Ancient amber fossils from Myanmar in Southeast Asia reveal the preserved remains of lizards.
Sept. 15, 2011 --
A stunning array of prehistoric feathers, including dinosaur protofeathers, has been discovered in Late Cretaceous amber from Canada. The 78 to 79-million-year-old amber preserved the feathers in vivid detail, including some of their diverse colors. The collection, published in this week's Science, is among the first to reveal all major evolutionary stages of feather development in non-avian dinosaurs and birds. In this slide, an isolated barb from a vaned feather is visible trapped within a tangled mass of spider's web.
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"These specimens were most likely blown into the tacky resin, or were plucked from an animal as it brushed against resin on a tree trunk," lead author Ryan McKellar told Discovery News. "The fact that we have found some specimens trapped within spider webs in the amber would suggest that wind played an important role in bringing the feathers into contact with the resin," added McKellar, a postdoctoral fellow at the University of Alberta's Department of Earth and Atmospheric Sciences. The feather filaments shown here are similar to protofeathers that have been associated with some dinosaur skeletons.
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McKellar and his team made the discovery after screening over 4,000 amber samples from Grassy Lake, Alberta. The amber, collected by the Leuck family, is now housed at the Royal Tyrrell Museum. The researchers ruled out that the inclusions were mammal hairs, plant or fungal remains based on their structure. Some dinosaur fossils retain skin impressions, so the scientists could match dinosaur protofeathers (hair-like projections) to some of the objects within the amber. Here, a feather is visible near a plant bug. The high number of coils in the this feather suggests it could have come from a water-diving bird.
The translucent tree resin provides a window into feather evolution, from non-avian dinosaurs to birds. "Part of what makes this particular set of feathers interesting is that we find the very simple Stage I and II feathers alongside advanced feathers that are very similar to those of modern birds, Stages IV and V," McKellar said. The researchers aren't yet certain why feathers first evolved, but the density of the protofeathers suggests that they helped dinosaurs with regulating temperature. Dinosaurs such as Troodon or Deinonychus may have produced the feathers. The cork-screw shaped structures in this slide are the tightly coiled bases of feather barbules.
As feathers continued to change, they developed tufts, barbs, branching features, little hooks, and more. Some of the most advanced feathers in the collection are comparable to those of modern grebes. They appear to help diving, indicating that some of the prehistoric birds were divers. McKellar suspects the marine birds might have been Hesperornithiformes, a specialized flightless diving bird from the Dinosaur Era. This is a white belly feather of a modern grebe, showing coiled bases comparable to those seen in the Cretaceous specimen.
Some of the feathers appear transparent now, but would have been white in life. A range of colors for the feathers is evident, though, with grays, reds and various shades of brown preserved. This, and prior research, suggests that non-avian dinosaurs and prehistoric birds could be quite flashy. The pigment within this fossilized feather suggests it would have originally been medium- or dark-brown in color.
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In an accompanying "Perspectives" article in Science, Mark Norell points out that the dinosaur Sinosauropteryx is thought to have had a reddish banded tail, while Anchiornis likely possessed a striking black body, banded wings and a reddish head comb. Norell, chair and curator of the American Museum of Natural History's Division of Paleontology, told Discovery News that the newly discovered feathers are "very exciting." Here, a feather barb within Late Cretaceous Canadian amber shows some indication of original coloration.
Some dino aficionados have wondered if DNA could be extracted from the feathers. "Almost anything is possible," Norell said, quickly adding that most DNA-extraction studies have been conducted on much younger amber, dating to around 20-30 million years ago, and even those led to questionable results. "Maybe bits and pieces could be identified, but not the whole genome." Shown are 16 clumped feathers in Late Cretaceous amber.
People with amber objects, such as jewelry, also probably don't have prehistoric feather inclusions, since such items are extremely rare and dealers isolate the best pieces. Nevertheless, McKellar said, "There is some hope that you could have small feather fragments that have been overlooked." An unpigmented feather and a mite in Canadian Late Cretaceous amber.
The fossil, dated to 100 million years ago, is an incredible 78 million years older than the previous oldest chameleon on record, according to a study, published in the journal Science Advances.
In addition to significantly pushing back chameleon origins, the fossil reveals that the infant lizard somehow became stuck in the resin of a coniferous tree during the Dinosaur Age. The predicament led to the eventual death and preservation of the chameleon.
The amber collection, housed at the American Museum of Natural History, also contained a fossilized gecko and another archaic lizard, both of which will be described in a future study. At least 10 other lizards were found in the amber, but they were not as well preserved.
“It was mind-blowing,” co-author Edward Stanley said of when he saw the fossils for the first time. “Usually we have a foot or other small part preserved in amber, but these are whole specimens — claws, toepads, teeth, even perfectly intact colored scales. I was familiar with CT technology, so I realized this was an opportunity to look more closely and put the lizards into evolutionary perspective.”
Stanley is a University of Florida postdoctoral student of herpetology at the Florida Museum of Natural History. Using a micro-CT scanner, he and his team looked inside the amber pieces without damaging the fossils. The scientists then digitally pieced together the tiny bones and soft tissues that they spotted.
“These fossils tell us a lot about the extraordinary, but previously unknown diversity of lizards in ancient tropical forests,” Stanley said in a press release. “The fossil record is sparse because the delicate skin and fragile bones of small lizards do not usually preserve, especially in the tropics, which makes the new amber fossils an incredibly rare and unique window into a critical period of diversification.”
The fossil of the chameleon challenges the view that these animals first evolved in Africa. It also suggests the evolutionary order of some of the lizard’s most distinctive features.
For example, the amber-trapped lizard has the iconic projectile tongue of modern chameleons, but it had not yet developed the unique body shape and fused toes specially adapted for gripping that we associate with chameleons today.
The ancient lizards have modern counterparts living in the same region, providing evidence for the inherent stability of tropical forests without significant human intervention.
“These exquisitely preserved examples of past diversity show us why we should be protecting these areas where their modern relatives live today,” Stanley said.