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In recent decades, intensive research on non-avian dinosaurs has strongly suggested that these animals were restricted to terrestrial environments 1 . Historical proposals that some groups, such as sauropods and hadrosaurs, lived in aquatic environments 2 , 3 were abandoned decades ago 4 , 5 – 6 . It has recently been argued that at least some of the spinosaurids—an unusual group of large-bodied theropods of the Cretaceous era—were semi-aquatic 7 , 8 , but this idea has been challenged on anatomical, biomechanical and taphonomic grounds, and remains controversial 9 , 10 – 11 . Here we present unambiguous evidence for an aquatic propulsive structure in a dinosaur, the giant theropod Spinosaurus aegyptiacus 7 , 12 . This dinosaur has a tail with an unexpected and unique shape that consists of extremely tall neural spines and elongate chevrons, which forms a large, flexible fin-like organ capable of extensive lateral excursion. Using a robotic flapping apparatus to measure undulatory forces in physical models of different tail shapes, we show that the tail shape of Spinosaurus produces greater thrust and efficiency in water than the tail shapes of terrestrial dinosaurs and that these measures of performance are more comparable to those of extant aquatic vertebrates that use vertically expanded tails to generate forward propulsion while swimming. These results are consistent with the suite of adaptations for an aquatic lifestyle and piscivorous diet that have previously been documented for Spinosaurus 7 , 13 , 14 . Although developed to a lesser degree, aquatic adaptations are also found in other members of the spinosaurid clade 15 , 16 , which had a near-global distribution and a stratigraphic range of more than 50 million years 14 , pointing to a substantial invasion of aquatic environments by dinosaurs. Discovery that the giant theropod dinosaur Spinosaurus has a large flexible tail indicates that it was primarily aquatic and swam in a similar manner to extant tail-propelled aquatic vertebrates.

We describe adaptations for a semiaquatic lifestyle in the dinosaur Spinosaurus aegyptiacus. These adaptations include retraction of the fleshy nostrils to a position near the mid-region of the skull and an elongate neck and trunk that shift the center of body mass anterior to the knee joint. Unlike terrestrial theropods, the pelvic girdle is downsized, the hindlimbs are short, and all of the limb bones are solid without an open medullary cavity, for buoyancy control in water. The short, robust femur with hypertrophied flexor attachment and the low, flat-bottomed pedal claws are consistent with aquatic foot-propelled locomotion. Surface striations and bone microstructure suggest that the dorsal “sail” may have been enveloped in skin that functioned primarily for display on land and in water.

The loss of the tail is among the most notable anatomical changes to have occurred along the evolutionary lineage leading to humans and to the ‘anthropomorphous apes’ 1 – 3 , with a proposed role in contributing to human bipedalism 4 – 6 . Yet, the genetic mechanism that facilitated tail-loss evolution in hominoids remains unknown. Here we present evidence that an individual insertion of an Alu element in the genome of the hominoid ancestor may have contributed to tail-loss evolution. We demonstrate that this Alu element—inserted into an intron of the TBXT gene 7 – 9 —pairs with a neighbouring ancestral Alu element encoded in the reverse genomic orientation and leads to a hominoid-specific alternative splicing event. To study the effect of this splicing event, we generated multiple mouse models that express both full-length and exon-skipped isoforms of Tbxt , mimicking the expression pattern of its hominoid orthologue TBXT . Mice expressing both Tbxt isoforms exhibit a complete absence of the tail or a shortened tail depending on the relative abundance of Tbxt isoforms expressed at the embryonic tail bud. These results support the notion that the exon-skipped transcript is sufficient to induce a tail-loss phenotype. Moreover, mice expressing the exon-skipped Tbxt isoform develop neural tube defects, a condition that affects approximately 1 in 1,000 neonates in humans 10 . Thus, tail-loss evolution may have been associated with an adaptive cost of the potential for neural tube defects, which continue to affect human health today. An insertion of an Alu element into an intron of the TBXT gene is identified as a genetic mechanism of tail-loss evolution in humans and apes, with implications for human health today.

A new specimen of Archaeopteryx with extensive pennaceous feather preservation. Feathers prominent on latest Archaeopteryx fossil The discovery of numerous feathered dinosaurs and early birds has set the iconic 'Urvogel' (or 'first bird') Archaeopteryx in a broader context. But this venerable taxon still has the capacity to surprise. A newly discovered specimen from the Solnhofen limestone in Bavaria — only the eleventh since 1861 — shows a generous covering of feathers all over the body. Of particular note is a hindlimb covering resembling feathered 'trousers'. Analysis of feather distribution on the limbs and tail strongly suggests that pennaceous feathers — the type we are familiar with on birds today — evolved for reasons other than flight, perhaps for display. Discoveries of bird-like theropod dinosaurs and basal avialans in recent decades have helped to put the iconic ‘Urvogel’ Archaeopteryx 1 into context 2 , 3 , 4 , 5 , 6 and have yielded important new data on the origin and early evolution of feathers 7 . However, the biological context under which pennaceous feathers evolved is still debated. Here we describe a new specimen of Archaeopteryx with extensive feather preservation, not only on the wings and tail, but also on the body and legs. The new specimen shows that the entire body was covered in pennaceous feathers, and that the hindlimbs had long, symmetrical feathers along the tibiotarsus but short feathers on the tarsometatarsus. Furthermore, the wing plumage demonstrates that several recent interpretations 8 , 9 are problematic. An analysis of the phylogenetic distribution of pennaceous feathers on the tail, hindlimb and arms of advanced maniraptorans and basal avialans strongly indicates that these structures evolved in a functional context other than flight, most probably in relation to display, as suggested by some previous studies 10 , 11 , 12 . Pennaceous feathers thus represented an exaptation and were later, in several lineages and following different patterns, recruited for aerodynamic functions. This indicates that the origin of flight in avialans was more complex than previously thought and might have involved several convergent achievements of aerial abilities.

Armoured dinosaurs are well known for their evolution of specialized tail weapons—paired tail spikes in stegosaurs and heavy tail clubs in advanced ankylosaurs 1 . Armoured dinosaurs from southern Gondwana are rare and enigmatic, but probably include the earliest branches of Ankylosauria 2 – 4 . Here we describe a mostly complete, semi-articulated skeleton of a small (approximately 2 m) armoured dinosaur from the late Cretaceous period of Magallanes in southernmost Chile, a region that is biogeographically related to West Antarctica 5 . Stegouros elengassen gen. et sp. nov. evolved a large tail weapon unlike any dinosaur: a flat, frond-like structure formed by seven pairs of laterally projecting osteoderms encasing the distal half of the tail. Stegouros shows ankylosaurian cranial characters, but a largely ancestral postcranial skeleton, with some stegosaur-like characters. Phylogenetic analyses placed Stegouros in Ankylosauria; specifically, it is related to Kunbarrasaurus from Australia 6 and Antarctopelta from Antarctica 7 , forming a clade of Gondwanan ankylosaurs that split earliest from all other ankylosaurs. The large osteoderms and specialized tail vertebrae in Antarctopelta suggest that it had a tail weapon similar to Stegouros . We propose a new clade, the Parankylosauria, to include the first ancestor of Stegouros —but not Ankylosaurus —and all descendants of that ancestor. Stegouros elengassen , an ankylosaur from the late Cretaceous of Chile, has a large tail weapon, named a macuahuitl after the Aztec club, with a frond-like structure formed by seven pairs of laterally projecting osteoderms encasing the distal half of the tail.

Reconstructing the earliest phases of primate evolution has been impeded by gaps in the fossil record, so that disagreements persist regarding the palaeobiology and phylogenetic relationships of the earliest primates. Here we report the discovery of a nearly complete and partly articulated skeleton of a primitive haplorhine primate from the early Eocene of China, about 55 million years ago, the oldest fossil primate of this quality ever recovered. Coupled with detailed morphological examination using propagation phase contrast X-ray synchrotron microtomography, our phylogenetic analysis based on total available evidence indicates that this fossil is the most basal known member of the tarsiiform clade. In addition to providing further support for an early dichotomy between the strepsirrhine and haplorhine clades, this new primate further constrains the age of divergence between tarsiiforms and anthropoids. It also strengthens the hypothesis that the earliest primates were probably diurnal, arboreal and primarily insectivorous mammals the size of modern pygmy mouse lemurs. Understanding the earliest phases of primate evolution is obscured by gaps in the fossil record, but some light is shed by the discovery of a nearly complete and substantially articulated skeleton of a tiny primate from the early Eocene; the new primate lies near the pivotal evolutionary dichotomy separating the tarsier and anthropoid lineages and it possesses features that are characteristic of subsequent members of both lineages. A well preserved early primate Our knowledge of the earliest phases of primate evolution is limited by the gaps in the fossil record. Some light is shed by the discovery of a nearly complete and substantially articulated skeleton of a tiny and very ancient primate from the early Eocene of China, dating to 55 million years ago. The newly discovered primate appears to be the earliest known relative of the tarsiers, suggesting a very early divergence of the anthropoid lineage from the other primates. The animal was about the size of the modern pygmy mouse lemur, and skeletal features suggest that it was an agile insectivore with a diurnal habit.

A longstanding question in evolutionary biology is how change might be restricted or biased due to developmental constraints. To address this question, we investigated three recurrently evolving characters in rhabditid nematode male tails: tail tip morphogenesis, the number of genital papillae (GPs or \"rays\"), and phasmid position relative to the three most posterior GPs. This new analysis incorporates taxa (rhabditids Cruznema tripartitum, Haematozoon subulatum, Poikilolaimus oxycercus, diplogastrid Diplogasteroides nasuensis, and outgroup representative Brevibucca saprophaga) representing more and deeper divergence points in the rhabditid phylogeny than in previous analyses, allowing better resolution of ancestral states and changes. Analysis of GP characters was accomplished via immunofluorescent staining of adherens junctions at different stages of GP development and laser microbeam ablations of GP primordia. Findings include the following: (1) Loss and gain of tail tip morphogenesis occurred multiple times, possibly involving differences in fusion. (2) The pattern of GP anlagen in early L4 males is highly conserved and compatible with the previously proposed \"archetype,\" but is established at different developmental times in different species, consistent with constraint on GP patterning by the cell lineage and anteroposterior and dorsoventral patterning systems. (3) The stem species of Rhabditina likely had 8 GPs, with the second GP (v2) gained after the divergence of Poikilolaimus; within rhabditids, a different GP (v6) appears to be lost twice independently. (4) Laser ablation showed that changes in phasmid position relative to GPs are not due to changes in cell lineage, but instead due to migratory switches in the relative positions of precursors of phasmid socket cells and GPs; these cell migrations occur at different developmental times in different species. In summary, our results indicate a strong constraint imposed on the cell lineage and dorsoventral positioning of GP precursors, with GP pattern diversity allowed by cell-specific migratory behavior.

Body shape is a fundamental expression of organismal biology, but its quantitative reconstruction in fossil vertebrates is rare. Due to the absence of fossilized soft tissue evidence, the functional consequences of basal paravian body shape and its implications for the origins of avians and flight are not yet fully understood. Here we reconstruct the quantitative body outline of a fossil paravian Anchiornis based on high-definition images of soft tissues revealed by laser-stimulated fluorescence. This body outline confirms patagia-bearing arms, drumstick-shaped legs and a slender tail, features that were probably widespread among paravians. Finely preserved details also reveal similarities in propatagial and footpad form between basal paravians and modern birds, extending their record to the Late Jurassic. The body outline and soft tissue details suggest significant functional decoupling between the legs and tail in at least some basal paravians. The number of seemingly modern propatagial traits hint that feathering was a significant factor in how basal paravians utilized arm, leg and tail function for aerodynamic benefit. Soft tissues are rarely preserved in the fossil record; therefore, body shape of extinct vertebrates is usually inferred indirectly. Here, the authors use laser-stimulated fluorescence of fossils to detect and reconstruct the body outline of the paravian dinosaur Anchiornis from the Late Jurassic.

Single-pixel holography (SPH) is capable of generating holographic images with rich spatial information by employing only a single-pixel detector. Thanks to the relatively low dark-noise production, high sensitivity, large bandwidth, and cheap price of single-pixel detectors in comparison to pixel-array detectors, SPH is becoming an attractive imaging modality at wavelengths where pixel-array detectors are not available or prohibitively expensive. In this work, we develop a high-throughput single-pixel compressive holography with a space-bandwidth- time product (SBP-T) of 41,667 pixels/s, realized by enabling phase stepping naturally in time and abandoning the need for phase-encoded illumination. This holographic system is scalable to provide either a large field of view (~83 mm 2 ) or a high resolution (5.80 μm × 4.31 μm). In particular, high-resolution holographic images of biological tissues are presented, exhibiting rich contrast in both amplitude and phase. This work is an important step towards multi-spectrum imaging using a single-pixel detector in biophotonics. Single-pixel holography generates holographic images with a single-pixel detector making this relatively inexpensive. Here the authors report a high-throughput single-pixel compressive holography method for imaging biological tissue which can either provide a large field of view or high resolution.

Gliding mammals, such as flying squirrels, exhibit remarkable flight abilities by dynamically controlling their wing membranes (patagia), using their limbs and tail to manoeuvre between trees. They achieve agile and manoeuvrable gliding by adjusting their body and wing shape to control trajectory and stability. While research on bio-inspired drones primarily focuses on avian flight, the aerodynamic implications of whole-body morphing paired with soft membrane deformations in mammalian gliders remain unexplored. To address this, we developed the SquirrelDrone, a bioinspired drone capable of continuously modulating its shape via limb and tail actuation, coupled with passive deformations of its skin-like membrane. This design enables the investigation of how coordinated limb motion and membrane morphing affect aerodynamic forces during flying. Wind-tunnel and flight experiments show that gliding-mammal-inspired morphing significantly improves drone stability, agility, and manoeuvrability, providing a bioinspired framework for understanding how whole-body morphing contributes to flight control in future morphing aircraft. Whole-body morphing in the SquirrelDrone, inspired by gliding mammals, enhances aerodynamic performance through coordinated limb and tail actuation. Wind-tunnel experiments reveal improved stability, agility, and maneuverability, demonstrating significant advancements in drone flight control capabilities.