaurinae is a Glade of hadrosaurid dinosaurs characterized by hypertrophied nasal passages housed within distinctive cranial crests. Large sample sizes, taxonomic diversity, and increasing resolution of their chronostratigraphic and paleoecological contexts make the group an ideal model Glade with which to test hypotheses related to Late Cretaceous dinosaur evolution. Anatomy and variation in the poorly known taxa Lambeosaurus magnicristalus and Hypacrosaurus altispinus are described in detail and both taxa are systematically revised. A complete digital endocranial cast derived from H. altispinus braincase reveals that the cerebral hemispheres are large and that the auditory system of lambeosaurines closely resembles those of other hadrosauroids. An abundance of juvenile specimens make lambeosaurines ideal subjects for comparative studies of growth and variation. The precise taxonomic identification of crestless juvenile specimens has proven difficult in the Dinosaur Park Formation (Campanian) of Alberta, Canada, where six closely related taxa are known. Discrete cranial characters are identified to distinguish lambeosaurine genera at early ontogenetic stages. Cranial ontogeny is compared among lambeosaurines with morphometric and qualitative approaches. Analyses of allometry confirm the general trends observed for Lambeosaurus and Corythosaurus in a larger subset of taxa that includes Hypacrosaurus. The first species-level phylogenetic analysis of Lambeosaurinae recovers completely resolved relationships within the Parasauolophini and Corythosaurim, and corroborates monophyly of the genera Lambeosaurus, Hypacrosaurus, and Parasaurolophus. The time-calibrated phylogeny and distribution of autapomoiphies allows for first order assessment of anagenesis in the clade. Previous hypotheses of anagenetic ancestor-descendant relationships can be rejected, although data does not reject the possibility that the biostratigraphic successions of Corythosaurus and Lambeosaurus species in the well-sampled Dinosaur Park Formation represent phyletic evolution within two independent, co-occuring dinosaur lineages. Hypotheses of sexual dimorphism in the cranial crests of Corythosaurus and Lambeosaurus are tested within a high-resolution biostratigraphic framework. Biostratigraphic succession of cranial morphotypes in both taxa is inconsistent with previously proposed sexual dimorphism, and, instead, indicates that the formation hosts a taxonomically diverse assemblage of lambeosaurines.
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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 | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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 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".