Tiong-seng-tāi sī chi̍t toāⁿ tē-chit sî-tāi, sî-kan sī 250 Ma (pah-bān nî chêng) kàu 65 Ma chó-iū. Chit tāi ē-kha koh hun saⁿ toāⁿ: Trias-kì, Jura-kì, kap Creta-kì.

Tiong-seng-tāi ê chá chi̍t tāi sī Kó͘-seng-tāi; oàⁿ chi̍t tāi sī Sin-seng-tāi. Tiong-seng-tāi sī tùi Se-kok gí-giân ê hoan-e̍k, pí-lūn kóng Eng-gí ê tùi-èng "Mesozoic", sī Hi-lia̍p-gí meso- (ì-sù: tiong-ng) kap zoon (ì-sù: tōng-bu̍t, sèⁿ-miā) ê cho͘-ha̍p.

Tiong-seng-tāi sǹg sī "khióng-liông ê sî-tāi", in-ūi chit chūn khióng-liông siāng heng-ōng, siōng-boé tī āu-kî in-ūi Chicxulub chhiong-kek téng in-sò͘ bia̍t-choa̍t.