Monkey lemur

Classification and phylogeny

There are two species within the genus Archaeolemur: Archaeolemur edwardsi and the Archaeolemur majori. Recently, there have been findings of fossils in the north to north east of Madagascar. These findings of the Archaelolemur edwardsi fossils are enough to create an almost complete reconstruction of what the hands and feet looked like. These reconstructions indicate that the extinct lemurs did not climb very often and imply that they were much more at home on the ground. In fact, the indication is that they were more ground-oriented than most living strepsirrhines. They are not believed to have been exclusively terrestrial, but rather to have had a combined habitat of ground and arboreal life. A modest degree of curvature found in the remains support this idea. The hands and feet are very robust and large in size, but are very short and said to be closer to the likeness of a baboon's hand. The hind-limbs are also known to be short, which implies that the hands and feet are relatively short for the lemur's body weight. While the hands and feet of Archaeolemur may have a likeness to the hands of baboons, they are not considered to be similar to either baboons or other strepirrhines at all. Instead they are more akin to Mandrillus and macaques. Archaeolemur is unique in the combination of post-cranial features. The overall look of the lemur, beyond just the hands and feet, was a relatively short and stocky one which gave them limited leaping abilities. This indicates that the Archaeolemur may have inhabited large portions landscapes, which is consistent with its spread over practically the entire island of Madagascar. This implies they had a high tolerance for broad habitats. They are also known to be omnivores from the fossilized droppings of a younger individual. An imaging technique shows pictures of the mandibles, showing the bone structure of the mouth. Further studies on their enamel indicate that Archaeolemur also had the ability to exploit resources that may have been indigestible to other species, showing a great robustness in their dietary tracts as well. It comes as no surprise, then, that once humans migrated to Madagascar, Archaeolemur was able to outlive most of the other currently extinct species of lemur before finally also going extinct.

Archaeolemurs’ bones are more robust than any extant primitives and their hands are relatively much shorter than most other subfossil species and lemurs. Archaeolemur’s feet are more closely akin to indriids and Eulemur amongst living lemurs. Compare the differences between Archaeolemur's manual and pedal phalangeal, their hands are similar to primitive that spend much of their time on the ground. Archaeolemurs on the ground are more often than any extent strepsirrhine and probably more time than other subfossil lemurs. Their body size approximately just over 48% of baboons. Archaeolemurs’ hallucal experienced a reduction of length of thumbs, which could explain to reduction of manual grasping capabilities or different demands that requires them to change their hallucal. Archaeolemurs’ hindlimbs and forelimbs are short and extraordinary robust, which unlike the extant strepsirrhine that have the similar pedal length but due to the very long hindlimbs. The wrist of Archaeolemur most similar to extant palmigrade monkeys such as Cercopithecus mitis. Consequently, wrist and hand provides the morphology evidence that Archaeolemurs have both arboreal and terrestrial traits .

Hadropithecus stenognathus is the only species of the Genus Hadropithecus, which is more commonly referred to as the "monkey lemur", belonging to the family Archaeolemuridae. The species was discovered in Madagascar in the year 1899 by a renowned paleontologist by the name of Ludwig Lorenz von Liburnau, who associated the monkey lemurs with apes. Three years later in the year 1902 Liburnau classifies Hadropithecus stenogathus as a lemur. Unfortunately fossils of the monkey lemur are uncommon to find. Yet, in an article alalyzing the dental microware of Archaeolemuridae, some important information was discovered through fossilized teeth of the lemurs. In turn, helped distinguish between certain characteristics of the Archaeolemuridae monkey lemurs compared to Megalaclapid family of lemurs. The purpose of the analysis of the Archaeolemuridae dental microwear is to study the texture in order to gain a detailed idea of the monkey lemur diet. The analysis technique utilizes three dimensional surface measurement with a white-light confocal profiler for fractal analysis. The two families of Archaeolemuridae and Megalaclapid occasionally had similar diets observed from the overlapping textures of their dental microwear. However, the two families’ dental microwear differ at some points, indicating that the Archaeolemuridae monkey lemurs have a diet containing a variety of harder foods. Liburnau continued to make distinctions of the lemur monkeys by reconstruction of certain skulls which reaffirmed that the monkey lemurs are a sister family to sloth lemurs.

Hadropithecus stenognathus, referred to as the “monkey lemur” or “baboon lemur,” may have survived until the late First Millennium A.D. It was led to extinction mainly by human activity, like many other lemurs of Madagascar. However, it became extinct sooner than Archaeolemur, its sister genus. The last known record of Hadropithecus stenognathus was dated back to around 444-772 CE. It is believed that Hadropithecus was a more rare lemur, since there were not as many subfossils found of it. Similar to the sloth lemur, Hadropithecus was a large, slow, specialized lemur, that grazed and fed on seeds. Archaeolemur was more generalized, which led it to survive longer. Although it is not completely verified, Hadropithecus’ large body and large brain, compared to other species, led to the belief that it would have reproduced fairly slow, thus being susceptible to extinction. The slow reproduction rate goes hand in hand with weaning age. Hadropithecus stenognathus would not have weaned its young before 2.75 years of age, or even 3 years, making it the lemur with one of the slowest life cycles. It is believed that Hadropithecus stenognathus would have not given birth more than once every other year. In addition, Hadropithecus stenognathus would have spent most, if not all, of its time on the ground, making it readily available for hunting and exploitation by humans. It not only would have faced pressure from humans, but also from domestic livestock, which were grazers as well. To make matters worse for Hadropithecus, additionally, pigs and other animals were introduced by humans, putting more pressure on them. Though it could have climbed trees, it lacked adaptation for suspension or leaping. Both lemurs, Hadropithecus and Archaeolemur, like every other lemur, were endemic to Madagascar. No lemur subfossils have been found yet in other areas of the world.

Hadropithecus Stenognathus have similar cranial stricture and dental portions to hominins. H. stenognathus carbon isotope data show that they consumed CAM or C4 plants. The prior assumption that H. stenognathus ate C3 plants which included large seeds and hard fruits are wrong because it was too strong for the animal’s teeth. Testing the carbon samples along southern and southwestern Madagascar where H. stenognathus once lived and was endemic to; scientists found high values of carbon isotopes tied to C4 and Cam group of plants. The large teeth were meant to extract the nutrients from food that needed incisional however not tough preparation.

The H. stenognathus species was well-suited to processing large amounts of small and/or flat, displacement-limited foods. Rather than a previously thought diet of resistant, stress-limited foods. Hadropithecus stenognathus lived in environments in southern and southwestern Madagascar in which the bulbs and corms of grasses and sedges were eaten for nutrient content. The consumption of large quantities of bulbs and corms compensates for their low nutritional quality. Having to eat bulbs and corms shorter limbs were adapted by the H. stenognathus over generation for an efficiency in ground locomotion through their body shape. Although skeletons are rare to find, subfossils have indicated

that the H. stenognathus was a medium shaped lemur with short limbs to walk around, unlike relatives with long limbs to reach for tree branches.