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Paromomyidae

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Paromomyidae
Restoration of Ignacius graybullianus
Scientific classification Edit this classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Infraclass: Placentalia
Order: Plesiadapiformes
Family: Paromomyidae
Simpson, 1940[1]
Genera

Paromomyidae is an extinct family of "plesiadapiform" mammals (early primates or close relatives) which lived during the Paleocene and Eocene epochs (Torrejonian to Chadronian stages).[1] They were the most widespread and long-lasting family of plesiadapiforms, ranging through North America as far south as New Mexico and as far north as the Canadian Arctic.[2] One paromomyid, Arcius, inhabited parts of Europe,[3] and undescribed fossils have also been found in China.

Complete paromomyid skeletons show that they were probably arboreal (tree-living). They would have moved in a similar manner as modern squirrels and treeshrews, relying on an agile bounding gait alongside strong hands and feet to grip trunks and branches. Compared to modern primates, they were probably most similar to marmosets and tamarins, sharing a rather small size (100–500 grams (0.22–1.10 lb)) and a diet of mainly tree sap, fruit, and insects.[4][5] Unlike living primates, the snout is rather long and the small eyes are on the side of the head, rather than the front.[4] This probably indicates a greater reliance on smell rather than vision when foraging.[6][7]

Paromomyids may have preferred cooler temperatures than most primates; they were most common during cooler intervals such as the mid-Paleocene (Torrejonian) and briefly again in the early Eocene (mid-Wasatchian). On the other hand, they were very rare during hot intervals such as the Paleocene-Eocene Thermal Maximum (PETM) and the Early Eocene Climatic Optimum (EECO). The EECO may have pushed paromomyids to the brink of extinction, as their fossils continue to be very rare after the early Eocene.[8]

Paromomyids are often considered close relatives to some members of the families Palaechthonidae and Picrodontidae. Together, they form a broader subgroup of Plesiadapiformes, known as Paromomyoidea.[6] Most paromomyid genera appear to be paraphyletic.[9] Historically, a few studies argued that paromomyids were gliding mammals within the order Dermoptera (modern colugos or "flying lemurs"). This argument was debunked when better-preserved skeletons revealed a complete lack of gliding adaptations.[4][5]

References

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  1. ^ a b Bloch, Jonathan I.; Silcox, Mary T.; Boyer, Doug M.; Sargis, Eric J. (January 23, 2007). "New Paleocene skeletons and the relationship of plesiadapiforms to crown-clade primates". Proceedings of the National Academy of Sciences of the United States of America. 104 (4): 1159–1164. doi:10.1073/pnas.0610579104. PMC 1783133. PMID 17229835.
  2. ^ Scott, Craig S.; López-Torres, Sergi; Silcox, Mary T.; Fox, Richard C. (2023). "New paromomyids (Mammalia, Primates) from the Paleocene of southwestern Alberta, Canada, and an analysis of paromomyid interrelationships". Journal of Paleontology. 97 (2): 477–498. Bibcode:2023JPal...97..477S. doi:10.1017/jpa.2022.103. ISSN 0022-3360.
  3. ^ López-Torres, Sergi; Silcox, Mary T. (2018). "The European Paromomyidae (Primates, Mammalia): taxonomy, phylogeny, and biogeographic implications". Journal of Paleontology. 92 (5): 920–937. Bibcode:2018JPal...92..920L. doi:10.1017/jpa.2018.10. ISSN 0022-3360.
  4. ^ a b c Bloch, Jonathan I.; Silcox, Mary T.; Boyer, Doug M.; Sargis, Eric J. (2007-01-23). "New Paleocene skeletons and the relationship of plesiadapiforms to crown-clade primates". Proceedings of the National Academy of Sciences. 104 (4): 1159–1164. doi:10.1073/pnas.0610579104. PMC 1783133. PMID 17229835.
  5. ^ a b Boyer, Doug M.; Bloch, Jonathan I. (2008), "Evaluating the Mitten-Gliding Hypothesis for Paromomyidae and Micromomyidae (Mammalia, "Plesiadapiformes") Using Comparative Functional Morphology of New Paleogene Skeletons" (PDF), in Sargis, Eric J.; Dagosto, Marian (eds.), Mammalian Evolutionary Morphology: A Tribute to Frederick S. Szalay, Dordrecht: Springer Netherlands, pp. 233–284, doi:10.1007/978-1-4020-6997-0_11, ISBN 978-1-4020-6997-0, archived from the original on 2012-07-14
  6. ^ a b Silcox, Mary T.; Gunnell, Gregg F. (2008), "Plesiadapiformes", in Janis, Christine M.; Gunnell, Gregg F.; Uhen, Mark D. (eds.), Evolution of Tertiary Mammals of North America: Volume 2: Small Mammals, Xenarthrans, and Marine Mammals, vol. 2, Cambridge: Cambridge University Press, pp. 207–238, doi:10.1017/CBO9780511541438.015, ISBN 978-0-521-78117-6, retrieved 2026-05-02
  7. ^ Silcox, Mary T.; Dalmyn, Claire K.; Bloch, Jonathan I. (2009-07-07). "Virtual endocast of Ignacius graybullianus (Paromomyidae, Primates) and brain evolution in early primates". Proceedings of the National Academy of Sciences. 106 (27): 10987–10992. Bibcode:2009PNAS..10610987S. doi:10.1073/pnas.0812140106. ISSN 0027-8424. PMC 2708683. PMID 19549862.
  8. ^ López-Torres, Sergi; Silcox, Mary T.; Holroyd, Patricia A. (2018). "New omomyoids (Euprimates, Mammalia) from the late Uintan of southern California, USA, and the question of the extinction of the Paromomyidae (Plesiadapiformes, Primates)". Palaeontologia Electronica. 21 (3): 756. Bibcode:2018PalEl..21..756L. doi:10.26879/756.
  9. ^ Scott, Craig S.; López-Torres, Sergi; Silcox, Mary T.; Bohach, Lisa L. (2025). "New species of the plesiadapiform Paromomys Gidley (Primates, Paromomyidae) from the Paleocene of southwestern Alberta, Canada". Journal of Vertebrate Paleontology. 45 (3) e2549081. Bibcode:2025JVPal..4549081S. doi:10.1080/02724634.2025.2549081. ISSN 0272-4634.