PMJs and TMJs: convergence in the craniomandibular joints of crocodilians and mammals
Bibliographic record
Abstract
Crocodyliforms evolved a series of key features responsible for their Mesozoic adaptive radiation. Among these is the pterygoid buttress, the characteristic hypertrophied pterygoid flange in the skull. Although historically approached simply as a palatal element, the buttress forms a prominent articulation with the mandible here referred to as the pterygomandibular joint (PMJ). The joint bears the necessary anatomical features, such as a capsule and fibrocartilage, to be considered an enthesis organ. Biomechanically, the joint acts as a fulcrum between the dentary and jaw muscle attachments and stabilizes the mandible from medial bending and long axis rotation during orthal and twist feeding. Although all jaw muscles act about the jaw joint (i.e., the quadratoarticular joint), they also create strong mediolaterally and vertically‐oriented moments about the pterygomandibular joint such that this secondarily‐acquired craniomandibular joint is heavily loaded during most feeding behaviors. The joint originates early in pseudosuchian evolution prior to the evolution of an akinetic skull, laterally‐wrapping pterygoideus muscles, sutured mandibular symphysis, secondary palate, and skull flattening suggesting it was the key factor that stabilized the mandible and released the lineage to evolve high bite forces and robust skulls. Finally, the crocodyliform pterygomandibular joint bears resemblance to the eutherian temporomandibular joint as both joints possess sesamoid‐like fibrocartilages, such as the TMJ articular disc, within evolutionarily conserved muscle attachments. Thus, crocodyliforms and mammals convergently evolved dual craniomandibular joint systems with similar joint morphologies albeit at different locations. These new findings enable significant new insights into cranial biomechanical modeling, skeletal development and vertebrate evolution.
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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 | 0.001 |
| 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 | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.005 | 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".