1. A girl or guy is on all fours, similar to how he/she would position themselves for doggy style sex. This person is the middleman/woman. Another guy stands in front and 1 more each on the left and right. A blowjob is given to the man in the center while the guys on the left and right each receive handjobs.
This gives you the Pterodactyl, as the middleman bobbing his/her head up and down while jerking off the guys on the left and right resembles the prehistoric creature of flight.
2. A guy (or girl with strap on dildo) then positions him/herself behind the middleman/woman and has sex in doggy style position.
3. The resulting effect is 4 people surrounding the one in the middle giving the 2 handjobs, 1 blowjob, and receiving doggy style sex. All four people on the outside then put all their hands raised towards the middle of the circle to form a tower over the person in the center.
A variation called the "fruit loop" can be added where another ring of guys/girls surround the first circle and have sex in doggy style position. This gives you one middleman/woman, an inner circle, and an outer circle - for a total of 9 people in the party.
"Yea, but the 4 of us really need to try the Towerdactyl on Kim."