The evolution, development and skeletal identity of the crocodylian pelvis: Revisiting a forgotten scientific debate
Bibliographic record
Abstract
Unlike most tetrapods, in extant crocodylians the acetabulum is formed by only two of the three skeletal elements that constitute the pelvis, the ilium, and ischium. This peculiar arrangement is further confused by various observations that suggest the crocodylian pelvis initially develops from four skeletal elements: the ilium, ischium, pubis, and a novel element, the prepubis. According to one popular historical hypothesis, in crocodylians (and many extinct archosaurs), the pubis fuses with the ischium during skeletogenesis, leaving the prepubis as a distinct element, albeit one which is excluded from the acetabulum. Whereas the notion of a distinct prepubic element was once a topic of considerable interest, it has never been properly resolved. Here, we combine data gleaned from a developmental series of Alligator mississippiensis embryos, with a revised interpretation of fossil evidence from numerous outgroups to Crocodylia. We demonstrate that the modern crocodylian pelvis is composed of only three elements: the ilium, ischium, and pubis. The reported fourth pelvic element is an unossified portion of the ischium. Interpretations of pelvic skeletal homology have featured prominently in sauropsid systematics, and the unambiguous identification of the crocodylian pubis provides an important contribution to address larger scale evolutionary questions associated with locomotion and respiration.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.002 | 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 | 0.001 | 0.001 |
| 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".