MACNBR   00242
MUSEO ARGENTINO DE CIENCIAS NATURALES "BERNARDINO RIVADAVIA"
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Early diversification of Asteraceae from Patagonia: fossil pollen grains related to some basal groups
Autor/es:
TELLERÍA, M.C.; BARREDA, V.; PALAZZESI, L.; KATINAS, L.
Lugar:
Bonn
Reunión:
Congreso; 12th International Palynological Congress; 2008
Resumen:
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The
Oligocene-Miocene interval is considered as one of the most important times in
the early evolution of the sunflower family. Worldwide fossil records of
Asteraceae indicate that Mutisiinae (Mutisieae) is the oldest tribe recorded so
far (Africa, Australia, New Zealand, South America).
In this contribution we present a chronological scheme of fossil Asteracean
records from Patagonia, based on previous reports of Mutisiinae and Gochnatiinae subtribes and a new record of pollen type comparable to
those of Cardueae. Four pollen types were identified on the basis of their
exine features (sculpture, structure, and thickness). Morphotype 1 -Mutisiapollis sp.- (Late Oligocene), have
spines with swollen bases, internal cavities and endosexine three times thicker
than ectosexine; it appears to be closely allied to Serratula type (Cardueae) and, to Gongylolepis type (Mutisiinae from the Guayana group). Morphotype 2
-Mutisiapollis viteauensis (Barreda)
Barreda- (latest Oligocene-Early Miocene),
characterized by having microspines, with microperforated tectum, ecto- and
endosexine equally thickened. This morphotype is close to Cnicothamnus type (Gochnatiinae). Morphotype 3 -Mutisiapollis sp.- (Late Miocene), with conspicuous
microspines, comparable to Quelchia
type (Gochnatiinae from the Guyana Group). Morphotype 4 Mutisiapollis patersonii Macphail and Hill- (Late Miocene), with miscrospines hardly distinguishable
and exine very thickened at the equatorial level; it is close to some species
of Chaetanthera and Mutisia (Mutisiinae). Some of extant
members of Mutisieae (the Guayana group) are palynologically linked. The
nearest living relatives of the fossil morphotypes here presented are no longer
recorded in southeastern Patagonia. Most of
them occur in northern South America (Guyana)
or in the high altitudes of the Andes.