Usually, it's because the sperm gets into the fallopian tube before the egg is released. Once there, the sperm wait for an egg to arrive. After fertilization, it can take 5-10 days for the fertilized egg to begin to attach itself to the lining of the uterus. Pregnancy begins when this happens.
The arrangement of spikes originally had no distinct name; the term Thagomizer was coined in 1982 by cartoonist Gary Larson in his comic The Far Side, and thereafter became gradually adopted as an informal term within scientific circles, research, and education.
Thallium was discovered spectroscopically in l861 by William Crookes. The metal was isolated both by William Crookes and by Claude-Auguste Lamy in 1862. The element name comes from the Greek word 'thallos' meaning a green shoot or twig, after the green spectral line which identifies the element.