Newly discovered ammonites in mid-Cretaceous Burmese amber
Bibliographic record
Abstract
Amber is famous for preserving detailed records of terrestrial and soft-bodied organisms that have a low preservation potential elsewhere in the fossil record. Because preservation in amber is biased toward animals such as insects that live in close association with resin-producing trees, inclusions of marine fossils in Mesozoic amber are extremely rare. Here, we report unusual fossil assemblages consisting of ammonites preserved alongside terrestrial arthropods in Burmese amber. Under X-ray microcomputed tomography (CT), we made detailed observations of the preserved septa and sutures in the ammonite samples. On the basis of the suture structure, moderately involute shell, and smooth shell surface without ornamentation, we classified one of the new ammonites within the superfamily Desmoceratoidea. The partial filling of shell chambers with calcite suggests that the ammonites were buried for a short time in the sediment, which started the fossilization process prior to encapsulation in resin. Sand infills within the shell chambers indicate significant weathering and transport within a high-energy environment prior to encapsulation. The arthropod inclusions are represented by terrestrial and possibly aquatic associated forms belonging to Acari (mites); Hemiptera: Cimicomorpha: Vetanthocoridae; and Diptera: Muscomorpha. These insects are surrounded by powdered wood, insect frass, and plant fragments. The combined fossil assemblage seems to suggest that at least some amber-producing trees grew close to the coast, capturing a mixture of forest floor communities and partially fossilized shells redeposited from high-energy coastal waters.
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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 | 0.002 | 0.001 |
| 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) | 0.001 | 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".