MAYTENOXYLON (CELASTRACEAE) IN THE EARLY DANIAN SALAMANCA FORMATION, PATAGONIA, ARGENTINA

BREA MARIANA; ARI IGLESIAS; RAIGEMBORN M. SOL

BUenos Aires

Congreso; Comgreso Paleontológico Argentino; 2021

Asociación Paleontológica Argentina

The early Danian Salamanca Formation (SF) crop out in severalareas of the Golfo San Jorge Basin, Patagonia. Among its southernmost exposuresit is the Laguna Manantiales locality in the northern Santa Cruz Province.In this area, the SF iscondensed in ~17 m thick section, composed of glauconitic sandstones and siltstonesof estuarine paleoenvironments. It overlies the Baqueró Formation (LowerCretaceous) and conformably underlies pedogenized continental strata of the RíoChico Group (Paleocene??Eocene). The SF uppermost silty facies preserve leafcompressions and cuticles, while marine fauna has been found in the basal sectionof the unit. In the middle section, within glauconitic sandy facies, silicifiedwoods with very good anatomical preservation have been recovered. Thepreviously studied microflora has indicated to be diverse and compositionally dissimilarin relation to other areas in the basin, with an important continental source. Inthis contribution, we describe a wood piece (more than 20 cm in stem diameter)with a particular combination of character with simple perforated ray cells anddimorphic fibres in parenchymatous bands alternating with other normal fibres,distinctive of Celastraceae. The presence of wooddiffuse-porous; distinct growth rings; vessels mainly solitary, occasionally inradial multiples and in clusters; exclusively simple perforation plates; non-septateand septate fibres; axial parenchyma diffuse apotracheal scanty and vasicentricparatracheal; and heterocellular rays; all links the fossil to the genus MaytenoxylonFranco (that is related to the extant genus Maytenus Molina). Maytenoxylonis known from a single small twig (less than 2 cm in diameter) specimen fromthe late Miocene in northeastern Argentina. Maytenus is now widely distributedin the Americas, Africa, Indian Ocean margins, Micronesia, and Australasia,with species mostly adapted to ever-wet conditions, but others linked togallery forests in marked dry season climates. On the other hand, theCelastraceae are pantropical with Northern Hemisphere and Upper Cretaceous toPaleogene fossil records. The new specimen corresponds to the oldest record forthe family in the Southern Hemisphere and the oldest record of Maytenoxylon, thereby rooting the whole lineagethat includes Maytenus. The new Patagonian record from the early Paleocenesuggests a revision of the Northern Hemisphere presumed centre of origin anddispersal for the Celastraceae.