A mid-Cretaceous flora from the Kachaike Formation, Patagonia, Argentina

An overview of a new mid-Cretaceous flora from Bajo Comisión, southern Patagonia, is presented. The flora was collected from previously studied deposits of the late Albian–Cenomanian Kachaike Formation in Santa Cruz Province, Argentina. The fossil assemblage consists of about 20 species mostly of pteridophytes, pteridosperms and conifers but it also includes fronds of uncertain affinity. Bryophytes, bennettites and ginkgophytes are subordinate components. The presence of angiosperm leaves is noteworthy. This flora is from a critical time interval between the earliest Cretaceous assemblages of the Springhill Formation and Baqueró Group and the younger Late Cretaceous assemblage of the Mata Amarilla Formation in southern South America. During this period of time, profound changes were taking place in the Earthʹs vegetation with the radiation and diversification of angiosperms. Comparisons with other Jurassic and Cretaceous assemblages indicate links with southern and eastern Gondwanan floras. Among them, the flora of the Triton Point Formation of Alexander Island (Antarctica) is most similar to that of the Kachaike Formation. Both share the presence of Athrotaxis ungeri (= Athrotaxites ungeri), taxa at generic level including Phyllopteroides, Aculea, Ptilophyllum and Ginkgoites, a similar matoniaceous species, and a relatively diverse angiosperm record.