You’ve heard of leaping lizards, but what about flying lemurs? Movie goers learned to love lemurs thanks to the popular films Madagascar (Pixar) and Dinosaur (Disney). And now, there’s more to love about them.

It seems the furry fellows are just one notch below the Primate group, to which humans belong. That’s according to a new study showing that the colugos, nicknamed the flying lemurs, is the closest group to the primates within the entire class of living mammals. The findings are based on new molecular and genomic data.

Caption: Photo right, Colugo in Flight- Colugos glide from tree to tree in Malaysia forests using their special skin fold, or patagium, for support. This mother and baby (Cynocephalus variegatus) looks like a living kite but is closely related to primates, the order of mammals that includes lemurs, monkeys, apes, and humans. Credit: Norman Lim, National University of Singapore

Caption: Photo Left, Colugos on a tree- Colugos, like this mother and baby (Cynocephalus variegatus) from southeast Asia, represent the taxonomic group that is the closest to primates, according to a new study to be published in Science on Nov. 2, 2007. Credit: Norman Lim, National University of Singapore

Debates over which of several mammalian groups is the closest relative to the primates have become more intense in the last ten years because of new fossil and molecular evidence. Some scientists have suggested that the group Scandentia, which includes the small tree shrews that scamper up and down trees in Asia, deserves the honor. Tree shrews have fluffy tails, long, pointed snouts, and a very large brain size for their body size.

Others scientists favor dermopterans, a relatively little-known group that includes two living species of colugos in southeast Asia. Although colugos are colloquially termed “flying lemurs,” they are not lemurs and they do not fly. Instead, they have a specialized skin fold, called a patagium, that stretches from the neck to the forelimbs, back to the hindlimbs, and finally to the tail. A colugo gliding from tree to tree at dusk uses its patagium for support and resembles nothing so much as a furry kite.

Since 1999, all three groups — primates, scandentians, and dermopterans — have been recognized as comprising a single taxonomic unit, or clade, known as Euarchonta, or “true ancestors.” The exact evolutionary relationships among the three groups within Euarchonta have proven elusive due to their overall closeness and the existence of a number of features that are shared among the groups.

Three hypotheses have been generated by researchers prior to this study. The “Primatomorpha hypothesis” is that colugos and primates together comprise a single group, the Primatomorpha, which separated evolutionarily from a common ancestor with the tree shrew group. A second hypothesis is that tree shrews and colugos — inhabiting the geographic region known as Sunda and having many features in common — are more closely related to each other than to primates. Thus, in this “Sundatheria hypothesis,” primates split off from the sundatherians, which later subdivided into scandentians and dermopterans. The third hypothesis is that primates are most closely related to tree shrews alone, with colugos being more distant from both, which can be called the “tree shrew hypothesis.”