Abstract
Abstract: The new register of the family Lactoridaceae ( Rosannia manika Srivastava) in Tierra del Fuego, Austral basin correspond to a sedimentary succession located at the south of the Irigoyen River, nearby the Cerro Malvinera To calibrate the age of this outcrop was analized the palynology (principally dinoflagellates cysts) of different Paleogene formations (La Barca, Punta Torcida and Puesto Jose) in the Austral basin. This result was compared with large datasets of organic dinoflagellate cyst (dinocyst) assemblages from Southern Pacific Ocean shelf sediments and other sections of the world. The majority of palynomorph taxa from the Cerro Malvinera succession are present in the upper member LB2 of the La Barca Formation and both shared the presence of Lactoridaceae ( Rosannia manika Srivastava) and the age-diagnostic dinocysts Pentadinium laticinctum (First Occurrences 51.95) and Batiacasphaera micropapillata . These dinocysts, which are also recorded in the lower part (Early Eocene) of the Agua Fresca Formation, Chile, indicate an age not older than early Eocene for the LB2 member of theLa Barca Formation and the Cerro Malvinera strata. This data expands the known fossil range of the Lactoridaceae in Patagonia and contributes to elucidate the probably migration routes of this family. A migration via Antarctica is postulated in this paper due to the record of this family in the Maastrichtian (Lopez de Bertodano Formation). Depending on new records due to the presence of this family in the Colorado Basin in the Danian, a migration route from the north of Patagonia to the south (Austral basin) it is not descarded.
Highlights
In this paper we report a new fossil finding of Lactoridaceae tetrads form the Paleogene of southern Patagonia (Austral Basin), southern South America
In comparing the palynomorphs of Cerro Malvinera with those recorded in La Barca, Punta Torcida and Puesto José formations (Table 3) it should be noted that the majority of taxa of this profile are present in La Barca Formation (7 species in common)
A migration via Antarctica is postulated in this paper due to the record of this family in the Maastrichtian (Lopez de Bertodano Formation)
Summary
In this paper we report a new fossil finding of Lactoridaceae tetrads form the Paleogene of southern Patagonia (Austral Basin), southern South America. Lactoridaceae are a monotypic family of shrubby angiosperms represented by a lone species: Lactoris fernandeziana Phil., endemic to the cloud forests of Masatierra Island (= Robinson Crusoe) located at an altitude of 500 m and above (Crawford et al, 1991, 1994; Stuessy et al, 1997, 1998). Endress (1994) has summarized features of Lactoris which he considers implies a relationship with the Aristolochiales (Aristolochia). This is supported by phylogenetic analysis based on nucleotide sequences in the plastid gene rbcL (Chase et al, 1993)
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