STRUCTURE OF TRILOBITE COMMUNITIES ALONG A DELTA-MARINE GRADIENT (LOWER ORDOVICIAN; NORTHWESTERN ARGENTINA)
Bibliographic record
Abstract
ABSTRACT Throughout their long history, trilobites occupied various ecological niches, colonizing a wide variety of marine environments. However, the paleoecology of this group is mostly based on shelf–slope environments and less is known about their distribution in marginal environments. To understand how trilobite communities respond to a deltaic influence, we studied changes in the taxonomic composition and structure of a diverse and well-known Lower Ordovician olenid-dominated fauna from the Argentine Cordillera Oriental along a delta–marine gradient. Cluster analysis revealed two distinct associations, and ordination analysis revealed a clear biotic gradient within each. The ecological structure and diversity trends of both associations follow a predictable response to a depth-related gradient. Impoverished communities with a highly nested structure characterize the lower offshore, whereas rich and even communities occur in the upper offshore. The trend towards higher diversity and greater taxonomic turnover in shallower environments corresponds to greater habitat heterogeneity. Towards the other extreme, only the ubiquitous genus Jujuyaspis was a successful colonizer in deltaic settings. This marked contrast with the more diverse and abundant assemblages of fully marine deposits indicates stressful physiological conditions in marginal-marine environments, where alternating and contrasting normal-marine to brackish-water conditions and high input of siliciclastic material were among the key factors controlling the distribution of these early trilobite communities.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| 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 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.006 | 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 teacher head, 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".