In my head, Gargoyles are a separate classification which (in the past) I've nicknamed "Gargates". Both Gargoyles and Gargoyle Beasts evolved from this grouping, just as Primates include both humans and various apes. The Gargate-ancestor species go back to the time of the dinosaurs, so to answer your first set of questions, I'd have to ask you how you are defining the word "Dinosaur"? Colloquially, i.e. to include all species that existed during what we popularly think of as the age of dinosaurs, or are you using the term in a scientific sense, which would leave out a number of species that we generally think of as dinosaurs?
As for the various clans, appearances are superficial and can be deceiving. Leo has much more in common biologically with Goliath than he does with a Lion. Zafiro has much more in common with Griff, Leo, Una and Goliath, etc. then he does with a snake. All are Gargates. None are Mammals or Reptiles or Marsupials or Birds, though they may share a few characteristics with one or more of those groups. They are, I believe, warm-blooded, for example.
2. Why do certain sets of gargoyles have appearances so different from most other gargoyles (such as the London clan or Zafiro)?
The simplest answer is nothing more than regional genetic differences. Greg has also suggested that gargoyles have a "chameleon mutation gene" that creates such incredible variations in some parts of the species.
3. Why are there both gargoyles and gargoyle beasts?
The in-show answer is that they're simply both members of the gargate family of Earth life-forms. The out-of-show answer is that they wanted to represent both types of architectural gargoyles.
4. What's the relation between gargoyle beasts and gargoyles?
Gargoyle beasts are to gargoyles as chimpanzees are to humans. More or less. Despite the fact that they superficially resemble dogs, they are not dog gargoyles.
5. Are there any kind of gargoyle beasts that aren't dog-like?
Greg's answer: Does Bronx really look like any dog you know or does his behavior make him seem more dog-like?
[Later, he adds...] Well, I won't deny Bronx's doggy qualities. My point was simply that he's more beast than dog. More Gargoyle than dog. We're trying to keep them a separate species. Not simply model them on other animals. There are obvious exceptions, Griff, Leo, Una, Zafiro. And there may be other exceptions as well, but frankly, I'd have to see the justification in architecture or legend. I'm not going to simply start creating Zebra-goyles, Giraffe-goyles and Ostritch-Goyles.
6. Can gargoyle beasts have wings?
No. Their skeletal structure might have vestigal wing-bones, but that's all.
7. Are there aquatic gargoyles?
Yes. The Loch Ness clan, for example.
8. How does stone sleep work?
At sunrise (more or less), the entire gargoyle body turns into an organic substance that resembles stone, placing the gargoyle in a state of suspended animation. The body does function to some degree. The organic "stone-like" substance absorbs solar energy. The internal biological clock continues to function. Healing takes place. Dreaming too. But to a large degree, a daytime gargoyle is for all intents and purposes a stone statue.
At sunset (more or less), the transformation reverses from the inside out, leaving only a shedable outer layer of "stone" that cracks off as the gargoyle awakens.
9. How is it possible that stone sleep is a natural biological process?
It's one of many amazing biological processes, such as the bio-electricity of electric eels; the color-changing of the chameleon; the ability of some frogs and lungfish to hibernate without food, water, or even air for amazing lengths of time; or the ability of one species of deep-sea worms to feed directly on thermal energy. Just because it isn't a presently seen biological process doesn't mean it can't be. The boundaries on what is considered "valid" biological processes change all the time.
10. Why do gargoyles' clothes and personal property turn to stone with them?
During the time of Caesar Augustus, gargoyles would come to his court, and when they awoke at night their clothes would be torn to shreds. Augustus was a man of strong "family values," and in AD 10, he had a powerful mage (the original Magus) cast a Spell of Humility on the race. As a result, anything they considered "theirs" would turn to stone with them if they were in physical contact with it at sunrise.
11. What happens to a gargoyle when he is damaged (but not smashed) in stone sleep?
Depends on the severity of the damage and how much sunlight remained before the gargoyle awoke. Minor damage (such as cuts and scrapes) might heal over the day, but anything more major (gouges, lost limbs) would likely be fatal (or at least, permanent).
12. What effect would the 6-month-day/6-month-night at the polar regions have on a gargoyle's stone sleep cycle?
Gargoyles would most likely adjust to 12-hour stone sleep cycles after some time.
13. Why do gargoyle males have white glowing eyes and gargoyles females have red glowing eyes?
The out-of-show answer is to be consistent with what was established way back in "Awakening" Part I. The in-show answer is just that it's hormones activated by adrenaline.
14. How often do gargoyle breeding seasons occur? How many eggs can a female lay at one time? How long does it take gargoyle eggs to hatch? How many children can a female have in their lifetime?
Gargoyles can have children every 20 years, and a female can only lay one egg at a time. The eggs take 10 years to hatch. Females generally lay no more than three eggs in a lifetime, at ages 50, 70, and 90 (biological ages 25, 35, and 45 respectively).
Gargoyle beasts have the same frequency of breeding seasons (20 years between) and number of years to hatch (10), but usually lay more than three eggs in their lifetimes.
15. What controls the frequency of gargoyle breeding seasons?
The seasons are connected to the natural bio-rhythms of the earth.
16. When is the next gargoyle breeding season to take place?
The year 2008, which neatly coincides with both the "normal" and Avalon breeding seasons.
17. Do gargoyles only engage in mating for breeding purposes?
No, they do it for pleasure as well, just like humans. But they can generally only have children three times in their entire life.
18. How long does a female gargoyle's pregnancy last?
19. If gargoyles usually don't know who their relatives are, what keeps them from becoming inbred?
Gargoyles (and gargoyle beasts) who are related have scent markers that discourage them from breeding with one another.
20. Do gargoyle eggs turn to stone by day?
The outer shell of the egg is made of the same organic stone-like substance that gargoyles turn into by day. The fetus inside the egg changes back and forth like an adult.
21. Can there be twins among gargoyles?
Yes, but it's extraordinarily rare (maybe once every few hundred years). When it does happen, the twins share the same egg.
22. Are newborn gargoyles more self-sufficient than newborn humans?
They are slightly more advanced than human infants. They are able to support their own heads for example. They start crawling much quicker. But mentally, they aren't that much further along.
[Later, he adds...] Walking on all fours comes fast. Walking upright takes much longer. Gliding can sometimes come before or after upright walking.
23. Do gargoyle babies nurse?
Yes. They were usually breast-fed by clan mothers.
24. What happens to a gargoyle's body when they die?
If they die during the day, they remain stone. If they die at night, they remain flesh. (See also FAQ XVII.4.)
25. Do gargoyles have hollow bones?
[...] nothing about Goliath's strength suggests a hollow skeleton to me.
26. Do gargoyles need to eat? Can they survive entirely on the sunlight they absorb during the day?
They need to eat for energy, just as much as they need to absorb sunlight. Both of these are essential to a gargoyle's survival. Still, they're not significantly negatively affected by a lack of sunlight for one day (it's akin to skipping a meal). Long-term lack of sunlight could cause problems, though.
27. Can gargoyles get sick?
It's possible, but it wouldn't last very long thanks to the healing properties of stone sleep.
28. How likely are gargoyles to be obese?
Not likely, due to their general lifestyles. (For the record, Broadway and Hudson are overweight, not obese.)
29. What effect does smoking have on gargoyles?
The same negative effects it has on humans.
30. Do gargoyles need to shave?
Some do. Some don't.
31. Why are the clone gargoyles' colorations so different?
It's a side effect of the accelerated aging process used to mature them to adulthood.
32. What makes some languages (like Hebrew and Latin) more magical than others?
Their older and the given spells were WRITTEN in them originally.
[Earlier, Greg also said...] In theory, English could work, but it would take more than a literal translation to imbue modern English with the correct magical cadences.
33. How do gargoyles eliminate wastes?
They're stored in their stone skin, until it's broken off and discarded when they awaken. (As an aside, don't ask Greg questions in this vein- he's leaving bathroom functions a private matter.)