Abstract Detail



Paleobotany

Pfeiler, Kelly [1], Atkinson, Brian [2], Matsunaga, Kelly [3].

Anatomically preserved cheirolepidiaceous pollen cones from the Cretaceous of western North America.

Cheirolepidiaceae is an extinct, enigmatic conifer family with poorly understood phylogenetic relationships. Common components of the Mesozoic flora, members of Cheirolepidiaceae have unique combinations of morphological characters that can provide insight into the deep evolution of conifers. The macrofossil record of the family begins in the Late Triassic and extends through the Cretaceous, but pollen assigned to the family (Classopollis) extends into the Paleogene. Cheirolepidiaceae are primarily known from compression fossils and only five species have been described from anatomically preserved specimens. Our knowledge of the anatomy of these conifers is therefore limited. New permineralized fossils of this family will be essential for advancing our understanding of phylogenetic relationships and morphological evolution in conifers. Here we describe two anatomically preserved pollen cones with cheirolepidiaceous morphology from the Late Cretaceous (lower Campanian) Holz Shale of the Santa Ana mountains in Southern California. Specimens were studied from serial peels using light and scanning electron microscopy and a 3D reconstruction has been produced for one of the cones. The cones are up to 2.2 mm long and 1 mm wide. They are subtended by a few non-fertile leaves that are swollen at the base and taper distally to 1 mm in total length. Sporophylls are peltate with elongate distal tips, helically arranged, and contain two microsporangia per sporophyll. Pollen sacs contain in situ spheroidal Classopollis-type pollen ca.15 µm in diameter, that have anastomosing striations on internal pollen walls, a rimula, and a distal pore. The excellent preservation of the specimens reveals large parenchymatous cells and abundant transfusion tracheids in the distal regions of the sporophylls, which has a ca. 8 µm thick cuticle. Resin canals are absent throughout the entire cones. These characters indicate relationships with Cheirolepidiaceae, permineralized pollen cones of which are assigned to Classostrobus. The only other permineralized Cheirolepidiaceae pollen cones documented to date are Classostrobus elloitii from the Lower Jurassic of Antarctica and Classostrobus crossii from the Middle Jurassic of England. The new pollen cones from California differ from these in their small size and number of sporangia per sporophyll. Among cheirolepidiaceous pollen organs, Late Cretaceous occurrence are known only from Europe and those found in the North America are much older in age (Upper Triassic – Lower Cretaceous), making these the first Late Cretaceous pollen organs from North America in the family. These new pollen cones add to the sparse record of anatomically preserved reproductive organs of Cheirolepidiaceae and provides insight into the structure and diversity of pollen cones in a group that is pivotal for understanding the evolutionary history of conifers.


1 - University of Kansas, Ecology and Evolutionary Biology, 1200 Sunnyside Avenue, Lawrence, KS, 66045, USA
2 - University Of Kansas, Ecology And Evolutionary Biology, 1200 Sunnyside Avenue, Lawrence, KS, 66045, United States
3 - University Of Kansas, Ecology And Evolutionary Biology, 1200 Sunnysive Ave., Lawrence, KS, 66045, United States

Keywords:
Cheirolepidiaceae
conifer
pollen cone
Anatomy
fossil
Upper Cretaceous.

Presentation Type: Oral Paper
Session: PB1, Cookson & Moseley Awards I
Location: Lupine/Hilton
Date: Monday, July 25th, 2022
Time: 11:15 AM(EDT)
Live or Virtual Live
Number: PB1005
Abstract ID:141
Candidate for Awards:Isabel Cookson Award,Maynard F. Moseley Award


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