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The natricine snake genus Smithophis Giri, Gower, Das, Lalremsanga, Lalronunga, Captain, and Deepak, 2019, is represented by four species, three of which are distributed in northeast India and Bangladesh, and a single species in Yunnan and Myanmar. In the past, S. bicolor (Blyth, 1855) was said to be widespread across northeast India and Myanmar; however, recent studies have shown it to be a species complex. Here, we describe a new species of the complex from the Indian state of Mizoram that resembles S. bicolor. The new species differs in bearing a patterned dorsum, a darker venter, and moderately keeled sacral scales. Re-examination of types of S. arunachalensis Das, Deepak, Captain, Wade, and Gower, 2020, shows the presence of strongly keeled sacral keels in males, which is an important diagnostic character. A revised key to members of the genus is presented with notes on S. arunachalensis.

The Common Krait (Bungarus caeruleus) shares a distribution range with many other ‘phenotypically-similar’ kraits across the Indian subcontinent. Despite several reports of fatal envenomings by other Bungarus species, commercial Indian antivenoms are only manufactured against B. caeruleus. It is, therefore, imperative to understand the distribution of genetically distinct lineages of kraits, the compositional differences in their venoms, and the consequent impact of venom variation on the (pre)clinical effectiveness of antivenom therapy. To address this knowledge gap, we conducted phylogenetic and comparative venomics investigations of kraits in Southern and Western India. Phylogenetic reconstructions using mitochondrial markers revealed a new species of krait, Romulus’ krait (Bungarus romulusi sp. nov.), in Southern India. Additionally, we found that kraits with 17 mid-body dorsal scale rows in Western India do not represent a subspecies of the Sind Krait (B. sindanus walli) as previously believed, but are genetically very similar to B. sindanus in Pakistan. Furthermore, venom proteomics and comparative transcriptomics revealed completely contrasting venom profiles. While the venom gland transcriptomes of all three species were highly similar, venom proteomes and toxicity profiles differed significantly, suggesting the prominent role of post-genomic regulatory mechanisms in shaping the venoms of these cryptic kraits. In vitro venom recognition and in vivo neutralisation experiments revealed a strong negative impact of venom variability on the preclinical performance of commercial antivenoms. While the venom of B. caeruleus was neutralised as per the manufacturer’s claim, performance against the venoms of B. sindanus and B. romulusi was poor, highlighting the need for regionally-effective antivenoms in India.