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There are several extant species which exhibit this intermediate format - somewhere between ground predator and primate. Examples of these are the Raccoon (Procyon lotor), Kinkajou (Potos flavus), and Madagascan Fossa and so viability of this way of life is evident. In time, perhaps millions of years, selection for features which are essentially primate-like will come about in these animals. This is because primate characteristics and forms are the best suited for the maximum exploitation of arboreal life.


Let us have a closer look at some of these modern intermediates.



The Raccoon (Procyon lotor)


Our pioneering rainforest dog, at the stage described above, could have had traits similar to the raccoon. They are quite capable of climbing up into trees. They are relatively small (around 30 inches in length) and some aspects of ‘primatisation’ are already present. These include the five fingered  and manipulative hands and the long and narrow hind feet (plantigrade) which rest flat on the ground - as in all primates. Diet is omnivorous and mainly relates to resources found in trees including fruit, eggs, nuts, insects and rodents. However, the raccoon could only develop into a monkey and not an ape because it lacks the brain architecture required to produce an intelligent ape.


The Kinkajou (Potos flavus)


Kinkajous are of a similar size to the raccoon. They are more dedicated to life in the rainforest canopy than the racoon which roams at ground level too. Hence, as one would expect, they are endowed with characteristics which are more monkey-like. They have shorter snouts, forward facing eyes, rounded ear lobes, and a prehensile tail. They also have, the primate-like long fingered hands and long feet.


The brain morphology of the kinkajou is comparable with that of the raccoon - and so it could be that they are just further along the path of primatisation than raccoons.  

Kinkajous and raccoons are classed as ‘small bears’ - the Procyonids in the Order Carnivora. Being omnivorous they are intermediate between monkeys (mainly leaf-eating) and true carnivores. Perhaps the kinkajou will reach true monkey-ness when it’s diet matches that of monkeys.  


A Closer Look at Primatisation   



In the diagrams below the skeleton of a dog illustrates the long carpals and tarsals of the digitigrade form. Dogs, like many other mammals and birds stand on their toes. Primates and some mammals like the raccoons and kinkajous, mentioned above, have short carpals and tarsals and are described as plantigrade.





In the process of primatisation, the carpals and tarsals are reduced to form long flat feet and hands. I have digitally modified the original dog skeleton to show this in the next illustration.












I have also orientated the skeleton into an upright stance, rotating the cranium to a position at right-angles to the vertebral column. The other skulls depicted show the stages of the foreshortening of the snout. To complete the primatisation process I have removed the tail vertebrae and depicted the vestigial tail (pigostyle).




















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The kinkajou
Racoon hands