Re: Two more gaps in the fossil record

Stephen E. Jones (
Tue, 19 Oct 1999 06:58:49 +0800


I apologise for sending an earlier draft by mistake to the List. Please
delete it and read this one instead. Thanks.


On Fri, 15 Oct 1999 19:02:04 +0000, wrote:


>CL>How do we know it's *transitional*? If we know it's transitional, how do we
>>know in which *direction* the transition is occurring? Maybe all we can say
>>is that it's *intermediate* morphologically. If birds generally come later in
>>the fossil record, how do we know they didn't exist as a rare type for a long
>>time, prior to becoming widespread?

While I accept that birds probaly arose from dinosaurs, at 140-120 mya (Early


Yahoo! News Science Headlines

Thursday October 14 7:30 PM ET
Fossils of Flying Dinosaur Found

AP Photo

By PAUL RECER AP Science Writer

WASHINGTON (AP) - A fierce turkey-sized animal with sharp claws and
teeth may have been the first flying feathered dinosaur, a missing link
between the lumbering lizards of millions of years ago and the graceful
birds of today.

Fossils of the animal, called Archaeoraptor liaoningensis, suggest that it
lived 120 million to 140 million years ago when a branch of dinosaurs was
evolving into the vast family of birds that now live on every continent,
researchers said Thursday.

"We're looking at the first dinosaur that was capable of flying," said Philip
Currie of the Royal Tyrrell Museum in Alberta, Canada, a dinosaur expert
who helped analyze the new fossil.

"We don't know how good a flier it was, but it certainly has all of the
structures you would expect to see in a flying animal," he said. The animal's
shoulder girdle and breast bone resemble that of modern birds, said Currie,
and its hands had been modified to form part of the wing structure. It also
had a full set of feathers and a long tail that probably gave it stability in

"The long stiff tail suggests that it helped maneuver in flight, but it also
suggests that the animal wouldn't have been a very good flier," Currie said.

Archaeoraptor also had hollow bones, typical of birds. Such bones are
strong, but light enough to help the birds the fly.

"This animal was about the size of a small turkey," Currie said. "That is
relatively big for a bird, but small for a dinosaur."

The fossils, to be unveiled for the first time on Friday at the National
Geographic Society's Explorers Hall in Washington, are among a group of
feathered dinosaur remains unearthed recently in the Liaoning Province of

Another animal, called Sinornithosaurus millenii, or "Chinese bird-reptile of
the millennium", had birdlike features and short downy feathers. It also was
about the size of a turkey, but probably was not capable of flight.

The Sinornithosaurus, however, "had this terrible claw on its hind legs and
much longer claws on its hands," said Currie.

"It would have been quite fearsome for its size," he said. "You can imagine
being attacked by a turkey with claws."

Fossils of another feathered dinosaur, called Beipiaosaurus inexpectus, also
are being made public by the National Geographic. This animal was larger
than the others, about 7 feet long, and apparently had stiff, narrow feathers
that provided warmth. It is not thought to have been capable of flight.

The three animals are all theropod dinosaurs, a group that included the
ultimate meat-eater, the Tyrannosaurus rex. Theropods all walked upright
on their hind legs, had long tails and were thought to be fast and deadly.

The new findings also suggest that many theropods, including
Tyrannosaurus, may have had feathers at some point of their development.
The National Geographic-sponsored researchers suggest that
Tyrannosaurus infants may have hatched with a coat of down that was shed
as they got older.


Copyright (c) 1996-1999 The Associated Press. All rights reserved.

this fossil is probably too late to be a plausible ancestor of birds.
Archaeopteryx from the Upper Jurassic (Portlandian) at 150-145 mya
(Harland W.B., et. al., "A Geologic Time Scale 1989", pp54-55), is already
5-30 mya older:

"Archaeopteryx, from the Upper Jurassic (Portlandian) of the Solenhofen
region in southern Germany, remains the prime example of a genus that
occupies the position of a "missing link" uniting two major vertebrate
groups." (Carroll R.L., "Vertebrate Paleontology and Evolution", 1988,

The Yixian Formation in China's Liaoning Province where these so-called
`feathered dinosaur' fossils are being found is later (ie. younger) than the
Solnhofen Lithographic Limestones where Archaeopteryx was found:

"Two spectacular fossilized dinosaur skeletons were recently discovered in
Liaoning in northeastern China.

An exceptionally well-preserved theropod dinosaur from the Yixian
Formation of China.


The Jehol biota was widely distributed in eastern Asia during latest Jurassic
and Early Cretaceous times...the specimens described here consist of two
nearly complete skeletons of a small theropod discovered by farmers in
Liaoning. The skeletons are from the basal part of the Yixian
Formation......These sediments are rich in fossils of mixed Jurassic-
Cretaceous character. The primitive nature of the fossil birds of the
Jianshangou fossil group has led to suggestions that the beds could be as
early as Tithonian in age. But although Confuciusornis and the other birds
are more advanced than Archaeopteryx in a number of significant features,
we can only conclude that the beds that the fossils came from are probably
younger than the Solnhofen Lithographic Limestones (Early Tithonian).
The presence of Psittacosaurus in the same beds is more consistent with an
Early Cretaceous age, as are the palynomorphs..." (Chen P-j, Dong Zm &
Zhen S-n, "An exceptionally well-preserved theropod dinosaur from the
Yixian Formation of China", Nature, vol. 391, 1998, p147)

GM>We don't. That is one of the things about the fossil record that is little
>known. However, if you are engaged in an exercise of doubt, to see how
>much data you can doubt, then no data will suffice for any conclusion
>whatsoever. What one must deal in is probabilities. It is highly probable
>that birds came after dinosaurs and it is highly probable that hollow boned
>animals were not alive too much earlier than this creature. There is
>selective pressure against hollow bones among land dwellers


GM>There are no hollow-boned animals except birds and hollow boned animals are
>found AFTER the solid boned dinosaurs.

This is not so. As it happens I was watching a dinosaur show on TV the
other might and the first episode featured a small lightweight late-Triassic/
early Jurassic (ie. ~200-190 mya) dinosaur called Coelophysis which they
said had hollow bones. And Carroll and Colbert confirm this:

"A number of relatively completely known theropods have been described
from the late Triassic and early Jurassic. Coelophysis (Colbert, 1972) and
Syntarsus (Raath, 1969) are small, lightly built forms known from western
North America and eastern Africa, respectively. Similar genera, which are
placed in the family Podokesauridae, are present to Europe, South
America, and Asia. Coelophysis (Figure 14-6a) is a small form that has
been considered typical of the coelurosaurs. The skeleton is approximately
22 meters long and extremely lightly built. The limbs are long and slender,
and the bones are hollow." (Carroll R.L., "Vertebrate Paleontology and
Evolution", 1988, pp290-291).

"The earliest carnivorous theropod dinosaurs are well represented by the
North American genus Coelophysis, in recent years made known by
extraordinarily complete and beautifully preserved fossil skeletons, found in
the upper Triassic sediments of northern New Mexico. Coelophysis was an
animal about six feet in length, so lightly built (the bones were hollow) that
in life it probably did not weigh more than forty or fifty pounds." (Colbert
E.H., "Evolution of the Vertebratese", Fourth Edition, 1992, pp150-151).

GM>Archaeopteryx is solid boned (see
>Carroll, Vertebrate Paleontology and Evolution, 1988, p. 339)

Glenn has misunderstood Carroll. Carroll says that Archaeopteryx's bones
are "thick walled", not that they are hollow:

"The bones are thick walled, without the pneumatic ducts common to both
modern birds and pterosaurs." (Carroll R.L., "Vertebrate Paleontology and
Evolution", W.H. Freeman & Co: New York NY, 1988, p339).

Indeed, they couldn't be said to be "walled" at all, if they weren't

Moreover, in an article on Archaeopteryx in Scientific American,
Wellnhofer says that Archaeopteryx had "hollow bones":

"In reptiles the centers of growth are in the shafts of their hollow bones,
whereas growth in young birds takes place at the bones' thick cartilaginous
ends, called epiphyses. During the final stage of a bird's growth, its
epiphyses turn from cartilage into bone, leaving a scar that then disappears
when the bird matures. None of these Archaeopteryx specimens shows any
such scars on its hollow bones." (Wellnhofer P., "Archaeopteryx",
Scientific American, May 1990, p46).


"Suppose contemporary evolutionary theory had blind chance built into it so
firmly that there was simply no way of reconciling it with any sort of divine
guidance. It would still be perfectly possible for theists to reject that theory
of evolution and accept instead a theory according to which natural
processes and laws drove most of evolution, but God on occasion abridged
those laws and inserted some crucial mutation into the course of events.
Even were God to intervene directly to suspend natural law and inject
essential new genetic material at various points in order to facilitate the
emergence of new traits and, eventually, new species, that miraculous and
deliberate divine intervention would by itself leave unchallenged such key
theses of evolutionary theory as that all species derive ultimately from some
common ancestor. Descent with genetic intervention is still descent-it is
just descent with nonnatural elements in the process." (Ratzsch D.L., "The
Battle of Beginnings: Why Neither Side is Winning the Creation-Evolution
Debate," InterVarsity Press: Downers Grove, Ill., 1996, pp187-188)
Stephen E. Jones | |