Euarchonta

Upper molars of Apatemys sp., from Czaplewski & Morgan (2015).

Belongs within: Boreoeutheria.
Contains: Primates, Scandentia, Dermoptera, Plesiadapoidea, Paromomyidae.

Beginning to grasp things
Published 15 February 2010
Skull of Plesiadapis tricuspidens, from Gingerich (1976).

The name Euprimateformes was coined fairly recently by Bloch et al. (2007) for a clade uniting crown-group Primates and the extinct plesiadapoids (the exact definition was “the clade stemming from the most recent common ancestor of Carpolestes simpsoni and Homo sapiens), excluding even more basal stem Primates such as paromomyids. The plesiadapoids include the taxa Plesiadapidae, Carpolestidae, Saxonella and Chronolestes and were found in North America and Eurasia from the late Early Palaeocene to the end of the Early Eocene (a possible plesiadapoid has also been described from Africa).

Reconstruction of Carpolestes from here.

Plesiadapoids would have been not dissimilar to squirrels or modern tree shrews in size and appearance. They possessed large, forward-pointing lower incisors and originally fairly long skulls. Few plesiadapoids are known from extensive postcranial remains but what we do know indicates a fair amount of ecological divergence (Bloch et al. 2007). Carpolestes possessed a nail rather than a claw on its hallux (opposible big toe) and shorter claws overall, indicating that it was a grasping climber (wrapping its digits around branches) like modern primates rather than a clinging climber (hanging onto branches with its claws) like squirrels. Plesiadapis, on the other hand, had long narrow claws and was probably more of a clinging climber. Some authors have suggested a more terrestrial lifestyle for Plesiadapis; such interpretations are not currently popular (Kirk et al., 2008) but it would be interesting if postcrania were available for the largest and one of the latest of the plesiadapids, the European Platychoerops, which was comparable in size to a groundhog (Gingerich 1976). Also notable among plesiadapids was Chiromyoides which appears to have been a specialised seed-eater with a short and deep jaw (and presumably skull) and massive incisors.

Lower jaw of Carpolestes simpsoni from Bloch & Gingerich (1998).

Carpolestids also showed a trend towards reduction in the length of the skull, but the really neat thing is what they did with their teeth, for which Carpolestes simpsoni can be taken as one of the best-known examples (Bloch & Gingerich 1998). In the lower jaw, the anterior teeth were greatly reduced except the large first incisors which were followed by two teeth reduced to mere nubbins (identified as the second incisor and the canine). Only a single premolar remained (identified as the fourth) but to make up for it that tooth was huge, a massive blade-like multi-cusped structure that ground against the similar obscenely complex third and fourth premolars in the upper jaw (another derived carpolestid, Carpomegodon jepseni, retained a small third premolar in the lower jaw—Bloch et al. 2001). In comparison to all this, the three molars that followed were rather pedestrian. Biknevicius (1986) interpreted this tooth arrangement (comparable only to the multituberculates among other mammals) as indicative of a diet of foods with a tough exterior that would have been pierced by the premolars but a soft interior that did not require a huge amount of molar processing. Carpolestids were probably omnivorous, feeding on insects, seeds and fruit, with later forms becoming increasingly frugivorous.

Upper dentition of Carpolestes simpsoni from Bloch & Gingerich (1998).
This has nothing to do with the above post but as soon as I found it (here) I thought it was too fantastic not to share. From a German book published in the early 1900s, illustrated by one F. John, comes perhaps the creepiest reconstruction of the giant lemur Megaladapis ever.
Systematics of Euarchonta
<==Euarchonta (see below for synonymy)NG13
| i. s.: Dracontolestes Gazin 1941V67
| Remiculus Russell 1964V67
| Picromomys [Picromomyidae]R06
|--+--PrimatesNG13
| `--SundatheriaOB13
| |--ScandentiaOB13
| `--+--Navajovius Matthew & Granger 1921BS07, S35a
| | `--*N. kohlhaasae Matthew & Granger 1921S35a
| `--+--Eudaemonema Simpson 1935NG13, S35b
| | `--*E. cuspidata Simpson 1935S35b
| `--+--DermopteraBS07
| `--MicrosyopidaeV67
| |--Uintasorex montezumicus Lillegraven 1976W96
| |--ArctodontomysR06
| |--Megadelphus lundeliusiR06, BS07
| |--Craseops Stock 1934V67
| | `--C. sylvestrisW96
| |--Cynodontomys Cope 1882V67
| | |--C. angustidensG52
| | |--C. knightensis Gazin 1952G52
| | |--C. latidens Cope 1882G52
| | |--C. lundeliusi White 1952G52
| | `--C. scottianus (Cope 1881)G52
| `--Microsyops Leidy 1872NG13, V67 (see below for synonymy)
| |--M. annectens (Marsh 1872)W96
| |--M. knightensisBS07
| |--M. kratos Stock 1938W96
| |--M. latidensNG13
| `--M. lundeliusiMHL03
`--+--+--Bessoecetor Simpson 1966HUG17, SFY02
| | `--*B. septentrionalis (Russell 1929)SFY02 (see below for synonymy)
| `--+--Mixodectes Cope 1883NG13, V67 [incl. Indrodon Cope 1884V67, Olbodotes Osborn 1902V67]
| | `--M. pungensNG13
| `--Apatemyidae [Apatemyoidea, Apatotheria]V67
| | i. s.: Aethomylos simplicidens Novacek 1976W96
| |--Unuchinia Simpson 1937 [Unuchiniinae]V67
| `--ApatemyinaeV67
| |--Jepsenella Simpson 1940V67
| |--Eochiromys Teilhard de Chardin 1927V67
| |--Heterohyus Gervais 1848-1852 (see below for synonymy)V67
| |--Stehlinella Matthew 1929 [incl. Stehlinius Matthew 1921]V67
| |--Sinclairella Jepsen 1934V67
| |--Labidolemur Matthew & Granger 1921V67
| | |--*L. soricoides Matthew & Granger 1921S35a
| | `--L. kayiS35a
| `--Apatemys Marsh 1872HUG17, V67 [incl. Teilhardella Jepsen 1930V67]
| |--A. bellus Marsh 1872W96
| |--A. downsi Gazin 1958W96
| |--A. hendryi Robinson 1966S96
| |--A. pygmaeusHUG17
| `--A. uintensis (Matthew 1921)W96
`--+--Palenochtha Simpson 1935NG13, S35b
| |--*P. minor (Gidley 1923) [=Palaechthon minor]S35b
| `--P. weissaeOB13
`--+--PandemoniumBS07
|--PalaechthonidaeSM93
| |--AnasaziaR06
| |--Plesiolestes Jepsen 1930SM93
| | `--P. problematicusNG13
| |--PalaechthonNG13
| | |--P. alticuspis Gidley 1923S35b
| | `--P. nacimientiBS07
| `--Torrejonia wilsoniKSW17
`--+--PlesiadapoideaNG13
`--+--ParomomyidaeBS07
`--+--+--Niptomomys doreenaeNG13
| `--ToliapinidaeR06
| |--AveniusBS07
| |--ToliapinaBS07
| `--Berruvius Russell 1964BS07, SM93
| |--B. gingerichiBS07
| `--B. lasseroni Russell 1964RLS67
`--Micromomyidae [Micromomyinae]BS07
|--Tinimomys graybulliensisNG13
|--Chalicomomys Beard & Houde 1989BS07
| `--C. antelucanusBS07
|--Dryomomys Bloch, Silcox et al. 2007BS07
| `--*D. szalayi Bloch, Silcox et al. 2007BS07
`--Micromomys Szalay 1973BS07
|--M. fremdiBS07
`--M. silvercouleeiBS07

*Bessoecetor septentrionalis (Russell 1929)SFY02 [=Diacodon septentrionalisSFY02, Propalaeosinopa septentrionalisSFY02; incl. Palaeosinopa diluculi Simpson 1935SFY02, Bessoecetor diluculiSFY02, Propalaeosinopa albertensis diluculiSFY02, S67, B. thomsoni Simpson 1936SFY02, Pr. thomsoniSFY02]

Euarchonta [Bimanes, Dermosimii, Euprimateformes, Mixodectidae, Mixodectoidea, Oldobotidae, Paromomyiformes, Paromomyoidea, Plesiadapiformes, Primatomorpha]NG13

Heterohyus Gervais 1848-1852 [incl. Amphichiromys Stehlin 1916, Heterochiromys Stehlin 1916, Necrosorex Filhol 1890]V67

Microsyops Leidy 1872NG13, V67 [incl. Bathrodon Marsh 1872V67, Mesacodon Marsh 1872V67, MicrosusBB03, Palaeacodon Leidy 1872V67]

*Type species of generic name indicated

References

Biknevicius, A. R. 1986. Dental function and diet in the Carpolestidae (Primates, Plesiadapiformes). American Journal of Physical Anthropology 71 (2): 157–171.

[BB03] Bloch, J. I., & D. M. Boyer. 2003. Response to comment on “Grasping primate origins”. Science 300: 741c.

Bloch, J. I., D. C. Fisher, K. D. Rose & P. D. Gingerich. 2001. Stratocladistic analysis of Paleocene Carpolestidae (Mammalia, Plesiadapiformes) with description of a new Late Tiffanian genus. Journal of Vertebrate Paleontology 21 (1): 119–131.

Bloch, J. I., & P. D. Gingerich. 1998. Carpolestes simpsoni, new species (Mammalia, Proprimates) from the Late Paleocene of the Clarks Fork Basin, Wyoming. Contributions from the Museum of Paleontology, The University of Michigan 30 (4): 131–162.

[BS07] Bloch, J. I., M. T. Silcox, D. M. Boyer & E. J. Sargis. 2007. New Paleocene skeletons and the relationship of plesiadapiforms to crown-clade primates. Proceedings of the National Academy of Sciences of the USA 104 (4): 1159–1164.

[G52] Gazin, C. L. 1952. The Lower Eocene Knight Formation of western Wyoming and its mammalian faunas. Smithsonian Miscellaneous Collections 117 (18): 1–82, 11 pls.

Gingerich, P. D. 1976. Cranial anatomy and evolution of Early Tertiary Plesiadapidae (Mammalia, Primates). The Museum of Paleontology, University of Michigan, Papers on Paleontology 15: 1–141.

[HUG17] Halliday, T. J. D., P. Upchurch & A. Goswami. 2017. Resolving the relationships of Paleocene placental mammals. Biological Reviews 92 (1): 521–550.

Kirk, E. C., P. Lemelin, M. W. Hamrick, D. M. Boyer & J. I. Bloch. 2008. Intrinsic hand proportions of euarchontans and other mammals: implications for the locomotor behavior of plesiadapiforms. Journal of Human Evolution 55: 278–299.

[KSW17] Ksepka, D. T., T. A. Stidham & T. E. Williamson. 2017. Early Paleocene landbird supports rapid phylogenetic and morphological diversification of crown birds after the K–Pg mass extinction. Proceedings of the National Academy of Sciences of the USA 114 (30): 8047–8052.

[MHL03] Meng, J., Y. Hu & C. Li. 2003. The osteology of Rhombomylus (Mammalia, Glires): implications for phylogeny and evolution of Glires. Bulletin of the American Museum of Natural History 275: 1–247.

[NG13] Ni, X., D. L. Gebo, M. Dagosto, J. Meng, P. Tafforeau, J. J. Flynn & K. C. Beard. 2013. The oldest known primate skeleton and early haplorhine evolution. Nature 498: 60–64.

[OB13] O’Leary, M. A., J. I. Bloch, J. J. Flynn, T. J. Gaudin, A. Giallombardo, N. P. Giannini, S. L. Goldberg, B. P. Kraatz, Z.-X. Luo, J. Meng, X. Ni, M. J. Novacek, F. A. Perini, Z. S. Randall, G. W. Rougier, E. J. Sargis, M. T. Silcox, N. B. Simmons, M. Spaulding, P. M. Velazco, M. Weksler, J. R. Wible & A. L. Cirranello. 2013. The placental mammal ancestor and the post-K-Pg radiation of placentals. Science 339: 662–667.

[R06] Rose, K. D. 2006. The Beginning of the Age of Mammals. John Hopkins University Press: Baltimore.

[RLS67] Russell, D. E., P. Louis & D. E. Savage. 1967. Primates of the French early Eocene. University of California Publications in Geological Sciences 73: 1–46.

[SFY02] Scott, C. S., R. C. Fox & G. P. Youzwyshyn. 2002. New earliest Tiffanian (late Paleocene) mammals from Cochrane 2, southwestern Alberta, Canada. Acta Palaeontologica Polonica 47: 691–704.

[S35a] Simpson, G. G. 1935a. The Tiffany fauna, Upper Paleocene. I.—Multituberculata, Marsupialia, Insectivora, and ?Chiroptera. American Museum Novitates 795: 1–19.

[S35b] Simpson, G. G. 1935b. New Paleocene mammals from the Fort Union of Montana. Proceedings of the United States National Museum 83 (2981): 221–244.

[S96] Storer, J. E. 1996. Eocene-Oligocene faunas of the Cypress Hills Formation, Saskatchewan. In: Prothero, D. R., & R. J. Emry (eds) The Terrestrial Eocene–Oligocene Transition in North America pp. 240–261. Cambridge University Press.

[SM93] Stucky, R. K., & M. C. McKenna. 1993. Mammalia. In: Benton, M. J. (ed.) The Fossil Record 2 pp. 739–771. Chapman & Hall: London.

[V67] Van Valen, L. 1967. New Paleocene insectivores and insectivore classification. Bulletin of the American Museum of Natural History 135 (5): 217–284.

[W96] Walsh, S. L. 1996. S. Middle Eocene mammal faunas of San Diego County, California. In: Prothero, D. R., & R. J. Emry (eds) The Terrestrial Eocene–Oligocene Transition in North America pp. 75–119. Cambridge University Press.

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