In situ fossil seedlings of a Metasequoia-like taxodiaceous conifer from Paleocene river floodplain deposits of central Alberta, Canada

Fossil seeds and seedlings of a Metasequoia-like taxodiaceous conifer occur in Paleocene deposits at the Munce's Hill and Gao Mine localities of centr al Alberta, Canada. Compression/impression specimens are preserved in uprig ht growth positions among seedlings of the cercidiphyllaceous dicot Joffrea speirsii Crane & Stockey. There are a large number of seeds, a few of whic h were buried while germinating and show a radicle or short primary root. M ore than 500 Metasequoia-like seedlings have been identified that have two Linear cotyledons with parallel margins and rounded tips. Three specimens h ave been found that display three cotyledons. Slightly older seedlings show decussate pairs of leaves attached to the stem distal to the cotyledons. S till older seedlings have axillary branches that show varying sizes and num bers of opposite leaves arranged in a single plane distal to the opposite p airs. These specimens reveal that both Joffrea and this extinct taxodiaceou s conifer were early colonizers of North American floodplain communities at the beginning of the Tertiary.