Eastern Pacific Black Chimaera

description

Description. Morphometric measurements of the holotype and paratypes, expressed as percentage of body length (% BDL) or head length (% HDL), are presented in Table 3. A medium to large bodied species with a relatively large head (HDL 24.9 - 26.3 % BDL) which is about 20.1 – 20.4 % of PCL. Snout relatively short, blunt, PRN 26.0 – 31.8 % HDL and POR 37.2 – 43.8 % HDL. Eyes relatively large (EYL 30.6 – 30.9 % HDL) and oval in shape (EYH 58.5 – 63.2 % EYL). Trunk stout, body depth remains similar to origin of pelvic fins where it quickly tapers posteriorly, transitioning to a caudal filament. Skin is smooth, without denticles, non-deciduous. Oral and preopercular canals sharing a short common branch off the infraorbital canal (Fig. 4). Lateral line canal of trunk originates at a fork between occipital and otic canals with a sigmoid curve, and then with slight undulations, extends posteriorly to caudal region, where it becomes ventral and continues to caudal filament. First dorsal fin base relatively short (D 1 B 10.3 – 12.5 % BDL) and preceded by a robust dorsal fin spine. Dorsal fin spine tall (DSA 28.4 – 31.0 % BDL), greater than head length (DSA about 1.14 – 1.18 times HDL) and ext

Records of chimaeroid fishes (Holocephali: Chimaeriformes) from the Pacific coast of Costa Rica, with the description of a new species of Chimera (Chimaeridae) from the eastern Pacific Ocean

diagnosis

Diagnosis. A species of the genus Chimaera based on the presence of an anal fin. Chimaera orientalis sp. nov is distinguished from its congeners by the following combination of characters: oral and preopercular canals sharing a short common branch off the infraorbital canal; dorsal spine long (DSA 28.4 – 31.0 % BDL), longer than first dorsal fin, when depressed reaches beyond to origin of second dorsal fin; first dorsal fin high (D 1 H 20.8 – 26.7 % BDL) with a short base (D 1 B 10.3 – 12.5 % BDL); interdorsal space long (IDS 8.1 – 10.2 % BDL); pectoral fin long (P 1 A 40.0 – 43.5 % BDL), when depressed reaches beyond to origin of pelvic fin base; pelvic claspers long (CLT 17.5 – 17.7 % BDL), bifurcate, divided at about distal 40.9 – 43.1 % of its length; dorsal caudal space long (DCS 2.0 – 2.5 % BDL); ventral caudal margin ending slightly posterior to dorsal caudal margin; and dark brown coloration with the ventral portion of the trunk and all fins slightly darker, without distinctive markings or mottling

Records of chimaeroid fishes (Holocephali: Chimaeriformes) from the Pacific coast of Costa Rica, with the description of a new species of Chimera (Chimaeridae) from the eastern Pacific Ocean

discussion

Remarks. Chimaera orientalis sp. nov. is the first species of the genus C himaera described from the eastern Pacific and can be distinguished from its other congeners by a combination of morphological and coloration differences. Chimaera orientalis sp. nov. differs from C. argiloba Last, White & Pogonoski 2008, from the eastern Indian (Last et al. 2008, Didier et al. 2012), in having a shorter head length (24.9 – 26.3 vs. 31.3 – 36.1 % BDL), a shorter pre-orbital length (11.8 – 12.6 vs. 14.7 – 18.7 % BDL), a shorter pre-first dorsal length (26.5 – 29.7 vs. 29.8 – 36.2 % BDL), a shorter pre-second dorsal length (47.2 – 48.7 vs. 55.5 – 64.2 % BDL), a shorter length of first dorsal fin base (10.3 – 12.5 vs. 17.5 – 21.9 % BDL), a larger dorsal caudal space (2.0 – 2.5 vs. 0.8 – 1.9 % BDL), a shorter total caudal length (40.1 – 45.5 vs. 61.5 – 76.8 % BDL), a shorter ventral caudal margin (24.2 – 31.7 vs. 37.7 – 61.3 % BDL), a shorter total clasper length (17.5 – 17.7 vs. 25.1 – 26.5 % BDL), a shorter length of lateral clasper branch from fork to tip (7.2 – 7.6 vs. 15.2 – 15.5 % BDL), and in the coloration pattern (the last being uniformly silvery greyish dorsally and laterally, paler ven

Records of chimaeroid fishes (Holocephali: Chimaeriformes) from the Pacific coast of Costa Rica, with the description of a new species of Chimera (Chimaeridae) from the eastern Pacific Ocean

distribution

Distribution. The three type specimens were collected (2 specimens) from off Costa Rica (9 º 26 ' 16.44 " N, 85 º 29 ' 56.04 " W) and (1 specimen) from off Peru (9 º 18 ' 07 " – 9 º 20 ' 00 " S, 79 º 47 ' 04 " – 79 º 47 ' 08 " W), eastern Pacific, at depths between 560 and 1138 m. As noted by Didier & Meckley (2009 b), Chimaera orientalis sp. nov. may be more widely distributed in the eastern Pacific region.

Records of chimaeroid fishes (Holocephali: Chimaeriformes) from the Pacific coast of Costa Rica, with the description of a new species of Chimera (Chimaeridae) from the eastern Pacific Ocean