WINDOWS ON THE EVOLUTION OF PICRODUS (PLESIADAPIFORMES: PRIMATES): MORPHOLOGY AND RELATIONSHIPS OF A SPECIES COMPLEX FROM THE PALEOCENE OF ALBERTA
Bibliographic record
Abstract
Since 1908, the peculiar North American primate Picrodus Douglass, 1908 (Picrodontidae; Plesiadapiformes) has been thought to contain only a single species, P. silberlingi Douglass, 1908, of late Paleocene age. However, new collections from the Paskapoo Formation, Alberta, Canada, reveal that instead a rich complex of Picrodus species lived during the Paleocene. Three of these, Picrodus calgariensis, P. canpacius, and P. lepidus, are described herein as new. Others, represented by more fragmentary specimens from Canada and the United States, are included in this paper, but are not named. P. calgariensis, from Who Nose? (late Torrejonian), Calgary, is the most primitive known species of Picrodus, having molars with little crenulation of the enamel. P. canpacius, from Cochrane 2 (earliest Tiffanian), northwest of Calgary, most resembles P. silberlingi sensu stricto, but differs in P4 structure, denser enamel crenulation, and weaker molar cusps. P. lepidus, from DW-2 (middle Tiffanian), near Red Deer, is the most advanced, having, for example, a two-rooted P4, tiny p3, and single-rooted p4. At least two of these species also occur in the United States, documented by fossils referred to P. silberlingi by previous workers. Dental evolution within Picrodus seems marked by several trends, including increase in size of i1, simplification of P4, reduction of molar cusps and crests, enlargement of the horizontal occlusal surfaces of the molars, and greater crenulation of enamel. From present knowledge, Zanycteris paleocenus Matthew, 1917 is dentally more primitive than Picrodus, Draconodus Tomida, 1982 is a valid genus, and picrodontids probably originated from “purgatoriid-grade” plesiadapiforms in earliest Paleocene time.
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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 | 0.001 | 0.001 |
| 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 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".