Decoupled evolution of ventral and dorsal scales in agamid lizards: ventral keels are associated with arboreality.

Arboreality has evolved in all major vertebrate lineages and is often associated with morphological adaptations and increased diversification concomitant with accessing novel niche space. In squamate reptiles, foot, claw, and tail morphology are well-studied adaptations shown to be associated with transitions to arboreality. Here, we examined a less well understood trait-the keeled scale-in relation to microhabitat, climate, and diversification dynamics across a diverse lizard radiation, Agamidae. We found that the ancestral agamid had keeled dorsal but not ventral scales; further, dorsal and ventral keels are evolutionarily decoupled. Ventral keeled scales evolved repeatedly in association with arboreality and may be advantageous in reducing wear or by promoting interlocking when climbing. We did not find an association between keeled scales and diversification, suggesting keels do not allow finer-scale microhabitat partitioning observed in other arboreal-associated traits. We additionally found a relationship between keeled ventral scales and precipitation in terrestrial species where we posit that the keels may function to reduce scale degradation. Our results suggest that keeled ventral scales facilitated transitions to arboreality across agamid lizards, and highlight a need for future studies that explore their biomechanical function in relation to microhabitat and climate.

Carrying eggs uphill: are costs of reproduction stronger on steeper slopes?

Locomotor impairment during pregnancy is a well-documented cost of reproduction, but most empirical studies have not incorporated ecological complexity, such as locomotion on sloping inclines rather than horizontal surfaces. Biomechanical factors suggest that carrying a heavy burden-including shifts in the body's centre of mass-may impair locomotor ability even more when an animal is running uphill. If so, then measuring costs of reproduction on horizontal racetracks may underestimate these costs in nature for arboreal species. To evaluate this prediction, we measured the pregnancy-induced reduction in speed for jacky dragons (Amphibolurus muricatus) at inclines ranging from 0 to 45°. Both pregnancy and steeper slopes reduced lizard performance, but pregnancy did not exacerbate the locomotor decrement on steeper racetracks. An ability to maintain mobility on steep slopes during pregnancy may be a target of selection in arboreal taxa. To understand the evolutionary context of locomotion-based costs of reproduction, we also need studies on the relationship between organismal performance and ecologically relevant measures such as predation risk.

Untangling the structural and molecular mechanisms underlying colour and rapid colour change in a lizard, Agama atra.

With functions as diverse as communication, protection and thermoregulation, coloration is one of the most important traits in lizards. The ability to change colour as a function of varying social and environmental conditions is thus an important innovation. While colour change is present in animals ranging from squids, to fish and reptiles, not much is known about the mechanisms behind it. Traditionally, colour change was attributed to migration of pigments, in particular melanin. More recent work has shown that the changes in nanostructural configuration inside iridophores are able to produce a wide palette of colours. However, the genetic mechanisms underlying colour, and colour change in particular, remain unstudied. Here we use a combination of transcriptomic and microscopic data to show that melanin, iridophores and pteridines are the main colour-producing mechanisms in Agama atra, and provide molecular and structural data suggesting that rapid colour change is achieved via melanin dispersal in combination with iridophore organization. This work demonstrates the power of combining genotypic (gene expression) and phenotypic (microscopy) information for addressing physiological questions, providing a basis for future studies of colour change.

A Contribution to the Nematode Fauna of Two Agamid Lizards from Afghanistan.

Information on the recent herpetological and related parasitological collections are very rarely available for Afghanistan. We examined two species of the family Agamidae, Laudakia nuristanica and Paralaudakia caucasia for the presence of the intestinal helminth fauna. Overall, we examined 13 specimens of these lizards and found three species of helminths (Abbreviata achari, Thelandros masaae, T. taylori) in a single specimen of L. nuristanica and four species (A. achari, T. baylisi, T. taylori, P. kasauli) in three specimens of P. caucasia. Here in, we present the first report on the helminth fauna from L. nuristanica, record a new helminth host for P. caucasia and three new country records for the helminth fauna of Afghanistan.

Changes in ontogenetic patterns facilitate diversification in skull shape of Australian agamid lizards.

BACKGROUND: Morphological diversity among closely related animals can be the result of differing growth patterns. The Australian radiation of agamid lizards (Amphibolurinae) exhibits great ecological and morphological diversity, which they have achieved on a continent-wide scale, in a relatively short period of time (30 million years). Amphibolurines therefore make an ideal study group for examining ontogenetic allometry. We used two-dimensional landmark-based geometric morphometric methods to characterise the postnatal growth patterns in cranial shape of 18 species of amphibolurine lizards and investigate the associations between cranial morphology, and life habit and phylogeny. RESULTS: For most amphibolurine species, juveniles share a similar cranial phenotype, but by adulthood crania are more disparate in shape and occupy different sub-spaces of the total shape space. To achieve this disparity, crania do not follow a common post-natal growth pattern; there are differences among species in both the direction and magnitude of change in morphospace. We found that these growth patterns among the amphibolurines are significantly associated with ecological life habits. The clade Ctenophorus includes species that undergo small magnitudes of shape change during growth. They have dorsoventrally deep, blunt-snouted skulls (associated with terrestrial lifestyles), and also dorsoventrally shallow skulls (associated with saxicolous lifestyles). The sister clade to Ctenophorus, which includes the bearded dragon (Pogona), frill-neck lizard (Chlamydosaurus), and long-nosed dragon (Gowidon), exhibit broad and robust post-orbital regions and differing snout lengths (mainly associated with scansorial lifestyles). CONCLUSIONS: Australian agamids show great variability in the timing of development and divergence of growth trajectories which results in a diversity of adult cranial shapes. Phylogenetic signal in cranial morphology appears to be largely overwritten by signals that reflect life habit. This knowledge about growth patterns and skull shape diversity in agamid lizards will be valuable for placing phylogenetic, functional and ecological studies in a morphological context.

The mathematics of thermal sub-optimality: Nonlinear regression characterization of thermal performance of reptile metabolic rates.

Although several approaches have been suggested, there is no broadly accepted single approach for quantitative characterization of thermal performance in ectotherms. I sought to identify the most appropriate non-linear function with which to represent thermal performance of ectothermic metabolic rate, and to interrogate the biological relevance of the thermal parameters of this function. I used published data for exercise-induced metabolic rates of eight species of reptile from a broad phylogenetic base and global distribution. Using an Akaike Information Criterion, I compared 12 different models proposed to characterize thermal performance adapted from a broad range of disciplines, finding that a beta-distribution model described the reptile metabolic rate data most parsimoniously. Using the beta-distribution model, unique functions were parameterized for each species. Four parameters were extracted from each species-specific fit: the temperature coincident with the peak of the thermal performance curve, Topt; the point at which the function intersected the x-axis, CTmax; and two points indicative of thermal breadth, Td(lower) and Td(upper). There was a positive relationship between the species' preferred body temperatures (Tpref) reported in the scientific literature and both Topt and Td(lower) extracted from the species-specific beta functions. While Td(lower) estimates were not different to published Tpref values, Topt estimates were statistically higher than Tpref. This is consistent with previous observations that the point of peak performance does not match Tpref. The predicted CTmax also correlated well with published values. The model in its current form was not able to estimate CTmin, and this parameter was not explored here, but should be in future research. By providing a quantitative description of the thermal performance, the beta-distribution function offers a new theoretical basis for thermal optimality. I contend that Tpref aligns with the mathematical threshold Td(lower), where metabolic rate is at its maximum prior to thermal inhibition.

IDENTIFICATION OF HELODERMATID ADENOVIRUS 2 IN A CAPTIVE CENTRAL BEARDED DRAGON (POGONA VITTICEPS), WILD GILA MONSTERS (HELODERMA SUSPECTUM), AND A DEATH ADDER (ACANTHOPHIS ANTARCTICUS).

Adenoviruses are medium-sized DNA viruses with very high host fidelity. The phylogenetic relationships of the adenoviruses strongly resemble that of their hosts, consistent with evolutionary codivergence. The genus Atadenovirus appears to have evolved in squamate hosts. Perhaps the best known of the squamate adenoviruses is Agamid adenovirus 1 (AgAdV1), found most commonly in central bearded dragons (Pogona vitticeps), where it is a prevalent cause of hepatitis/enteritis, especially in young animals. All previous reports of adenoviruses in bearded dragons were AgAdV1. Helodermatid adenovirus 2 (HeAdV2) was first seen in Mexican beaded lizards (Heloderma horridus). Subsequently, partial adenoviral polymerase gene sequence from a western bearded dragon (Pogona minor) in Australia was found to share 99% nucleotide homology with HeAdV2. This article reports the discovery of a virus identical to HeAdV2 in a captive central bearded dragon in Florida and wild Gila monsters (Heloderma suspectum) in Arizona. Additionally, a partial adenoviral polymerase gene sharing 98% homology with this HeAdV2 was discovered in a death adder (Acanthophis antarcticus) in Australia. These findings call into question the provenance of HeAdV2. Further studies of atadenoviral host range, diversity of adenoviruses in captive animals, and characterization of adenoviruses from wild squamates are indicated.

New Host and Locality Record of Parapharyngodon Japonicus (Nematoda: Oxyuroidea) from the Egyptian Changeable Lizard Agama Mutabilis (Agamidae): A Light and Scanning Electron Microscopy.

Parapharyngodon (Oxyurida) is a lizard gastrointestinal nematode parasite with a life cycle including lizards as main hosts. However, some species are known to parasitize anurans. In the present study, P. japonicus isolated from the large intestine of the Egyptian changeable lizard, Agama mutabilis was described and illustrated. Forty five specimens of these animals were collected from south Sinai desert, Egypt during the period from May to September 2017. After necropsy, the body was opened by a longitudinal incision from vent to throat, and the gastrointestinal tract was removed. The esophagus, stomach, small and large intestines were examined separately for helminthes. The recovered nematodes were examined by light and scanning electron microscopy. Thirty six specimens (80.0 %) were found to be naturally infected. The parasite was robust with prominent cuticular transverse annulations. Mouth surrounded by three bilobed lips, each with tiny labial papillae. Three pairs of caudal papillae were observed in male worms; 1 pair precloacal, 1 pair sublateral in cloacal opening line, 1 pair in proximal region of caudal appendage on its narrowed point. The posterior extremity beard dorsally directed caudal appendages. Females were with a conical posterior end terminated at a terminal spike. Ovaries reached esophageal isthmus but not wrapped around corpus. The parasite recorded was compared morphologically and morphometrically with the most similar species, it was found that it was most similar to P. japonicus with new host and locality records.

Motion-based signaling in sympatric species of Australian agamid lizards.

Signaling species occurring in sympatry are often exposed to similar environmental constraints, so similar adaptations to enhance signal efficacy are expected. However, potentially opposing selective pressures might be present to ensure species recognition. Here, we analyzed the movement-based signals of two pairs of sympatric lizard species to consider how reliable communication is maintained while avoiding misidentification. Our novel approach allows us to quantify signal contrast with plant motion noise at any site we measure, including those utilized by other species. Ctenophorus caudicinctus and Gowidon longirostris differed in display complexity and motor pattern use. They also differed in overall morphology, but their signal contrast scores are strikingly similar. These results demonstrate similar adaptations to their shared environment while maintaining species recognition cues. In contrast, Ctenophorus fordi and Ctenophorus pictus are much closer in appearance, but C. pictus produces considerably higher signal contrast scores, which we suggest is attributable to the absence of territoriality in C. fordi. Taken together, our data provide evidence for adaptation to the local environment in movement-based signals, while also meeting species recognition requirements, but the selective pressure to deal with local conditions is mediated by signal function.

Many Paths to a Common Destination: Morphological Differentiation of a Functionally Convergent Visual Signal.

Understanding the interacting outcomes of selection and historical contingency in shaping adaptive evolution remains a challenge in evolutionary biology. While selection can produce convergent outcomes when species occupy similar environments, the unique history of each species can also influence evolutionary trajectories and result in different phenotypic end points. The question is to what extent historical contingency places species on different adaptive pathways and, in turn, the extent to which we can predict evolutionary outcomes. Among lizards there are several distantly related genera that have independently evolved an elaborate extendible dewlap for territorial communication. We conducted a detailed morphological study and employed new phylogenetic comparative methods to investigate the evolution of the underlying hyoid that powers the extension of the dewlap. This analysis showed that there appear to have been multiple phenotypic pathways for evolving a functionally convergent dewlap. The biomechanical complexity that underlies this morphological structure implies that adaptation should have been constrained to a narrow phenotypic pathway. However, multiple adaptive solutions have been possible in apparent response to a common selection pressure. Thus, the phenotypic outcome that subsequently evolved in different genera seems to have been contingent on the history of the group in question. This blurs the distinction between convergent and historically contingent adaptation and suggests that adaptive phenotypic diversity can evolve without the need for divergent natural selection.

Spectral sensitivity of cone photoreceptors and opsin expression in two colour-divergent lineages of the lizard Ctenophorus decresii.

Intraspecific differences in sensory perception are rarely reported but may occur when a species range extends across varying sensory environments, or there is coevolution between the sensory system and a varying signal. Examples in colour vision and colour signals are rare in terrestrial systems. The tawny dragon lizard Ctenophorus decresii is a promising candidate for such intraspecific variation, because the species comprises two geographically and genetically distinct lineages in which throat colour (a social signal used in intra- and inter-specific interactions) is locally adapted to the habitat and differs between lineages. Male lizards from the southern lineage have UV-blue throats, whereas males from the northern lineage are polymorphic with four discrete throat colours that all show minimal UV reflectance. Here, we determine the cone photoreceptor spectral sensitivities and opsin expression of the two lineages, to test whether they differ, particularly in the UV wavelengths. Using microspectrophotometry on retinal cone photoreceptors, we identified a long-wavelength-sensitive (LWS) visual pigment, a 'short' and 'long' medium-wavelength-sensitive (MWS) pigment and a short-wavelength-sensitive (SWS) pigment, all of which did not differ in λmax between lineages. Through transcriptome analysis of opsin genes we found that both lineages express four cone opsin genes, including the SWS1 opsin with peak sensitivity in the UV range, and that amino acid sequences did not differ between lineages with the exception of a single leucine to valine substitution in the RH2 opsin. Counts of yellow and transparent oil droplets associated with LWS+MWS and SWS+UVS cones, respectively, showed no difference in relative cone proportions between lineages. Therefore, contrary to predictions, we find no evidence of differences between lineages in single cone photoreceptor spectral sensitivity or opsin expression. However, we confirm the presence of four single cone classes, suggesting tetrachromacy in C. decresii, and we also provide the first evidence of UV sensitivity in agamid lizards.

Intraspecific lineages of the lizard Phrynocephalus putjatia from the Qinghai-Tibetan Plateau: impact of physical events on divergence and discordance between morphology and molecular markers.

The Northeastern Qinghai-Tibetan Plateau (NQTP) contains many physical features that may have contributed to its rich biological diversity. We explored the systematics and genetic structures of the sand lizards Phrynocephalus putjatia, distributed across semi-deserts or rocky steppe habitats, and Phrynocephalus guinanensis, found only in sand dune habitats, from the NQTP using mitochondrial (ND2 and tRNAs) and nuclear (RAG-1) markers. Bayesian analyses revealed two main monophyletic mtDNA groups that separate populations of the Qinghai Lake Basin (QLB) from populations to the southeast of this basin (SEQL), but these did not correspond to the two morphological species. The QLB populations are divided into western and eastern groups. Two major groups with similar geographical structuring were also detected for the nuclear RAG-1 marker, but with some geographical discordance. A Bayesian species delimitation analysis did not support division of P. putjatia/P. guinanensis into separate species. Bayesian dating of mtDNA suggests that the earliest divergence within this group occurred less than 2 Ma, which seems to be explained by mountain uplift between the QLB and the SEQL regions. Other Pleistocene events may explain further genetic structuring. Overall, we do not detect reciprocal monophyly of markers between morphological species but note that they do appear to represent ecological forms.

A multi-locus molecular phylogeny for Australia's iconic Jacky Dragon (Agamidae: Amphibolurus muricatus): phylogeographic structure along the Great Dividing Range of south-eastern Australia.

Jacky dragons (Amphibolurus muricatus) are ubiquitous in south-eastern Australia and were one of the first Australian reptiles to be formally described. Because they are so common, Jacky dragons are widely used as a model system for research in evolutionary biology and ecology. In addition, their distribution along the Great Dividing Range of eastern Australia provides an opportunity to examine the influence of past biogeographical processes, particularly the expansion and contraction of forest habitats, on the diversification of this iconic agamid lizard. We generated sequence data for two mitochondrial and three nuclear DNA loci (4251base pairs) for 62 Jacky dragons sampled from throughout their distribution. Phylogenetic analyses based on maximum likelihood and Bayesian species-tree methods revealed five geographically structured clades separated by up to 6% mitochondrial and 0.7% nuclear sequence divergence. We also quantified body proportion variation within and between these genetic clades for more than 500 specimens and found no evidence of any significant differentiation in body proportions across their range. Based on body proportion homogeneity and lack of resolution in the nuclear loci, we do not support taxonomic recognition of any of the mitochondrial clades. Instead, A. muricatus is best thought of as a single species with phylogeographic structure. The genetic patterns observed in the Jacky dragon are consistent with fragmented populations reduced to multiple refugia during cold, arid phases when forested habitats were greatly restricted. Consequently, the inferred biogeographic barriers for this taxon appear to be in line with lowland breaks in the mountain ranges. Our results are congruent with studies of other reptiles, frogs, mammals, birds and invertebrates, and together highlight the overarching effects of widespread climatic and habitat fluctuations along the Great Dividing Range since the Pliocene.

A hybrid phylogenetic-phylogenomic approach for species tree estimation in African Agama lizards with applications to biogeography, character evolution, and diversification.

Africa is renowned for its biodiversity and endemicity, yet little is known about the factors shaping them across the continent. African Agama lizards (45 species) have a pan-continental distribution, making them an ideal model for investigating biogeography. Many species have evolved conspicuous sexually dimorphic traits, including extravagant breeding coloration in adult males, large adult male body sizes, and variability in social systems among colorful versus drab species. We present a comprehensive time-calibrated species tree for Agama, and their close relatives, using a hybrid phylogenetic-phylogenomic approach that combines traditional Sanger sequence data from five loci for 57 species (146 samples) with anchored phylogenomic data from 215 nuclear genes for 23 species. The Sanger data are analyzed using coalescent-based species tree inference using (*)BEAST, and the resulting posterior distribution of species trees is attenuated using the phylogenomic tree as a backbone constraint. The result is a time-calibrated species tree for Agama that includes 95% of all species, multiple samples for most species, strong support for the major clades, and strong support for most of the initial divergence events. Diversification within Agama began approximately 23 million years ago (Ma), and separate radiations in Southern, East, West, and Northern Africa have been diversifying for >10Myr. A suite of traits (morphological, coloration, and sociality) are tightly correlated and show a strong signal of high morphological disparity within clades, whereby the subsequent evolution of convergent phenotypes has accompanied diversification into new biogeographic areas.

Morphology and fibre-type distribution in the tongue of the Pogona vitticeps lizard (Iguania, Agamidae).

Agamid lizards use tongue prehension for capturing all types of prey. The purpose of this study was to investigate the functional relationship between tongue structure, both surface and musculature, and function during prey capture in Pogona vitticeps. The lack of a detailed description of the distribution of fibre-types in the tongue muscles in some iguanian lizards has hindered the understanding of the functional morphology of the lizard tongue. Three methodological approaches were used to fill this gap. First, morphological analyses were performed (i) on the tongue surface through scanning electron microscopy, and (ii) on the lingual muscle by histological coloration and histochemistry to identify fibre-typing. Secondly, kinematics of prey capture was quantified by using high-speed video recordings to determine the movement capabilities of the tongue. Finally, electromyography (EMG) was used to identify the motor pattern tongue muscles during prey capture. Morphological and functional data were combined to discuss the functional morphology of the tongue in agamid lizards, in relation to their diet. During tongue protraction, M. genioglossus contracts 420 ± 96 ms before tongue-prey contact. Subsequently, Mm. verticalis and hyoglossus contract throughout tongue protraction and retraction. Significant differences are found between the timing of activity of the protractor muscles between omnivorous agamids (Pogona sp., this study) and insectivorous species (Agama sp.), despite similar tongue and jaw kinematics. The data confirm that specialisation toward a diet which includes more vegetal materials is associated with significant changes in tongue morphology and function. Histoenzymology demonstrates that protractor and retractor muscles differ in fibre composition. The proportion of fast glycolytic fibres is significantly higher in the M. hyoglossus (retractor muscle) than in the M. genioglossus (protractor muscle), and this difference is proposed to be associated with differences in the velocity of tongue protrusion and retraction (5 ± 5 and 40 ± 13 cm s(-1) , respectively), similar to Chamaeleonidae. This study provides a way to compare fibre-types and composition in all iguanian and scleroglossan lizards that use tongue prehension to catch prey.

Seasonal Variation in the Thermoregulation Pattern of an Insular Agamid Lizard.

Ectotherms, including lizards, rely on behavioral thermoregulation to maintain their body temperature within an optimal range. The benign climate of islands is expected to favor the thermoregulation efficiency of reptiles throughout their activity period. In this study, we investigated the seasonal variation in thermoregulation in an insular population of the roughtail rock agama (Laudakia stellio) on Naxos Island, Greece. We measured body, operative, and preferred temperatures across three seasons (spring, summer, and autumn), and we evaluated the effectiveness of thermoregulation, using the Hertz index (E). Our results revealed that the effectiveness of thermoregulation was significantly influenced by seasonality. E was quite high in summer (0.97) and spring (0.92), and lowest in autumn (0.81). Accordingly, the quality of the thermal environment was significantly low during autumn, and maximum during summer. However, despite the environmental temperature fluctuations, lizards exhibited remarkable stability in body temperatures. They also adjusted their preferred temperatures seasonally and doubled the thermal niche breadth they occupied during summer, thus enhancing thermoregulation efficiency. Whether or not these adjustments are plastic or fixed local adaptations remains to be explored in further research across multiple years and seasons, including additional insular populations.

First record of Calotesvindumbarbatus Wagner, Ihlow, Hartmann, Flecks, Schmitz & Böhme, 2021 (Squamata: Agamidae) from China, with revised diagnosis of this species.

BACKGROUND: Three new species were recently described from the Calotesmystaceus Duméril & Bibron, 1837 complex. Of the three new species, C.vindumbarbatus Wagner, Ihlow, Hartmann, Flecks, Schmitz & Böhme, 2021 was known only from northern Myanmar. NEW INFORMATION: Seven specimens of lizard were collected from Tongbiguan Nature Reserve, western Yunnan, China. Phylogenetically, these specimens clustered with the type specimens of Calotesvindumbarbatus from Myanmar with strong support and showed inappreciable genetic divergence from the type specimens of C.vindumbarbatus. We report the first country record of C.vindumbarbatus from China. In addition, a supplementary description, based on the newly-collected specimens and revised diagnosis of this species, was provided.

The complete mitochondrial genome of the forest crested lizard, Calotes emma (Squamata, Agamidae) in China by the next generation sequencing.

The whole mitogenome can prove useful tools for phylogenetic reconstruction and efficiently recover with reasonable taxon sampling. Calotes emma is widely distributed and arboreal in habits. However, studies of C. emma are still very limited, including population genetics and evolutionary biology. In this study, we reported the complete mitochondrial genome of the C. emma by next-generation sequencing for future more researches on systematics and evolution of C. emma from the perspective of mitochondrial DNA. The length of mitogenome was 17,688 bp, including 13 protein-coding genes (PCGs), 2 ribosomal RNA (rRNA) genes, 22 tRNA genes and a control region. The phylogenetic tree recovered the monophyly of the Calotes and revealed that newly sequenced C. emma well supported as the sister taxon to C. mystaceus by very high posterior probabilities (1.0). The complete mitochondrial genome of C.emma in this study will be helpful for understanding the phylogenetic systematics and relationships, and molecular evolution of Calotes in Agamidae.

The Review of the Autotomy of Agamid Lizards with Considerations about the Types of Autotomy and Regeneration.

We present a review of the data on the intervertebral autotomy and regeneration of agamid lizards based on an analysis of information obtained over a 35-year period after the publication of thorough reviews (Arnold, 1984, 1988 and Bellairs, Bryant, 1985). It is supplemented by our own studies of 869 specimens of agamid lizards (Sauria, Agamidae) stored in the herpetological collections of the Zoological Institute of the Russian Academy of Sciences (St. Petersburg, Russia) and the Zoological Museum of the Moscow State University (Moscow, Russia), represented by 31 species of 16 genera. The manifestations of the ability for autotomy and regeneration in phylogenetic lineages within the family-Leiolepidinae, Amphibolurinae, Agaminae, Draconinae-are considered. A comparative morphological analysis of the structure of the caudal vertebrae was carried out using the Computer Microtomography Methods (micro-CT) in the following ecomorphological types of agama: (1) with developed abilities to caudal autotomy and regeneration, (2) with the ability to caudal autotomy but without regeneration and (3) without the ability to autotomy. The phenomenon of intervertebral autotomy (urotomy) in snakes is considered too. Possible ways of evolution of the ability to caudal autotomy as a defense strategy against predators are discussed in the phylogenetic context.

A new of species of the Agama lionotus Boulenger, 1896 complex (Squamata: Agamidae) from northern Kenya.

Kenya has a high diversity of agamid lizards and the arid northern frontier area has the highest species richness. Among the Kenyan agama species, Agama lionotus has the widest distribution, occurring from sea level to inland areas in both dry and moist savanna as well as desert areas. This species mostly prefers rocky areas, both in granitic/metamorphic and volcanic rocks, although it also makes use of tree crevices as well as man-made structures. Recently in Marsabit, northern Kenya, a small-sized agama species, distinct from A. lionotus, was collected within a rocky lava desert area. This new species is characterized by its small size (mean SVL ~83 mm) as compared to typical A. lionotus (mean SVL ~120 mm). Past studies have shown the value of adult male throat coloration for the identification of species within the A. lionotus complex. Herein we also highlight female dorsal color pattern, which is a key character for distinguishing the new species from others in the group, including the similar A. hulbertorum. As in A. lionotus, displaying adult males have an orange to yellow head, a vertebral stripe, a bluish body coloration and an annulated white/blue tail. But the most diagnostic character is the coloration of females and non-displaying males, which exhibit a series of regular pairs of dark spots along the vertebrae as far posterior as the tail base. In addition, females have a pair of elongated orange or yellow marks on the shoulders and another on the dorsolateral margins of the abdomen. This study shows that more cryptic species in the Agama lionotus complex may still await discovery. The new species was found inhabiting dark desert lava rocks but should additionally be present in suitably similar sites in the northern frontier area. This underscores the need to re-examine populations of Agama lionotus from different microhabitats in this country.