Tiny fossil reveals what happened to birds after dinosaurs went extinct

The fossils of a tiny bird found on Native American land in New Mexico are giving scientists new ideas about what happened after most dinosaurs went extinct. A 62-million year-old mouse bird shows that, after the great dino die-off, bird rebounded and diversify rapidly, make today’s dizzying variety of feathery form.

The newly found fossils, depicted online today in the Proceeding of the National Academy of Science, are a collection of bits and pieces rather than a complete skeleton. But several most outstanding characteristics such as its fourth toe, which it could turn around forward or backward help it to climb or grasp – convinced the team that is a ancient mousebird. Researchers found the fossils in New Mexico on ancestral Navajo land, in rocks dating to between 62.2 to 62.5 million years old. They named the creature Tsidiiyazhi abini-Navajo for “little morning bird”. Its mousebird descendants – about the size of sparrow and marked by their soft, grayish or brownish hair like feathers – still dwell in tree in sub-Sahara, Africa today.

But it is the interesting fossil age. It is just a few million years after an asteroid struck Earth and brought the age of dinosaurs to the sudden end 66 million years ago. Groups such as mammals and frogs are known to have rebounded rapidly after that event, diversifying into multiple new forms as they occupied newly available niches – an evolutionary biologists called adaptive radiation. But there have been some giant fossil evidence for what happened to birds – the only dinosaurs to survive the extinction – in its aftermath.

Paleontologists have suspected that birds make a quick rebound. However, bird fossils from early Paleogen period immediately after extinction –  particular those of small tree-dwelling animal – are very rare. A few lineage survived extinction and had a really fast radiation right afterwards.

The new study highlight the notion with fossil evidence, and helps fleshes out the fate of birds during this crucial time period. The team combined the new fossil evidence with previously collected genetic data from living birds to update the phylogenetic tree of bird evolution. Previous trees used this data to differentiate the bird into different groups, but weren’t able to determine when they had diverged. Now, with the new fossils so precisely dated, the team could determine when exactly different bird lineages split off from one another. As a result, Ksepka and his colleague estimate that the ancestors of some 9 major land bird lineages – from mousebirds to owls to raptors like eagle and hawks – must have emerged in quick succession, all practically in the shadow of extinction event.

Ksepka says:” There is only 3.5 million years for all of these groups begin to split off”. He adds that the new finding suggests that water birds such as penguins  did the same thing. Earlier this year, researchers found a 61 year old fossil of a 1.5 meter high penguin in what is today New Zealand.


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