Reconstructing the ecology of a Cretaceous cockroach: destructive and high-resolution imaging of its micro sensory organs.

Animals highly depend on their sensory organs to detect information about their surrounding environment. Among animal sensory organs, those of insects have a notable ability to detect information despite their small size, which might be, therefore, one of the reasons for the evolutionary success of insects. However, insect sensory organs are seldom fossilized in sediments due to their small size and fragility. A potential solution for this problem is the study of exceptionally well-preserved fossil material from amber. Unfortunately, the resolution of existing non-destructive analysis is insufficient to observe details of these micro sensory organs even with amber preservation. Here, we focus on the analysis of the micro sensory organs of an extinct male cockroach (Huablattula hui Qiu et al., 2019) in Cretaceous amber by combining destructive and non-destructive methods. Compared to extant species inhabiting dark environments, H. hui has relatively large compound eyes, and all the antennal sensilla for detecting multimodal information observed here are fewer or smaller. The characteristics of these sensory organs support the diurnality of the bright habitats of H. hui in contrast to many extant cockroaches. Like extant male mantises, grooved basiconic type sensilla exist abundantly on the antenna of the fossilized specimen. The abundance of grooved basiconic sensilla in mantid males results from using sex pheromones, and therefore, H. hui may have likewise used mantis-like intersexual communication. These lines of evidence suggest that the ecology and behavior of Cretaceous cockroaches were more diverse than those of related extant species.

Sensory evidence for complex communication and advanced sociality in early ants.

Advanced social behavior, or eusociality, has been evolutionarily profound, allowing colonies of ants, termites, social wasps, and bees to dominate competitively over solitary species throughout the Cenozoic. Advanced sociality requires not just nestmate cooperation and specialization but refined coordination and communication. Here, we provide independent evidence that 100-million-year-old Cretaceous ants in amber were social, based on chemosensory adaptations. Previous studies inferred fossil ant sociality from individual ants preserved adjacent to others. We analyzed several fossil ants for their antennal sensilla, using original rotation imaging of amber microinclusions, and found an array of antennal sensilla, specifically for alarm pheromone detection and nestmate recognition, sharing distinctive features with extant ants. Although Cretaceous ants were stem groups, the fossilized sensilla confirm hypotheses of their complex sociality.

Past emergent phase of Shatsky Rise deep-marine igneous plateau.

The Cretaceous Period stands out in Earth's geologic history by ubiquitous and sustained massive eruption of lava, forming several enormous igneous plateaus in the ocean basins worldwide. It has been proposed that the subaerial phases of Cretaceous oceanic plateau formation spurred the global environmental deterioration, yet this view is supported by patchy fossil and/or rock evidence for uplifting of the plateau summits above the sea level. Reported here is by far the most comprehensive case of Cretaceous plateau emergence at northern Shatsky Rise, Northwest Pacific, based on the integration of unique micropalaeontological and seismic evidence. From just above the flat-topped igneous edifice, recent Integrated Ocean Drilling Program (at Site U1346) recovered early Cretaceous (Hauterivian) ostracod and foraminiferal assemblages showing marked shallow-marine preferences. Most intriguing discovery is an ostracod taxon with well-developed eye tubercles, which serves as compelling palaeobiological evidence for a very shallow, euphotic setting. By linking the nearshore biofacies (<20 m water depth) to the basement topography undoubtedly shaped by subaerial weathering and/or erosion, it is obvious that northern Shatsky Rise was remarkably emergent during its final emplacement phase. We suggest that early Cretaceous surface environments might have been affected, at least in part, by Shatsky Rise subaerial volcanism.

The early evolutionary history of belemnites: new data from Japan.

Belemnites (Order Belemnitida), a very successful group of Mesozoic coleoid cephalopods, dominated the world's oceans throughout the Jurassic and Cretaceous. According to the current view, the phylogenetically earliest belemnites are known from the lowermost Jurassic (Hettangian, 201-199 Ma) of northern Europe. They are of low diversity and have small sized rostra without clear grooves. Their distribution is restricted to this area until the Pliensbachian (191-183 Ma). Here we describe two new belemnite taxa of the Suborder Belemnitina from the Sinemurian (199-191 Ma) of Japan: Nipponoteuthis katana gen et sp. nov., which represents the new family Nipponoteuthidae, and Eocylindroteuthis (?) yokoyamai sp. nov. This is the first reliable report of Sinemurian belemnites outside of Europe and the earliest record of typical forms of Belemnitina in the world. The Sinemurian belemnites from Japan have small to large rostra with one deep and long apical groove. Morphologically these forms are completely different from coeval European genera of Hettangian-Sinemurian age. These new findings suggest that three groups of Belemnitina existed in the Hettangian-Sinemurian: 1) European small forms, 2) Japanese very large forms, and 3) the typical forms with a distinctive apical groove, reported here. The Suborder Belemnitina therefore did not necessarily originate in the Hettangian of northern Europe. The new material from Japan documents that the suborder Belemnitina had a much higher diversity in the early Jurassic than previously thought, and it also shows strong endemisms from the Sinemurian onwards.

Mesorbitolina (Cretaceous larger foraminifera) from the Yezo Group in Hokkaido, Japan and its stratigraphic and paleobiogeographic significance.

In this paper, we describe an Aptian (Early Cretaceous) larger foraminiferal species Orbitolina (Mesorbitolina) parva from the limestone olistoliths in the lower part of the Yezo Group in the Yubari-Ashibetsu area, central Hokkaido and from limestone pebbles in the lowermost part of the Yezo Group in the Nakagawa area, northern Hokkaido. This is the first report of this species from the circum-North Pacific regions. Based on its occurrences, the shallow-marine carbonates, re-deposited in the lower part of the Yezo Group, are precisely assigned in age to the Late Aptian. Comparison of the lower part of the Yezo Group in central and northern Hokkaido indicates differences of the Aptian-Albian depositional history between the two areas. This study reveals that after Late Aptian, Mesogean key taxa (typical Cretaceous Tethyan biota) demised in the Northwest Pacific.