Description from Flora of China
Trees evergreen, semievergreen, or deciduous, monoecious; trunk straight; main branches ± whorled. Leaves spirally arranged or scattered (decussate in Metasequoia), monomorphic, dimorphic, or trimorphic on same tree, lanceolate, subulate, scalelike, or linear. Microsporophylls and cone scales spirally arranged (decussate in Metasequoia). Pollen cones borne in panicles, or solitary or clustered at branch apices, or axillary, small; microsporangia with (2 or)3 or 4(-9) pollen sacs; pollen nonsaccate. Seed cones terminal or borne near apex of previous year’s growth, ripening in 1st year, persistent or late deciduous; cone scales developing after ovules originate in bract axils; bracts and cone scales usually spirally aranged (decussate in Metasequoia), sessile, opening when ripe (falling in Taxodium), semiconnate and free only at apex, or completely united; bracts occasionally rudimentary (in Taiwania); ovules 2-9 per bract axil, erect or pendulous; cone scales of mature cones flattened or shield-shaped, woody or leathery, 2-9-seeded on abaxial side. Seeds flat or triangular, wingless (in Taxodium), narrowly winged all round or on 2 sides, or with a long wing on proximal part. Cotyledons 2-9. 2n = 22*.
Nine genera and 12 species: Asia, North America, and (Athrotaxis D. Don) Tasmania; eight genera (one endemic, three introduced) and nine species (one endemic, four introduced) in China.
A merger of the Taxodiaceae and Cupressaceae is increasingly supported by both morphological and molecular evidence (see note under Cupressaceae). However, the two groups are kept as separate families here for pragmatic reasons.
Tsui Hung-pin, Cheng Wan-chün, Fu Li-kuo & Chao Chi-son. 1978. Taxodiaceae. In: Cheng Wan-chün & Fu Li-kuo, eds., Fl. Reipubl. Popularis Sin. 7: 281-312.
(Authors: Fu Liguo (傅立国 Fu Li-kuo) , Yu Yongfu (于永福) ; Robert R. Mill)