“Lungs” in Placoderms, a persistent palaeobiological myth related to environmental preconceived interpretations
Bibliographic record
Abstract
The presence of an aerial breathing organ in Placoderms is noticed in many textbooks on the history of breathing in Vertebrates. The origin of this interpretation is from a paper published in 1941 dealing with the interpretation of the differential sedimentary infilling of the armour of the antiarch Bothriolepis canadensis from the Late Devonian Escuminac formation of Canada. A revision of this material shows that if some sedimentary structures could be interpreted as traces of some digestive organs, none could be interpreted as putative lungs. The original proposal was based mainly on a presupposed mode of life of Bothriolepis in a freshwater environment of an alluvial plain. Recent studies of the Escuminac Formation environment conclude that it represents a marginal marine environment. Moreover, Bothriolepis has a worldwide distribution, notably in strictly marine environment. Thus, the presence of lungs in Bothriolepis remains highly questionable: it cannot be supported by anatomical, phylogenetic, nor biological arguments. La présence d’un organe respiratoire aérien chez les Placodermes est mentionnée dans nombre d’ouvrages généraux sur l’histoire de la respiration chez les vertébrés. La source de cette question se trouve dans un article de 1941, consacré à l’interprétation du remplissage sédimentaire de la carapace de l’antiarche Bothriolepis canadensis de la formation d’Escuminac. La révision de ce matériel montre que, s’il est possible d’interpréter certains remplissages comme une substitution possible des organes viscéraux digestifs, rien n’indique la présence d’organes pouvant représenter des poumons. L’interprétation proposée à l’époque reposait principalement sur un mode de vie présupposé de l’animal dans un environnement d’eau douce de plaine alluviale. Des études récentes de l’environnement de la formation d’Escuminac concluent à un milieu marin côtier. De plus, le genre Bothriolepis a une distribution mondiale, notamment dans de nombreux environnements marins francs. Morphologiquement non vérifiable, la présence de poumons chez Bothriolepis n’est soutenable, ni phylogénétiquement, ni biologiquement.
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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 | 0.001 | 0.002 |
| 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 | 0.019 |
| Scholarly communication | 0.002 | 0.003 |
| Open science | 0.001 | 0.002 |
| Research integrity | 0.002 | 0.002 |
| 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".