Hydrolagus macrophthalmus de Buen 1959

Big eye Chimaera

(Figure 7, Table 5)

Material examined. 4 specimens. UCR 2611–08, n=2, females, 435–581 mm TL, 223–343 mm BDL; in front of Playa Coyote, Península de Nicoya, Guanacaste, Costa Rica (9°40'50.02" N, 85°28'4.81" W), 650–700 m, 7 April 2000, collected by M. Vitola. UCR 2901–01, n=2, females, 543–639 mm TL, 334–349 mm BDL; 44.95 Km, 253.73 ° T from Cabo Blanco, Puntarenas, Costa Rica (9º26'16.44" N, 85º29'56.04" W), 560–620 m, 24 November 2010, collected by J.M. Carvajal.

Diagnosis. Body slender; snout short and bluntly rounded; head relatively short (HDL 24.2–24.5% BDL); eyes relatively large (EYL 30.9–34.2% HDL); oral and preopercular lateral line canals sharing a short common branch from the infraorbital canal; pectoral fins relatively large (P1A 36.5–40.8% BDL), extending posterior to the insertion of pelvic fins; lateral line canal of the trunk without sinusoidal undulations; anterior and posterior regions of second dorsal fin considerably taller than middle region; anal fin absent; tail region elongate and slender (PCA 58.3–59.9% BDL); caudal-fin axis horizontal with the fin nearly symmetrical, epaxial and hypaxial lobes equal sized; uniform brown coloration across entire body, with no white markings; bluish fins. Additional morphometric measurements, expressed as percentage of body length (% BDL) or head length (% HDL), and comparative data are presented in Table 5.

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Distribution. Eastern Pacific: Central coast of Mexico (González-Acosta et al. 2010), Costa Rica (this study), Peru and Chile, at depths of 590–1160 m (Didier & Meckley 2009b).

Remarks. Although this species has a postulated distribution extending from the central coast of Mexico (González-Acosta et al. 2010) to Chile (Didier & Meckley 2009b), there are no published records between Mexico and Peru (Didier & Meckley 2009b). The discovery of these specimens in Costa Rican waters increases the knowledge of its marine ichthyofauna and provides evidence of a broader distributional pattern for this species in the eastern Pacific region.