Report Abuse. An egg lives for around 12 hours after ovulation. Sperm can live for about five days inside the uterus, so providing those two time frames collide, it can be pretty soon after sex.
The tail arrangement is believed to have been a defensive weapon against predators. The term thagomizer was coined by Gary Larson in a 1982 Far Side comic strip, in which a group of cavemen in a faux-modern lecture hall are taught by their caveman professor that the spikes were named for the late Thag Simmons.
thagomizer (plural thagomizers) An arrangement of spikes found on the tails of various stegosaurs. 2001, Holtz, Thomas R.; Riley, Terry, The Little Giant Book of Dinosaurs, page 54: Like the thagomizer of the stegosaur, the ankylosaurid tail club was probably used to smash into attackers.