An extinct Eocene taxon of the daisy family (Asteraceae): evolutionary, ecological, and biogeographical implications

BARREDA, V.; PALAZZESI, L.; KATINAS, L.; CRISCI, J. V.; TELLERÍA, M. C.; BREMER, K.; PASSALIA, M.; BECHIS, F.; CORSOLINI, R.

ANNALS OF BOTANY

OXFORD UNIV PRESS

Lugar: Exeter; Año: 2012 vol. 109 p. 127 - 134

0305-7364

Background and Aims Morphological, molecular and biogeographical information bearing on early evolution of the sunflower alliance of families suggests that the clade containing the extant daisy family (Asteraceae) differentiated in South America during the Eocene, although paleontological studies on this continent failed to reveal a conclusive support for this hypothesis. Here we describe in detail Raiguenrayun cura gen. et sp. nov. an exceptionally well-preserved capitulescence of Asteraceae recovered from Eocene deposits of northwestern Patagonia, Argentina. Methods The fossil was collected from the 47.5 -million-year-old Huitrera Formation, at Estancia Don Hipólito locality, Río Negro Province, Argentina. Key Results The arrangement of the capitula in a cymose capitulescence, the many-flowered capitula with multiseriate-imbricate involucral bracts and the pappus-like structures indicate a close morphological relationship with Asteraceae. Raiguenrayun cura and the associated pollen Mutisiapollis telleriae do not match exactly any living member of the family, and clearly represent extinct taxa. They share a mosaic of morphological features today recognized in taxa phylogenetically close to the root of the Asteracean tree, such as Stifftieae, Wunderlichioideae and Gochnatieae (Mutisioideae sensu lato), and Dicomeae and Oldenburgieae (Carduoideae), today endemic or mainly distributed in South America and Africa, respectively. Conclusions This is the first fossil genus of Asteraceae based on an outstandingly preserved capitulescence that might represent the Mutisioideae-Carduoideae ancestor. It might have evolved in southern South America sometime during the early Paleogene, and subsequently entered Africa, before the biogeographical isolation of these two continents became much more pronounced. The new fossil represents the first reliable point for calibration, favoring an earlier date to the Barnadesioideae/rest of Asteraceae split than previously thought, which can be traced back at least 47.5 million years. This is the oldest well-dated Asteraceae and perhaps the earliest indirect evidence for bird pollination in the family.