'Arm brains' (axial nerves) of Jurassic coleoids and the evolution of coleoid neuroanatomy.

Although patchy, the fossil record of coleoids bears a wealth of information on their soft part anatomy. Here, we describe remains of the axial nerve cord from both decabrachian (Acanthoteuthis, Belemnotheutis, Chondroteuthis) and octobrachian (Plesioteuthis, Proteroctopus, Vampyronassa) coleoids from the Jurassic. We discuss some hypotheses reflecting on possible evolutionary drivers behind the neuroanatomical differentiation of the coleoid arm crown. We also propose some hypotheses on potential links between habitat depth, mode of life and the evolution of the Coleoidea. Supplementary Information: The online version contains supplementary material available at 10.1186/s13358-023-00285-3.

Strain-Driven Bidirectional Spin Orientation Control in Epitaxial High Entropy Oxide Films.

High entropy oxides (HEOs), based on the incorporation of multiple-principal cations into the crystal lattice, offer the possibility to explore previously inaccessible oxide compositions and unconventional properties. Here it is demonstrated that despite the chemical complexity of HEOs external stimuli, such as epitaxial strain, can selectively stabilize certain magneto-electronic states. Epitaxial (Co0.2 Cr0.2 Fe0.2 Mn0.2 Ni0.2 )3 O4 -HEO thin films are grown in three different strain states: tensile, compressive, and relaxed. A unique coexistence of rocksalt and spinel-HEO phases, which are fully coherent with no detectable chemical segregation, is revealed by transmission electron microscopy. This dual-phase coexistence appears as a universal phenomenon in (Co0.2 Cr0.2 Fe0.2 Mn0.2 Ni0.2 )3 O4 epitaxial films. Prominent changes in the magnetic anisotropy and domain structure highlight the strain-induced bidirectional control of magnetic properties in HEOs. When the films are relaxed, their magnetization behavior is isotropic, similar to that of bulk materials. However, under tensile strain, the hardness of the out-of-plane (OOP) axis increases significantly. On the other hand, compressive straining results in an easy OOP magnetization and a maze-like magnetic domain structure, indicating the perpendicular magnetic anisotropy. Generally, this study emphasizes the adaptability of the high entropy design strategy, which, when combined with coherent strain engineering, opens additional prospects for fine-tuning properties in oxides.

UV-Light-Tunable p-/n-Type Chemiresistive Gas Sensors Based on Quasi-1D TiS3 Nanoribbons: Detection of Isopropanol at ppm Concentrations.

The growing demand of society for gas sensors for energy-efficient environmental sensing stimulates studies of new electronic materials. Here, we investigated quasi-one-dimensional titanium trisulfide (TiS3) crystals for possible applications in chemiresistors and on-chip multisensor arrays. TiS3 nanoribbons were placed as a mat over a multielectrode chip to form an array of chemiresistive gas sensors. These sensors were exposed to isopropanol as a model analyte, which was mixed with air at low concentrations of 1-100 ppm that are below the Occupational Safety and Health Administration (OSHA) permissible exposure limit. The tests were performed at room temperature (RT), as well as with heating up to 110 °C, and under an ultraviolet (UV) radiation at λ = 345 nm. We found that the RT/UV conditions result in a n-type chemiresistive response to isopropanol, which seems to be governed by its redox reactions with chemisorbed oxygen species. In contrast, the RT conditions without a UV exposure produced a p-type response that is possibly caused by the enhancement of the electron transport scattering due to the analyte adsorption. By analyzing the vector signal from the entire on-chip multisensor array, we could distinguish isopropanol from benzene, both of which produced similar responses on individual sensors. We found that the heating up to 110 °C reduces both the sensitivity and selectivity of the sensor array.

Cephalopod palaeobiology: evolution and life history of the most intelligent invertebrates: Honoring Sigurd von Boletzky and his contributions to cephalopod research.

Sigurd von Boletzky was a cephalopod researcher who was world-renowned for his enthusiasm for his field of research, for his friendly and calm personality, and, of course, his publications. He dedicated most of his life as active researcher on the development, biology and evolution of coleoids. Nevertheless, he was always curious to learn about other cephalopods as well. Sigurd passed away in Switzerland on September 28th 2020. We dedicate this text and volume to his memory.

Direct Observation of Strong Anomalous Hall Effect and Proximity-Induced Ferromagnetic State in SrIrO3.

The 5d iridium-based transition metal oxides have gained broad interest because of their strong spin-orbit coupling, which favors new or exotic quantum electronic states. On the other hand, they rarely exhibit more mainstream orders like ferromagnetism due to generally weak electron-electron correlation strength. Here, a proximity-induced ferromagnetic (FM) state with TC  ≈ 100 K and strong magnetocrystalline anisotropy is shown in a SrIrO3 (SIO) heterostructure via interfacial charge transfer by using a ferromagnetic insulator in contact with SIO. Electrical transport allows to selectively probe the FM state of the SIO layer and the direct observation of a strong, intrinsic, and positive anomalous Hall effect (AHE). For T ≤ 20 K, the AHE displays unusually large coercive and saturation field, a fingerprint of a strong pseudospin-lattice coupling. A Hall angle, σxy AHE /σxx , larger by an order of magnitude than in typical 3d metals and an FM net moment of about 0.1 µB /Ir, is reported. This emphasizes how efficiently the nontrivial topological band properties of SIO can be manipulated by structural modifications and the exchange interaction with 3d TMOs.

Mesozoic origin of coleoid cephalopods and their abrupt shifts of diversification patterns.

Coleoids are the most diverse group of cephalopod mollusks. While their origin is date during the Mesozoic, the diversification pattern is unknown. However, two hypotheses have been proposed. The first suggests an increasing diversification rate after the Cretaceous-Paleogene extinction event (K-Pg) as consequence of empty habitats left by the ammonites and belemnites. The second hypothesis proposes a mid-Cenozoic increase in diversification rate related to distributional changes during ice ages and biotic interactions. To test these hypotheses, we estimated a lineage through time (LTT) and the gamma-statistic along with model-based diversification rates. These analyses were conducted on a dated molecular phylogeny for coleoids that we reconstructed using five molecular markers (cytochrome b, 16S rRNA, cytochrome oxidase I, rhodopsin, and PAX-6). Our divergence time estimation suggests that coleoids originated in the Mesozoic Era (Middle Triassic) and that both main clades (Decapodiformes and Octopodiformes) diverged in the Cretaceous/Jurassic Period. The LTT, gamma statistic, and diversification rates inferred with the Bayesian Analysis of Macro-evolutionary Mixtures (BAMM), indicate an acceleration in diversification rate over time since the origin of coleoids. Additionally, BAMM allowed us to detect abrupt increases in diversification rate before and after the K-Pg boundary. Our results partially support both hypotheses as all analyses indicate that the coleoid diversification rate was increasing during the Cenozoic. However, our results also indicate increasing diversification rates before the K-Pg boundary. We propose that the radiation of coleoids has been shaped by an acceleration in diversification rate over time, including exceptional episodes of abrupt increases before and after the K-Pg boundary.

Evolutionary development of the cephalopod arm armature: a review.

The cephalopod arm armature is certainly one of the most important morphological innovations responsible for the evolutionary success of the Cephalopoda. New palaeontological discoveries in the recent past afford to review and reassess origin and homology of suckers, sucker rings, hooks, and cirri. Since a priori character state reconstructions are still ambiguous, we suggest and discuss three different evolutionary scenarios. Each of them is based on the following assumptions: (1) Neocoleoidea uniting extant Decabrachia and Octobrachia is monophyletic (= proostracum-bearing coleoids); (2) extinct Belemnitida and Diplobelida are stem decabrachians; (3) proostracum-less coleoids (Hematitida, Donovaniconida, Aulacoceratida) represent stem-neocoleoids; (4) Ammonoidea and Bactritoidea are stem coleoids. We consider a scenario where belemnoid hooks derived from primitive suckers as well-supported. Regarding belemnoid hooks and suckers as homologues implies that belemnoid, oegopsid, and probably ammonoid arm hooks arose through parallel evolution. Our conclusions challenge the widespread opinion, whereupon belemnoid hooks evolved de novo, and instead support earlier ideas formulated by Sigurd von Boletzky.

Optically Modulated HfS2-Based Synapses for Artificial Vision Systems.

The simulation of human brain neurons by synaptic devices could be an effective strategy to break through the notorious "von Neumann Bottleneck" and "Memory Wall". Herein, opto-electronic synapses based on layered hafnium disulfide (HfS2) transistors have been investigated. The basic functions of biological synapses are realized and optimized by modifying pulsed light conditions. Furthermore, 2 × 2 pixel imaging chips have also been developed. Two-pixel visual information is illuminated on diagonal pixels of the imaging array by applying light pulses (λ = 405 nm) with different pulse frequencies, mimicking short-term memory and long-term memory characteristics of the human vision system. In addition, an optically/electrically driven neuromorphic computation is demonstrated by machine learning to classify hand-written numbers with an accuracy of about 88.5%. This work will be an important step toward an artificial neural network comprising neuromorphic vision sensing and training functions.

Distraction sinking and fossilized coleoid predatory behaviour from the German Early Jurassic.

Exceptional fossil preservation is required to conserve soft-bodied fossils and even more so to conserve their behaviour. Here, we describe a fossil of a co-occurrence of representatives of two different octobrachian coleoid species. The fossils are from the Toarcian Posidonienschiefer of Ohmden near Holzmaden, Germany. The two animals died in the act of predation, i.e. one had caught the other and had begun to nibble on it, when they possibly sank into hypoxic waters and suffocated (distraction sinking). This supports the idea that primitive vampyromorphs pursued diverse feeding strategies and were not yet adapted to being opportunistic feeders in oxygen minimum zones like their modern relative Vampyroteuthis.

A potential cephalopod from the early Cambrian of eastern Newfoundland, Canada.

Although an early Cambrian origin of cephalopods has been suggested by molecular studies, no unequivocal fossil evidence has yet been presented. Septate shells collected from shallow-marine limestone of the lower Cambrian (upper Terreneuvian, c. 522 Ma) Bonavista Formation of southeastern Newfoundland, Canada, are here interpreted as straight, elongate conical cephalopod phragmocones. The material documented here may push the origin of cephalopods back in time by about 30 Ma to an unexpected early stage of the Cambrian biotic radiation of metazoans, i.e. before the first occurrence of euarthropods.

Taphonomic patterns mimic biologic structures: diagenetic Liesegang rings in Mesozoic coleoids and coprolites.

Because of physiology of coleoids, their fossils preserve soft-tissue-remains more often than other cephalopods. Sometimes, the phosphatized soft-tissues, particularly parts of the muscular mantle, display dark circular patterns. Here, we showcase that these patterns, here documented for fossil coleoids from the Jurassic of Germany and the Cretaceous of Lebanon, superficially resemble chromatophores (which enable living coleoids to alter their coloration). We examined and chemically analyzed the circular structures in these specimens, describe them, and discuss their genesis. Based on their structure and color, we visually differentiate between three types of circles. By comparison with similar structures, we suggest that these structures are not biogenic but Liesegang rings, which formed due to reaction-diffusion processes very soon after death.

Fossil evidence for vampire squid inhabiting oxygen-depleted ocean zones since at least the Oligocene.

A marked 120 My gap in the fossil record of vampire squids separates the only extant species (Vampyroteuthis infernalis) from its Early Cretaceous, morphologically-similar ancestors. While the extant species possesses unique physiological adaptations to bathyal environments with low oxygen concentrations, Mesozoic vampyromorphs inhabited epicontinental shelves. However, the timing of their retreat towards bathyal and oxygen-depleted habitats is poorly documented. Here, we document a first record of a post-Mesozoic vampire squid from the Oligocene of the Central Paratethys represented by a vampyromorph gladius. We assign Necroteuthis hungarica to the family Vampyroteuthidae that links Mesozoic loligosepiids with Recent Vampyroteuthis. Micropalaeontological, palaeoecological, and geochemical analyses demonstrate that Necroteuthis hungarica inhabited bathyal environments with bottom-water anoxia and high primary productivity in salinity-stratified Central Paratethys basins. Vampire squids were thus adapted to bathyal, oxygen-depleted habitats at least since the Oligocene. We suggest that the Cretaceous and the early Cenozoic OMZs triggered their deep-sea specialization.

Jaws of a large belemnite and an ammonite from the Aalenian (Middle Jurassic) of Switzerland.

Although belemnite rostra can be quite abundant in Jurassic and Cretaceous strata, the record of belemnite jaws was limited to a few specimens from Germany and Russia. Here, we describe and figure three cephalopod jaws from the Middle Jurassic Opalinus Clay of northern Switzerland. Although flattened, the carbonaceous fossils display enough morphological information to rule out an ammonoid, nautiloid or octobrachian origin of the two larger jaws. Their similarities to belemnite jaws from Germany and Russia conforms with our interpretation of these specimens as belemnite jaws. Based on their rather large size, we tentatively assign these two jaws to the megateuthidid Acrocoelites conoideus. The third jaw is a rather small upper jaw of an ammonoid. Since Leioceras opalinum is by far the most common ammonite in this unit in northern Switzerland, we tentatively suggest that the upper jaw belongs to this species.

First record of non-mineralized cephalopod jaws and arm hooks from the latest Cretaceous of Eurytania, Greece.

Due to the lower fossilization potential of chitin, non-mineralized cephalopod jaws and arm hooks are much more rarely preserved as fossils than the calcitic lower jaws of ammonites or the calcitized jaw apparatuses of nautilids. Here, we report such non-mineralized fossil jaws and arm hooks from pelagic marly limestones of continental Greece. Two of the specimens lie on the same slab and are assigned to the Ammonitina; they represent upper jaws of the aptychus type, which is corroborated by finds of aptychi. Additionally, one intermediate type and one anaptychus type are documented here. The morphology of all ammonite jaws suggest a desmoceratoid affinity. The other jaws are identified as coleoid jaws. They share the overall U-shape and proportions of the outer and inner lamellae with Jurassic lower jaws of Trachyteuthis (Teudopseina). We also document the first belemnoid arm hooks from the Tethyan Maastrichtian. The fossils described here document the presence of a typical Mesozoic cephalopod assemblage until the end of the Cretaceous in the eastern Tethys.

The role of mural mechanics on cephalopod palaeoecology.

Cephalopods transformed the molluscan shell into a buoyancy device that must be strong enough to resist external water pressure. Historically, unique features of the shell have been interpreted on the basis that the strength of the shell presents a hard limit on maximum habitat depth. One such feature is the mural flap, which is a semi-prismatic layer deposited on the inner surface of some coleoid septa that has been suggested to strengthen the shell and permit colonization of deeper waters. We test this hypothesis by constructing finite-element models that show how mural modifications affect the response of the shell to hydrostatic pressure. The mural flaps are found to have no notable structural function. Another mural modification discovered here is the adapical ridge flap that initially seemed to have a potential function in shifting peak stress away from the attachment site of the septum; however, the irregular distribution of this feature casts any functional interpretation in doubt. Ecological separation of belemnites and decabrachians is likely not mediated by the presence/absence of mural flaps. This work illustrates a potential caveat that not all unique septal features formed in response to increasing hydrostatic pressure and deeper habitats.

Spatial distribution of oncocerid cephalopods on a Middle Devonian bedding plane suggests semelparous life cycle.

Reproductive strategies of extinct organisms can only be recognised indirectly and hence, they are exceedingly rarely reported and tend to be speculative. Here, we present a mass-occurrence with common preservation of pairs of late Givetian (Middle Devonian) oncocerid cephalopods from Hamar Laghdad in the Tafilalt (eastern Anti-Atlas, Morocco). We analysed their spatial occurrences with spatial point pattern analysis techniques and Monte Carlo simulations; our results shows that the pairwise clustering is significant, while ammonoids on the same bedding plane reveal a more random distribution. It is possible that processes such as catastrophic mass mortality or post-mortem transport could have produced the pattern. However, we suggest that it is more likely that the oncocerids were semelparous and died shortly after mating. These findings shed new light on the variation and evolution of reproductive strategies in fossil cephalopods and emphasise that they cannot be based on comparisons with extant taxa without question.

Anatomy and evolution of the first Coleoidea in the Carboniferous.

Coleoidea (squids and octopuses) comprise all crown group cephalopods except the Nautilida. Coleoids are characterized by internal shell (endocochleate), ink sac and arm hooks, while nautilids lack an ink sac, arm hooks, suckers, and have an external conch (ectocochleate). Differentiating between straight conical conchs (orthocones) of Palaeozoic Coleoidea and other ectocochleates is only possible when rostrum (shell covering the chambered phragmocone) and body chamber are preserved. Here, we provide information on how this internalization might have evolved. We re-examined one of the oldest coleoids, Gordoniconus beargulchensis from the Early Carboniferous of the Bear Gulch Fossil-Lagerstätte (Montana) by synchrotron, various lights and Reflectance Transformation Imaging (RTI). This revealed previously unappreciated anatomical details, on which we base evolutionary scenarios of how the internalization and other evolutionary steps in early coleoid evolution proceeded. We suggest that conch internalization happened rather suddenly including early growth stages while the ink sac evolved slightly later.

Predatory behaviour and taphonomy of a Jurassic belemnoid coleoid (Diplobelida, Cephalopoda).

We describe four complete specimens of the early squid-like cephalopod Clarkeiteuthis conocauda from the Toarcian Posidonienschiefer (Jurassic) each preserved with the bony fish Leptolepis bronni in its arms. Based on the arrangement of prey and predator, we suggest that the cephalopods caught and killed the fishes while still in well-oxygenated waters and then descended into oxygen-depleted water layers (distraction sinking) where the cephalopod suffocated. This explains the exceptional preservation, for which the Posidonienschiefer is famed. This association raises the question for the hunting behaviour of belemnoid Coleoidea. Using the proportions of soft and skeletal body parts of diplobelids and belemnitids, we estimated their body mass and buoyancy and determined the centres of mass and buoyancy. These two points were very close to each other in belemnitids, implying a low hydrodynamic stability (when ignoring the fins), while in diplobelids, the distance between those centres was greater. This suggests that diplobelids usually assumed an oblique to vertical orientation of the body axis while belemnitids could effortlessly achieve a horizontal orientation of their body. Presuming larger fins were attached to the bigger belemnitid rostra, belemnitids were better swimmers and perhaps pursuit predators while diplobelids rather ambushed their prey.

Updated molecular phylogeny of the squid family Ommastrephidae: Insights into the evolution of spawning strategies.

Two types of spawning strategy have been described for ommastrephid squids: coastal and oceanic. It has been suggested that ancestral ommastrephids inhabited coastal waters and expanded their distribution into the open ocean during global changes in ocean circulation in the Oligocene. This hypothesis could explain the different reproductive strategies in oceanic squids, but has never been tested in a phylogenetic context. In the present study, we assess the coastal-to-open-ocean hypothesis through inferring the evolution of reproductive traits (spawning type) of ommastrephid squids using the phylogenetic comparative method to estimate ancestral states and divergence times. This analysis was performed using a robust molecular phylogeny with three mitochondrial genes (COI, CYTB and 16S) and two nuclear genes (RHO and 18S) for nearly all species of ommastrephid squid. Our results support dividing the Ommastrephidae into the three traditional subfamilies, plus the monotypic subfamily Todaropsinae as proposed previously. Divergence times were found to be older than those suggested. Our analyses strongly suggest that early ommastrephid squids spawned in coastal areas, with some species subsequently switching to spawn in oceanic areas, supporting previous non-tested hypotheses. We found evidence of gradual evolution change of spawning type in ommastrephid squids estimated to have occurred since the Cretaceous.