GANDOLFO, MARIA A.*, KEVIN C. NIXON, AND WILLIAM L. CREPET. L. H. Bailey Hortorium, Cornell University, Ithaca, NY 14853. - A phylogenetic analysis of modern and cretaceous Triuridaceae (Monocotyledoneae).
The monocotyledonous family Triuridaceae includes seven genera of
tropical and subtropical achlorophyllous, saprophytic herbs which live
symbiotically with mycorrhizal fungi. Traditionally the family is
divided into two tribes, Sciaphileae and Triurideae. Sciaphileae is
characterized by unappendaged tepals and a basal style and comprises
the genera Sciaphila, Soridium, Hyalisma and
Seychellaria, and Triurideae is characterized be appendaged
tepals and a lateral style and comprises Triuris,
Peltophyllum, and Triuridopsis. Even though flower
characters are highly variable, the morphology of the perianth,
androecium and gynoecium and various embryological characters are
commonly used to segregate genera and species within this family .
Fossil flowers assignable to Triuridaceae are one of the most abundant
elements of the Raritan Formation flora (Upper Cretaceous, ~90 MYBP)
of New Jersey. When added to higher level morphological phylogenetic
analyses of angiosperms and monocots, the fossils are found to nest
within the modern Triuridaceae. The fossils include four distinctive
forms, which are best treated as three genera and four species on the
basis of generic concepts in the extant family. The fossil flowers
vary in tepal, stamen and pollen grain morphology, and in presence of
pistillodes. The relationships among the fossil taxa and the modern
genera were explored through a preliminary phylogenetic analysis (48
morphological and anatomical characters, 3 fossil and 20 extant
species of Triuridaceae, plus the outgroup Petrosavia) of
Triuridaceae. These analyses place the fossils together in a clade
that is the sister group of a clade composed of the all the members of
the tribe Triurideae and all the American members of the tribe
Sciaphileae . Based on these analyses, Sciaphila seems to be
polyphyletic or paraphyletic. Further more detailed analyses are being
pursued to confirm this placement based on more complete samples of
modern species.
Key words: cretaceous flowers, Monocotyledoneae, phylogenetic analysis, Triuridaceae