<i>Saccoglossus testa</i> from the Mazon Creek fauna (Pennsylvanian of Illinois) and the evolution of acorn worms (Enteropneusta: Hemichordata)
Bibliographic record
Abstract
Abstract The limited fossil record of enteropneust hemichordates (acorn worms) and the few external features that distinguish the four families have provided a challenge to our understanding of the evolution of the group and their various feeding adaptations. The middle Pennsylvanian Saccoglossus testa sp. nov. from the Mazon Creek, Westfalian D Carbonate Formation, Francis Creek Shale of northern Illinois provides evidence for the exploitation of surface sediments. Saccoglossus testa has a long proboscis characteristic of the extant genus Saccoglossus, a specialist in surface deposit feeding. The collar is as long as it is wide. The anterior trunk lacks a distinctively wide branchial region. These three features distinguish it from its sympatric enteropneust species Mazoglossus ramsdelli Bardack that has a proboscis characteristic of an infaunal deposit feeder. It is the seventh known species of fossil enteropneust, including a resting trace of a Lower Triassic fossil that has collar lips that characterize the extant deep‐sea family Torquaratoridae, and which represents a second parallel evolution of surface deposit feeding. An analysis of the seven fossils shows that the earliest Enteropneusta had a relatively simple harrimaniid‐like body plan, and that the spengelid, the torquaratorid and lastly the most complex ptychoderid body plan appeared in that chronological order.
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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 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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 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".