A quantitative ecomorphological study was carried out on the sagitta otoliths of Antarctic and Subantarctic nototheniids, a particularly interesting family due to its fast adaptive radiation into different life strategies. We analyzed the otolith shape and size of 18 nototheniids to test the relationship between phylogeny, otolith characters and trophic niche. Relative size (area, length, width, perimeter and weight) and shape (biometric warp analysis based on homologous and pseudo-homologous landmarks) measurements were compared with phylogenic, habitat dwelling and food composition analyses. The results of the multivariate analysis of these factors indicate that there is a weak relationship between otolith shape of nototheniids and phylogeny; however, there is a clear correspondence between relative otolith size and shape and their trophic niche. The most benthic feeders of the family had the largest sagittae in relation to body size, and pelagic species had smaller and rounder shaped sagittae than benthic species. Consequently, in ecomorphological studies, it is useful to analyze the size and shape of sagittae. The discoidal shape of pelagic species, such as Pleuragrama antracticum, can be considered as a paedomorphic characteristic, converging to the juvenile sagittae of many species, which exhibit round sagittae that become elongated as they grow.

SUMMARY: A new species of the family Merlucciidae is presented, Merluccius patagonicus sp. nov., from the waters of the Argentine Sea. Besides the description of the new species, a brief diagnosis and a key to identification are added, with the purpose of easily separating the species from its similar relatives among the genus Merluccius Rafinesque, 1810 reported in the region: M. hubbsi and M. australis. -Se presenta una nueva especie Merluccius patagonicus sp. nov. perteneciente a la familia Merlucciidae, capturada en aguas del mar Argentino. En el presente trabajo, se adjunta además de la descripción, una breve diagnosis y una clave de identificación con el propósito de identificar fácilmente las especies similares del género Merluccius Rafinesque, 1810 citadas en la región: M. hubbsi y M. australis.

A new hake species, Merluccius tasmanicus sp. nov., is described from New Zealand waters and another species, Merluccius australis is redescribed. Merluccius tasmanicus sp. nov. differs from all other congeneric species in the following combination of characters: upper profile of the head slowly concave; lateral line slowly concave in the caudal region; body depth 4.9–5.9 times in standard length (SL); orbital diameter 6.1–7.1 times in head length, 2.1–2.2 times in snout length and 1.6–1.9 times in interorbital width; second dorsal fin rays, 42–43; anal fin rays, 42–44; lateral line scales ∼164. Merluccius australis is redescribed to clarify the identity of this species. Merluccius australis differs from all other congeneric species in the following combination of characters: upper profile of the head straight; lateral line straight in the caudal region; body depth 6.6–7.1 times in SL; orbital diameter 4.5–5.4 times in head length, 1.2–1.7 times in snout length and 1.0–1.3 times in interorbital width; second dorsal fin rays, 40–43; anal fin rays, 40–43; lateral line scales, more than 155. Merluccius tasmanicus sp. nov. is found in New Zealand and Patagonian waters and occasionally in Japanese waters; Merluccius australis is reported in both New Zealand and Patagonian waters.

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