Resumen

FRANCO, María Jimena  y  BREA, Mariana. Fossil woods from Paraná Formation (Middle Miocene), Toma Vieja, Paraná, Entre Ríos, Argentina: record of seasonal mixed forests. Ameghiniana [online]. 2008, vol.45, n.4, pp.699-717. ISSN 1851-8044.

Petrified woods of Middle Miocene from Paraná Formation are described and assigned to Anacardiaceae, Leguminoseae and Solanaceae. The fossil descriptions are based on three anatomically preserved stems. The presence of a combination of characters in each one allowed to distinguish these families from other dicotyledonous and to assign the material to three new morfotaxa. The most related extant genera are Astronium Jacq., Parapiptadenia Brenan. and Solanum N. The affinities and paleogeographical relations are discussed. The fossil woods described in this contribution together with fossil material previously studied for this Formation (Entrerrioxylon victoriensis Lutz, Anadenantheroxylon villaurquisense Brea et al. and Astroniumxylon portmannii Brea et al.), suggest the existence of a paleocommunity linked seasonally dry tropical forest (SDTF), which at present are relict in localities isolated in the North of Argentina, Southeast of Bolivia and Brazil, but in the past represented a continuous extension in in South America. The presence of these woods in the Middle Miocene would indicate a climate warmer than the present for this region.

Palabras clave : Argentina; Entre Ríos; Paraná Formation; Middle Miocene; Fossil woods; Anacardiaceae; Mimosoideae; Solanaceae.