A new calymmate mimosoid polyad from the Miocene of Argentina

CACCAVARI, M.; BARREDA, V. D.

REVIEW OF PALAEOBOTANY AND PALYNOLOGY

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2000 vol. 109 p. 197 - 203

0034-6667

A palynomorph with an unequivocal relationship to the eight-grain polyads of the mimosoid genus CalliandraBenth., is described from the Miocene sediments of San Juan Province, Argentina. Comparison of the fossilpalynomorph with polyads of the extant Calliandra species shows a resemblance to those which have one, highlyspecialized, appendiculate monad. The new palynomorph has a rudimentary appendix, apparently transitional in thepath leading to the more highly developed appendiculate forms in the extant Calliandra group. This specialized polyadtype is considered to be one of the most highly evolved forms in subfamily Mimosoideae. The closest affinity of thenew fossil polyad is with the eight-grain calymmate polyads of Calliandra chilensis Benth., a species which hasdeveloped in the extra-tropical, xerophilous shrub, habitat of north-central Chile. The disappearance of Calliandraspecies in San Juan Province is thought to be related to the culmination of the Andean rising, and the consequentinterruption to the Pacific Ocean climatic influence. This new discovery is the first fossil record of Calliandra forArgentina, as well as being the most southerly and the oldest. It reinforces the hypothesis of an early origin anddiversification for the Leguminosae in Tropical America.