Revisión crítica de la colección de Hünicken, Río Guillermo Fm., Santa Cruz, Argentina

MARÍA GANDOLFO; BARBARA VENTO; KEVIN NIXON; MERCEDES PRAMPARO

La Plata

Simposio; Simposio Argentino de Paleobotanica y Palinologia; 2015

The main purposes of this contribution is to present a critical taxonomical revision of Hünicken?s original angiosperm collection from the Tres Marías locality, Río Guillermo Formation (middle-upper Oligocene) Santa Cruz, Patagonia, Argentina, and provide an update of its paleofloristic composition. Additionally, three fossil species of Nothofagus recognized within the collection are placed in a phylogenetic context. Seven species and one morphotype are recognized. Five species belonging to the genus Nothofagus (N. subferruginea, N. serrulata, N. crenulata, N. elongata and N. variabilis) together with Myrcia bagualense and Acaena brandmayri are recognized. For exploring the phylogenetic position of the fossil species Nothofagus subferruginea, N. elongata and N. variabilis, preliminary phylogenetic analyses were performed. Fossil and extant South American Nothofagus were included in a morphological matrix; fifteen characters of leaf architecture were coded for each species, and Nothofagus alessandri was used as outgroup. Three analyses were performed; each one included only one fossil species. For each analysis, one most parsimonious tree was obtained and two monophyletic clades are always recognized; one clade includes the living species Nothofagus glauca, N. obliqua and N. alpina while the other includes N. antarctica, N. betuloides, N. dombeyi, and N. pumilio. The fossil N. elongata shows a close relationship with Nothofagus alpina. N. subferruginea is closely related to N. alessandri and N. varibilis to N. antarctica. The results allowed a better understanding of the phylogenetic positions of the fossils in relation to the living species of the South American.