During fieldwork in the early 1990s at the then still active quarry near Nasiłów, on the left bank of the River Vistula (Wisła), accompanied by Professor Andrzej Radwański, some lobster remains were collected. A fragmentary anterior portion of a decapod crustacean carapace, recovered from a level about 2 m below the Cretaceous–Paleogene (K/Pg) boundary, in a siliceous chalk unit locally referred to as ‘opoka’, constitutes the oldest record of the thaumastocheliform genus Dinochelus Ahyong, Chan and Bouchet, 2010, D. radwanskii sp. nov. The other, more complete, individual is from c. 3 m above the K/Pg boundary, coming from marly gaizes or ‘siwak’; this is ascribed to a new species of Hoploparia M’Coy, 1849, H. nasilowensis sp. nov., the first to be recorded from Danian (lower Paleocene) strata. Although both ‘opoka’ and ‘siwak’ facies in the Nasiłów area are very rich in diverse biota, including some brachyurans, no macruran remains had so far been recorded from the region.
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