Gorgosaurus libratus Lambe 1914
Bibliographic record
Abstract
Gorgosaurus libratus. — G. libratus Lambe, 1914 is known from more than twenty skeletons from southern Alberta. Good specimens of Gorgosaurus in the Museum of the Rockies and the Indianapolis Children’s Museum have also been recovered from Montana, although these have not been studied closely enough to be sure that they are the same species. Russell (1970) distinguished “ Albertosaurus ” libratus from A. sarcophagus because of differences in the times when these animals lived, and because of differences in relative lengths of the dentary tooth row (compared with the fourth metatarsal), the scapulocoracoid (compared with the femur) and the tibia plus astragalus (also compared with the femur). However, differences in relative proportions are not very reliable for taxa in which growth is allometric for most cranial and appendicular dimensions. This is confirmed by plotting tooth row versus metatarsal measurements against each other for Albertosaurus (four specimens) and Gorgosaurus (seven specimens). This particular calculation and others done by Currie (2003) fail to show any significant differences between the regression curves of these genera. The most detailed comparison (Bakker et al. 1988) used braincase characters to distinguish various tyrannosaurid genera, including Albertosaurus and Gorgosaurus. The basal tubera were observed to be wide and thick in Gorgosaurus, but reduced and thin in Albertosaurus, presumably reflecting a reduction in the size of tendonous muscle attachments. Paired pneumatic foramina in the ceiling of the basisphenoid recess are larger in Albertosaurus than Gorgosaurus, and the occipital condyle is more ventrally oriented in Albertosaurus. Holtz (2001) distinguished Albertosaurus and Gorgosaurus on the basis of 14 characters, two of which he considered unique in Gorgosaurus amongst tyrannosaurids. These include differences in the nasal−frontal suture (his character 48), orientation of the lacrimal horn (52), presence of the suborbital process (57), orientation of the occiput (65), size of the basal tuber (67), number of foramina on the ventral surface of the palatine (71), number of incisiform maxillary teeth (78), expansion of the distal end of the scapula (82), size of deltapectoral crest (83), relative size of manual phalanx I−1 (85), position of the promaxillary fenestra (93), postorbitallacrimal contact (94), nature of the anterior margin of the suborbital process (95), and position of the foramina in the basisphenoidal recess (96). Although this long list should be enough to convince anyone of the distinctness of the two genera, many of the characters apply only to specific specimens. There is enough variability in anatomy in Gorgosaurus that any single individual is unlikely to show more than half the differences from Albertosaurus. Using the entire suite of character states of Bakker et al. (1988), Holtz (2001) and Currie et al. (2003), reasonably complete specimens of Gorgosaurus can be distinguished from Albertosaurus. However, it is likely that some of the characters will not code in the expected way, or will not code at all. Of the cranial characters, those associated with the braincase seem to be the most reliable for separating the two albertosaurine genera.
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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 | 0.001 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.005 | 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".