Clan - A group of individuals with a common ancestry.
In the Gargoyles Universe, the word clan is most often associated with groups of gargoyles who defend a territory, including their rookery if present, and usually form a protectorate of some sort. However, Macbeth also refered to his people in ancient Scotland as 'Clan Moray'.
Ancient and Extinct Clans
We know of several clans that once existed, but have gone extinct. Goliath once said that at one point (probably while humans were still in the stone age) there were gargoyle clans all over the world. Gargoyles were probably the dominant species at that time, though it is unlikely their numbers equaled the current human population. Following is a list of extinct clans. Keep in mind that as Goliath's comment indicates, this list is far from complete.
The Irish Clan - Ireland - Destroyed sometime between 10 AD and 1996. The Wyvern Clan - Wyvern, Scotland - Destroyed in 994. The Wyvern Clan (Split) - Scotland - A branch of the original Wyvern Clan. Destroyed between 988 and 1020. The Demona's Clan - Moray, Scotland - Destroyed in 1057. The Camelot Clan (Ancient) - Camelot, Britain - Destroyed after the fall of Camelot.
Greg Weisman has also confirmed that in addition to this list, Norway once had at least one clan (which makes sense, given Odin's comment about not seeing many gargoyles in Norway in recent times), that the continent of Africa had at least one clan at some point. Other locations that he hints had clans are Italy, and more specifically Rome, Greece, Persia, and Egypt. Gargoyles from these and other Mediterranean location would go on to form a clan on New Olympus. Basically, as Goliath said, there were clans locationed all over the planet at one point. However, Greg Weisman has said that there were no gargoyle clans existing in Antarctica in ancient times, probably due to the climate.
The Surviving Clans
In 1993, shortly before Goliath's Clan was awakened there only eight clans alive in the world. They are all quite old, and have managed to survive by hiding from humans, living in extremely remote locations, or forming solid bonds with human allies.
The London Clan - London, England The Ishimura Clan - Ishimura, Japan The Mayan Clan - ChacIxChel, Guatemala The Korea Clan - Pukhan, Korea The Xanadu Clan - Xanadu, China The Loch Ness Clan - Loch Ness, Scotland The New Olympian Clan - Mount Thanatos, New Olympus The Avalon Clan - Oberon's Palace, Avalon
It is unclear which of these clans is the oldest, but the Avalon Clan is probably the youngest clan (being founded in 995) and the New Olympus Clan is likely the next youngest because it was founded from other clans that existed at the time. Greg Weisman usually lists the clans in this exact order, so it is possible that they are in order of how old they are (oldest to youngest), though that is merely speculation.
The First New Clans
Between 1994 and 1996, two new clans would be founded. One was awakened from a magic spell that left them sleeping for a thousand years, while the other was created through scientific cloning.
Sometime between 1996 and 2188, gargoyles from the ten existing clans will go on to form two new clans.
As the years go by, one can assume that the gargoyle population will continue to climb and more clans will be formed, once again bringing about a time when gargoyle clans are throughout the world.