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Re: possible FAQs



 From: Neil Taylor <neil@arc.ug.eds.com>
 > 
 > * Are there any Dinosaurs still around?
 > * Might there be some still, in the depths of Loch Ness/jungles of 
 > Africa/Amazon 
 >   rain-forest/...

This depends on whether you consider birds to be dinosaurs.
[See the discussion of that under the question "Are birds
dinosaurrs?"].

Other than that, no, despite the claims of one crackpot to that
sauropods still exist in tropical Africa.  [For one thing, sauropods
were never forest dwellers, so they would hardly be hiding out in
dense jungle today].

The Loch Ness monster is an admitted hoax, but even if it weren't
it would not be a dinosaur, since the "best" pictures looked more
like a plesiosaur than a dinosaur.

 > 
 > * Were dinosaurs reptiles?

This is a matter of definitions and of the rules used for creating
classifications.

By one set of definitions and rules, yes they are.

By another set of definitions and rules (the ones used by a
group called cladists), "reptiles" either do not exist as a
recognized group, or are restricted to lepidosauromorphs
(the living forms of which are lizards, snakes and tuataras).

 > * Were dinosaurs lizards?

No.

 > * Were dinosaurs cold-blooded like lizards?
 > 
 > * Popular books suggest dinosaurs might be warm-blooded - were they?
 >   How can we tell?

We do not know for sure.  This is currently being researched,
and the final answers are not yet in.  There are some indications,
from isotopic ratios, predator-prey ratios, and nose structure,
that at least some of them may have been endothermic (the scientific
term used to describe "warm-blooded" animals).  There is also
contrary evidence, such as growth rings in the bone.

Even if most dinosaurs were warm-blooded, the giant sauropods
(like Brachiosaurus) probably were not, as they were so large that
they could maintain their temperature just through bulk alone.
This style of temperature regulation is called bulk or intertial
homeothermy.

Also, since birds are endothermic, it is almost certain that
rtheir immediate ancestors among the dinosaurs were (since feathers
had to evolve as insulation before they could be used for flight).
This means that at least some of the later small theropod dinosaurs
were probably "warm-blooded".
 > 
 > * Are the Pterosaurs (flying lizards) Dinosaurs?

No, although they are among the dinosaur's closest relatives.

 > * Are the sea-going "dinosaurs" actually Dinosaurs? (Icthyosaurs, Mosasaurs, 
 >   Plesiosaurs...)

No.  In fact Mosasaurs are plain old lizards (monitor lizards
to be exact).

 > * Were there any sea-going Dinosaurs?  If not sea-going, were any swimmers?

No, all dinosaurs were essentially terrestrial.

As to swimmers, most terrestrial animals can swim at need, but none
were regular, "full-time" swimmers.
 > 
 > * Are crocodiles Dinosaurs?

No, but, other than birds, they are the closest living relatives
to dinosaurs.

By the way, the fact that croodiles alone of living reptilians
have an effectively four-chambered heart suggests that dinosaurs
may have had a four-chambered heart, like their descendents the
birds.

 > * Are Birds really considered to be Dinosaurs?

[This one has already been discussed in another part of this chain].
 > 
 > * Were dinosaurs scaley?
 >   (reports of fur on Pterosaurs; speculation of feathers on bodies 
 > pre-Archie)

They seem more to have been naked-skinned, rather like an elephant,
but with lots of bumps.  At least this is true of the larger forms.
So far we do not have any skin impressions or mummy casts of smaller
dinosaurs, so what they were like is still a matter for speculation.

Archaopteryx most assuredly did have body feathers.  And at least
one pterosaur clearly had a fur-like covering.

 > * How did scales change to feathers/fur?

The basic sequence from scales to feathers involved the scales
getting longer and slowly developing scalloped or fringed edges.
Such long, subdivided scales would be somewhat effective at
retaining body heat in an incipiently "warm-blooded" animal.
Continued elaboration of the structure into more complex,
interlocking forms, would tend to increase the effectiveness
of temperature regulation.

This is supported both by the way feathers grow in living birds,
and by a recently discovered stem archosaur (thecodont) with
elongate, fringed scales.
 > 
 > * Did dinosaurs lay eggs?  Did they raise them like birds, or abandon them 
 > like 
 >   lizards?

They layed eggs, and indeed we have found quite a few fossil dinosaur
eggs.  The most famous of these are the several dozen complete
nests of the "duck-billed" dinosaur named Maiasaura.

Some, like Maiasaura, took care of their young after hatching.
Others, like Troodon and its relatives, apparently abandoned
their eggs.

It is possible that some dinosaurs may have retained the eggs
internally until hatching, but there is still little evidence
for this.
 > 
 > * How fast did they move?

This varied quite a bit.  The large sauropods were slower than
elephants.  Many of he theropod dinosaurs were built for speed,
and could probably run quite fast.  Exactly how fast is hard to
say, as the only reliable evidence for speed is in trackways, and
since even fast animals spend most of their time walking, almost
all known trackways are of walking animals.  In fact it is probable
that there are NO trackways of any dinosaur moving at full speed.

In spite of this, there are one or two trackways of small theropod
dinosaurs moving at around 20 mph or so.

 > * What did they live on?

This varied greatly, depending on the group.

Large theropods ate meat.
At least some small theropods probably ate insects.
Some forms, like the ornithomimids, may have been omnivores
or frugivores (that means fruit-eaters).
The sauropods, ornithopods, and many other dinosaurs ate leaves.

 > * How big were they?

The largest were Brachiosaurus and its close relatives, which
got to be around 50-60 tons.  The longest was probably Seismosaurus,
at well over a hundred feet.

Of the theropods, Tyrannosaurus was probably the heaviest at
around 5-7 tons, but some others may have been longer.

Some of the "duck-blilled" dinosaurs (hadrosaurs) were also
quite large, some, like Shantungosaurus and Anatotitan, exceeding
30 feet in length.

 > * How small did they come?

The smallest certain dinosaur known is Compsognathus, at less than
2 feet in length, and less than 1 kilogram in weight.  If Protoavis
is a dinosaur it is even smaller.
 > 
 > * How intelligent were Dinosaurs?

Mostly more so than living reptiles, but less so than birds.
The smartest dinosaurs, that is the ones with the largest
relative brain size, were Troodon and its relatives, with
a brain size within the lower range of bird brain sizes.

However, the sauropods and stegosaurs had smaller brains for
their size than living reptiles.

 > * Did some (Stegosaurs,...) really have two brains?

No.  All dinosaurs had a sacral ganglion, that is an enlargement
of the spinal cord in the pelvis.  This is not a brain, no matter
how large it is. In Stegosaurus the cavity for this ganglion was
larger than the skull.  However there is reason to believe alot
of the volume of this cavity was filled with fatty tissue, not
nerve tissue.

 > * Is it true the brains of the big Dinosaurs were only the size of a walnut?

Some did, but most had larger brains than that.
[I think this only true for Stegosaurus, even the sauropods had
larger absolute brain sizes than this].
 > 
 > * Are the frozen Mammoths of Siberia Dinosaurs?

No.  Mammoths are elephants.

 > * Is it true that some Dinosaur remains were found in a coal mine last 
 > century 
 >   and thawed out to yield preserved meat? (Or a scaley thing that flapped 
 >   away/croaked and died then disintegrated...)

No.  That was a hoax.
 > 
 > 
 > *** Jurassic Park (that great Authority on Dinos, courtesy of Prof.Spielberg)
 > 
 > * How big were Deinonychus and Velociraptor?

I do not have the figures at hand for this.

 > * Did Dilophosaurs have frills and spit poison?

No.  And it was about 10 feet long as well.

 > * Could we clone a Dinosaurs starting from a frog's egg?

Not a snowball's chance in ****.

*If* by some miracle we could get enough DNA fragments from
dinosaur bones and mosquitoes to assemble a reasonable part
of a dinosaur genome (set of genes), we would either have to
use ostrich eggs or crocodile eggs to have any chance at all
of succeeding.  (And even there, there is reason to believe that
the composition of the eggs would substantially alter the
development of the "dinosaur").

However, the reality is that if we get one or two complete
genes (out of many, many thousands), we will be exceedingly
lucky.  Small fragments of several genes is the most likely
real result of the current research into dinosaur genetics.

 > * Have we really extracted DNA, blood,... from Dinosaur remains?

Not yet, but there are people working on extracting DNA from
dinosaur bones.

swf@elsegundoca.ncr.com         sarima@netcom.com

The peace of God be with you.