Plesiadapis tricuspidens (Gervais 1877) Paleocene ~55 mya. The Plesiadapiformes were widely thought to be the earliest representatives of the primate order, but here they nest basal to rodents + shrews + multituberculates, derived from Henkelotherium.

Plesiadapis had a deeper shorter rostrum and a higher orbit, but a smaller braincase. The jugal was more robust. The ear was raised. The mandible was more robust with deeper surfaces for muscle attachement and a more robust angular process and a longer coronoid process. The cervicals were shorter. The dorsals, ribs and lumbars were more robust along with the caudals. Chevrons developed at a likely sitting point. The limbs and girdles were more robust. The radius was anteriorly boewed and the ulna developed a large olecranon process (elbow). The unguals were large and deep. The feet were larger than the hands. The joints were nearly all transversely aligned indicating a simple extension/flexion motion for the fingers and toes.

Henkelotherium guimarotae (Krebs 1991; Jäger, Lu and Martin 2019; Late Jurassic 150 mya) was traditionally considered a eupantothere (replaced by Dryolestida). Here Henkelotherium nests with Pleisiadapis. basal to multituberculates, shrews and rodents. The manus was small and the pes had long digits with asymmetric metatarsals. The lumbar region was long and flexible.

Castor canadensis (Kuhl 1820, extant, up to 90cm svl + 35cm flat tail) is the North American beaver, a traditional rodent here nesting with Plesiadapis. This large, aquatic forest dweller chews down trees to create dams and ponds. The nasals are widest at mid-length. The auditory bullae have extended necks.

Bloch JI and Boyer DM 2006. Grasping primate origins. Science 298:1606-1610.

Gervais P 1877. Enumeration de quelques ossements d’animaux vertebres recueillis aux environ de Reims par M. Lemoine. Journal de Zoologie (Paris) 6:74–79.

Gingerich PD 1976. Cranial Anatomy and Evolution of Early Tertiary Plesiadapidae (Mammalia, Primates). Papers on Paleontology, Museum of Paleontology, The University of Michigan. 1-141. online pdf

Jäger KRK, Lu Z-K and Martin T 2019. Postcranial skeleton of Henkelotherium guimarotae (Cladotheria, Mammalia) and locomotor adaptation. Journal of Mammalian Evolution https://doi.org/10.1007/s10914-018-09457-2

Krebs B 1991. Skelett von Henkelotherium guimarotae gen. et sp. nov. (Eupantotheria, Mammalia) aus dem Oberen Jura von Portugal. Berl Geowiss Abh A.: 133:1–110.

Kuhl H 1820. Castor Canadensis. Beiträge zur Zoologie und vergleichenden Anatomie. Frankfurt: Verlag der Hermannschen Buchhandlung: 64–65.

wiki/Henkelotherium
wiki/Dryolestida
wiki/Plesiadapis
/wiki/North_American_beaver = Castor