Abstract A small faunule of fragmentary Hettangian (earliest Jurassic) psiloceratoid ammonites collected from dark-coloured, clay-rich sediments in a subrosion pipe at Quarry III of the Winterswijk quarry complex is described. The genera Alsatites, Saxoceras and Schlotheimia are determined by comparison to extensive literature on coeval, north German faunas. Taphonomic features are apparent indicating condensation and reworking. Despite this, the portion of the subrosion pipe sediment fill which yielded this material can be dated as middle to late Hettangian.
Abstract Global biodiversity patterns in deep time can only be understood fully when the relative preservation potential of each clade is known. The relative preservation potential of marine arthropod clades, a diverse and ecologically important component of modern and past ecosystems, is poorly known. We tackled this issue by carrying out a 205‐day long comprehensive, comparative, taphonomic experiment in a laboratory by scoring up to ten taphonomic characters for multiple specimens of seven crustacean and one chelicerate species (two true crabs, one shrimp, one lobster, one hermit crab, one stomatopod, one barnacle and one horseshoe crab). Although the results are preliminary because we used a single experimental setup and algal growth partially hampered observations, some parts of hermit crabs, stomatopods, swimming crabs and barnacles decayed slowly relative to other parts, implying differential preservation potentials within species, largely consistent with the fossil record of these groups. An inferred parasitic isopod, manifested by a bopyriform swelling within a hermit crab carapace, decayed relatively fast. We found limited variation in the decay rate between conspecifics, and we did not observe size‐related trends in decay rate. Conversely, substantial differences in the decay rate between species were seen after c . 50 days, with shrimps and stomatopods decaying fastest, suggesting a relatively low preservation potential, whereas the lobster, calico crabs, horseshoe crabs and barnacles showed relatively slow decay rates, suggesting a higher preservation potential. These results are supported by two modern and fossil record‐based preservation potential metrics that are significantly correlated to decay rate ranks. Furthermore, we speculate that stemward slippage may not be ubiquitous in marine arthropods. Our results imply that diversity studies of true crabs, lobsters, horseshoe crabs and barnacles are more likely to yield patterns that are closer to their true biodiversity patterns than those for stomatopods, shrimps and hermit crabs.
ABSTRACT Drillholes on shells provide a useful way to investigate prey and predator relationships. The current study documents predator–prey interactions exemplified by a faunal assemblage of the fossil gastropod Turritella cingulifera from the Pleistocene Szekou Formation in Hengchun Peninsula, Taiwan. All recognisable skeletal and shell fragments that are larger than 3 mm in size were collected and recorded. Processed bulk sediments (5.24 kg) contained 1462 molluscan shells, including 824 specimens of T. cingulifera , and 27 non-molluscan invertebrates. In the current study, approximately 41.6% (609/1462) of molluscs are drilled with at least one hole. Drilling intensities (DIs) regardless of shell completeness in all gastropods, bivalves and the turritelline gastropod T. cingulifera are 0.546, 0.060 and 0.413, respectively. DI on turritellids is significantly lower than that on other gastropods ( χ 2 = 21.039, P < 0.001). Furthermore, the percentage of drillholes that occur in multiply drilled specimens is 34.7% (95/275) for turritelline gastropods based on complete to nearly complete specimens ( n = 588). Our study shows no significant preference of drillhole position either on the suture or on the whorl ( χ 2 = 0.055, P = 0.814). Most drillholes are located in whorls two to four proximal to the aperture. Drillhole diameters of the shells with one drillhole and ones with multiple drillholes are 1.0 and 0.5 mm on average, and the results of Mann–Whitney tests indicate that they are significantly different ( P < 0.001). The first turritelline gastropod shell with an incomplete drillhole from Taiwan is documented here. The dominant drilling predators were naticids based on the drillhole morphology and the presence of naticids in the same assemblage. No apparent prey size selectivity is observed, so a ‘size refugium’ does not exist for the turritellids in the current study.
Parasites are common in modern ecosystems and are also known from the fossil record. One of the best preserved and easily recognisable examples of parasitism in the fossil record concerns isopod-induced swellings in the branchial chamber of marine decapod crustaceans. However, very limited quantitative data on the variability of infestation percentages at the species, genus, and family levels are available. Here we provide this type of data for a mid-Cretaceous (upper Lower Cretaceous, upper Albian) reef setting at Koskobilo, northern Spain, on the basis of 874 specimens of anomurans and brachyurans. Thirty-seven specimens (4.2%), arranged in ten species, are infested. Anomurans are more heavily infested than brachyurans, variability can be high within genera, and a relationship may exist between the number of specimens and infestation percentage per taxon, possibly suggesting host-specificity. We have also investigated quantitative patterns of infestation through geological time based on 88 infested species (25 anomurans, 55 brachyurans, seven lobsters, and one shrimp), to show that the highest number of infested species can be found in the Late Jurassic, also when corrected for the unequal duration of epochs. The same Late Jurassic peak is observed for the percentage of infested decapod species per epoch. This acme is caused entirely by infested anomurans and brachyurans. Biases (taphonomic and otherwise) and causes of variability with regard to the Koskobilo assemblage and infestation patterns through time are discussed. Finally, a new ichnogenus and -species, Kanthyloma crusta, are erected to accommodate such swellings or embedment structures (bioclaustrations).
In de huidige zeeen en oceanen en die uit het verleden is en was eten en gegeten worden aan de orde van de dag. Waar wij de supermarkt binnenlopen, doet het zeeleven iedere dag weer zijn best een maaltijd binnen te slepen en probeert te voorkomen dat het zelf een prooi wordt. Dat geldt ook voor gastropoden (slakken). Een deel van deze gastropoden heeft de kunst ontwikkeld om gaten te boren in andere mollusken zoals bivalven en scaphopoden en in gastropoden zelf (kannibalisme!). De gastropoden maken af en toe onvoorstelbare blunders en dit artikel laat er een achttal van zien.
Abstract Horseshoe crabs (Xiphosura) have a long evolutionary history starting in the Ordovician, but they have rarely been reported from the Netherlands. We report on the first Triassic horseshoe crab from the Netherlands identifiable to the species level, a specimen of the limulid Limulitella bronnii . We provide the first diagnosis for this species and refigure the holotype. The new specimen was found in the Middle Triassic (Anisian) Muschelkalk sediments of the Vossenveld Formation, in the Illyrian part of the stratigraphic profile of the Winterswijk quarry complex. The Winterswijk specimen represents the youngest occurrence of L. bronnii . The inferred non-marine habitat of this horseshoe crab species elsewhere in conjunction with occurrences of plant and insect remains within the same layer at Winterswijk suggest the specimen herein most probably did not live in marine conditions either. This species has previously been found in non-marine sediments in France and Germany, expanding its geographic range northward. Several faunal elements from Winterswijk including L. bronnii show resemblance to the roughly co-eval non-marine components of the Anisian Grès à Voltzia Formation in NE France, suggesting a paleobiogeographic connection between these regions in Western Europe.
