Great Balls Of Fire

http://www.forteantimes.com/artic/111/asteroid.html

So, you think the dinosaurs were wiped out in a meteorite impact 65 million years ago? Think again! This idea of mass-extinction is so widely-held, even amongst scientists, that it is often cited as a fact. Paul Chambers discovers clear evidence to the contrary as he reports on a paradigm in revision.

The Earth's predicted near-miss with asteroid XF11 in the year 2028 has once again focussed attention on the fear that a large asteroid or comet hitting our planet could trigger a global catastrophe.

To back this up, every article and television program about XF11 boldly asserted that the dinosaur extinction was caused by a giant asteroid impacting into the Earth 65 million years ago. This has typically been accompanied by a picture of frightened dinosaurs looking skyward at a huge flaming meteorite streaking across the horizon. This scenario is so widely accepted that few commentators bother to question it any more. There is, however, much evidence to suggest that an asteroid may not have hit the Earth 65 million years ago and that, even if it did, it did not cause the mass extinction of life attributed to it. There is also the possibility that dinosaurs may not have been around to witness it!

By the second world war it was known that, after a reign of 180 million years, the dinosaurs had died out 65 million years ago at the end of the Mesozoic era. During the 1960s and 70s, palaeontologists discovered that, at the same time as the dinosaurs had died out, a large number of other fossil groups became extinct or suffered huge drops in species numbers.(1,2) Amongst those that became extinct were the ammonites, belemnites, marine reptiles, flying reptiles and the reef-buildingbivalves whilst those suffering partial extinction included many types of marine plankton, sea urchins and some corals. All of this occurred around the transition from the Cretaceous period to the Tertiary period and became known as the 'K-T boundary' mass extinction event (K stands for keta, the Greek for chalk, T for Tertiary).

In rock outcrops, the K-T boundary itself is represented by a thin layer of red clay, only a couple centimetres in thickness. Below this clay are Mesozoic fossils, such as the dinosaurs, whilst above it are Tertiary ones. This was the situation, as science saw it when, in 1976, Dr. Walter Alvarez came across an exposure of K-T boundary red clay in Italy and collected some samples for later analysis. Walter Alvarez mentioned the mass extinction and his find to his physicist father, Dr. Louis Alvarez, who suggested chemically analysing the clay.

The results showed that the sample unexpectedly contained huge quantities of iridium, an element that is so rare on Earth that it was hard to explain its association with the K-T boundary clay. Other K-T boundary clays from around the world showed similarly high levels suggesting that the iridium spike (as it was known) was a global phenomenon and not just a local geological anomaly in Italy.

The Alvarez' knew that such high levels of iridium could only be found during volcanic eruptions or in asteroids from outer space. At that time there was no evidence for widespread volcanic eruptions 65 million years ago and so an extraterrestrial solution was sought. At the time of this research, a group of anti-nuclear scientists had begun promoting their ideas about the global effects of a nuclear holocaust that, in the depths of the cold war, seemed a realistic possibility. Their chief proposal was that a global nuclear war would produce a `nuclear winter' in which dust, water and other material sucked into the upper atmosphere would form a blanket around the Earth effectively preventing the heat and light of the sun from reaching the planet's surface. Beneath this atmospheric blanket the Earth would freeze, destroying tropical and temperate animal species, whilst the lack of sunlight would remove the base of the food chain by killing off all the plant life and plankton. In addition to this, large amounts of radioactive fall-out would accumulate inside the world's sediments poisoning the soils and seabed. The result would be the sudden mass extinction of almost all the plant and animal life on Earth with only the hardiest of creatures, such as rats and cockroaches, able to survive. It is this that caught the attention of Walter and Luis Alvarez.

They adapted the nuclear winter scenario to suggest that an asteroid impact 65
million years ago would have had a similar effect by throwing a huge quantity of
debris into the upper atmosphere, blocking out the sun. This would have
shattered the food chain and led to the demise of many groups and species,
including the dinosaurs. Instead of radiation, the Alvarez envisaged that the
iridium found inside the asteroid would also be thrown into the upper atmosphere
where it would have rained down into the world's sediments to form the elevated
levels seen in the K-T boundary clay. To do this, the asteroid was calculated to
have been at least 10 kilometres across and travelling at a speed of 80,000
kilometres an hour. In this form, the Alvarez published their theory in 1980.(3)


Under normal circumstances, the scientific community reacts badly to new and
radical ideas and it can take a generation for them to become widely accepted.
This was not the case with the asteroid impact theory; it was quickly grasped and
heralded as a masterpiece of scientific deduction. The K-T boundary suddenly
became a hot research topic.

It is here that, in my opinion, the first problem occurred. Having agreed with the
impact theory, now a large generation of scientists were setting out with the sole
aim of finding the evidence to reinforce it. As most forteans will know, people
looking for evidence to prove an existing theory will by and large find it, whether it
is there or not. A more scientific way to approach a research topic is to first gather
together the evidence and to build up conclusions from that database.

**This did not occur and scientists began to find circumstantial evidence for
widespread bush fires4, tidal waves5, freezing temperatures and acid rain as well
as the iridium spikes and mass extinction of life at every K-T boundary site around
the world. Each new observation reinforced the asteroid-impact theory with very
few objections being tolerated by the scientific press. The only variation was the
discovery of huge levels of volcanic activity in India at the time of the K-T boundary
which led to a small band of people advocating this as the cause of the extinction
and accompanying iridium spike.(6 )

By the mid-1980s it was common knowledge that it was an asteroid that had
wiped out the dinosaurs and today this is cited as a fact in most popular scientific
journals and television programs. There is, however, a small minority of
palaeontologists whose research was at odds with the asteroid impact theory.

Chief amongst these are the micropalaeontologists who study the fossil remains
of plants and animals which are less than one millimetre in size. Unlike dinosaurs,
ammonites, corals and trees, which are large and rare in the fossil record, a small
chip of rock can contain millions of microfossils (my record is 24 million per gram)
and can therefore give a better clue as to what the local environment was like
when they died. They are particularly common in deep sea sediments and,
throughout the 1980s, a world-wide program of deep sea coring produced a
whole series of new and well-preserved K-T boundary sediments in which the
micropalaeontologists began to find inconsistencies with the asteroid theory.

Some of the common microfossil groups did seem to suffer a mass extinction of
species across the K-T boundary.(7) For example, the calcareous nannofossils
lost 92 percent of their species and planktonic foraminifera between 50 and 85
percent.7 However, when a detailed examination of these groups was done, it
was discovered that many of the species did not die out all at once but in a series
of stages that began at least 300,000 years before the K-T boundary and carried
on for 200,000 years afterwards.(8,9 )Other microfossil groups proved to be
unaffected by the K-T boundary at all (eg. the radiolaria, diatoms, dinoflagellates
and bottom-dwelling foraminifera) (7,10,) something that was completely at odds
with the theory of nuclear winter followed by plankton collapse in the oceans.

Together these and other discoveries cast doubt on the notion of a sudden mass
extinction of species within a few years following a large asteroid impact. Many of
the fossils that had started the debate about the K-T boundary in the first place
were found not have died out suddenly at the K-T boundary, but to have been in
a serious decline for millions of years beforehand.(7) Groups like the
reef-buildingbivalves, marine and flying reptiles were proved to have become
extinct before the K-T boundary whilst the dinosaurs, ammonites, belemnites,
scleractinian corals and sea urchins had been in decline long before it.

The evidence was now beginning to point towards a long term global decline in
many fossil groups in the final stages of the Cretaceous rather than a sudden
extinction event at its end. For example, the dinosaur diversity had dropped from
45 genera, 85 million years ago, to just 12 at the K-T boundary. No dinosaur
remains at all are known from the K-T boundary and the youngest known dinosaur
fossil was found some 3 metres below the iridium clay, suggesting that they may
have become extinct before the proposed asteroid impact.

New geochemical techniques seemed to back this up by producing evidence of
serious climatic fluctuations in the three million years prior to the K-T boundary
event.(8,11)

The Mesozoic world of the dinosaurs had a stable greenhouse climate with a much
higher sea level and warmer temperatures than present. There were inland seas
across central of America, Europe, Africa, Russia and South America and tropical
conditions occurred as far north as Britain and New York. There were no polar ice
caps. This began to change 70 million years ago when the sea level began to drop
causing the climate to de-stabilise and the globe to cool rapidly. The gradual
decline in many fossil species including the dinosaurs, ammonites, belemnites,
reef-buildingbivalves, etc., appears to be closely linked to the dropping sea level
and climate change in this last part of the Cretaceous period. (11)

Recent geochemical and fossil evidence now suggests that, 300,000 years before
the K-T boundary, there was a large and sudden drop in sea level that triggered
the final collapse in the world's biosphere which resulted in the extinction of some
fossil groups and a dramatic loss of species in others.(12 )This change possibly
due to a change-over from the `greenhouse' climate of the Cretaceous, where
ocean circulation and weather were driven by heat in the tropics, to our Tertiary
`icehouse' climate where they are driven by the polar ice caps.(11 )The evidence
for this comes from the observation that Polar fossil species were largely
unaffected by the mass extinction.(13,14)

Further research on K-T boundary exposures world-wide seemed to suggest that
they were not as complete as was first thought. Many of the sections were shown
to have long periods of time where sediment had not been deposited causing
small, but significant, gaps in the fossil record.(15 )Thus, when data from a
number of locations was assembled together and compared, it was realised that
many more species had survived into the Tertiary than was previously thought
and that the `sudden' extinction within some fossil groups was in fact staggered
over a period of 500,000 years.(7,9)

Alvarez' iridium spike also came under suspicion after widespread geochemical
analysis found that iridium clays are actually quite common in the geological
record, can be caused by natural processes and did not need to coincide with a
mass extinction.(16 )By the beginning of the 1990s it was beginning to look like
the small band of opponents to the asteroid impact theory were winning ground.

One particular problem for the pro-asteroid camp was the visible lack of an impact
crater. A solid object 10 kilometres in diameter could be expected to have done a
massive amount of crustal damage on its impact, the signs of which ought still to
be detectable after 65 million years. As there are no known large craters of the
right age on land, the ocean floors were next logical place to look. Here, too, there
were no obvious candidates and for a long time it was supposed that the crater
must have been recycled into the Earth's interior by the action of plate tectonics.
However, exploration around the Gulf of Mexico, in 1990, revealed a large circular
structure, buried beneath 1.5 kilometres of sediment, that appeared to be the
right size, rock type and age for it to be associated with the K-T boundary asteroid
impact.(17) In addition to this, K-T boundary sediments on local Caribbean
islands were shown to contain crystals which had been `shocked' (ie. cracked) by
the force of a near-by explosion. The pro-asteroid camp declared that it had found
its impact crater, situated at Chicxulub, to the south of USA, off the Yucatán
peninsular.
The evidence for this being an impact crater is quite strong although, being buried
under 1.5 kilometres of sediment and only accessible using samples from six deep
boreholes, there is still some controversy about the structure's exact age, size
and origin. The discovery of the Chicxulub crater has added considerable weight to
the theory that an asteroid impacted into the Earth 65 million years ago and many
scientists believe that the matter of the `death of the dinosaurs' is now fully
resolved. Objections by palaeontologists are largely ignored and are certainly not
reflected in the mainstream media. Beyond this, the debate has reached a
stalemate and there are currently three main areas of belief on the matter ...

The first belief is that an asteroid impact at the K-T boundary was responsible for
a sudden mass extinction of approximately 50 to 85 percent of life on Earth. This
still has by far the greatest scientific following.

The second belief is that most of the extinction had occurred prior to the K-T
boundary and that the effect of an asteroid impact, if it occurred, was minimal. This
is the view taken here.

The third group believes in a combination of the two with an asteroid, sometimes
in conjunction with volcanic activity, delivering the coup de grace to already
declining fossil groups. This is possible but, in my view, not supported by the
evidence.

The answer is clearly not straight forward and this leads onto the final point I
would like to make. The asteroid impact theory as proposed by Walter and Luis
Alvarez is too neat and convenient to be applicable to the complex nature of the
evidence that has been found since 1980. The impact theory has all the features
of a Hollywood film script (ie. dinosaurs, explosions, death, widespread disaster
and, with the rise of us mammals, a happy ending) which is probably why it has
been so widely publicised and accepted by the media. Although there is evidence
for a bolide impact at, or near, the K-T boundary, it would have come too late to
seriously affect many already extinct or declining fossil groups, especially the
dinosaurs who were well and truly on their way out by then, whilst it appears not
to have affected others at all. Add to this the gaps in the fossil record, problems
with dating rocks, the changes in global environment and other iridium spikes in
the geological record, and the Hollywood script starts to have too many subplots
to become coherent.


This proves that we currently do not know the cause(s) of the mass extinction at
the end of the Cretaceous and anybody that claims to have a definite answer is
wrong. Even the assertion that the dinosaurs became extinct is wrong. As was
covered in FT 108, one important branch of the dinosaurs not only survived into
the Tertiary but continues to thrive in our mammal dominated world. In fact, I can
see half a dozen of these dinosaur ancestors from where I sit and I ate part of
one in a curry last night. I refer, of course, to the birds who, like some scientists,
are prone to flights of fantasy.

SURVIVAL OF THE FITTEST?

When, in 1980, Walter and Luis Alvarez proposed their asteroid impact theory,
very little detailed or integrated work had been done on fossil groups in relation
to the K-T boundary. It was estimated that 50 percent of life on Earth had died at
the K-T boundary(18,) a figure that is meaningless when it is considered that we
have no information at all on many fossil groups such as the beetles (currently the
most diverse group of animals on Earth) and all soft-bodied organisms. Amongst
the animals deemed to have become suddenly extinct were the dinosaurs,
ammonites, belemnites, reef-buildingbivalves, marine and flying reptiles whilst
those badly affected include all the plankton, all shallow water marine life and land
plants. It was also known that some fossil groups, such as the mammals and
crocodiles, survived rather well, although this was little commented on.(2,3,18)

Now, eighteen years later, we know much more about the global distribution of
species across the K-T boundary and what happened in the few million years
preceding it. This has thrown up some inconsistencies.

The `nuclear winter' was envisaged to have wiped out all life on Earth evenly with
only a few hardy species surviving. Yet on land, we see the dinosaurs become
extinct whilst their close and cold-blooded relatives the crocodiles, amphibians and
lizards survive with no unusual effects. The mammals and birds also survived well,
leaving the dinosaurs as the only major on land animal group to become extinct.
A similar story is seen in the oceans where, amongst the plankton, the diatoms,
radiolaria and dinoflagellates all come across the K-T boundary unscathed whilst
the nannofossils and planktonic foraminifera were badly affected. All the plankton
groups lived in the same environment and have the same requirements, so why
did some die and some live? An asteroid should have affected them all to the
same degree. Similarly, in the shallow seas, the ammonites were dying whilst their
very close relatives, the nautiloids, survived intact. Other fossil groups such as the
reef-buildingbivalves, marine and flying reptiles and possibly the belemnites, were
distinct before the K-T boundary.(12)

Another problem is the apparent difference between the extinction rates in the
polar regions and those in the tropics. On land there is a noticeable decline in
temperate and tropical plant species as the polar trees spread south with the
changing climate(19), whilst in the seas warmer water species, including the
ammonites, belemnites and plankton foraminifera, also show a decline.(7) In
general, polar species survive the K-T boundary event much better than their
tropical relatives and in one Antarctic rock outcrop there is so little evidence of a
mass extinction that the boundary itself has been very hard to pin-point at all.

CHICXULUB

In 1975 the Mexican government began to explore for oil around an unusual
circular feature buried beneath 1.5 kilometres of sediment on the Yucatán
peninsular. The feature, called the Chicxulub Structure after a local village, proved
to be fruitless and interest was abandoned.
Fifteen years later, when the science community was beginning to panic at the
lack of an impact crater, two journalists remembered Chicxulub and suggested it
as a possible site. The idea was leapt upon and the old 1970s borehole samples
were recovered and re-assessed.

On first sight Chicxulub meaning `tail of the devil' in Mayan looked ideal. It was
circular 180 to 300 kilometres in diameter (nobody can agree on its size) and had
a layer of cracked and melted rock that was thought to represent the layer where
the asteroid had impacted. All seemed perfect.

However, work in the 1970s, and two studies since, firmly indicate that the K-T
boundary is at least 18 metres above the layer of melted rock making it several
million years too old to have caused the `death of the dinosaurs'.20,21 This was
overcome by using radiometric dating which suggested that the melted layer was
exactly 65 million years old. However, radiometric dating is notoriously inaccurate
and only one of the ten samples analysed gave this date with the others varying
over eight million years.(22 )

Another earlier K-T boundary candidate, the Manson Crater, was similarly
radiometrically dated at 65 million years but, later, proved to be 75 million years
old.(23 )The dating problems with Chicxulub have never been resolved and a
chemical analysis of the melted rock suggests that it has more in common with
volcanic lava than crater debris.
Other than the Chicxulub structure, many people have tried to find a link between
some of the 23 known other mass extinction events to asteroid impacts, and
failed. Despite many early claims, no other impact craters, some of them
approaching the size of the Chicxulub structure, have been linked to other mass
extinction events. In this century we have had the Tunguska explosion, the
Greenland meteorite (FT 108:8) and now XF11, suggesting that asteroid impacts
are not that rare. Mass extinctions, on the other hand, are rare events.

THE SIXTH MASS EXTINCTION

During the last 10,000 years a large number of animal and plant species have
become extinct, including the mammoths, the great Auk, sabre-tooth tiger and
others. Since the civilisation of our species, this rate of extinction has increased so
rapidly that it is estimated that the activities of man now results in the loss of two
or three plant or animals species a day. There are, at the moment, five
recognisable mass extinction events in geological history and it is speculated that
man might be currently manufacturing the sixth one.

In terms of geological time 10,000 years would barely be represented by a
centimetre of deep sea clay. It may therefore be that, in millions of years time,
future palaeontologists may deduce that a sudden mass extinction event had
occurred in a geological instant, whereas it was in fact spread across a wider
period of time. Could the thin layer of the K-T boundary clay in fact represent tens
of thousands of years rather than the few decades proposed by some
palaeontologists?

REFERENCES:

GENERAL REFS:
Alvarez, W. - T.Rex And TheCrater Of Doom! (Princeton University Press, 1997)
Archibald, JD.- Dinosaur Extinction And The End Of An Era (Columbia UniversityPress, 1996)
Carlise, D. - Dinosaurs, Diamonds And Things FromOuter Space (Stanford University Press, 1995)

CITED REFS:
1 - Schindewolf, O. - `Neokatastrophismus?'in Deutsch Geologische Gesellschaft Zeitschrift Jahrgang, 1962, 114,p.430-445
2 - Russel, D. - `The enigma of the extinction of thedinosaurs' in Annual Review Of Earth And Planetary Sciences, 1979, vol.7, p.163-82
3 - Alvarez, LW., Alvarez, W., Asaro, F., Michel,H. - `Extraterrestrial cause for the cretaceous-tertiary extinction' inScience, 1980, vol. 208, 4448, p.1095-1108
4 - Wolbach, W.,Gilmour, I., Anders, E., Orth, C., Brooks, R. - `Global fire at thecretaceous tertiary boundary' - Nature, 1988, vol.334, no.6184,pp.665-669
5 - Stinnesbeck, W., Barbarin, JM., Keller, G.,Lopezoliva, JG., Pivnik, DA., Lyons, JB., Officer, CB., Adatte, T., Graup, G.,Rocchia, R., Robin, E. - `Deposition of channel deposits near theCretaceous-Tertiary boundary in Northeastern Mexico - catastrophic or normalsedimentary deposits' in Geology, 1993, vol.21, no.9,pp.797-800
6 - Courtillot, V. - `Deccan volcanism at theCretaceous Tertiary boundary - past climatic crises as a key to the future' inGlobal And Planetary Change, 1990, vol.89, no.3, pp.291-299
7- Macleod, N., Rawson, PF., Forey, PL., Banner, FT., Boudagherfadel,MT., Bown, PR., Burnett, JA., Chambers, P., Culver, S., Evans, SE., Jeffery, C.,Kaminski, MA., Lord, A.R., Milner, AC., Milner, AR., Morris, N., Owen, E.,Rosen, BR., Smith, AB., Taylor, PD., Urquhart, E., Young JR. - `TheCretaceous-Tertiary biotic transition' in Journal Of The GeologicalSociety, 1997, vol.154, no.pt2, pp.265-292
8 - Zachos, JC.,Arthur, MA., Dean, WE. - `Geochemical evidence for suppression of pelagicmarine productivity at the Cretaceous Tertiary boundary' in Nature, 1989,vol.337, no.6202, pp.61-64
9 - Keller, G. - `Extended period ofextinctions across the Cretaceous Tertiary boundary in planktonic-foraminiferaof continental-shelf sections - implications for impact and volcanism theories -Reply' in Geological Society Of America Bulletin, 1991, vol.103, no.3,pp.435-436
10 - Hollis, CJ. - `Latest Cretaceous to latePaleocene radiolarian biostratigraphy - a new zonation from the New Zealandregion' in Marine Micropaleontology, 1993, vol.21, no.4,pp.295-327
11 - Macleod, K., Huber, B., Ward, P. - `The biostratigraphy and paleobiogeography of maastiichtian inoceramids' inGeological Society Of America Special Paper 307, 1996,p.361-374
12 - Archibald, JD. - Dinosaur Extinction and theEnd of an Era (Columbia University Press, 1996)
13 -Zinsmeister, WJ., Feldmann, RM., Woodburne, MO., Elliot, DH. - `LatestCretaceous/earliest Tertiary transition on Seymour Island, Antarctica' inJournal Of Paleontology, 1989, vol. 63, p.731-38.
14 -Keller, G - `The Cretaceous-Tertiary boundary transition in the AntarcticOcean and its global implications' in Marine Micropaleontology, 1993,vol.21, no.1-3, pp.1-45
15 - Macleod, N, Keller, G - `Howcomplete are Cretaceous Tertiary boundary sections - a chronostratigraphicestimate based on graphic correlation' in Geological Society Of AmericaBulletin, 1991, vol.103, no.11, pp.1439-1457
16 - Orth, CJ.,Attrep, M, Maox, X, Kauffman, EG., Diner, R And Elder, WP. - `Iridiumabundance patterns across bio-event horizons in the fossil record' inGeophysical Research Letters, 1988, vol. 15, p.346-9
17 -Sharpton, VL., Marin, LE. - `The Cretaceous-Tertiary impact crater and thecosmic projectile that produced it' in Annals Of The New York Academy OfSciences, 1997, vol.822, pp.353-380
18 - Russel, D. -`Reptilian diversity and the Cretaceous-Tertiary boundary in North America' inGeological Association Of Canada Special Report 13, 1975,p.119-36
19 - Golovneva, LB. - `The flora of theMaastrichtian-Danian deposits of the Koryak Upland, Northeast Russia' in Cretaceous Research, 1994, vol.15, p.89-100
20 - Ward, WC.,Keller, G., Stinnesbeck, W., Adatte, T. - `Yucatan subsurface stratigraphy:implications and constraints for the Chicxulub impact' in Geology, 1995,vol. 23, p.873-6
21 - Meyerhoff, AA., Lyons, JB., Officer, CB.- `Chicxulub structure: a volcanic sequence of Late Cretaceous age' inGeology, 1994, vol. 22, p.3-4.
22 - Swisher, CC.,Grajalesnishimura, JM., Montanari, A., Margolis, SV., Claeys, P., Alvarez, W.,Renne, P., Cedillopardo, E., Maurrasse, FJMR., Curtis, GH., Smit, J.,Mcwilliams, MO. - `Coeval Ar-40/Ar-39 ages of 65.0 million years ago fromChicxulub crater melt rock and Cretaceous-Tertiary boundary tektites' inScience, 1992, vol.257, no.5072, pp.954-958
23 - Hartung, JB.,Kunk, MJ., Anderson, RR. - `Geology, geophysics, and geochronology of theManson impact structure' in Geological Society Of America Special Paper247, 1990, p.207-22
24 - Kerourio, P., Sige, B. - `L'aportdes coquilles d'ouefs de dinosairs de Laguna Umayo a l'age de la formationVilquechico (Perou) et a la comprehension de Perutherium altiplanense' inNewsletters On Stratigraphy, 1984, vol. 13, p.133-42
25 -Stets, J., Ashraf, A., Erben, HK., Hahn, G., Hambach, U., Krumsiek, K., Thein,J., Wurster, P. - `The Cretaceous-Tertiary boundary in the Nanxiong Basin(continental facies, Southeast China)' in Macleod And Keller (Eds.) TheCretaceous-Tertiary Mass Extinction: Biotic And Environmental Effects. W.W.Norton, 1995
26 - Marshall, CR., De Muizon, C. - `The dawn ofthe age of mammals in South America' in National Geographic Research,1988, vol. 4, p.23-55

About The Author
Dr Paul Chambersspent five years researching fossil diatoms and the K-T boundary but has sinceleft academia for a career in publishing. He is the author of ParanormalPeople (Blandford, April 1998), Life of Mars - The Complete Story(Blandford, February 1999) and has recently finished a book on the K-T boundaryevent. He currently lives in London and can be contacted at paul@atlantis.simplyonline.co.uk.

Australia finds its lost animals

http://news.bbc.co.uk/hi/english/sci/tech/newsid_911000/911408.stm

A flesh-eating kangaroo and a crocodile that jumped down on its prey from the trees are drawing the crowds in Sydney, Australia.

The extinct animals are just two examples of the extraordinary giant creatures that once roamed the continent.

Their remains have only recently been unearthed and are throwing new light on the so-called megafauna that lived in the region many thousands and even millions of years ago and more.

An exhibition - Australia's Lost Kingdoms - presents life-sized representations of some of the creatures. It includes a turtle as big as a small car and a carnivorous duck equipped with a bill the size and shape of an axe.

Professor Mike Archer, director at the Australian Museum, says new scientific discoveries show Australia was once a land of giants.

"Contrary to what the Americans have tried to tell us - that the biggest of everything comes from Texas - in the way of dinosaurs the biggest things were actually in Australia. We had monsters that made the rest of the world's dinosaurs look like geckos!"

Meat cleavers

One of those monsters was a seven-metre long goanna lizard (Megalania prisca). An adult would have weighed up to 600 kg. Then there were the tree-climbing crocodiles, (Trilophosuchus rackhami) nicknamed the "drop crocs" for the way
they are thought to have leapt down on to their victims.

"And if that didn't get you," Professor Archer said, "there were meat-eating kangaroos that would have stood up at your shoulder and torn your arm off.

Fulgurotherium roamed Australia 110 million years ago

"This was no Skippy. Another was a creature we called the "demon duck of doom' (Dromornis stirtoni). It's the largest bird that lived anywhere in the world. But as if that wasn't enough of a problem, at three metres in height and about 400 kg in size, this thing was a flesh-eater."

Professor Archer says a species of marsupial lion (Thylacoleo carnifex) which existed more than 40,000 years ago could weigh up to 160 kilograms - as big as the largest sabre-toothed tiger roaming Asia and Europe.

A model of the creature features in the exhibition and shows it to have the fur of a wombat, the nose of a koala and claws like meat cleavers.

Climate change

Dr Anne Musser, a palaeontologist at the Australian Museum who directed the reconstruction of many of the models on display, believes science can explain why so many of the animals grew so big.

"It was a worldwide phenomenon," she says. "It seems to be that a lot of lineages basically became more specialised. They tended to get larger in response to climate change, as well.

"As the climate started to dry and cool, particularly, animals tended to get larger. And a lot of the megafauna culminated in the cool, if not icy conditions of the Pleistocene (1.8 million to 11,000 years ago). And Australia was no exception.

Scientists have based their new interpretation on fossils found in sites like the one at Riversleigh in outback Queensland.
Palaeontologist Phil Creaser says animal remains have been preserved better there than almost anywhere else in the world.

"The waters that they either fell in or were moved by were very rich in calcium carbonate. This is the limestone rock that we see today.

"What we assume has happened is that these fossils, or the animals once they've fallen in these waters and pools, quickly had a coat of this calcium carbonate, the limestone around them. They became entombed, which means that you've got nearly perfect preservation.

"There's been no movement of the fossils. There've been no scavengers to chew them up."

Human habitation

Perhaps most intriguing of all is the knowledge that many of these animals, including the marsupial lion, existed at the same time as the earliest Aboriginal inhabitants of Australia, who are thought to have come to the continent around 50,000 years ago. "In fact all of the animals that you see in the exhibition - the huge horned turtle, the marsupial lion and the large kangaroo overlapped with humans," Dr Musser says.

The large kangaroo has been found at a site called Cuddie Springs in conjunction with human habitation."

Today, Australia is losing species at a rate not seen since the extinction of the dinosaurs. The museum hopes that its exhibition, which runs until next April, will help people better understand the past - and learn to conserve the present.

Australia's Lost Kingdoms will visit the UK in 2002.

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