The contribution of X-ray microtomography to paleobiology illustrated by a Tremadocian (Early Ordovician) radiolarian species
Bibliographic record
Abstract
Based on Tremadocian (Early Ordovician) material from Nevada, the genus Protoentactinia was first introduced in 1996 by Kozur, Mostler & Reptski as a spicular test initiated by a median bar that bears three rays at each end; the externally subglobular test was described as formed by a repeatedly branching pattern of spicules, which accommodated a rather spherical inner empty space. Based on lower Tremadocian material from the Cow Head Group of Newfoundland (Canada) and thanks to X-ray microtomography we here provide, for the first time, details of the number of spicular branching re-iterations, number of spicular branches and skeleton growth development of species Protoenctinia gracilispinosa Kozur et al. 1996. Skeleton analysis of individual radiolarian specimens was conducted at the Ghent University’s Centre of X-ray Tomography (UGCT) in Belgium, together with the EXCITE network. These scans were performed using the custom-built Nanowood X-ray CT scanner at a voxel size of 900 nm. Our results establish that P. gracilispinosa displays 8 branching stages. In general, each existing ray grows by producing a crown-like ray triplet, but there are cases of 4 or even (rarely) 5 crown-like ray structures. The opposite has been also observed, with either 2 or just one new ray being grown. We counted for P. gracilispinosa the number of branches/rays produced at each successive stage of skeleton growth; starting with 18 branches formed at stage 2, the total number of branches increased continuously up to a maximum of 110 at stage 5, after which their number decreased down to six at stage 8 (63 at stage 6, 13 at stage 7). Our observations on 3D models establish that during the first two stages of growth the skeleton develops in a symmetric way with respect to the median bar. However, subsequently, progressive reduction of the number of rays emplaced proximally (close to the median bar), combined with full growth of rays distally, has as a result the rapid formation, during stages 3 to 5, of a rapidly formed external subglobular shape.
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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 | 0.002 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 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".