As paleontologists increasingly unearth evidence of feathers in prehistoric fossils, our conceptions of what dinosaurs looked like when they roamed the earth has gradually evolved.
Instead of the reptilian appearance we all recognize from childhood toys and films like Jurassic Park, many dinosaurs in fact more closely resembled birds, kind of like this recently discovered little guy, Eosinopteryx brevipenna, a flightless theropod dinosaur that roamed China during the Middle/Late Jurassic period.
Archaeopteryx, also known as Urvogel, the German word for "original bird" or "first bird," was first discovered in 1860 and later fossils of this species presented some of the earliest evidence of flight in these prehistoric animals.
An intermediate creature that was not quite dinosaur but not exactly a bird either when it lived 150 million years ago, Archaeopteryx had teeth, a long tail, and wings capable of flight with claws at the end for grabbing prey.
A century after the discovery of Archaeopteryx, paleobiologists increasingly found anatomical connections between birds and dinosaurs. In the 1970s, artists began to portray dinosaurs with feathers based on accumulating evidence.
Megapnosaurus, shown here, was another species with whom researchers began early to identify with feathers. A lightweight animal that could reach up to 10 feet in length and roamed Jurassic Zimbabwe, Megapnosaurus, also known as Syntarsus, traveled in packs and preyed on small reptiles and fish.
Many of the fossils unearthed that provided evidence of feathers had deteriotated over the eons they remained buried. It wasn't until 2010 that researchers identified color pigments in feathers from dinosaurs and early birds.
Sinosauropteryx, illustrated here, was a theropod dinosaur that had "simple bristles -- precursors of feathers -- in alternate orange and white rings down its tail," according to a description of the study's findings.
Given that so many feathered dinosaurs were in fact flightless, the purpose of the feathers has been a subject of debate. Some dinosaurs may have evolved feathers for social signaling; others had plumage to provide insulation.
In the cases of some dinosaurs, such as the two oviraptors, herbivores related to T. rex that lived during the Cretaceous period, researchers believe the feathers were used for mating displays, similar to modern-day peacocks and turkeys.
Jason Brougham/University of Texas
You might be fooled into thinking the animals in this illustration are something between a murder of crows and a band of blue jays. In fact they are Microraptors that lives more than 130 million years ago.
These four-winged, plumed dinosaurs were no larger than modern-day pigeons and sported iridescent tail feathers.
Researchers believe the shimmering plumage was likely used in mating and other social interactions.
Like the diversity among birds today, not all feathered dinosaurs were lightweight, agile animals. A massive tyrannosaur that lived in China until about 65 million years ago, Yutyrannus huali, meaning "beautiful feathered tyrant," grew up to 30 feet long and could weigh more than 3,000 pounds.
This titanic tyrannosaur, as it was described, significantly increases the size range for feathered dinosaurs.
In a stunning find published in the journal Science in 2011, paleontologists uncovered dinosaur feather preserved in amber that dated back some 79 million years ago.
This discovery provided scientists a new window into the evolution of feathers in terms of structure in the evolutionary timeline from dinosaurs to birds. Even shades of color remained well preserved in the amber.
A giant dinosaur found in Tanzania once lived during a lush, green period when flowering plants flourished, about 100 million years ago, paleontologists report. The new dino species is a rare find in sub-Saharan Africa, where far fewer dinosaur fossils are discovered than in South America, the researchers said.
Paleontologists discovered the massive fossil in 2007 during fieldwork in the Rukwa Rift Basin in southwestern Tanzania.
Political instability in certain parts of Africa can prevent dinosaur digs, but fossils in this part of the world are also elusive for geological reasons. As the continents drifted apart, Africa did not move as much as the other continents did, leaving its fossils buried instead of pushed up by plate tectonics, said Patrick O'Connor, a professor of anatomy at Ohio University in Athens, Ohio, and one of the researchers on the new study. [See photos of the dinosaur dig in Tanzania]
Africa also had fewer ideal areas where sediment could quickly bury a creature and begin the fossilization process. Politics and geology, "those two things together account for why we don't know so much about continental Africa as we do about other parts of the world," O'Connor said.
Joseph Sertich, then a graduate student at Stony Brook University in Long Island, New York, and now a paleontologist at the Denver Museum of Nature & Science, was the first to spot the bones in the Rukwa Rift Basin.
"He scrambled into a gully and found the skeleton coming out the cliff surface," O'Connor said.
A careful excavation by local coal miners and paleontologists in 2007 and 2008 suggests that muddy elements had buried the dinosaur's remains — not once, but twice, O'Connor told Live Science. About 100 million years ago, the dinosaur likely died on a muddy floodplain. Mudstone eventually covered its body, but shortly after, a river running through the plain cut away at the mudstone, exposing part of the skeleton and encasing it in sandstone.
A river still runs near the site, and its drainage through the cliff face had begun to uncover the ancient skeleton, O'Connor said.
The researchers recovered about two dozen fossilized bones, enough to determine that they had a new species on their hands, O'Connor said. An analysis of the bones' shapes and features suggest the dinosaur was a titanosaurian, a member of the giant, long-necked and plant-eating sauropod dinosaurs.
The paleontologists named the dinosaur Rukwatitan bisepultus for the Rukwa Rift Basin and its titanosaurian roots — an allusion to the powerful and mythical Greek Titan deities. In Latin, bisepultus means "twice buried," said Eric Gorscak, the study's lead researcher and a doctoral candidate of biological sciences at Ohio University. [Image Gallery: 25 Amazing Ancient Beasts]
"A lot of what we know about titanosaurian evolution and their biology stems from South America, where there's a lot of specimens," Gorscak said. Titanosaurian remains are found on every continent including Antarctica, but "the early evolutionary history outside of South America is fuzzy."
The new finding helps bridge that gap, said Matthew Lamanna, a curator of vertebrate paleontology at the Carnegie Museum of Natural History in Pittsburgh, who was not involved with the study.
Rukwatitan is important because it's "one of the very few Cretaceous-aged dinosaurs known from Africa south of the Sahara Desert," Lamanna told Live Science in an email. "That part of the world is one of the biggest 'black holes' in our understanding of dinosaurs," he said.
Previously, paleontologists found thetitanosaurian Malawisaurus dixeyi in Malawi, but the Rukwatitan fossils are markedly different in shape and size from that specimen and other titanosaurians found in northern Africa, O'Connor said.
Rukwatitan weighed between 10 and 15 tons — about as much as two elephants but not nearly as much as Dreadnoughtus schrani, another type of titanosaurian, discovered in Argentina, that weighed about 65 tons, Gorscak said. He and his colleagues used a computed tomography (CT) scan to view Rukwatitan's bones and its internal structure. Like other titanosaurians and meat-eating theropods — dinosaurs that may have given flight to birds — Rukwatitan's neck bone was hollow and filled with air.
"It's important for understanding the whole rest of the evolution of the group, especially since it comes from such a rare time and place," said Michael D'Emic, a research instructor in the department of anatomical sciences at the Stony Brook University School of Medicine, who was not involved in the study.
The study was published today (Sept. 8) in the Journal of Vertebrate Paleontology.
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Wipe Out: History's Most Mysterious Extinctions
Paleo-Art: Dinosaurs Come to Life in Stunning Illustrations
Images: Uncovering the Colossal Dreadnoughtus Dinosaur