Sleeper sharks (family Somniosidae) are large, slow-growing deep-sea sharks that are rarely documented in the southeastern Pacific, and records from the Chilean waters have remained taxonomically uncertain. Here, we report a confirmed record of a large-bodied southern Somniosus from northern Chile based on a gravid female incidentally captured by a commercial deep-sea longline fishery off Antofagasta and a late-stage male embryo aborted during handling. The embryo measured 90.5 cm in total length and exhibited morphological and meristic characters consistent with large-bodied S. antarcticus, including a cylindrical body, short rounded snout, spineless dorsal fins, hook-like dermal denticles, and a 40-turn spiral valve. Additionally, a 639 bp fragment of the mitochondrial cytochrome C oxidase subunit I (COI) gene was obtained from both the female and embryo, and the two sequences were identical, consistent with maternal inheritance. Comparative analyses using public records placed the Chilean haplotype within the large-bodied Somniosus species complex. The Chilean haplotype was identical to an Antarctic record labelled S. pacificus and differed by two substitutions from a New Zealand record labelled S. antarcticus. However, the COI does not fully resolve species boundaries within the pacificus/antarcticus complex, as the divergence between nominal species remains low. These results provide the first well-documented record of the Antarctic sleeper shark in northern Chile and expand the documented occurrence of southern large-bodied Somniosus along the Chilean margin. More broadly, this record highlights the importance of integrating internal meristics, morphology, and molecular data when documenting rare deep-sea sharks in fishery bycatch.
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