Egg capsules and adults of Aforia obesa Pastorino and Sánchez, 2016 were collected at the Mar del Plata Submarine Canyon in the Argentine continental slope at 780–1398 m depth during 2012 and 2013. Egg capsules were iridescent white, dome-shaped, solitary with tough and thick walls. The capsule diameter was 8.5–12 mm. The uncleaved eggs with a diameter of 1.6–1.9 mm (X = 1.8 ± 0.1 mm) confirm a previous report for the genus and are by far the largest eggs known within Conoidea and, as far as we know, the largest ever described among Caenogastropoda from the Southwestern Atlantic. Embryos undergo complete intracapsular development with no evidence of oophagy, adelphophagy, late cannibalism, or other supplementary food. Young emerge as crawling juveniles throughout an elliptic and transparent exit hole in the top center of the egg capsule. Fil: Sánchez, Noelia Carolina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; Argentina Fil: Pastorino, Roberto Santiago Guido. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; Argentina Fil: Penchaszadeh, Pablo Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; Argentina