Abstract Detail

Paleobotany

Doyle, James [1], Endress, Peter [2].

Phylogenetic position of mid-Cretaceous members of Magnoliales: updated status and implications.

Discoveries of new fossils and phylogenetic analyses of their position in molecular trees of living Magnoliales refine and modify previous inferences on ages of clades, the course of character evolution, and past morphological and ecological diversity of the order. Our previous analysis indicated that Archaeanthus, based on bilobed leaves and flowers with an elongate receptacle from near the Albian-Cenomanian boundary in Kansas, could be either a stem relative of Magnoliaceae or nested in the crown group. A recent analysis that nested Archaeanthus in the crown group with Liriodendron was compromised by use of too distant outgroups and correlated characters; our reanalysis indicates that the position of Archaeanthus and therefore the age of crown Magnoliaceae are still unresolved. We previously associated the older genus Endressinia, known from leafy shoots and flowers with inner staminodes from the late Aptian of Brazil, with the clade comprising Degeneria, Galbulimima, Eupomatia, and Annonaceae, which is united by inner staminodes (lost within Annonaceae). However, our present study supports the conclusion of a more recent analysis that Endressinia and Schenkeriphyllum, from the same deposits, are stem relatives of Magnoliaceae. This implies that the line leading to Magnoliaceae originally had inner staminodes but later lost them, and that the typical sheathing leaf base evolved before the elongate receptacle. The occurrence of these fossils in Brazil suggests that the magnoliaceous line originated in Gondwana, where other Magnoliales are still centered, and migrated into Laurasia. Their small leaves and other paleoclimatic indicators indicate that early Magnoliales were able to adapt to more arid tropical conditions than might be inferred from living members. The largest living family of Magnoliales, Annonaceae, is well represented by seeds with typical endosperm ruminations from near the end of the Cretaceous and the Eocene. Our analyses do not support the proposal that Pecinovia, a flower from the Cenomanian of Bohemia, is related to Annonaceae. However, Futabanthus, from later in the Cretaceous (Coniacian) of Japan, indicates that crown group Annonaceae had originated by this time. Our analyses confirm that Futabanthus is a near-basal member of the clade comprising all Annonaceae other than Anaxagorea, based on its combination of no inner staminodes, which were lost after divergence of the basal genus Anaxagorea, and tongue-shaped stamens, which contrast with the so-called peltate stamens of most Annonaceae.

1 - University Of California Davis, DEPT OF EVOL & ECOLOGY, One Shields Avenue, Davis, CA, 95616, United States
2 - BOT GARTEN & INST FUR SYS BOT, Zollikerstrasse 107, Zurich, CH-8008, Switzerland

Keywords:
angiosperms
Magnoliales
paleobotany
phylogeny
Cretaceous.

Presentation Type: Oral Paper
Session: 24, Late Mesozoic and Cenozoic Paleobotany
Location: 109/Mayo Civic Center
Date: Tuesday, July 24th, 2018
Time: 10:30 AM
Number: 24002
Abstract ID:215
Candidate for Awards:None