John W. M. Jagt

Amongst the most extraordinary extinct ophiuroids is the genus Astrosombra from the Upper Cretaceous of Germany. Initially known from isolated ossicles only, the extremely expanded lateral arm plates suggested an aberrant body shape comparable to that seen in the extraordinary astrophiurid genus Astrophiura . Here, we describe the first articulated specimen of Astrosombra rammsteinensis , the type and only known species of the genus, from the type locality of the taxon, showing the highly modified lateral arm plates in their anatomical context and providing insights into the general skeletal morphology. The new specimen confirms the presence of extremely widened arms, formed by the aberrantly expanded lateral arm plates articulating with unusually wide vertebrae and covered dorsally by multiple rows of dorsal arm plates. The width of the arms is further increased by large, flat, feather-like arm spines. MicroCT images of the articulated disc revealed morphological details, in particular, high oral plates with wing-like expansions, suggesting transfer of Astrosombra from the Amphilimnidae to the Ophiopsilidae. In analogy with Astrophiura , the extremely widened arms, the fringe of flat arm spines, the large tentacle pores and the overall flat body shape suggest that Astrosombra inhabited the small, patchy hard substrates formed by the skeletal remains of other organisms.

Two new species of pedunculate cirripede are described from lower Campanian basinal limestones of Höver and Misburg (Hannover area), northern Germany. These are the myolepadid Bosquetlepas schneideri sp. nov. and the large cretiscalpellid Jagtscalpellum kaeckei sp. nov. The occurrence of Bosquetlepas in basinal limestones is remarkable, as the genus was largely confined to shallow-marine and coastal habitats.

Recent advances in molecular phylogenies have revolutionised our understanding of brittle star systematics and evolutionary history. Although genetic data have provided new grounds for age estimates of phylogenetic divergences, direct fossil evidence is currently the only robust means to determine the minimum age of clades. The present study discusses an exceptional opportunity to robustly pinpoint the minimum age of an extant genus of brittle star. The presumed ophiolepidid brittle star species Ophiolepis? falsa Jagt & Kutscher, in Jagt, 2000, from lower upper Campanian (Upper Cretaceous, c. 79 Ma) deposits in north-east Belgium, is here recorded from coeval strata in the Münsterland Basin (northern Germany) and transferred to the previously monospecific extant hemieuryalid genus Actinozonella Stöhr, 2011. An unusually well-preserved specimen, completely free from mineralised matrix, allows both dorsal and ventral sides of the disc and short arm stumps to be examined. In this way, characters not visible in the holotype of Ophiolepis? falsa could be analysed; these revealed its taxonomic affinity with Actinozonella, dating that genus to at least 79 Ma. The close morphological similarity between Actinozonella and Ophiomisidium Koehler, 1914, and to some species currently assigned to Ophiomastus Lyman, 1878, is discussed.

A new species of the irregular echinoid genus Cyclaster, C. pectiformis, is erected to accommodate a single, small-sized, fairly well-preserved test from an unspecified level within the lower upper Campanian (probably stobaei/basiplana Zone or vulgaris/basiplana Zone) as exposed at the Heidelberg Materials/Teutonia I quarry at Hannover-Misburg (Lehrte West Syncline, Lower Saxony Basin, northern Germany). The prime feature that distinguishes this new taxon from its congeners are the conspicuous, comb-shaped proximal margins of interambulacral plates 2.1 and 3.1. Petals are short, the frontal ambulacrum is flush with the test, sternal plates 5.b.2 and 5.a.2 are subequal, being divided by an oblique suture and the labral plate is long, slender and flask shaped. The peripetalous fasciole is rudimentary, while the subanal one is well developed. The comb-shaped plates guarding the anterior margin of the peristome are unique among the Spatangoida and are interpreted as structures supporting food intake by scraping off mucus and mud from the tips of the buccal podia.

We provide a reassessment of the hypothesis of ammonite survival across the Cretaceous–Paleogene (Maastrichtian–Danian) boundary, based on new data from the lower Danian Cerithium Limestone Member at Stevns Klint, eastern Denmark. The occurrence of this unit in disjunct basins between eroded crests of uppermost Maastrichtian bryozoan mounds prompts a reconsideration of ammonite redeposition as an alternative to the survival hypothesis. We describe new ammonite specimens from the Cerithium Limestone, representing the genera Hoploscaphites, Baculites and Fresvillia. In order to elucidate the nature of these fossils, we study their local depositional settings, based on detailed, chiefly taphonomic and sedimentological (microfacies) observations. Results for the main part of the Cerithium Limestone point to the autochthonous nature of the enclosed ammonites, which implies that they are Danian survivors. Only a single individual from the lowermost part of the Cerithium Limestone is considered a reworked Maastrichtian fossil. In summary, our results confirm ammonite survival into the Danian for the bulk of the Cerithium Limestone fauna, stimulating questions for further research of what actually killed the last ammonites that lived on Earth.

The family Dercetidae comprises a diverse array of marine aulopiform actinopterygians. Until now, merely seven specimens, assigned to five species, were recorded from the Maastrichtian type area. Here, around two dozen dercetid fossils, originating from a number of quarries and outcrops in north-eastern Belgium and the south-eastern Netherlands are described and illustrated. This material comprises two new genera, Beukidercetis gen. nov. and Petrodercetis gen. nov., and four new species: Caudadercetis taverni sp. nov., Beukidercetis lissus gen. et sp. nov., Cyranichthys sideralis sp. nov., and Petrodercetis bidirectus gen. et sp. nov. Newly collected specimens of Cyranichthys jagti, Dercetis triqueter and Ophidercetis italiensis are also added, because these extend their respective stratigraphical ranges in the study area. Moreover, material here assigned to Dercetoides venator and a specimen resembling Cyranichthys ornatissimus markedly expand their geographical and stratigraphical ranges. In general, the present material reflects an underappreciated diversity of dercetids in the Maastrichtian type area, even though that they fossilize well compared to other late Maastrichtian actinopterygians from the study area. This high degree of preservation may be related to a benthic lifestyle, or to their slender, scute-covered bodies that may have been less vulnerable to disruption than those of other actinopterygians.

A new pylochelid hermit crab, Cretatrizocheles rodfeldmanni new species, is recorded from a Lower Cretaceous (Aptian/Albian) olistolith reefal limestone block near the village of Velika Strmica, southeast Slovenia. It adds to the fossil record of the symmetrical pagurid subfamily Trizochelinae, whose members appear to have been successful inhabitants of shallow-marine reefal settings during at the least the Late Jurassic and Early Cretaceous across Europe. Given their exclusive occurrence in shallow-marine, reef-related facies of Mesozoic age and the present-day confinement to deep-marine settings, trizocheline paguroids may also illustrate the effect of the Mesozoic Marine Revolution.UUID: http://zoobank.org/b3f862ca-3b4d-44c1-911c-820af4426029

Because our modern world is characterized by climate change, it is useful to study climate conditions of past greenhouse worlds in order to obtain a better understanding of what a similar world would entail. An example of such a past greenhouse climate is represented by the Late Maastrichtian Warming Event (LMWE), a global temperature increase of approximately 2.5-5°C that occurred 300-100 kyr prior to the Cretaceous-Paleogene boundary meteorite impact and the ensuing mass extinction. This warming event has traditionally been linked to a major pulse of Deccan Traps volcanism. Previous research has also recorded the LMWE in the Maastrichtian type region (SE Netherlands, NE Belgium), where this event is marked by characteristic blooms of the dinoflagellate Palynodinium grallator and a sudden appearance of hermatypic corals. A recent study using clumped-isotope analyses on fossil bivalves has shown that the LMWE was characterized by a 5 degrees warming in average annual sea water temperatures in this region (40° paleolatitude). However, little is known about changes in seasonality across this warming event, as high-resolution paleoseasonality reconstructions have not been previously attempted. Here, we present a seasonal, stable-isotope record through the LMWE for the Maastrichtian type area (SE Netherlands, NE Belgium), using stratigraphically well-constrained oyster specimens. This new record contributes to our understanding of the effects of a global warming event on seasonality in a mid-latitude shelf sea. Consistent with previous results, we have found a decreasing trend in δ18O values in the interval corresponding to the peak of the warming event, followed by an increase during the cooling-down period. Our results show that the LMWE also had profound effects on the seasonality in the Maastrichtian type area. The δ18O seasonality temporarily decreased at the onset of the event, suggesting that winter temperatures warmed disproportionately. Possibly, this could have allowed the previously recorded establishment of hermatypic corals in the region. Subsequently, seasonality increased again through the warming event, with the highest seasonality recorded in the later part of the event. Over the coming months, additional oyster specimens will be assessed for both stable and clumped isotopes to obtain a more complete record of seasonality throughout the LMWE.

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.