Southeast Asia, Sundaland, and Australasia are some of the most sought-after biogeographical regions within which to test hypotheses pertaining to dispersal and diversification. While cyclic fluctuations in sea levels, and the land bridges that were periodically exposed and submerged as a consequence, have been invoked to explain the accumulation of biodiversity in the region, recent geological studies have shown that most of the region remained aerially exposed until as recently as 500 KYA. This implies that contrary to historical belief, alternate processes may have driven the dispersal and diversification of terrestrial and semi-aquatic organisms in SE Asia, the Sunda plate, and Australia. In this collaborative paper, Bernstein, de Souza, et al. examine these ‘alternate processes’, specifically the influence of major shifts in river systems around 17 MYA, as drivers for diversification and dispersal in the widespread, yet poorly studied ‘OrientalAustralian Mud Snakes’ (Serpentes: Homalopsidae). These snakes, given their predominantly semi-aquatic habit, form an ideal model system to study biogeographic processes, given that they have the rare advantage of the availability of both terrestrial and aquatic dispersal routes. In our paper, we use a target capture genomic approach to resolve the phylogeny of this hitherto understudied group, identify their biogeographic origins, and highlight the impacts of paleoclimate (sea-level fluctuations vs. riverine connectivity) on their present-day ranges and abundances. We use recently developed methodology for the extraction of DNA from formalin-preserved museum tissue to present the most complete phylogeny of homalopsids to date (species/genera coverage of 81% and 90% respectively, up from 45%/45%). Our phylogenomic and divergence time dating elucidate that these snakes are much younger than previously thought (~27.7 MYA vs ~45.3 MYA) with the origin of the crown group occurring in the Oligocene. I further incorporate Ancestral Trait Reconstructions (ATRs) which form a portion of my PhD’s Chapter 1, to elucidate that the most recent common ancestor of this clade was a terrestrial serpent (vs. prior assumption that it was aquatic). While our data were neither able to resolve the ancestral range of the crown homalopsid, nor was it able to conclusively comment on the drivers for homalopsid diversification, our divergence dating in tandem with the ATR analyses was able to identify Indochina was the cradle for all aquatic homalopsids. This implies that the single switch from terrestrial to aquatic habit in ancient homalopsids, in combination with riverine connectivity has resulted in the surprisingly high diversity of aquatic homalopsids vs. their terrestrial extant counterparts. In this presentation, I also touch upon my ongoing research towards my Chapter 2 (phylogeographic comparisons between brackish water-tolerant homalopsids and freshwater-restricted natricids) and Chapter 3 (species distribution models predicting current and future habitat suitability for semiaquatic snakes within the Indian biogeographical region) chapters.