Before the conclusive identification of Necrolestes, only one member of the Meridiolestida was known to have survived the extinction event, and that species died out soon after, early in the Tertiary Period (651.8 million years ago). Necrolestes is therefore the only remaining member of a supposedly extinct group. Its the supreme Lazarus effect, comments Wible. How in the world did this animal survive so long without anyone knowing about it?
In the Lazarus effect, a species previously thought to be extinct is rediscoveredsometimes living, sometimes elsewhere in the fossil record. The Lazarus effect is well represented by the ginkgo tree, thought to be extinct until it was rediscovered growing in China in the 17th century.
The researchers believe that Necrolestess supreme burrowing adaptations are exactly what enabled it to survive for 45 million years longer than its relatives. Theres no other mammal in the Tertiary of South America that even approaches its ability to dig, tunnel, and live in the ground, explains Wible. It must have been on the edges, in an ecological niche that allowed it to survive. The researchers point out that other extinct digging species are known by many specimens, while Necrolestes is only known from a few fossils from a narrow geographic area. This means it was not abundant in its time, which fits with the model of a life form existing in a marginal environment. Rougier comments, In a way, while not related, its somewhat similar to how the platypus lives today. There arent many of them, they are found only in Australia, and they live in a specific niche among modern mammalsjust as Necrolestes is an isolated lineage only found in South America, with very few individuals living among large numbers of marsupials.
Necrolestess survival for 45 million years longer than expected challenges more than
|Contact: Leigh Kish|
Carnegie Museum of Natural History