Bibliographic record
Abstract
Amniota is the name assigned to a large group of limbed vertebrates that includes not only extant reptiles, birds, and mammals because of their reproductive strategy involving the amniotic egg, but also a rich record of extinct animals whose reproductive mode cannot be determined directly. The origin of amniotes is therefore anchored by two disparate disciplines: developmental biology and vertebrate paleontology. The amniotic egg is at the center of the great evolutionary success of the crown group Amniota. The developmental strategy of amniotes is characterized by the evolutionary innovation of a series of four extraembryonic membranes—the yolk sac, allantois, chorion, and amnion—that provide a complete developmental environment for the embryonic life of a reptile, bird, or mammal. These extraembryonic membranes allowed the common ancestor of amniotes and its descendants to invest the mother’s resources into fewer but larger eggs; protect the developing embryos by placing them in a nest or retain them in the reproductive canal; and therefore also eliminate the need for a prolonged larval stage and metamorphosis. It has been suggested that this evolutionary innovation provided an unprecedented opportunity to complete the conquest of the terrestrial realm by amniotes and has led to the great success of aquatic reptiles, Mesozoic dinosaurs and their descendants, the birds, and the Cenozoic mammals, including humans. Interestingly, it also appears to have been instrumental in allowing amniotes to invade other parts of the biosphere, including the air, through flying or gliding organisms, and even to return repeatedly to the aquatic environment. The fossil record of crown amniotes is very rich and extends over at least 318 million years of earth’s history, providing a detailed accounting of the evolutionary history of Amniota. As such, they provide the primary evidence for the origin and early evolution of this important clade of animals. Unfortunately, the fossil record is quite limited in the preservation of amniotic eggs, with the oldest documented evidence of fossilized amniotic eggs being those of 195-million-year-old dinosaurs. Thus, the origin and early diversification of amniotes, the transition from anamniotes to amniotes, and the composition of crown Amniota can only be determined by studies of the fossil record and through phylogenetic analyses. Since the fossil record of amniotes and their presumed close relatives is represented mainly by the remains of their bony skeletons, analyses can only be based on the morphological information provided by the skeletons of these ancient limbed vertebrates. The results of these analyses will determine the nature not only of the anamniote-amniote transition, but also the composition of crown Amniota, even in the absence of direct evidence of their embryology.
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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 | 0.005 |
| Scholarly communication | 0.002 | 0.002 |
| Open science | 0.001 | 0.003 |
| Research integrity | 0.002 | 0.002 |
| Insufficient payload (model declined to judge) | 0.003 | 0.002 |
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".