The Aries and Taurus symbols go together like salt and pepper, P's and Q's, ketchup and mustard...just pick any Yin and Yang common match up. Both represent hoofed animals, ungulates, for power and with horns.
Tauries are a real thing, since these signs are right next to each other. Thus persons born on or near April 20th, or 4/20, get this odd combo dedicated to these wild versions of the Ox and Sheep. And note their domesticated versions are a part of the Eastern-Chinese Zodiac, as Year of the Sheep and Year of the Ox.
Coincidentally cows are in second place, in both the Eastern and Western Zodiacs. The Year of the Ox follows in second, following the first Year of the Rat as does Taurus follow in 2nd as the month of the Ox, following the first sign of Aries. Coincidence?