A previously unknown species of gnat found in a piece of 54 million-year-old Indian amber may throw into question a long-held theory about the formation of the subcontinent.
Available evidence had indicated that the chunk of the supercontinent Gondwana that became India split off about 130 million years ago, travelled north and collided with Asia about 59 million years ago, forming the Himalayas in the process.
The timing of the continental drift was supported, in part, by fossil finds that suggested Indian and European fauna were strongly isolated from each other until after the collision.
However, a team of researchers led by Frauke Stebner of the Stuttgart State Museum of Natural History in Germany reveal a preserved fungus gnat that appears closely related to other species – fossil and extant – found in Europe.
Stebner and colleagues report in the journal PeerJ that the previously unknown species, named Palaeognoriste orientale, is very similar to one found in northern Europe in Baltic amber. The European gnat dates to a slightly more recent period.
The gnats belong to the family Lygistorrhinidae, which comprises both extinct and still-living species. To date, the fossil side of the family contains two species known from Europe and three from Asia.
The dating of the latest find – in a type of amber known as Cambay, found in lignite mines in the Indian state of Gujarat – indicates, say the researchers, fauna exchange between the two land masses may have occurred before the formation of the Himalayas.
Although Baltic amber has been well studied, Cambay amber represents a relatively untouched resource, with entomologists expecting to find a wide range of new preserved species that may provide new evidence of insect spread and evolution.
The Lygistorrhinidae species, for instance, are currently held to have been rare, but that may well be because there has been comparatively little work done on the Indian amber. The status could change if further finds are made.
Stebner believes the gnats may have travelled via “land bridge connections between drifting India and Africa”, but concedes much more research will be needed before the picture becomes clear.
“This issue remains difficult,” she adds. “Insects in Cambay amber can add pieces in a huge puzzle.”
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