For those wanting to know what the new Snapchat emoji symbols mean, there is several different things that they repersent and these emojis have replaced the âBest Friendsâ feature with Friend Emojis smilies.
(plural tetrads) 1  A group of four things. ( 2 chemistry) A tetravalent atom or radical. ( biology) Two pairs of sister chromatids (a dyad pair) aligned in a certain way and often on the equatorial plane during the meiosis process.
The superclass Tetrapoda (Ancient Greek ÏÎµÏÏÎ±ÏÏÎ´Î·s tetrapodÄs, four-footed), or the tetrapods /ËtÉtrÉpÉd/ , comprises the first four-limbed vertebrates and their descendants, including the living and extinct amphibians, reptiles, mammals, birds, and some extinct fish.etrapods evolved from the lobe-finned fishes around 390 million years ago in the middle Devonian Period, with modern tetrapod groups having appeared by the late Devonian, 367.5 million years ago.