The historically important mosasaur fossil (known as ‘le grand animal fossile des carrières de Maestricht’) has been known as Mosasaurus hoffmanni for almost two centuries now. Recently, it has been proposed to amend the spelling of the species name, by adding a second ‘i’ to the species epithet. We present historical evidence to the contrary, and recommend, following article 33.2.3.1 of the ICZN, to retain the specific epithet hoffmanni.

Brachiopods from the lower upper Maastrichtian (Upper Cretaceous) white chalk succession exposed at Chełm (eastern Poland) comprise Lingula cretacea, Isocrania costata, Cryptoporella antiqua, Cretirhynchia sp., Neoliothyrina sp., Carneithyris sp., Terebratulina chrysalis, T. faujasi, T. longicollis, Terebratulina spp., Gisilina sp., Bronnothyris bronni, Magas chitoniformis, Leptothyrellopsis polonicus and ?Aemula sp. This assemblage is relatively poor in terms of taxonomic diversity and specimen abundance and is dominated by stratigraphically long-ranging species. It is best comparable to that from the micromorphic brachiopod Rugia tenuicostata–Meonia semiglobularis Zone as distinguished in the white chalk successions of Denmark and northern Germany, although this zone is usually placed in the upper lower Maastrichtian. The Chełm succession represents a relatively deep-water and ‘benthos-poor’ variety of white chalk deposited in the Boreal Chalk Sea of Europe. The brachiopod assemblage studied is typical of such a habitat, having been controlled largely by the low availability of minute skeletal substrates suitable for brachiopod settlement.

The Late Cretaceous was a time of blossoming teleost diversification that came to a sudden restriction and partial termination during the extinction event at the Cretaceous–Paleogene (K/Pg) boundary. Among the dominant and diverse Late Cretaceous teleost groups prior to the K/Pg boundary event were certain pelagic Aulopiformes (e.g., Ichthyotringoidei and Enchodontoidei) and a large variety of basal Acanthomorpha whose relationships are difficult to determine. The skeletal record diminishes during the late Campanian and is low in the Maastrichtian and Paleocene, constituting the so-called ‘Patterson’s Gap’. Recent studies of fossil otoliths, however, have significantly increased the number of taxa recognised for this time inerval, but most of the putative extinct forms lack adequate calibration with otoliths found in situ in articulated skeletons. However, the otolith assemblages do confirm the presence of great morphological diversity among Aulopiformes and Acanthomorpha incertae sedis that became extinct at the K/Pg boundary. In the present review, we elucidate the effect of the K/Pg boundary from an otolith perspective and categorise extinct lineages and survivors. It is interesting to recognise that several of the surviving lineages are represented by groups that probably originated during the Late Cretaceous but were not particularly common up to the K/Pg boundary and began to expand rapidly and diversify during the early Paleogene. Such lineages probably took advantage to populate void ecospace that may have opened following the extirpation of previously dominant lineages. During the early Paleogene, the otolith record shows that the Ophidiiformes and perciforms s. lat. were the ones that diversified the most rapidly and became the most abundant, and in certain areas associated with the Gadiformes.

The lower Maastrichtian (Upper Cretaceous) section at Nahoryany, south of Lviv (western Ukraine), has been known as a rich source of fossils since 1843. However, the section is not available since a long time ago and fossils collected from it can only be studied in museum collections. In the present paper, ammonites of the scaphitid genus Hoploscaphites are studied based on Nahoryany material, comprising Hoploscaphites pumilus, H. constrictus and H. sp. Specimens from Nahoryany in museum collections lack data on their provenance level within the section so it cannot be determined whether or not they occurred together or formed a succession; data on inoceramid bivalves indicate the presence of two successive zones at Nahoryany. Some specimens from Nahoryany here referred to as H. pumilus are similar to the controversial H. constrictus anterior from the lower Maastrichtian of Poland. This morphology suggests an ancestor–descendant relationship between H. pumilus and H. constrictus, a common species once considered as an informal index for the Boreal Maastrichtian in Europe. The inferred evolutionary transition from H. pumilus to H. constrictus was towards a less robust, recoiled shell, which would have enhanced the horizontal swimming ability and manoeuvrability of these cephalopods. Recoiling trends occurred in several lineages of Late Cretaceous scaphitids.

The first isolated and well-preserved phalanx (autopodial element) of a generically and specifically indeterminate (probably xenopsarian) plesiosaur from the Maastrichtian type area (south-east Netherlands) is described and illustrated. Morphological features of this bone, such as the articular subchondral surfaces, allow it to be distinguished from phalanges of co-occurring mosasaurs (Mosasauridae, Squamata) and could imply rapid growth in plesiosaurs, similar to that observed in extant leatherback turtles. The large size of the phalanx indicates that it originates either from a large juvenile or from a paedomorphic individual. The paucity of plesiosaur remains in biocalcarenites of late Maastrichtian age in the Maastrichtian type area could be explained by the shallow settings, in which these strata were deposited, which may not have offered suitable ecological resources conducive to abundant plesiosaur inhabitation. Presumably, the lack of steep continental slopes in the type Maastrichtian, at which oceanic upwelling of cold, nutrient-rich water supported a higher prey density for pelagic predators such as plesiosaurs, may have inhibited plesiosaur occupation. Rather, decomposing floating carcasses may have been the source of dissociated elements of plesiosaurs in this area, such as isolated teeth, vertebrae and the autopodial element described here.

The lower Maastrichtian chalk of the Isle of Rügen was deposited in a pelagic setting in the aphotic zone. Its rich fossil content has attracted research attention for centuries, whereas its ichnological characteristics remain poorly understood, even though horizons with intense bioturbation and occurrences of trace fossils in flint are common. The enhanced colour contrast of smooth chalk faces reveals repeated phases of benthic colonisation; larger burrows are commonly subject to silicification, while flint nodules also can preserve burrows in chalk. A total of 37 ichnogenera, including 47 ichnospecies of bioturbation and bioerosion trace fossils have been recognised; these are here briefly described, in addition to indeterminate material. Many ichnotaxa are recorded for the first time from the Rügen chalk. Bioerosion is restricted mainly to local hardgrounds in the form of biogenic components (such as shells and belemnite guards).

The Maastricht Formation is a mostly calcarenitic unit that belongs to the Chalk Group but is unlike the typical North Sea chalk in that it is much coarser and at times contains a significant terrigenous component. The formation was deposited between the late Maastrichtian and the early Danian in a proximal zone of the Chalk Sea immediately north of the Anglo-Brabant and Rhenish massifs. The formation crops out in South Limburg, the Netherlands, in the German state of North Rhine–Westphalia, near Aix-la-Chapelle (Aachen), and in the Belgian provinces of Liège and Limburg, and it is present in the subsurface in the Campine Basin and in the Roer Valley Graben, in Belgium and the Netherlands.

The often spectacular fossil content of the Maastricht Formation has been extensively studied but its sedimentological aspects remain understudied. Indeed, the lithostratigraphy of the formation is largely informal and based on the abundance and morphology of flint and on the quantification of fossil content. The paucity of facies studies and the lack of a lithostratigraphic framework based on modern facies studies hampers stratigraphic correlation between outcrops and, more importantly, boreholes. A facies characterisation and facies-based lithostratigraphic framework of the Maastricht Formation in South Limburg is particularly urgent because groundwater is abstracted from aquifers in the formation and geological models currently in place fail to predict facies heterogeneity and, consequently, aquifer properties.

We studied eight outcrops of the Maastricht Formation across South Limburg and carried out a (micro)facies analysis of the outcrops. We show that the Maastricht Formation can be subdivided into three lithofacies and five microfacies. The lithofacies reflect the traditional subdivision of the formation into Maastricht and Kunrade limestones. Our results suggest that the current subdivision of the Maastricht Formation into six members is untenable. The formation is best subdivided into lower and upper members. The Kunrade limestone should be afforded the status of formation.

We interpret the Maastricht Formation as having been deposited in an epeiric ramp, in which facies distribution was controlled by water temperature, nutrient levels and storminess. The (micro)facies of the Maastricht Formation can be organised into two depositional stages: stage 1, representing the lower part of the formation, is characterised by heterozoan carbonates deposited under cooler, mesotrophic conditions in a nutrient-rich, more proximal region of the epeiric sea; stage 2 is characterised by heterozoan-photozoan carbonates deposited in a warmer and stormier environment with slightly lower nutrient levels.

Maastrichtian scleractinian corals from 94 localities in 26 Maastrichtian regions world-wide with strata of that age are taxonomically and palaeobiogeographically evaluated. A total of 205 taxa, belonging to 116 genera and 37 families, are included in the present study. Most coral taxa have been recorded from non-reefal environments. A significant majority of these taxa (genera = 70.7%; species = 75.6%) appear to have been endemic during the Maastrichtian. The Maastrichtian coral fauna is dominated by solitary and cerioid-plocoid forms (both accounting for 41 genera = 70%), having mainly medium- and large-sized corallites. The most diverse coral assemblages are those that have been recorded from arid (Jamaica: 63 species, Mexico: 29 species), warm-temperate (the Netherlands-Belgium: 32 species) and tropical regions (Iran: 27 species). The occurrence of Cunnolites polymorphus (Goldfuss) is newly recorded for the Netherlands (southern Limburg). Compared to the microstructural composition of the coral fauna of the lowermost Cretaceous (Berriasian; 91% of the species and 83% of the genera belonged to previously established microstructural groups), in the Maastrichtian, corals belonging to previously established microstructural groups were of minor importance (genera = 26%; species = 29.3%). The majority of Maastrichtian scleractinian taxa (both solitary and colonial) from the type area of the Maastrichtian Stage in the southeast Netherlands and northeast Belgium are illustrated.

For centuries, fossils from the Maastrichtian type locality and adjacent quarries have provided key evidence of vertebrate diversity during the latest Cretaceous, yet until recently the Maastrichtian type area had revealed no important insights into the evolutionary history of birds, one of the world’s most conspicuous groups of extant tetrapods. With the benefit of high-resolution micro-CT scanning, two important avian fossils from the Maastrichtian type area have now been examined in detail, offering profound, complementary insights into the evolutionary history of birds. The holotype specimens of these new taxa, Janavis finalidens Benito, Kuo, Widrig, Jagt and Field, 2022, and Asteriornis maastrichtensis Field, Benito, Chen, Jagt and Ksepka, 2020, were originally collected in the late 1990s, but were only investigated in detail more than twenty years later. Collectively, Janavis and Asteriornis provide some of the best evidence worldwide regarding the factors that influenced stem bird extinction and crown bird survivorship through the Cretaceous-Palaeogene transition, as well as insights into the origins of key anatomical features of birds such as an extensively pneumatised postcranial skeleton, a kinetic palate, and a toothless beak. Asteriornis also provides scarce evidence of a Cretaceous-aged divergence time calibration within the avian crown group, while together, Janavis and Asteriornis constitute the only documented co-occurrence of crown birds and non-neornithine avialans. Here, we review key insights into avian evolutionary history provided by these discoveries from the Maastrichtian stratotype, document undescribed and newly discovered Maastrichtian fossils potentially attributable to Avialae and provide the first histological data for the holotype of Asteriornis, illustrating its skeletal maturity at the time of its death.

Renewed interest in bryozoan assemblages from the various members of the Gulpen Formation (upper Campanian–upper Maastrichtian) in the Liège-Limburg area (southeast Netherlands and northeast Belgium) during recent years has resulted in the discovery of a number of species previously unrecorded from the area. Nineteen species are here recorded from the Zeven Wegen, Vijlen, Lixhe and Lanaye members (Gulpen Formation) in the study area, occurring in three distinct assemblages. The vast majority of the bryozoan taxa belong to the order Cheilostomata; only two taxa are assigned to the order Cyclostomata. The species recorded here are Clinopora aff. costulata, Disporella obvallata, ‘Vincularia’ (sensu lato) marssoniana, Herpetopora laxata, Heteroconopeum ovatum, Wilbertopora aff. oxyteichos, Biaviculigera sacerdotalis, Semiflustrella britannica, Aechmellina anglica, Escharifora papyracea, Onychocella cyclostoma, Onychocella cylindrica, Onychocella matrona, Rhebasia disparilis, Stichomicropora sicksi, Coscinopleura elegans, Coscinopleura lamourouxi, Pachydermopora pachyderma and Beisselina aviculifera. While not previously recorded from the Liège-Limburg area, the bryozoan taxa identified from the Gulpen Formation are well known from coeval Cretaceous strata elsewhere in Europe, North America and Russia, highlighting their broad palaeobiogeographical distribution.

The geographical and stratigraphical distribution of the heteromorph ammonite genus Diplomoceras within the North-West Pacific Province is briefly reviewed. Although Diplomoceras ranks amongst the more important, globally distributed taxa during the latest Cretaceous, its precise stratigraphical range still is uncertain. Moreover, the status of the various species assigned to this genus is a matter of debate; for instance, two commonly cited forms, Diplomoceras cylindraceum and D. notabile, are considered to be conspecific by some authors, but treated as discrete taxa by others. The majority of records of species of Diplomoceras are from Maastrichtian strata; however, several late Campanian finds bring some discrepancy into the discussion about their biostratigraphical significance. Here we record new specimens from the upper Maastrichtian Kokuy Unit, refer them to Diplomoceras cylindraceum and briefly consider the geographical, biostratigraphical and taxonomic issues surrounding the genus Diplomoceras.

Over recent decades, the type area of the Maastrichtian Stage in southern Limburg (the Netherlands) and contiguous Belgian territory, and the former ENCI-HeidelbergCement Group quarry (Sint-Pietersberg, Maastricht) in particular, has yielded an exquisitely preserved ichnocoenosis of bioerosional trace fossils, mainly preserved as natural casts in scleractinian corals. More than 20 ichnospecies are here documented, the majority from the type Maastrichtian for the first time. These ichnotaxa constitute a good record of successive colonisation sequences; the present bioerosional ichnocoenosis is regarded to belong to the Entobia ichnofacies.