A review of walking shark (Hemiscylliidae: Hemiscyllium) distributions in Papua New Guinea and description of a new species

Walking sharks (Hemiscyllium) comprise 9 morphologically similar species whose identification relies on distinctive color patterns, genetic markers, and geographically restricted distributions. The genus is endemic to Australia and the island of New Guinea, a region that coincides with the global hotspot for carpet shark diversity (Orectolobiformes) that has been shaped by complex tectonic and sea‑level histories. Although knowledge of walking shark distributions has been updated over the past two decades, the species endemic to eastern Papua New Guinea remain poorly known. This study addresses these gaps by investigating the distributions of walking sharks in eastern Papua New Guinea. We used a series of in-situ surveys to review the ranges of walking shark species and to document their species-specific color patterns, complemented by an assessment of genetic markers to confirm the updated geographical distributions across species and explore phylogeographic patterns in the region. We present updated distributions for two species (H. michaeli and H. hallstromi)¸ as well as a theory for the development of a mosaic of disjunct, non-overlapping distributions previously unreported for the genus. Additionally, we describe a tenth member of the genus, Hemiscyllium dudgeonae, n. sp., which is likely to be highly threatened. We present possible mechanisms that may have produced this mosaic of distributions and influenced speciation in the region. Finally, we discuss the conservation implications of these findings.