Massospondylus embryos and hatchling provide new insights into early sauropodomorph ontogeny
Bibliographic record
Abstract
Abstract Ontogeny and patterns of growth provide crucial insights into the evolution of dinosaurs and their biology, however, ontogenetic changes of the postcranial skeleton are generally poorly known and restricted to few species. Here, we report on the discovery of embryonic, eggshell, and hatchling material of the Early Jurassic sauropodomorph Massospondylus and provide new insights into the early life stages of early-diverging sauropodomorphs. The embryos described here represent a more advanced developmental stage than previously known embryonic materials and together show eggshells with progressive degrees of resorption correlating to embryonic development. The prominent “thumb” typical of early-diverging sauropodomorph dinosaurs also appears to be precociously ossified and ontogenetically variable. Together, these new Massospondylus embryos and hatchling indicate a quadrupedal posture and the resulting growth trajectory points to an important ontogenetically influenced ecological shift predicated on a continuum of locomotory dependent postural change, from obligate quadrupeds to obligate bipeds . Other Late Triassic and Early Jurassic sauropodomorph dinosaurs known from few ontogenetic stages also fit well on the extensive growth trajectory of Massospondylus with only modest variations in skull, neck, and limb proportions. This generally conservative body plan of early-diverging sauropodomorphs likely suggests a similar postural change for the early members of this large clade that preceded the obligate quadruped sauropods.
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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 | 0.000 | 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".