Breaking the mold: using biomechanical experiments to assess the life orientation of dorsibiconvex brachiopods
Bibliographic record
Abstract
Abstract Understanding the life orientation of fossil organisms, such as brachiopods, is not only important for understanding the biology of the organism in question, but it also can be used to interpret paleoecological information about the assemblages from which the specimens were derived. The dorsibiconvex brachiopod morphology is particularly common, especially among the Order Atrypida, yet there have been few independent, biomechanical studies to assess the life orientation of these brachiopods. In this study, we assess potential orientations of two end-member morphologies of a dorsibiconvex brachiopod, Pseudoatrypa lineata, from the Mid–Late Devonian of North America by placing realistic models in a flume. Using materials with the specific gravity of calcium carbonate, we modeled two well-preserved Pseudoatrypa lineata from the Waterways Formation (Givetian–Frasnian, Alberta, Canada) to represent the original shell. The hydrodynamic stability of the models was assessed by placing the models in a recirculating flume in one of three initial orientations: (1) anterior commissure upstream, (2) umbo upstream, and (3) lateral (specimen perpendicular to flow), each with the dorsal and ventral valve topmost. The entire process was conducted both on a Plexiglas substrate and on well-sorted, mediumgrained sand. All scenarios were repeated five times for a total of sixty trials per specimen (120 total). Flume trials indicate that neither brachiopod had a true hydrodynamically stable orientation. Reorientations occurred at low velocities (~0.2 m/s), with transport occurring soon after (~0.3 m/s). Assuming that a juvenile, pedunculate, dorsibiconvex brachiopod would initially have been oriented with its ventral valve topmost, our results suggest two outcomes: the brachiopods either (1) were attached via pedicles throughout their lives or (2) lived in quiet, undisturbed waters. Given the abundance of dorsibiconvex brachiopods in observed high-energy environments, our results indicate it is more conservative to assume dorsibiconvex brachiopods retained pedicles throughout their lives.
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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 | 0.000 | 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 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 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".