Reptiles are still being described worldwide at a pace of hundreds of species a year. While many discoveries are from remote tropical areas, biodiverse arid regions still harbor many novel taxa. Here, we present an updated phylogeny of colubrid snakes from the Western Palearctic by analyzing a supermatrix of all available global snake species with molecular data and report on the discovery of a new genus and species of colubrine snake from southeastern Iran. The new taxon, named Persiophis fahimii Gen. et sp. nov., is nested within a clade containing Middle Eastern and South Asian ground racers (Lytorhynchus, Rhynchocalamus, Wallaceophis, and Wallophis). This species has a derived morphology including an edentulous pterygoid and occurrence of short and blunt teeth on the palatine, maxillae and dentary bones, an elongated snout and a relatively trihedral first supralabial scale that is slightly bigger than the second, and elongated toward the tip of rostral. We also report on the osteology and phylogenetic placement of several poorly studied colubrines: Hierophis andreanus (reassigned to Dolichophis) and Muhtarophis barani.

Iran is a country characterized by high biodiversity and complex biogeographic patterns. Its diverse landscape and steep climatic gradients have resulted in significant faunal diversity and high level of endemism. To better understand these patterns, we investigated the historical environmental drivers that have shaped Iran’s current geological and climatological conditions, and, consequently, have shaped the current zoological distribution patterns. Furthermore, we provide an overview of the country’s zoological diversity and zoogeography by reviewing published studies on its fauna. We analyzed nearly all available catalogs, updated checklists, and relevant publications, and synthesized them to present a comprehensive overview of Iran’s biodiversity. Our review reports approximately 37,500 animal species for Iran. We also demonstrated that the country serves as a biogeographic transition zone among three zoogeographical realms: the Palearctic, Oriental, and Saharo-Arabian, where distinct faunal elements intersect. This biogeographic complexity has made it challenging to delineate clear zoogeographical zones, leading to varying classifications depending on the taxon. The uplift of mountain ranges, in particular, has played a crucial role in shaping faunal diversity by serving as barriers, corridors, and glacial refugia. These mountains are largely the result of orogeny and plate collisions during the Mesozoic and Cenozoic eras, coupled with the development of the Tethyan Sea and the uplift of several ranges during the Miocene. Despite these insights, our understanding of biodiversity distribution in Iran remains incomplete, even for some well-studied taxa, such as certain vertebrate families and arthropods. We highlight the existing gaps in knowledge regarding zoogeographical patterns and propose approaches to address these gaps, particularly concerning less-studied species and the highly diverse group of insects.

The kukri snakes of the genus Oligodon Fitzinger, 1826 reach the westernmost limits of their distribution in Middle and Southwest Asia (Afghanistan, Iran, and Turkmenistan), and the Palearctic portions of Pakistan. In this article, we review the systematics and distribution of the two species native to this region, Oligodon arnensis (Shaw, 1802) and Oligodon taeniolatus (Jerdon, 1853) based on an integrative approach combining morphological, molecular, and species distribution modeling (SDM) data. Phylogenetic analyses recover O. taeniolatus populations from Iran and Turkmenistan in a clade with the O. arnensis species complex, rendering the former species paraphyletic relative to O. taeniolatus sensu stricto on the Indian subcontinent. To correct this, we resurrect the name Contia transcaspica Nikolsky, 1902 from the synonymy of O. taeniolatus and assign it to populations in Middle–Southwest Asia. So far, Oligodon transcaspicus comb. et stat. nov. is known only from the Köpet–Dag Mountain Range of northeast Iran and southern Turkmenistan, but SDM mapping suggests it may have a wider range. Genetic samples of O. “arnensis” from northern Pakistan are nested in a clade sister to the recently described Oligodon churahensis Mirza, Bhardwaj & Patel, 2021, and are phylogenetically separate from O. arnensis sensu stricto in south India and Sri Lanka. Based on morphological similarity, the Afghanistan and Pakistan populations are assigned to Oligodon russelius (Daudin, 1803) and we synonymize O. churahensis with this species. Our investigation leads us to remove O. taeniolatus from the snake fauna of Afghanistan, Iran, and Turkmenistan, with the consequence that only Oligodon transcaspicus comb. et stat. nov. and O. russelius are present in these countries. Additional studies are needed to resolve the taxonomy of the O. taeniolatus and O. arnensis species complexes on the Indian subcontinent, and an updated key for both groups is provided.

To date there are few quantitative studies investigating the evolution of tooth shape and function in aglyphous snakes in relation to diet. A considerable evolutionary decrease in body size is observed in whip snakes of the genus Dolichophis and their sister-group Eirenis. This was coupled with a considerable shift in diet from a regime consisting mainly of prey with endoskeleton to prey bearing a hard exoskeleton. Three-dimensional (3D) geometric morphometrics revealed that the maxillary and palatine teeth of E. persicus are blunt and conical in shape, while the same teeth are sharp and elongated in E. punctatolineatus and D. schmidti. Blunt and conically shaped teeth, as observed in E. persicus, seem to be more adapted for biting hard-bodied, arthropod prey. In contrast, the sharp and elongated teeth in Dolichophis and E. punctatolineatus, are likely specialized for puncturing prey with an endoskeleton. The results of a finite element analysis confirms that during the biting of a hard-bodied prey, the generated stresses in E. persicus teeth are well below the von Mises yield criterion, while in D. schmidti the value is roughly two to three times higher, indicating that E. persicus teeth are better suited for biting hard-bodied prey such as arthropods.