Plesiadapis

Name: Plesiadapis ‭(‬Near Adapis‭)‬.
Phonetic: Plees-e-ah-dap-is.
Named By: Paul Gervais‭ ‬-‭ ‬1877.
Synonyms: Menatotherium,‭ ‬Nothodectes.
Classification: Chordata,‭ ‬Mammalia,‭ ‬Plesiadapiformes,‭ ‬Plesiadapoidea,‭ ‬Plesiadapidae.
Species: P.‭ ‬tricuspidens‭ (‬type‭)‬,‭ ‬P.‭ ‬anceps,‭ ‬P.‭ ‬churchilli,‭ ‬P.‭ ‬cookei,‭ ‬P.‭ ‬dubius,‭ ‬P.‭ ‬fodinatus,‭ ‬P.‭ ‬gingerichi,‭ ‬P.‭ ‬insignis,‭ ‬P.‭ ‬praecursor,‭ ‬P.‭ ‬remensis,‭ ‬P.‭ ‬rex,‭ ‬P.‭ ‬russelli,‭ ‬P.‭ ‬simonsi,‭ ‬P.‭ ‬walbeckensis.
Diet: Uncertain‭ ‬-‭ ‬refer to main text for more details.
Size: Around‭ ‬80‭ ‬centimetres long and‭ ‬2‭ ‬kilograms in weight.
Known locations: Europe and North America.
Time period: Selandian to Thanetian of the Paleocene.
Fossil representation: Multiple specimens numbering well over a hundred.‭ ‬Many of these are fragmentary but a few are almost complete and some even show the impression of skin and hair as an outline of carbonaceous film.

       Plesiadapis is popularly depicted as the ancestor of the primates,‭ ‬something that is reflected in its name that means‭ ‘‬near Adapis‭’‬,‭ ‬one of the earliest known primates.‭ ‬This idea is not without its critics however,‭ ‬with most palaeontologists preferring to treat it as a representative of an ancestral form rather than‭ ‘‬the‭’ ‬ancestor of the primates.‭ ‬Some palaeontologists go even further than this and treat Plesiadapis as part of a sister group separate to but related to the ancestors of primates.‭ ‬The type species name P.‭ ‬tricuspidens is a reference to the incisors of the holotype specimen which have three cusps‭ (‬points‭) ‬to them.
       The dental formula for Plesiadapis is‭ ‬2.1.3.3‭ (‬two incisors,‭ ‬1‭ ‬canine,‭ ‬three premolars,‭ ‬three molars‭) ‬across both upper and lower jaws,‭ ‬yielding a total of‭ ‬36‭ ‬teeth.‭ ‬Unfortunately it is currently impossible to be certain about just what it ate.‭ ‬Plesiadapis would have come from insectivorous/carnivorous ancestors and the teeth would still be suited to a carnivorous diet.‭ ‬However there also seems to be a shift towards herbivory which suggests that Plesiadapis was eating parts of plants like fruits and nuts.‭ ‬It is also just as possible that Plesiadapis was an omnivorous creature that foraged for whatever was edible.
       There has also been a lot of discussion and opinion regarding the lifestyle of Plesiadapis with some proposing that Plesiadapis was a cursorial creature that lived upon the ground.‭ ‬However more popular thinking depicts Plesiadapis as an arboreal creature that would climb up trees and move from branch to branch through the tree canopy.‭ ‬Although perhaps not as graceful as later more specialised arboreal mammals,‭ ‬Plesiadapis does possess skeletal features such as limbs that face towards one another and long clawed fingers that would have helped it more to grip hold of branches rather than run across the ground.
       When first described in‭ ‬1877,‭ ‬Paul Gervais based his description upon a partial left mandible‭ (‬lower jaw‭)‬.‭ ‬Since this discovery however many other remains of Plesiadapis have been discovered with some of the best and most complete coming from France.‭ ‬Skin and fur are also known to be preserved as carbonaceous film,‭ ‬a preservation process where intense pressures and heat from the weight of overlying sediments press down upon a fossil creating a‭ ‘‬print‭’ ‬of the soft tissues in the form a thin layer of carbon upon the rock.‭ ‬Because carbonaceous film is only known from Europe and North America it is thought to have travelled across Greenland when an ancient land bridge still connected these two parts of the world.



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