The snake-eyed skink Ablepharus kitaibelii is one of the smallest European lizards, but despite its minute size it is able to feed on comparatively large prey. Here we investigate the diet of A. kitaibelii and the mechanisms that allow the skink to overpower relatively large and even noxious prey. High-speed cinematography showed that A. kitaibelii uses a series of shaking and battering movements to immobilise and kill prey prior to swallowing. During this process, the skinks rises up on the hind limbs and then whacks the prey sidewise on the substrate by twisting the trunk, neck and head laterally. Our analysis showed that the shaking kinematics is very uniform among the investigated specimens. The morphological investigation of the cranio-cervical system revealed that A. kitaibelii possesses a well-developed synovial joint between the odontoid process of the axis, the atlas, and the basioccipital. The odontoid process is cylindrical and slim and together with the atlas and the basioccipital it forms a highly specialised pivot joint for lateral head rotation. We propose that the occipito-atlanto-axial complex of A. kitaibelii represents a functional adaptation for additional stabilisation of the cranio-cervical complex during prey shaking. Digital data from morphological databases showed that specialised joints of this type are very rare, but do also occur in other squamate groups. Thus we hypothesise that specialised cranio-cervical joints have evolved parallel as functional adaptations to different feeding and locomotion patterns. Future studies that link feeding kinematics and locomotion to cranio-cervical morphology might elucidate the function of various specialised occipito-atlanto-axial systems of squamates.

Cranial kinesis refers to intracranial movements in the vertebrate skull that do not concern the jaw joint, the middle ear or the hypobranchial skeleton. Different kinds of cranial kinesis have been reported for lizards, including mesokinesis, metakinesis, amphikinesis (simultaneous mesokinesis and metakinesis) and streptostyly. Streptostyly is considered relatively widespread within lizards, whereas mesokinesis has been documented only for geckos, varanids and anguids. The present study investigated cranial kinesis in the miniaturised scincid Ablepharus kitaibelii by integrating morphological and experimental data. Based on micro computed tomography, we provide a description of skull osteology. Cranial joints were studied with histology, which results in the first detailed description of cranial joint histology for a member of the Scincidae. Taken together, the morphological data indicate a high potential for amphikinesis and streptostyly, which was also corroborated by skull manipulations. High-speed cinematography demonstrated that mesokinesis occurs during food uptake, processing and intraoral transport cycles. Bite force measurements showed prolonged and reasonably hard biting even at large gape angles. Based on these data, we formulate a model of the amphikinetic A. kitaibelii skull mechanism, which provides an extension of Frazzetta's quadric-crank model by placing a special emphasis on metakinesis. According to this model, we hypothesise that metakinetic intracranial movements may provide a means for reducing strain in jaw adductor muscles. Presented hypotheses can be addressed and tested in future studies.

The slow-worm lizards (Anguis) comprise five species occurring throughout most of the Western Palearctic. Although these species are relatively uniform morphologically – with the exception of A. cephallonica, which exhibits a quite unique morphology – they are genetically deeply divergent. Here, we provide detailed distribution maps for each species and discuss their biogeography and conservation based on updated genetic data and a robust distribution database. We pay particular attention to the so called ‘grey zone’, which typically represents secondary contact zones and in some cases confirmed or presumed hybrid zones. Four of the five species live in parapatry, while only two species, A. cephallonica and A. graeca from the southern Balkans occur in partial sympatry. Further research should focus on the eco-evolutionary interactions between species in contact, including their hybridization rates, to reveal deeper details of the slow-worm evolutionary and natural history.

Most of the studies dealing with the Snake-eyed skink (Ablepharus kitaibelii) treat predominantly aspects of the distribution and taxonomy of the species. In the present study we provide information concerning the mechanism of hatching in the Snake-eyed skink and the dimensions of the hatched specimens. We collected data from wild animals, as well as from indoor incubated juveniles. The present study provides the first data concerning the weight of the newly hatched juveniles of the species and discuss on potential misleading data concerning the size of the juveniles in A. kitaibelii.

First record of tail bifurcations in the snake-eyed skink Ablepharus kitaibelii Bibron & Bory de Saint-Vincent, 1833 from Pastrina hill (northwestern Bulgaria).-We report for the first time on the occurrence of tail bifurcations in the snake-eyed skink (A. kitaibelii). This morphological anomaly was identified during a four-year monitoring program conducted in a herpetological hot-spot at Pastrina hill (northwestern Bulgaria). From a total of 415 captured specimens, four animals (0.96%) showed symmetrical or asymmetrical lateral duplication of the tail. Only bifurcations of the distal-most caudal section were detected in contrast to some other lizards (e.g. Gekkonidae, Lacertidae, Teiidae) that are reported to survive with bifurcations at more proximal tail sections.

New localities of Hierodula transcaucasica Brunner von Wattenwyl, 1878 from Bulgaria and illustrations of the species are provided.

In a recently published paper (Popgeorgiev et al. 2019), we compiled for the first time published and unpublished data on localities of the herpetofaunal species observed up to ca. 10 km south of the Bulgarian Danube River. Overall, we identified 687 published records belonging to 62 cells of the 10×10 km MGRS grid. Another 1918 records with real coordinates of our unpublished data from the past ca. 13 years belong to 1269 cells of the 1×1 MGRS grid. As a result, 34 native species – 15 amphibians (4 salamanders and 11 frogs) and 19 reptiles (1 turtle, 2 tortoises, 8 lizards and 8 snakes), and one invasive turtle, have been recorded; further species findings are unlikely. This study further identifies areas that are under-sampled and species such as Pelophylax lessonae that are cryptic. Our data are especially relevant concerning the high economic incentives to change the hydrology of the Danube, which will likely negatively impact the biodiversity along the river and its surrounding.

Karyotype divergence may strongly affect the rate of hybridization between species in their secondary contact zones. Slow worms (Anguis, Anguidae) are morphologically relatively cryptic legless lizards representing two evolutionary lineages, A. cephallonica from the southernmost Balkans, and the A. fragilis species complex (comprising two sister-species pairs A. fragilis + A. veronensis and A. colchica + A. graeca) distributed in the Western Palearctic. To identify their level of chromosomal variation, we surveyed karyotype of all species except formerly studied A. veronensis and included Pseudopus apodus as an outgroup. We applied conventional and molecular cytogenetic methods and whole-chromosome painting using macrochromosome probes from Varanus komodoensis and interpreted the results within the evolutionary framework of the common clade Anguiformes. Unlike New World anguids with remarkable karyotype variation, all Anguis species and P. apodus have conserved diploid chromosome number 2n = 44 (20 macrochromosomes, 24 microchromosomes) and morphology. The sister species A. colchica and A. graeca (divergence 4.4 Mya) displayed highly similar karyotype features within our sample. In contrast, despite the generally conserved chromosome morphology, the phylogenetically older A. cephallonica (divergence 12.0 Mya), and A. colchica versus A. fragilis (divergence 6.7 Mya) exhibited distinct patterns of constitutive heterochromatin distribution and telomeric repeat accumulation. The chromosome painting revealed that slow worm karyotype mostly evolved by fissions of ancestral macrochromosomes, which likely occurred already in an Anguis + Pseudopus common ancestor. Our findings thus demonstrate karyotype stasis in Anguis and Pseudopus for > 25 My, with fixed species-specific differences which may serve as cytotaxonomic markers useful in hybrid zone studies of slow worms.