Thalattosauriform Reptiles in Triassic Marine Ecosystems: Digital Cranial Retrodeformation, 3D Reconstruction and Functional Anatomy
Bibliographic record
Abstract
Thalattosauriformes, are an exclusively Triassic clade of secondarily aquatic reptiles that are characterized by their bizarre and highly disparate cranial shapes, dentition types and body sizes. Its members have long been considered to be rare faunal components in Triassic ecosystems; thus, the evolutionary origins and biology of thalattosaurs have remained relatively poorly understood. This dissertation aims to provide a first detailed glimpse into the three-dimensional cranial anatomy and functional ecology of this group. Chapter I Focusses on the earliest representatives of the clade. Material from the Early and Middle Triassic of British Columbia was studied to compare to the putative weigeltisaurid Wapitisaurus problematicus. This taxon was shown to instead likely represent an early diverging thalattosauroid, and the close morphological similarities, including distinct aquatic adaptations, with later thalattosauroids. Their high abundance in the shallow marine settings of Canada may indicate an earlier invasion of the aquatic realm than previously assumed. Chapter II revolved around the cranial anatomy and functional ecology of the namesake species for the entire group, Thalattosaurus alexandrae. Multiple individuals were CT-scanned and digitally segmented providing unprecedented detail on aspects of their anatomy and biology, such as cranial kinesis, tooth composition, replacement and implantation. Although highly durophagous in appearance, thalattosauroids are incomparable to placodonts in terms of crunching capabilities. It is likely that niche differentiation occurred along a prey hardness scale and that durophagy developed in the presence of other tooth morphologies in thalattosaurs, as in some extant lepidosaurs, to widen the dietary range, thus crudely said: they specialize to be better generalist. Chapter III dealt with another historic specimen, one of the best known taxa, Askeptosaurus italicus. Despite their relatively good fossil record with several virtually complete skeletons, the high degree of compaction and fragmentation reduced the morphological information that could be extracted. By using innovative scanning methods, traditional problems with data extraction are overcome, allowing for a 3D cranial and muscle model to be produced. This in order to discuss the closure of the upper temporal fenestra in thalattosaurs and the consequences for muscle attachment and feeding ecology. Chapter IV Widened the scope to contemporaneous clades of secondarily aquatic marine reptiles, such as the placodonts. In this chapter, Placochelys placodonta is subjected to detailed radiological analyses to provide insight on tooth replacement, wear and tooth composition in highly specialized durophagous predators. This in order to contextualize the functional ecological data obtained from thalattosauroid thalattosaurifoms. It represents a preliminary study for a large ecosystem approach of the Monte San Giorgio fauna and their ecological niches.
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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 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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".