Four previously unknown hypogean species of cyclopoid copepods were collected in cenotes and wells of the Yucatan Peninsula, Mexico. Diacyclops chakan sp. n. and D. puuc sp. n. differ from their congeners in combining 3-segmented swimming legs, 11-segmented antennules, and legs 1-4 endopodite segment 2 all with 2 setae. Species of Diacyclops rarely occur in tropical regions, and the Diacyclops described here are only the second and third species recorded from Mexico. The benthic D. puuc was found in the large underground reservoir of a cenote. Diacyclops chakan was encountered in such large open subterranean water basins, but more frequently and abundantly in wells. The two Mesocyclops species, M. chaci sp. n. and M. yutsil sp. n., most closely resemble their epigean benthic congener M. reidae Petkovski, but are modified by loss of some body ornament and attenuation of swimming legs and mouthparts. Mesocyclops chaci sp. n. occupies crevicular spaces (wells and small caverns). The second species, M. yutsil sp. n., with more pronounced attenuation of legs, has a planktonic life in large subterranean water volumes. The extremely attenuated appendages of both species distinguish them from all other Mesocyclops, and resemble those of the hypogean Kieferiella delamarei Lescher-Moutoué. These three species are considered as a species-flock which have radiated as specialists within a highly dynamic geomorphological environment.
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The early to middle Selandian fossiliferous Orp Sand Member of the Heers Formation in Belgium has regularly been excavated at its type-locality Maret for its rich and diversified selachian fauna. Among the abundant vertebrate remains, extremely rare mammal specimens have been found. Three isolated teeth have been published previously, all with uncertain affinities. The purpose of this study is to present new specimens from the same deposits, including a small well-preserved dentary of an adapisoriculid attributable to “Afrodon” germanicus, a fragmentary upper molar, referred to Berrulestes sp., and a premolar of a large arctocyonid. Among the previous specimens we identified Arctocyonides cf. weigelti. The adapisoriculid dentary offers new clues that allow transferring “Afrodon” germanicus to the genus Bustylus. The five mammal taxa from Maret indicate an age intermediate between reference-levels MP1-5 of Hainin, Belgium and MP6 of Cernay, France and present the greatest correlation with the rich Walbeck fauna in Germany. The deposits from Walbeck were usually thought to be slightly older than the late Thanetian deposits of Cernay. We infer here that the age of Walbeck is likely to be Selandian. The strong differences observed between Hainin on the one hand, and Walbeck and Cernay on the other hand, document a dispersal event from North America to Europe around the Danian-Selandian boundary.
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