The end-Cretaceous event was catastrophic for terrestrial communities worldwide, yet its long-lasting effect on tropical forests remains largely unknown. We quantified plant extinction and ecological change in tropical forests resulting from the end-Cretaceous event using fossil pollen (>50,000 occurrences) and leaves (>6000 specimens) from localities in Colombia. Late Cretaceous (Maastrichtian) rainforests were characterized by an open canopy and diverse plant–insect interactions. Plant diversity declined by 45% at the Cretaceous–Paleogene boundary and did not recover for ~6 million years. Paleocene forests resembled modern Neotropical rainforests, with a closed canopy and multistratal structure dominated by angiosperms. The end-Cretaceous event triggered a long interval of low plant diversity in the Neotropics and the evolutionary assembly of today’s most diverse terrestrial ecosystem.

Biostratigraphical investigations of Miocene deposits from the southern North Sea Basin, the Oligocene and Miocene of the Bahamas, and the lower Pliocene of northern Iceland revealed the presence of new acritarch species. Halodinium eirikssonii n. sp. is recovered from the lower Pliocene Serripes Zone of the Tjörnes beds in northern Iceland, where its range is well constrained through magnetostratigraphy and biostratigraphy with dinoflagellate cysts. Leiosphaeridia spongiosa n. sp. is recovered from lower to upper Miocene deposits of the southern North Sea Basin and from upper Oligocene and Miocene deposits of the Bahamas. Palaeostomocystis orbiculata n. sp. appears restricted to the middle Miocene of the North Sea Basin

To clarify the systematic positions of the important gonyaulacacean genera Operculodinium Wall, 1967 emend. Matsuoka et al., 1997 and Protoceratium Bergh, 1881, we present in detail the tabulation of the Oligocene–Pleistocene, thermophilic, cyst-defined species Operculodinium bahamense Head in Head and Westphal, 1999 emend., and the extant, cosmopolitan, theca-defined species Protoceratium reticulatum (Claparède and Lachmann, 1859) Bütschli, 1885. Both species have a sexiform hyposomal tabulation, and L-type (Protoceratium reticulatum) or modified L-type (Operculodinium bahamense) ventral organization. Protoceratium reticulatum has dextral torsion of the hypotheca, requiring assignation of the genus to the subfamily Cribroperidinioideae Fensome et al., 1993, whereas Operculodinium bahamense has neutral torsion requiring assignation to the subfamily Leptodinioideae Fensome et al., 1993. The stratigraphic range of this subfamily is now extended upwards to the lower Pleistocene. Paradoxically, Protoceratium reticulatum produces a cyst whose morphology is circumscribed by the cyst-defined genus Operculodinium, either implying polyphyletic origins for this genus or that combinations of ventral organization and torsion used to subdivide the family Gonyaulacaceae cannot always be applied rigidly. In detail, Operculodinium bahamense is shown to have an unusual ventral tabulation in which the first apical plate contacts the apical pore complex but not the sulcus. The new term “episert” is proposed to describe this plate relationship, which appears to have evolved independently in several lineages of the suborder Gonyaulacineae.

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Despite the rich paleontological heritage of Colombia, in the equatorial Neotropics, the Putumayo is one of the least explored regions in terms of its fossil record, largely due to its considerable ground cover, thick vegetation, rock weathering, geographic remoteness, and overall inaccessibility to well-exposed outcrops. This precludes detailed comparisons with neighboring basins, and thus the generation of more comprehensive biostratigraphic correlations for western northern South America and other paleobiogeographic regions such as the Mediterranean Tethys, northern Africa, and the Western Interior Basin. Here, we report 70 occurrences of mid-Cretaceous macrofossils (e.g., ammonoids, bivalves, decapod crustaceans, fish remains), from the middle Albian of the uppermost Caballos Formation and the upper Albian-lower Cenomanian of the lower Villeta Formation, collected in-situ from a stratigraphic section cropping out on the Mocoa-San Francisco road in the Department of Putumayo, Colombia. Among the ammonoid taxa recovered are several morphotypes assignable to Oxytropidoceras, Elobiceras, Metoicoceras, Idiohamites, Hamites, Hysteroceras, Schloenbachia, and isolated aptychi. The occurrence of the ammonoids Schloenbachia and Oxytropidoceras suggest interconnection of the Putumayo Basin with the Upper Magdalena Valley in Colombia and the Oriente Basin in Ecuador during the mid-Cretaceous, which, together with the rest of the ammonoid assemblage, provide biostratigraphic data to define the Albian-Cenomanian boundary in the basin.

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