A LOWER CRETACEOUS (VALANGINIAN) SEED CONE PROVIDES THE EARLIEST FOSSIL RECORD FOR PICEA (PINACEAE)

作者：Klymiuk Ashley A^*; Stockey Ruth A

来源：American Journal of Botany, 2012, 99(6): 1069-1082.

DOI：10.3732/ajb.1100568

• conifer
• Cretaceous
• Midoriphyllum
• Picea
• Pinaceae
• Pityostrobus
• seed cone

Premise of study: Sequence analyses for Pinaceae have suggested that extant genera diverged in the late Mesozoic. While the fossil record indicates that Pinaceae was highly diverse during the Cretaceous, there are few records of living genera. This description of an anatomically preserved seed cone extends the fossil record for Picea A. Dietrich (Pinaceae) by similar to 75 Ma. %26lt;br%26gt;Methods: The specimen was collected from the Apple Bay locality of Vancouver Island (Lower Cretaceous, Valanginian) and is described from anatomical sections prepared using cellulose acetate peels. Cladistic analyses of fossil and extant pinaceous seed cones employed parsimony ratchet searches of an anatomical and morphological matrix. %26lt;br%26gt;Key results: This new seed cone has a combination of characters shared only with the genus Picea A. Dietr. and is thus described as Picea burtonii Klymiuk et Stockey sp. nov. Bisaccate pollen attributable to Picea is found in the micropyles of several ovules, corroborating the designation of this cone as an early spruce. Cladistic analyses place P. burtonii with extant Picea and an Oligocene representative of the genus. Furthermore, our analyses indicate that Picea is sister to Cathaya Chun et Kuang, and P. burtonii helps to establish a minimum date for this node in hypotheses of conifer phylogeny. %26lt;br%26gt;Conclusions: As an early member of the extant genus Picea, this seed cone extends the fossil record of Picea to the Valanginian Stage of the Early Cretaceous, ca. 136 Ma, thereby resolving a ghost lineage predicted by molecular divergence analyses, and offers new insight into the evolution of Pinaceae.

• 出版日期2012-6