Body growth is typically thought to be indeterminate in ectothermic vertebrates. Indeed, until recently, this growth pattern was considered to be ubiquitous in ectotherms. Our recent observations of a complete growth plate cartilage (GPC) resorption, a reliable indicator of arrested skeletal growth, in many species of lizards clearly reject the ubiquity of indeterminate growth in reptiles and raise the question about the ancestral state of the growth pattern. Using X-ray micro-computed tomography (µCT), here we examined GPCs of long bones in three basally branching clades of squamate reptiles, namely in Gekkota, Scincoidea and Lacertoidea. A complete loss of GPC, indicating skeletal growth arrest, was the predominant finding. Using a dataset of 164 species representing all major clades of lizards and the tuataras, we traced the evolution of determinate growth on the phylogenetic tree of Lepidosauria. The reconstruction of character states suggests that determinate growth is ancestral for the squamate reptiles (Squamata) and remains common in the majority of lizard lineages, while extended (potentially indeterminate) adult growth evolved several times within squamates. Although traditionally associated with endotherms, determinate growth is coupled with ectothermy in this lineage. These findings combined with existing literature suggest that determinate growth predominates in both extant and extinct amniotes.

Squamate reptiles are considered to exhibit indeterminate growth. Nevertheless, current literature disputes the available definitions of this growth type, presents new theoretical models, and questions its universality in cold-blooded vertebrates. We have followed up on our previous research employing micro-CT to explore growth plate cartilage (GPC) in the epiphysis of long bones, which is responsible for longitudinal skeletal growth by the endochondral ossification process. We focused on numerous and highly diversified group of the Iguania clade comprising Acrodonta (agamas and chameleons) and Pleurodonta (“iguanas”). We recorded the absence of GPC in most of the examined adult Pleurodonta specimens and interpret it as an irreversible arrest of skeletal growth. This finding clearly rejects the universality of indeterminate growth in lizards. On the other hand, we found apparent GPC preservation in most of the adult specimens belonging to Acrodonta. This suggests a preserved ability to continue body growth throughout most of their life. We discuss the uncovered disparity between Acrodonta and Pleurodonta and emphasize the importance of GPC degradation timing.

Micro-CT imaging is a well-established morphological method for the visualization of animal models. We used ethanol fixation of the mouse brains to perform high-resolution micro-CT scans showing in great details brain grey and white matters. It was possible to identify more than 50 neuroanatomical structures on the 5 selected coronal sections. Among white matter structures, we identified fornix, medial lemniscus, crossed tectospinal pathway, mammillothalamic tract, and the sensory root of the trigeminal ganglion. Among grey matter structures, we identified basal nuclei, habenular complex, thalamic nuclei, amygdala, subparts of hippocampal formation, superior colliculi, Edinger–Westphal nucleus, and others. We suggest that micro-CT of the mouse brain could be used for neurohistological lesions evaluation as an alternative to classical neurohistology because it does not destroy brain tissue.

Dermal armour, consisting of bony dermal structures known as osteoderms (ODs), is widespread in squamate reptiles. However, in some limbless taxa such as snakes, ODs are rare, probably due to a trade‐off between mechanical protection and the demands of locomotion and consumption of large prey. Recent findings of ODs restricted to the distal body regions of sand boas ( Eryx , Erycidae) challenge this paradigm, suggesting they provide passive mechanical protection against aggressive prey without significantly impairing locomotion. Building on these findings, we have continued the search and identified three additional snake species that have well‐developed caudal ODs, including the first‐ever discovery of ODs in shield‐tailed snakes (Uropeltidae). In these fossorial species, which are characterised by their unique tail morphology, ecological adaptations and colouration, the ODs at the tail tip may serve as passive protection against predators. However, an alternative role in locomotion or occasional phragmosis cannot be ruled out. In the Javelin sand boa ( Eryx jaculus ), the ODs are hypothesised to function as a mechanical defence against aggressive prey. These results highlight the functional and evolutionary plasticity of ODs and emphasise the urgent need for further studies on their specific role and adaptive significance in the ecology and evolution of snakes.

The Cupressaceae conifer Stutzeliastrobus bohemicus (Bayer) J.Kvaček comb. nov. is described from the Cenomanian Peruc-Korycany Formation of the Bohemian Cretaceous Basin. It is characterised by elongate ovuliferous cones with helically arranged thin, bilaterally symmetrical ovuliferous bract-scale complexes, bearing two to four winged elongate ovoid seeds per bract-scale complex. Ovuliferous cones are found attached to twigs of Cyparissidium-type shoots, showing amphistomatic scale-like leaves with an adaxial cuticle, bearing two stomatal bands with transversely or obliquely orientated monocyclic to amphicyclic stomata. The abaxial cuticle shows monocyclic to amphicyclic stomata scattered irregularly in the basal part of the leaf. The lectotype is compressed, but the 3D preserved lignified specimen, studied using X-ray microtomography, revealed its internal structure. It is compared to Stutzeliastrobus foliatus F.Herrera et al. from the Early Cretaceous of Mongolia, differing in morphology of its bract-scale complexes. The thin ovuliferous cone scales complexes of S. bohemicus bearing two to four winged seeds per cone scale argue for its relationship with Taiwanioideae, the basal subfamily of Cupressaceae.

High-resolution X-ray imaging techniques, usually known as microradiography and micro-computed tomography (CT), have become highly required and frequently used tools for biology, biomedical and preclinical research. State-of-the-art micro-CT scanners are capable of achieving a spatial resolution of few micrometers or even less, thanks to the constant development of compact microfocus X-ray sources together with simultaneous progress in detector technologies. The current standard in X-ray detection is a digital imaging device containing read-out circuitry coupled with a scintillation sensor. Such detectors are available in a variety of different sizes, and are easy to use and relatively affordable. Nevertheless, the mentioned technology suffers from inherent limitations like, for example, undesirable generation of dark current, that compromise the quality of the provided data. This work demonstrates the applicability of Timepix large-area hybrid-pixel photon-counting detectors (PCDs) for high-resolution X-ray imaging in biology research. Photon-counting detection technology provides dark-current-free quantum-counting operation. Therefore, an enhanced contrast-to-noise ratio of the acquired data is achieved. Furthermore, the biased semiconductor sensor achieves almost ideal point-spread function (PSF) resulting in images with high spatial-resolution. Both above-mentioned features make PCDs to be excellent tools for high-resolution X-ray imaging especially for samples with low intrinsic absorption contrast. We evaluated the imaging performance of large-area Timepix detectors compared to a state-of-the-art flat-panel detector dedicated for high-resolution X-ray imaging. The presented data demonstrate the versatility of the used detectors as it covers a wide range of samples from laboratory animals to single-cell marine organisms.