Morphology and function of the hyoid apparatus of fossil xenarthrans (mammalia)
Bibliographic record
Abstract
The analysis of the hyoid apparatus of fossil xenarthrans provides insight on the form of the tongue and its function in food intake and intraoral processing. The hyoid apparatus of xenarthrans is notable for fusion among its elements. The presence of a V-bone, a complex consisting of fused basihyal and thyrohyal bones, is a consistent and probably synapomorphic feature of xenarthrans. Fusion of other elements is variable in fossil xenarthrans. Most fossil sloths retain independent elements, as in living dasypodids and mammals generally. Among nothrotheriids, the elements are slender and their articular surfaces indicate considerable mobility, and the relatively long and horizontal orientation of the geniohyoid muscle suggests considerable tongue protrusion. Among mylodontines, such as Paramylodon and Glossotherium, the elements indicate relatively mobile articulations, except between the stylo- and epihyals. The relatively posterior placement of the apparatus and the length and alignment of the geniohyoid muscle indicate considerable capacity for tongue protrusion. Scelidotherium, however, had rigidly articulated stylohyal and epihyal, and the apparatus lies farther anteriorly, which together with the elongated, steeply inclined mandibular symphysis, indicates a relatively shorter geniohyoid muscle and thus more limited capacity for tongue protrusion. A similar situation is indicated for Megatherium, casting doubt on the classical reconstruction of this sloth as having a long prehensile tongue. Among cingulates Prozaedyus resembles living dasypodids, indicating considerable tongue protrusion important in food acquisition and intake. More extensive fusion of hyoid elements occurs in the cingulates Glyptodon and Proeutatus, in which the stylohyal and epihyal at least, are fused into a single element termed the sigmohyal. The presence of this element supports recent proposals of a sister-group relationship between glyptodonts and eutatines. The rigidity of the apparatus suggests limited tongue protrusion, but the tongue, in glyptodonts at least, was a powerful structure important for intraoral manipulation of food.
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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 | 0.000 |
| Science and technology studies | 0.000 | 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) | 0.003 | 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".