Nasua, Notharctus. Megaladapis, Maganadapis, Eupleres and Adapis

Nasua nasua (Linneaus 1766) is the extant coatimundi or coati. Here it nests with the Notharctus, as a basalmost primate. Traditionally nested with raccoons (Procyon) Nasua has three molars, all similar, and no carnasial tooth, distinct from all members of the Carnivora in the LRT.

Notharctus tenebrosus (Leidy 1870, Gregory 1920, Eocene 54-38mya, 40 cm snout to rump) was an adapid. Coatimundis (Nasua) phylogenetically precede primates.

Distinct from Ptilocercus, the skull of Notharctus had a cranial crest. Both eyes were directed forwards (narrower interoccular distance) for binocular vision and they were higher on the skull. The jawbones fused at the chin, creating a single solid mandible. The incisors and canines were smaller. Premolars 1 and 2 were larger. Premolars 3 and 4 were smaller. Lower molar 1 was not as sharp, without the carnasial shape.

The cervicals were shorter. The lumbars increased in number. The sacrals were relatively short. The caudals were more gracile and more 'expressive'.

The scapula was smaller. The forelimbs were longer and more slender. With these it was able to spring from branch to branch across great gaps. The radius bowed away from the ulna enabling greater pronation and supination. The metacarpals were shorter. The fingers were much longer. Digit I was more robust and rotated medially, opposing the others as a thumb. Notharctus held on to branches by grasping them with its hands, not by embedding its claws.

The hind limbs were longer and more gracile. The medial toe likewise became thumb-like, rotating medially to oppose the others. The foot had a better "thumb" than the hand did. The metatarsals were shorter. The toes were longer and more gracile. Metatarsal III extended further than II, IV or V. Pedal digit III also extended further than the others. More primitive than living lemurs, Notharctus still had claws, not nails.

If like a living lemur, Notharctus practiced vertical clinging and leaping, a new method of locomotion. Sitting erect is comfortable due to the angle of the neck as it inserts into the skull at its base, not from behind.

Diet includes plants, insects, small vertebrates and eggs. Lemurs usually have only one baby after a 126-day pregnancy. Newborns are not born premature. They ride on their mother's back as she forages. Juveniles mature in 18 months. A typical lifespan is 18 years. Lemurs are social, living in tribes of fewer than 15 individuals. Reciprocal grooming is practiced. Lemurs with larger canines tend to be more agressive.

Plesiadapids, like Plesiadapis, are in the lineage of rodents. Below is the skull of Notharctus in three views.

The mandible of Purgatorius, widely considered the most primitive primate. Here the skull is reconstructed with Notharctus and Vulpavus in mind, rather than Ptilocercus, the pen-tailed tree shrew, which is about the same size as Purgatorius.

If you want to read the book, "From the Beginning - The Story of Human Evolution" by David Peters (Little, Brown 1991), which is where the above images were first published, click here for the PDF.

Megaladapis insignis (Forsyth Major 1894, up to 1.5m in length) is the extinct koala lemur from Madagascar. The arms were longer than the legs. The snout remains unknown. Only three molars were present. Here it nests between Notharctus and the rest of the primates, but clearly has been evolving its koala-like shape for the entire Cenozoic.

Adapis parisiensis (Cuvier 1821, Gingerich 1975, Eocene, 40mya; size) nests between Notharctus and Mandrill in the LRT. So, it is in the human lineage. Note the forward-facing eyes, smaller rostrum, larger canines, upturned premaxilla making room for large lower canines and incisors.

Magnadapis quercyi (Godinot and Couette 2008, MNHN QU 10875 Late Eocene, 11cm skull length) is a sister to Adapis in the LRT.

Notharctus is basal to Homo in this lineage

Cuvier GB 1822. Recherches sur les ossemens fossiles 3:265.

Gingerich PD 1975. Dentition of Adapis parisiensis and the evolution of lemuriform primates in I. Tattersall et al. (eds.), Lemur Biology. Plenum Press, NY.

Gingerich PD 1981. Cranial morphology and adaptations in Eocene Adapidae. I. Sexual dimorphism in Adapis magnus and Adapis parisiensis.

Gingerich PD and Martin RD 1981. Cranial morphology and adaptations in Eocene Adapidae. II. The Cambridge skull of Adapis parisiensis. American Journal of Physical Anthropology. 56 (3): 235–257. doi:10.1002/ajpa.1330560304

Godinot M and Couette S 2008. Morphological diversity in the skulls of large adapines (Primates, Adapiformes) and its systematic implications. in E. J. Sargis and M. Dagosto (eds.), Mammalian Evolutionary Morphology: A Tribute to Frederick Szalay

Gregory WK 1920. On the structure and relations of Notharctus, an American Eocene primate. Memoirs of the American Museum of Natural History, new series 3(2):49-243.

Leidy J 1870. Descriptions of Palaeosyops paludosus, Microsus cupidatus and Notharctus tenebrosus. Proceedings of the Academy of Natural Sciences, Philadelphia 22:111-114

Linneaus C von 1766. Systema naturæ per regna tria naturæ, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio duodecima, reformata. pp. 1–532. Holmiæ. (Salvius)

Major CIF 1894. On Megaladapis madagascariensis, an Extinct Gigantic Lemuroid from Madagascar; with Remarks on the Associated Fauna, and on Its Geological Age. Philosophical Transactions of the Royal Society B: Biological Sciences. 185: 15–38.

Major CIF 1900. Extinct Mammalia from Madagascar. I. Megaladapis insignis, sp. N. Philosophical Transactions of the Royal Society B: Biological Sciences. 193 (185–193): 47–50.

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wiki/Magnadapis
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