A latest Cretaceous (68 to 65 million years ago) vertebrate microfossil assemblage discovered at Kakanaut in northeastern Russia reveals that dinosaurs were still highly diversified in Arctic regions just before the Cretaceous-Tertiary mass extinction event. Dinosaur eggshell fragments, belonging to hadrosaurids and non-avian theropods, indicate that at least several latest Cretaceous dinosaur taxa could reproduce in polar region and were probably year-round residents of high latitudes. Palaeobotanical data suggest that these polar dinosaurs lived in a temperate climate (mean annual temperature about 10 degrees C), but the climate was apparently too cold for amphibians and ectothermic reptiles. The high diversity of Late Maastrichtian dinosaurs in high latitudes, where ectotherms are absent, strongly questions hypotheses according to which dinosaur extinction was a result of temperature decline, caused or not by the Chicxulub impact.

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Abstract An extraordinarily well-preserved autochthonous angiosperm herbaceous community is described from the Lower Cretaceous deposits of the Frentsevka Formation, southern Primorye, Far East of Russia. The locality Bolshoy Kuvshin is situated on the coast of the Ussuri Bay on the Bolshoy Kuvshin Cape near the town of Bolshoy Kamen. The plant-bearing layer was determined to be early - middle Albian in age. The angiosperm assemblage includes six species: Achaenocarpites capitellatus Krassilov et Volynets, Ternaricarpites floribundus Krassilov et Volynets, Jixia pinnatipartita S.X.Guo et G.Sun, Asiatifolium elegans G.Sun, S.X.Guo et Shao L.Zheng and two new undetermined species. The majority of specimens are represented by fragments of branching stems with attached leaves or fruits or by almost complete plants. Two species (Jixia pinnatipartita and Asiatifolium elegans) are also in the angiosperm assemblage from the Chengzihe Formation (eastern Heilongjiang, China). The angiosperm remains are accompanied by the fern Onychiopsis psilotoides which is represented by almost entire young plants. The plant fossils were buried during a single flooding event and remained very close to their original location. They formed a pioneer open herbaceous community, consisting of ferns and angiosperms with a predominance of the latter and adapted to colonize fresh sediments in periodically flooded areas.

On the basis of new records and reexamination of described fossils a revision of morphology and systematics of fructifications, found in co-occurrence with Trochodendroides Berry leaves was undertaken. The general construction of racemose infructescences and fruits of all known specimens is practically identical. This similarity indicates that these plants were closely related with minor differences that are not sufficient for separate generic designation. We suggest applying the name Jenkinsella Reid et Chandler for dispersed follicular fruits, to fruits in racemes and to infructescences attached to the shoots. This is the earliest appropriate generic name designated for fruits with distinguishable morphology and critical details of inner structures. The diagnosis of the genus Jenkinsella is emended and five new species are described: Jenkinsella krassilovii Golovneva et P. Alekseev, sp. nov., J. knowltonii Golovneva et P. Alekseev, sp. nov., J. conferta P. Alekseev et Golovneva, sp. nov., J. makulbekovii Golovneva et P. Alekseev, sp. nov., J. vilyuensis Golovneva et P. Alekseev, sp. nov. Three new combinations (J. filatovii (Samylina) Golovneva et P. Alekseev, comb. nov., J. jiayinensis (G.P. Feng, C.S. Li, Zhilin, Y.F. Wang et Gabrielyan) Golovneva et P. Alekseev, comb. nov., J. gardnerii (Chandler) Golovneva et P. Alekseev, comb. nov.) are created. Investigation of infructescence arrangement in different species of Jenkinsella provides new data, allowing reinterpretation of fertile shoots construction in Joffrea speirsii.

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