G,Day all
The following article by Jeff Poling reports on 1994 palaeontologic
discoveries of the Confucius bird, then considered likely to have
"revolutionary effects on thinking about bird evolution". Does this still
represent current opinion on the subject?
Regards
Ian May
Tel: 0409 474 575
> Earliest beaked bird discovered
>
> Jeff Poling
>
> Long ago, during the Jurassic when dinosaurs ruled the earth and even
> birds had a toothy grin, there lived a bird by a lake surrounded by lush
> forest. This bird, about the size of a bantam rooster, had a long tail
> like its reptilian ancestors [later found to be only feathers, rather
> than bony as in other early birds] and forearms that ended in claws,
> handy for climbing trees. In one striking respect, this primitive bird
> had taken an evolutionary step that seemed to anticipate every bird of
> today, every eagle and robin and chickadee: there was not a tooth in its
> head. This was the earliest bird known to palaeontology to have
> abandoned the toothy jaws of its reptilian ancestors, replacing them
> with a avian style beak.
>
> Fossil remains of this bird were found in China last year, 1994, and
> palaeontologists, astonished and excited by the discovery, say the
> findings could have revolutionary effects on thinking about bird
> evolution.
>
> The exact age of the bird is not known, but palaeontologists say it was
> probably close in time to Archaeopteryx, the transitional reptile-bird
> that lived about 153 million years ago in what is now Germany and is
> recognized as the oldest known bird. If that is the case, the new fossil
> species lived 70 million years earlier than the previously oldest known
> toothless bird, Gobipteryx, from Mongolia. [More recent data shows the
> deposits which produced the fossils are actually early Cretaceous, 122 -
> 145 million years old]
>
> The discovery of a skull, wing, two feathered legs and a pelvis in
> ancient lake-bed sediments was made by a farmer in the Liaoning province
> in northeastern China, near the border with North Korea. Chinese and
> American palaeontologists describe the fossils and discuss their
> implications in a report published in the journal Nature. Their name for
> the new fossil species is Confuciusornis sanctus, for holy Confucius
> bird.
>
> The Confucius bird provides compelling evidence that nature's initial
> experimentation with birds must have spread quickly into a global
> phenomenon played out in different habitats and marked by seemingly
> rapid evolutionary transitions, even some false starts. Indeed, the
> researchers suggest that the Confucius bird occupied a separate limb of
> the avian family tree that branched off soon after the emergence of
> Archaeopteryx, leading to Gobipteryx and eventual extinction.
>
> These birds somehow lost their teeth and developed horny bills, an
> adaptation that the main line of avian evolution did not exhibit until
> the end of the Cretaceous period, about 65 million years ago.
>
> For almost a century Archaeopteryx has been alone on its perch as the
> early bird of the Jurassic geological period. But the new findings
> suggest that birds in several forms and stages of evolution probably
> existed at the time, or shortly thereafter.
>
> Since the Confucius bird was found on the other side of the world from
> Archaeopteryx, palaeontologists said, the discovery shows that birds in
> different forms were a widely dispersed phenomenon. They had even
> adapted to different habitats: the Chinese fossils were found in a
> freshwater environment; Archaeopteryx came from marine lagoons.
>
> "We now have birds that were different from Archaeopteryx, very
> different," said Dr. Larry D. Martin, a palaeontologist at the
> University of Kansas at Lawrence and one of the authors of the Nature
> report. "We also know there was some diversity in birds at that time,
> both in geography and in design."
>
> An analysis of the fossils showed that the wing skeleton, including the
> long fingers and big claws, and two legs retained the primitive, almost
> reptilian features found in Archaeopteryx. But the skull, with its beak,
> represented a dramatic innovation. The horny bill is assumed to have
> evolved from reptilian scales.
>
> Scientists also note that the Confucius bird showed another sign of
> modernity: the first direct evidence of body feathers. The only
> preserved feathers on Archaeopteryx are on its wings. Another author,
> Dr. Alan Feduccia, a specialist in bird evolution at the University of
> North Carolina at Chapel Hill, said the Confucius bird's "transition to
> a modern avian beak so swiftly is really astounding.'' It is not
> astounding, however, to those who, unlike Feduccia, consider birds to be
> closely related related to beaked dinosaurs such as the ornithomimids
> and segnosaurs.
>
> In their report, Martin, Feduccia and their Chinese colleagues, Lian-hai
> Hou of the Institute of Vertebrate Palaeontology in Beijing and Zhonghe
> Zhou, a graduate student at Kansas, say the findings hint at discoveries
> yet to be made at this critical stage in bird evolution. They write:
> "These specimens provide evidence for either an undiscovered
> pre-Archaeopteryx or a rapid post-Archaeopteryx evolution in birds.''
>
> Other palaeontologists familiar with the fossils quibble with the
> suggestion that the Confucius bird lived as early as the Jurassic
> period, and the authors of the Nature report acknowledge that the
> geology of the region made it difficult to pin down the timing.
>
> But the scientists echo the reaction of Dr. Mark Norell, a
> palaeontologist at the American Museum of Natural History in New York
> City: "It's a very, very important specimen.'' Dr. Luis Chiappe, a
> research associate at the museum who has examined the fossils, said they
> would yield valuable information about the early evolution of birds and
> made him all the more curious to discover the common ancestor of
> Archaeopteryx and Confuciusornis.
>
> But even members of the research team do not quite agree why an early
> bird might cast off its reptilian teeth. Feduccia says it was one more
> weight-saving modification to aid flight; this is the conventional
> explanation. But Martin doubts the beak offered any weight advantages.
> Instead, he suggests that as the early birds evolved and their forelimbs
> became completely dedicated to being wings, they no longer had
> appendages for manipulating food, for turning morsels to go head-first
> into the mouth. Teeth got in the way, and the wider beak, in effect
> enlarged reptilian scales over the top of the jaw, gave them room to
> slide food back and forth in the mouth before swallowing.
>
> Copyright © 1995 by Jeff Poling.
Birding-Aus is on the Web at
www.shc.melb.catholic.edu.au/home/birding/index.html
To unsubscribe from this mailing list, send the message
"unsubscribe birding-aus" (no quotes, no Subject line)
to
|
