Dental Topography and Dietary Ecology of the First North American Euprimates Paul E. Morse1,2, Jonathan I. Bloch2, Gabriel S. Yapuncich3, Doug M. Boyer3, Suzanne G. Strait4

1. Department of Anthropology, University of Florida; 2. Florida Museum of Natural History, University of Florida; 3. Department of Evolutionary Anthropology, Duke University; 4. Department of Biological Sciences, Marshall University

1. Introduction Occurrences of specimens 2. Materials & Methods used in this study Drier Wetter Cooler Warmer 109oW The Paleocene- Thermal Maximum (PETM) was a significant global warming event that occurred 56 mil- 45oN Wyoming 1 2-4 lion years ago , characterized by an increase of ~5-8 °C in mean annual global temperature . Among the pano- 70 2 108oW ply of physical, chemical, and biotic effects associated with the PETM, this brief interval ( 200 thousand years ) Beartooth ~ Mountains Polecat Bench marks the first appearance of of modern aspect, or ‘euprimates.’ The first euprimate immigrants to T55N 60 reach were the omomyid brandti and the notharctid Cantius torresi5-7. Big Red Bighorn Mountains Absaroka Range T53N A N Bighorn R C N Cantius Notharctidae 50 T A Shoshone R Teilhardina T51N C Arctodontomys Niptomomys Microsyopidae 65 60 55 50 45 40 35 30 25 40 T49N Mya A Paleogene Yellow-Grey Period T47N Worland 30 T Sand Creek Divide 10 km o Epoch Paleocene Eocene Oligocene R99W 44 N N NALMA Pu To Ti Cf Wa Br Ui Du Ch Or Wh Ar T45N N Lower Red Lower 20 T47N Worland HW 16

° C 12 20 km

CAB 10 Basin Axis Big Trails Fault

Transitional 10 18 δ O Coryphodon Honeycombs Thrust fault 10 MAP Enamel & North Butte CAB 3 Owl Creek Mountains Big Red Spit 0 & Pyramid Point meter sandst Red Yellow-Brown Sandst T45N 8 siltst level mudst Grey Purple Plant MAP R93W R91W R89W Modifed from Ref. 12 Modified from Ref. 10 6 PETM Primate specimens were collected in the Cabin Fork drainage in the southeastern Bighorn Basin of Wyoming. After a decade of fieldwork, this region has produced a collection of ~8,500 PETM fossils, high-resolution inte- 4 grated chemostratigraphy, lithostratigraphy and biostratigraphy10, and is the only place where the unique flora 4 of the PETM has been characterized . We used micro-CT to generate high-resolution 3D digital models of pri-

2 mate M2’s recovered from PETM sediments (see Results for summary table) and applied three complimentary quantitative dietary ecology metrics using the free MorphoTester software11: δ18O from deep-sea benthic foraminifera collected at Deep Sea Drilling Project and Ocean Drilling Program Sites; presented in Ref. 9

Estimated temperature above ice-free oceans ice-free above temperature Estimated 0 3D Occlusal View 2D Occlusal View Cantius Relief Index (RFI): While euprimates immigrated to North America just after • Compares three dimensional surface area to two dimen- 1 mm the Paleocene-Eocene boundary, plesiadapiform stem pri- sional surface area of tooth crown mates had already diversified during the Paleocene in • Performs well at differentiating extant prosimian diets North America. One family, the Microsyopidae, is com- based on the amount of incorporated structural monly found during the PETM and is represented by carboyhdrates13 Arctodontomys wilsoni and the diminutiveNiptomomys do- • Folivores have higher RFI than frugivores and granivores reenae. These endemic taxa are recovered from the same PETM fossil deposits as euprimate immigrants, are most Arctodontomys wilsoni likely arboreal, are of similar size, and have qualitatively similar tooth crown morphology. These factors suggest the Orientation Patch Count (OPCR): possibility of competition for dietary resources. We used • Groups ‘patches’ of tooth crown faces based on their quantitative metrics of dental topography that differ shared orientation (minimum # of faces = 3) among extant primates8 to test if primate taxa from the • Patch count averaged from eight views of tooth crown • Differentiates within orders based on the com- PETM showed evidence of dietary partitioning. Teilhardina Microsyops plexity of tooth crown morphology • Teeth of herbivorous taxa tend to have high OPCR, whereas carnivorous taxa have low OPCR14 3. Results Niptomomys doreenae Cantius torresi Euprimate taxa Microsyopid taxa Dirichlet Normal Energy: • Considers the normal direction of each point on the tooth face • If normal directions of adjacent points greatly diverge, the normal map between them grows orthogonally Tupaia Hapalemur • Calculated as an increase in the Dirichlet energy, capturing the curviness of crown morphology • Independent of position, orientation, or scale • Higher in taxa with molar crowns adapted for shearing such as insectivores and folivores8 1 mm 1 mm 1 mm 1 mm Microcebus Lepilemur From Ref. 8 Teilhardina brandti Cantius torresi Niptomomys doreenae Arctodontomys wilsoni Relief index (RFI) Orientation patch count (OPCR) Dirichlet normal energy (DNE) 4. Discussion 0.58 Relief Index of PETM Galago Alouatta senegalensis Avahi 120 seniculus 0.65 (3) laniger 300 Arctocebus (7) primates measured in calabarensis (7) 0.56 (5) Arctodontomys Propithecus Lagothrix this study compared wilsoni sp. 0.60 Tarsius (3) (5) sp. sp. Aotus (10)

0.54 Samiri

100 with extant primates Niptomomys (4) 250 sp. azarae doreenae (10) (2) Chiropotes 0.55 (7) satanas (6) 0.52 Dietary Categories: Pithecia Teilhardina Loris pithecia Microcebus brandti tardigradus griseorufus (4) (6) 80 Cantius

200 (6) 0.50 (7) torresi Cacajao 0.50 Insectivory (6) calvus Ateles (9) sp. (10) Indri Relief Index Relief 0.48 Frugivory 0.45 Lemur indri Hapalemur catta

150 (5) 60 griseus Perodicticus (6) (5) potto (6) Varecia 0.46 Folivory 0.40 sp. (8) Arctodontomys Cantius Niptomomys Teilhardina Arctodontomys Cantius Niptomomys Teilhardina Arctodontomys Cantius Niptomomys Teilhardina Omnivory Cheirogaleus Daubentonia 0.35 sp. madagascarensis (8) (6) Modified from Ref. 13 with data from Ref. 16 • Arctodontomys clear outlier for RFI, likely incorporating more structural carbohydrates into their diet than Ambiguous 3 4 5 6 7 8 9 other PETM primates Natural Log Body Mass • Kruskal-Wallis one-way analysis of variance significant for RFI and OPCR, but not for DNE Several trends emerge from our results: RFI is higher for the microsyopid primates compared to the euprimates, • Large-bodied taxa (Arctodontomys and Cantius) not significantly different for OPCR or DNE, but significantly dif- but only Arctodontomys is a significant outlier. This indicates that Arctodontomys may have been incorporating ferent for RFI by Mann-Whitney U test (p = 0.024) a higher proportion of insects in its diet compared to other PETM primates. The lower DNE ofTeilhardina relative • Small-bodied taxa (Niptomomys and Teilhardina) not significantly different for RFI or OPCR, but significantly dif- to the small-bodied Niptomomys reflects greater bunodonty in the euprimate and may indicate relatively greater ferent for DNE by Mann-Whitney U test (p = 0.002) emphasis on fruit eating. The larger-bodiedArctodontomys and Cantius have more complex crown morphology, as indicated by higher OPCR, which would have made them more adept at processing tough food items such as Taxon Group N Est. Body Mass (g)* x(RFI) x(OPCR) x(DNE) leaves. Despite marked differences for some taxa in certain metrics, we note that generally the PETM primates Cantius torresi Notharctid euprimate 6 530-830 0.49 88.7 227.1 are quite similar to one another, especially compared to the wide range calculated for these metrics in extant pri- Arctodontomys wilsoni Microsyopid plesiadapiform 3 120-270 0.58 101.2 278.9 mates (e.g., see above). Despite non-overlapping body size and potentially sharing the same habitat, either of Teilhardina brandti Omomyid euprimate 6 50-145 0.49 65.2 200.2 which could serve to differentiate diet, the teeth of both endemic microsyopids and immigrant euprimates Niptomomys doreenae Microsyopid plesiadapiform 7 10-30 0.51 77.4 267.4 appear adapted to process foods with similar mechanical properties. These early primates may therefore may *Body mass estimates based on area of M using Ref. 15, “Prosimian Grade” regression, reported as averaged 95% confidence intervals of full sample 1 have competed for food resources during the PETM.

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