Fossil of Earliest Bird Pollinator Found
Researchers have discovered the earliest fossil evidence of a bird visiting flowers, presumably to feed on the nectar. The new fossil indicates that bird–flower interactions were already taking place at least 47 million years ago.
Birds are important pollinators, like insects and bats, yet we don’t know very much about the evolutionary history of bird pollination (or ornithophily). Now, an ornithologist and paleobotantist duo, Gerald Mayr and Volker Wilde from Senckenberg Research Institute and Natural History Museum Frankfurt, report the first direct fossil evidence of flower-visiting by birds.
The complete skeleton of a small, ancient bird (Pumiliornis tessellatus) from the middle Eocene of Messel, Germany, was found in oil shale pits in 2012 with its stomach contents preserved. They contained two types of pollen grains from eudicotyledonous angiosperrms -- flowering plants with three grooves in its pollen grain -- which the researchers think were ingested when the bird was hunting for nectar in the flowers. Here’s the complete skeleton of P. tessellatus, with stomach contents circled.
The little nectar-drinking bird was about 8 centimeters long and probably weighed between 5 and 10 grams. That's about the size of hummingbirds and sunbirds we have today. Its skeletal morphology further suggests the bird was a nectarivorous flower-visitor. It had a long, slender bill with elongated nasal openings; in hummingbirds, these increase the flexibility of the bill tip, helping them probe for nectar deep in flowers. A fourth toe that could be turned backward meant the bird could clasp or climb branches, also helpful for visiting flowers.
P. tessellatus is only known from two other specimens (dating back 30-34 million years), and neither of them had preserved stomach contents. And despite similarities to our nectar-feeders now, this fossil bird doesn’t belong to any of the modern groups of flower-visiting birds, which suggests the origin of ornithophily in some lineages of flowering plants may have predated that of their existing avian pollinators. According to Mayr, flowering plants that are able to take advantage of birds for pollination likely existed before 47 million years ago; and bird pollination, he suspects, began shortly before this species took flight.
As for the ancient pollen grains, they also don’t match any known fossil or extant pollen. They’re large and appeared to clump together, indicating that their flowers must have been pollinated by animals and not by wind. Pictured on the right, a detailed look at the pollen preserved in the stomach contents.
Additionally, soft tissue, plumage, and claw sheaths were also remarkably preserved -- as well as iridescent insect remains among the stomach contents.
The work was published in Biology Letters this week.
Images: Mayr et al., Biology Letters (2014)
May 28, 2014