Chimaeriformes

Angulo, Arturo, López, Myrna I., Bussing, William A. & Murase, Atsunobu, 2014, 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, Zootaxa 3861 (6), pp. 554-574 : 571

Key to eastern Pacific species of the order Chimaeriformes

The following key is based on our research and data available in the literature (Didier & Nakaya 1999, Didier & Rosenberger 2002, Barnett et al. 2006, Nelson 2006, Quaranta et al. 2006, Didier & Meckley 2009a, b, James et al. 2009, González-Acosta et al. 2010, Bustamante et al. 2012, Didier et al. 2012).

1 Snout with elongate, flexible, hooklike process; lateral line canals closed; second dorsal fin not elongate; tail heterocercal ( Ecuador to Argentina)............................................. Callorhinchus callorynchus (Linnaeus 1758)

- Snout short and rounded or long and pointed, not hooklike; lateral line canals are open grooves; second dorsal fin elongate; tail diphycercal.......................................................................................... 2

2 Snout short and bluntly rounded; caudal-fin axis horizontal with the fin nearly symmetrical, epaxial and hypaxial lobes equal sized............................................................................................... 3

- Snout elongated and pointed; caudal-fin axis weakly raised with the fin asymmetrical, epaxial caudal-fin lobe narrower than hypaxial lobe........................................................................................ 8

3 Anal fin present ( Costa Rica to Peru, probably more widespread in the southeastern Pacific).... Chimaera orientalis sp. nov.

- Anal fin absent...................................................................................... 4

4 Anterior and posterior regions of second dorsal-fin considerably taller than middle region............................ 5

- Second dorsal-fin uniform in height throughout............................................................. 7

5 Anterior edge of dorsal-fin spine not serrated; uniform dark brown to reddish-brown across entire body with numerous white spots on the head and trunk (Gulf of Alaska to Costa Rica)................... Hydrolagus colliei (Lay & Bennett 1839)

- Anterior edge of dorsal-fin spine serrated; uniform brown across entire body with or without a distinct white spot on the lateral side above the pectoral fins............................................................................. 6

6 Snout blunt; EYL more than 40% HDL; tail region short and stout, PCA less than 57% BDL; uniform brown across entire body with a distinct white spot on the lateral side above the pectoral fins (Galapagos Islands)................................................................................. Hydrolagus alphus Quaranta, Didier, Long & Ebert 2006

- Snout pointed at tip; EYL less than 40% HDL; tail region elongate and slender, PCA more than 58% BDL; uniform brown across entire body with no white markings ( Mexico to Chile)................ Hydrolagus macrophthalmus de Buen 1959

7 EYL more than 10% BDL; two narrowly spaced columns of serrations on the posterolateral edges of the distal 66–75% of spine (in adults); uniform overall medium grey on dorsal and lateral parts extending to near the ventrum, and dorsum with many irregular circular and elongate white blotches (Galapagos Islands)................................................................................................. Hydrolagus mccoskeri Barnett, Didier, Long & Ebert 2006

- EYL less than 9% BDL; spine serrations very worn, posterior edge of spine serrated for last 6.5–13% of spine length (in adults); uniform dark brown to black across entire body with a lighter band over the snout ( Southern California, U.S.A. to Chile)............................................. Hydrolagus melanophasma James, Ebert, Long & Didier 2009

8 Tooth-plates with ridges and knobs; eyes virtually above mouth; upper edge of caudal fin without denticles or tubercles (Southern California, U.S.A., to Peru)......................................... Harriotta raleighana Goode & Bean 1895

- Tooth-plates nearly smooth; eyes distinctly behind level of mouth; caudal tubercles present along the upper edge of caudal fin .................................................................................................... 9

9 Snout broad and paddle-shaped with fleshy tip; junction of supraorbital and infraorbital canals on ventral side of snout closer to the tip of the snout than to the nasal canal; ONC/TIO greater than 1.4, TIO/SWF less than 1.5, TIO/LNC less than 3.0; 25–47 dorsal caudal tubercles in mature specimens; even dark brown color over entire body ( Costa Rica to Peru)............................................................. Rhinochimaera africana Compagno, Stehmann & Ebert 1990

- Snout narrow and conical shaped with the tip narrow and stiff; junction of supraorbital and infraorbital canals on ventral side of snout nearly equidistant between the tip of the snout and the nasal canal; ONC/TIO less than 1.4, TIO/SWF greater than 1.5, TIO/LNC greater than 3.0; 36–62 dorsal caudal tubercles in mature specimens; pale brownish-gray body color with fins darker ( Peru).............................................................. Rhinochimaera pacifica (Mitsukuri 1895)