Anti-evolutionary scoffers continually spout the claim that there are too many "gaps" in the fossil record for it to provide a coherent picture.
This claim is inaccurate and misleading, blowing the situation out of proportion. These so called gaps are merely the fossils which we have not found yet. Just in the past few months, (early 1999), many of these gaps are being filled at a fast rate, as new discoveries are being unearthed. Below are unedited news stories documenting these new finds.
Rare Skeleton Find Rounds View of Mammal Evolution
12.31 p.m. ET (1731 GMT) March 25, 1999
Chinese researchers have found the earliest known complete skeleton of a mammal, giving scientists new insights into how mammals evolved. The well-preserved remains of the mouse-sized, insect-eating creature belonged to a group of primitive animals called triconodont that roamed the Earth some 145 million years ago.
"It is a very exciting, important finding. Because of it we have a much better understanding of the relationship of this early relative to modern mammals," Dr. Luo Zhexi of the Carnegie Museum of Natural History in Pittsburgh said in a telephone interview on Wednesday.
Until now scientists have had to piece together the early history of mammals from fragments of isolated teeth and bones.
"For the first time ever we have discovered a very complete skeleton. We have a much more comprehensive picture of early mammalian evolution," Luo said.
Luo, the assistant curator of vertebrate paleontology at the museum, collaborated with scientists at the National Geological Museum of China in Beijing who found the 10-cm (four-inch) skeleton in a famous dinosaur site in northeastern China in 1997.
It is an extremely rare find and dates from the late Jurassic or early Cretaceous period.
A study of the skeleton, published in the science journal Nature, showed it was a young animal which had lost its first teeth, in much the way children lose their baby teeth.
It had a flexible shoulder blade and collarbone and was capable of walking almost erect. A puzzling combination of features suggests that different parts of the animal evolved at different rates.
"We learned that the body skeleton had a very complicated early evolutionary history and that the earliest mammals were probably ground-living animals," Luo said.
Timothy Rowe of the University of Texas in Austin described the skeleton as "one of the most complete and exquisitely preserved specimens ever found."
"The latest discovery helps to fill a wide gap in the fossil record, and brings new information to classic problems on the origin and interrelationships of early mammals," he said in a commentary in Nature.
Fossil Find Bridges Vertebrate Gap
A newly found fossil of a small, lizard-like creature is helping scientists fill a 30-million-year gap in the puzzle of vertebrate evolution.
Paleontologist Roberta L. Paton of the National Museums of Scotland in Edinburgh and her colleagues discovered a five-inch-long skeleton in a weathered block of Scottish rock. The fossil, Casineria kiddi, might be the granddaddy of most of today's land-dwelling vertebrates, including humans, Paton and her colleagues report in this week's journal Nature.
For years, paleontologists have known that amniotes -- a group that includes most land-dwelling vertebrates and a few water-dwellers like dolphins and whales -- probably evolved from fish with legs that lived approximately 370 million years ago.
But 30 million years separated the most recent known fossils of legged fish from the earliest known fossils of amniotes. Nobody knew what kinds of creatures populated this evolutionary gap, nor, as paleontologist Ted Daeschler of the Academy of Natural Sc iences in Philadelphia points out, when or if the gap would ever be filled.
"Fossils are rare and their preservation is a real statistical crap-shoot," says Daeschler. "Rarely do you expect to find intermediates and complete series of things."
Casineria was found by an amateur collector embedded in a rock several million years older than any of the known amniotes. The rock's age alone indicated that Casineria was an amphibian. But careful study of the bones revealed that it was st rikingly well-adapted for life on land. The shape and twist of its arm bone would have allowed it to walk on land, and the build of its five-fingered hand, to grasp.
"It probably looked somewhat like a lizard with funny, large feet," says Paton.
By feeding observations to a computer program, Paton and her colleagues have built a tentative family tree that shows that Casineria might be an ancestral amniote.
Amniotes seem to have had "a long, but previously unrecorded history," says Paton.
And more insights are probably on the way. "Different persons with different backgrounds will see different things in a fossil," says Daeschler. "Casineria is likely to provide raw material for many studies."
By Marina Chicurel, Discovery Online News
Jaw Evolution Gets Clearer
A 400-million-year-old relative of the shark may shed new light on the evolution of the jaw, information that also has implications for human evolution.
John Maisey, curator in the Vertebrate Paleontology department at the American Museum of Natural History, reported Friday that the Bolivian fossil, named Pucapampella, disputes a prevailing theory and provides a missing link in the evolution of jawed vertebrates.
"This is the earliest shark brain case that we can actually study in any detail," says Maisey. "The way we view the early evolution of the jaw now has to change."
The development of the jaw is one of the most significant evolutionary events in early vertebrate history, but not much is known about its origin. Few fossils exist from the period in which they first evolved, sometime before the Devonian period 412 to 354 million years ago.
Until now, the structure of the shark jaw was thought to be something way back along the evolutionary line, a precursor to the jaws of bony fish, the most common type of fish -- and our ancestor.
But this jaw defies that theory. It seems that Pucapampella's jaw is more like that of a bony fish than jaws of today's sharks.
"John Maisey's study suggests that there is a basic, primitive jaw structure shared by the very first fishes that evolved jaws," says Mike Gottfried, curator of vertebrate paleontology at the Michigan State University Museum in East Lansing.
"It also adds to the evidence that the more advanced sharks, with their alternative jaw structures, are highly specialized animals in many respects, and that we can't just assume that sharks represent the most primitive condition in jawed vertebrate evolution."
Maisey's report sheds some light on an important initial step toward human evolution: the development of jawed vertebrates from jawless ones.
Although we may not want to admit it, some of our defining anatomical features could come from our ancient, fishy ancestors.
"The psychology of evolution is interesting," says Maisey. "People don't mind being called a primate or a mammal, but they don't like being called a fish."
By Amy Sirot, Discovery Online News
Nature 409, 181 - 184 (2001) © Macmillan Publishers Ltd.
Fossil that fills a critical gap in avian evolution
MARK A. NORELL AND JULIA A. CLARKE
Despite the discoveries of well-preserved Mesozoic birds, a key part of avian evolution, close to the radiation of all living birds (Aves), remains poorly represented. Here we report on a new taxon from the Late Cretaceous locality of Ukhaa Tolgod, Mongolia, that offers insight into this critically unsampled period. Apsaravis and the controversial alvarezsaurids are the only avialan taxa known from the continental deposits at Ukhaa Tolgod, which have produced hundreds of fossil mammals, lizards and other small dinosaurs. The new taxon, Apsaravis ukhaana, is the best-preserved specimen of a Mesozoic ornithurine bird discovered in over a century. It provides data important for assessing morphological evolution across Avialae, with implications for, first, the monophyly of Enantiornithes and Sauriurae; second, the proposition that the Mesozoic sister taxa of extant birds, as part of an 'ecological bottleneck', inhabited exclusively near-shore and marine environments; and third, the evolution of flight after its origin.