Updated March 11, 2022
as Microcebus (Fig. 1) moves out of the Primates and into the Volitantia close to Ptilocercus (Fig 3a).
Now you have a choice.
Either go out looking for crumbling bits and pieces of basal primate jaws and teeth over vast stretches of badlands… Or go to Madagascar to study basal primates in the wild, and have them feeding from your hand, according to the latest addition to the LRT.
The gray mouse lemur,
(Microcebus murinus; Figs. 1, 2) nests at the base of the all the tested primates in the large reptile tree (LRT, 1692+ taxa; subset Fig. 3), basal to both larger adapid lemurs, Notharctus and Smilodectes.
Though living today in Madagascar forests,
Microcebus likely radiated during the Cretaceous, prior to the splitting of Madagascar from Africa 88 mya. Later it gave rise to all extinct and extant adapids and lemurs on that island.
Millions of years ago lemurs were
worldwide in distribution. Now only a few lemurs find refuge in Madagacar. and only in Madagascar.
Microcebus murinus (Miller 1777) is the extant gray mouse lemur an omnivore found only in Madagascar. This nocturnal arboreal basalmost primate in the LRT forages alone, but sleeps in groups, sharing tree holes during the day. Twin babies are typical. Offspring can reproduce after one year. Lifespan extends to ten years. The eyes are large, typical of nocturnal mammals. Relatives include Hapalodectes and Ptilocercus. Descendants include Notharctus and Smilodectes.
The newly expanded clade Scandentia (tree shrews) now unites
Volitantia (bats + pangolins + colugos), Primates and Glires (rodents, rabbits, multituberculates and kin) in the LRT, subset Fig. 3). The addition of Microcebus as the smallest lemur held the possibility that it was the most basal form or one leading to smaller galagos and tarsiers. This time Microcebus turned out to be more primitive.
Here’s a revised subset of the LRT
(Fig 3a) with more taxa and corrected scores.
With the addition of Microcebus to the LRT,
the extant pen-tailed tree shrew, Ptilocercus (Fig. 4) nests basal to colugos, which also lack upper incisors. That means an older, more plesiomorphic fossil taxon with a complete set of upper incisors is out there waiting to be discovered somewhere in Early Jurassic fossil beds.
Paleontologists have been looking for the ancestor of primates,
colugos and bats for ages. They find fewer and smaller bony scraps the deeper they look.
Here’s a solution:
Add extant taxa. Phylogenetic analyses that includes extant taxa can sometimes help by nesting late survivors at basal nodes. Sure the fossil taxa are the real ancestors. Sure, living lemurs are late survivors, radiating into new morphologies and niches, but the soft, cuddly, active chatterboxes (Fig. 1) are still worth studying and scoring.
Miller JF 1777. Cimelia Physica p.25