In addition to the type species, Binkhorstia ubaghsii, which is fairly common in the upper part of the Nekum Member (Maastricht Formation) in the wider vicinity of Maastricht (the Netherlands) and Binkhorstia euglypha, which appears to be restricted to the overlying Meerssen Member of the same formation (uppermost Maastrichtian), a third member, B. desaegheri nov. sp., is recorded from the upper middle Santonian of the Campine area in north-east Belgium. The history of Binkhorstia is convoluted, serving as a prime example of how attempts to unravel the higher-level taxonomic position of late Mesozoic crabs may prove difficult. Over time, the genus has been referred to various families or subfamilies, either podotreme or putative eubrachyuran; here the new family Binkhorstiidae is placed in the superfamily Retroplumoidea. Binkhorstiids appear to have been a relatively short-lived endemic group that fell victim to Cretaceous‒Paleogene (K/Pg) boundary perturbations.
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RBINS Staff Publications 2024
The mid-Maastrichtian carbon isotope event (MME), dated at ∼69 Ma, reflects a perturbation of the global carbon cycle that, in part, correlates with the enigmatic global extinction of ‘true’ (i.e., non-tegulated) inoceramid bivalves. The mechanisms of this extinction event are still debated. While both the inoceramid extirpation and MME have been recorded in a variety of deep-sea sites, little is known about their expression in epicontinental chalk seas. In order to study the shallow-marine signature of the MME in this epicontinental shelf sea, we have generated quantitative foraminiferal assemblage data for two quarries (Hallembaye, NE Belgium; ENCI, SE Netherlands) in the Maastrichtian type area, complemented by a species-specific benthic δ13C record. In contrast to deep-sea records, no significant changes in benthic foraminiferal assemblages and benthic foraminiferal accumulation rates are observed across the MME in the type-Maastrichtian area. At the Hallembaye quarry, the otherwise rare endobenthic species Cuneus trigona reaches a transient peak abundance of 33.3% at the onset of the MME, likely caused by a local transient change in organic matter flux to the seafloor. Nevertheless, high and near-constant species evenness shows that neither oxygen nor organic matter flux was limited across the extinction level or during the MME. Benthic foraminiferal data from the uppermost part of the studied section, above the MME, indicate a significant increase in food supply to the seafloor. Decreased amounts of terrigenous elements across this interval document a lesser riverine or aeolian influx, which means that the increased benthic productivity is linked to a different origin. Potentially, the continuous precipitation of chalk under nutrient-poor conditions in the Late Cretaceous chalk sea was enabled by efficient nutrient recycling in the water column. In shallower depositional settings, nutrient recycling took place closer to the seafloor, which allowed more organic matter to reach the bottom. These results provide insights in the importance of nutrient cycling for biological productivity in the NW-European chalk sea.
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RBINS Staff Publications 2022 OA
