The basalmost primate in the LRT is alive and living in Madagascar!

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.

Figure 1. The gray mouse lemur (Microcebus murinus) nests basal to primates in the LRT.

Figure 1. The gray mouse lemur (Microcebus murinus) nests basal to primates in the LRT.

This largest species in this smallest genus of primates
also nests between two tree shrew taxa, Tupaia (basal to Glires) and Ptilocercus (Fig. 4; basal to Volitantia).

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.

Figure 2. The skull of Microcebus murinus from Digimorph.org and used with permission. Here colors mark bones.

Figure 2. The skull of Microcebus murinus from Digimorph.org and used with permission. Here colors mark bones.

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.

Figure 3. Subset of the LRT focusing on the clade Scandentia (tree shrews) and the three arboreal clades that arise from it.

Figure 3. Subset of the LRT focusing on the clade Scandentia (tree shrews) and the three arboreal clades that arise from it.

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.

Figure 4. Ptilocercus is a sister to Microcebus nesting with colugos.

Figure 4. Ptilocercus is a sister to Microcebus nesting with colugos.

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.


References
Miller JF 1777. Cimelia Physica p.25

wiki/Microcebus

4 thoughts on “The basalmost primate in the LRT is alive and living in Madagascar!

      • Amongst the less specialised Malagasy prosimians are M. murinus & M. coquereli; Cheirogaleus major & Ch. medius; and possibly Phaner furcifer.

      • I recently discovered when the anterior dentary extend anteriorly, forming the famous lemur comb, that’s a derived trait not shared with other primates or basalmost primates. Although that’s one trait, it’s deal breaker, as far as I can tell at present. That can change.

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