Two main hypotheses have been proposed to explain the diversification of the Caatinga biota. The riverine barrier hypothesis (RBH) claims that the São Francisco River (SFR) is a major biogeographic barrier to gene flow. The Pleistocene climatic fluctuation hypothesis (PCH) states that gene flow, geographic genetic structure and demographic signatures on endemic Caatinga taxa were influenced by Quaternary climate fluctuation cycles. Herein, we analyse genetic diversity and structure, phylogeographic history, and diversification of a widespread Caatinga lizard (Cnemidophorus ocellifer) based on large geographical sampling for multiple loci to test the predictions derived from the RBH and PCH. We inferred two well-delimited lineages (Northeast and Southwest) that have diverged along the Cerrado-Caatinga border during the Mid-Late Miocene (6-14 Ma) despite the presence of gene flow. We reject both major hypotheses proposed to explain diversification in the Caatinga. Surprisingly, our results revealed a striking complex diversification pattern where the Northeast lineage originated as a founder effect from a few individuals located along the edge of the Southwest lineage that eventually expanded throughout the Caatinga. The Southwest lineage is more diverse, older and associated with the Cerrado-Caatinga boundaries. Finally, we suggest that C. ocellifer from the Caatinga is composed of two distinct species. Our data support speciation in the presence of gene flow and highlight the role of environmental gradients in the diversification process.

Two syntopic species of Cnemidophorus are described from the Caatingas of the Parque Nacional da Serra das Confusões (PNSC), located in the Southwestern region of the state of Piauí in Brazil. Both species are assigned to the ocellifer group, differing from all other members of the group by their distinct color pattern and lepidosis. Besides these differences, both new species share a number of particular features with other members of the group. One of them, C. venetacaudus, shares with C. abaetensis and C. littoralis the presence of spurs in the heels of males, six supraciliar scales, a high number of femoral pores (from 21–45), a row of enlarged scales in the dorsal region of the arm, 8–10 rows of ventral scales, and a bright bluish-green tail, while the other species, C. confusionibus, shares with C. ocellifer, C. mumbuca, and C. jalapensis a low number of femoral pores, enlarged scales in the temporal region (posterior to third subocular), 5 supraciliar scales, and 6–8 rows of ventral scales. Based on these comparisons, we suggest that the ocellifer group is more complex than previously admitted, being composed by at least two morphologically recognizable species subgroups.

Lizards of the family Teiidae (infraorder Scincomorpha) were formerly known as Macroteiidae. There are 13 species of such lizards in the Amazon, in the genera Ameiva (Meyer, 1795), Cnemidophorus (Wagler, 1830), Crocodilurus (Spix, 1825), Dracaena (Daudin, 1801), Kentropyx (Spix, 1825) and Tupinambis (Daudin, 1802). Cytogenetic studies of this group are restricted to karyotype macrostructure. Here we give a compilation of cytogenetic data of the family Teiidae, including classic and molecular cytogenetic analysis of Ameiva ameiva (Linnaeus, 1758), Cnemidophorus sp.1, Kentropyx calcarata (Spix, 1825), Kentropyx pelviceps (Cope, 1868) and Tupinambis teguixin (Linnaeus, 1758) collected in the state of Amazonas, Brazil. Ameiva ameiva, Kentropyx calcarata and Kentropyx pelviceps have 2n=50 chromosomes classified by a gradual series of acrocentric chromosomes. Cnemidophorus sp.1 has 2n=48 chromosomes with 2 biarmed chromosomes, 24 uniarmed chromosomes and 22 microchromosomes. Tupinambis teguixin has 2n=36 chromosomes, including 12 macrochromosomes and 24 microchromosomes. Constitutive heterochromatin was distributed in the centromeric and terminal regions in most chromosomes. The nucleolus organizer region was simple, varying in its position among the species, as evidenced both by AgNO3 impregnation and by hybridization with 18S rDNA probes. The data reveal a karyotype variation with respect to the diploid number, fundamental number and karyotype formula, which reinforces the importance of increasing chromosomal analyses in the Teiidae.

We provide the description for a new species from Catamarca province, Argentina that belongs to the Liolaemus darwinii group. The new species was previously considered as a population of L. ornatus, but it can be distinguished from that species mainly because of differences on coloration pattern, and its geographic distribution, which is disjunct from the populations of L. ornatus. The new species is characterized for having males with a dorsal background coloration of light brown to ferrous red, the head darker than the rest of the body, paravertebral markings rounded and never in contact, dorsolateral strips lightly marked, small dark brown spots on the throat, and a belly that is white or light red.

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Two new species of Cnemidophorus are described from the right bank of the São Francisco river, in the northwestern part of state of Bahia, Brazil. Both species are assigned to the Cnemidophorus ocellifer group and are distinguished from all other congeners on the basis of lepidosis and color pattern. One of them, Cnemidophorus cyanurus, shares with the species of the subgroup of C. littoralis (C. abaetensis, C. littoralis and C. venetacaudus), a bluish green tail, spurs on the heels of males, 6–7 supraciliaries, a high number of femoral pores (27–45), a row of enlarged scales in the dorsal part of the humerus, and 8 to 10 rows of ventral scales. The second species, Cnemidophorus nigrigula, shares with the C. ocellifer subgroup (composed of C. ocellifer, C. mumbuca, C. jalapensis and C. confusionibus) a low number of femoral pores (14– 21), enlarged scales in the temporal region posterior to the third subocular, 5 supraciliaries, 6 to 8 rows of ventral scales, and a brown tail color. It is also characterized by males being conspicuously larger than females and by females retaining the juvenile color pattern, which is lost in adult males. The latter characteristic has not been reported in any species of the C. ocellifer group before now. The two new species occur sympatrically at Santo Inácio.

We describe a new species of whiptail lizard genus Ameivula from Planalto dos Gerais, a sandstone plateau that extends along the Cerrado region in the states of Bahia, Tocantins, Piaui, and Minas Gerais, in Brazil. The new species is the third recognized speeies of the A. oeellifera group registered for the Cerrado. Quantitative analyses of morphometrie characters showed that Caatinga species are distinguished from their Cerrado congeners on basis of body size and shape. A discriminant analysis upon meristic characters showed that the new species can be clearly distinguished from the other two Cerrado speeies A. mumbuca and A. jalapensis, also the morphology of the finger lamellae, and clutch size distinguish these species.

A new species of bufonid frog, Rhinella bernardoi sp. nov., belonging to the granulosa group, is described from moderately high elevation (1400 m) at Ischigualasto Provincial Park, San Juan, Argentina. The morphology of the new species is compared to and diagnosed from other closely related species of the same group (R. bergi, R. fernandezae, and R. granulosa). We also describe the osteology of the skull and the vertebral column of the new species and present data on its geographic distribution and natural history.