Abstract Detail


Rothwell, Gar [1], Stockey, Ruth [2], Smith, Selena [3].

Evolutionary diversification of Cretaceous taiwanioid Cupressaceae.

Among the six species of conifers preserved within a newly re-described Late Cretaceous (Coniacian-Maastrichtian) flora from northern Alaska is a species of Cupressaceae, Subfamily Taiwanioideae that is represented by nine permineralized seed cones subtended by scale leaves. Other organs of the plant also may be present in the flora, but have not been identified yet. The seed cones are 12-13 mm long and 6.8-8.0 mm wide, consisting of an axis to which >25 mostly laminar bract-scale complexes are attached in a helical arrangement. Bract-scale complexes are narrowly attached, deltoid, and bend distally at the cone periphery to terminate in a bluntly pointed tip. There is no separate ovuliferous scale. Two inverted seeds with wide, lateral wings are attached adaxially near to the level where the complexes bend distally. Bract-scale traces diverge from the cone axis as a rods of xylem that branch at more distal levels. A resin canal originates de-novo on the abaxial side of the diverging bract-scale bundle, and a row of up to ~11 canals characterize the midregion of the complex. Among the currently recognized species of Taiwanioideae, this new species has numerous features that conform to the living Taiwania cryptomerioides, but are most similar to the newly described Mukawastrobus satoii from Campanian-Maastrichtian deposits of Hokkaido, Japan. Pertinent characters include cone size and shape, helical arrangement of laminar bract-scale complexes that lack a free scale tip, complexes that extend from the axis at 90o in the midregion and bend distally at the cone margin, a prominent row of resin canals at the midlevel, and adaxially borne inverted winged seeds. The Alaskan cone can be distinguished from M. satoi by the presence of scale leaves on the cone axis and the narrow attachment of deltoid bract-scale complexes. The new species also has only two (as compared to 2-3) seeds per complex that remain in the cone after they reach full size. Together with the living Taiwania cryptomerioides there is a rich record of compressed fossil Taiwania remains that extend from Upper Cretaceous to the recent. There also are four previously described, Late Cretaceous species of anatomically preserved seed cones that have been included in the Taiwanioideae (i.e., Mikasastrobus hokkaidoensis, Parataiwania nihongii, Comoxostrobus rossii, and Mukawastrobus satoi), and one lignified plant from Early Cretaceous deposits (i.e., Stutzeliastrobus foliatus) that chronical active diversification of taiwanioid Cupressaceae throughout the Cretaceous.

1 - Oregon State University, Department Of Botany And Plant Pathology, 2082 Cordley Hall, Corvallis, OR, 97331, United States
2 - Oregon State University, Department Of Botany And Plant Pathology, 2082 Cordley Hall, Corvallis, OR, 97331.0, United States
3 - Department Of Earth & Environmental Sciences, 1100 North University Avenue, Room 2534, NUB, Ann Arbor, MI, 48109, United States

Late Cretaceous
Seed Cone

Presentation Type: Oral Paper
Session: PAL3, Paleobotany I: Paleozoic and Mesozoic Paleobotany
Location: Virtual/Virtual
Date: Tuesday, July 28th, 2020
Time: 11:15 AM
Number: PAL3006
Abstract ID:179
Candidate for Awards:None

Copyright © 2000-2020, Botanical Society of America. All rights reserved