Phylogenetics and biogeography of two new species of paromomyid plesiadapiforms from a unique, High Arctic ecosystem of Eocene Canada
Bibliographic record
Abstract
The Margaret formation of the Eureka Sound Group in the Canadian Arctic Archipelago samples a unique, warm temperate ecosystem with a polar light regime that dates to the early Eocene epoch ~ 53 Ma. Previous paleontological expeditions into this region have yielded a wide array of vertebrate taxa including early crocodilians and a diversity of mammals. Although crown clade primates have never been recovered from the Eocene of Arctic Canada, at least two new taxa of paromomyid plesiadapiforms occur there. This research aims to describe the Arctic paromomyids from Ellesmere Island and assess their phylogenetic relationships with respect to other members of this clade with the goal of reconstructing the paleobiogeographic affinities of these arboreal taxa and constraining the timing by which they colonized the Canadian Arctic. A phylogenetic analysis was completed using a morphological character matrix utilizing 63 dental characters scored for 17 taxa. A parsimony analysis completed using PAUP* suggests the two new paromomyid species are sister taxa that are highly nested within the Ignacius clade. These results suggest the Arctic paromomyids are closely related to mid-latitude North American paromomyid clades and are not specially related to the European genus Arcius. The nested relationship also suggests the Arctic taxa dispersed into high northern latitudes after the initial diversification of North American paromomyids during the Paleocene. The date for the lower faunal zone of the Margaret Formation (where most of the mammalian taxa occur) coincides with increasing temperatures during the Early Eocene Climatic Optimum (EECO). This suggests the northerly dispersal of the Arctic paromomyids may have been in response to rising global temperatures during the EECO. Further research on the new taxa will be focused on dental topography analysis to better understand the ecological adaptations that allowed for their survival in an ecosystem with a polar light regime.
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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 | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| 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 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".