Chiloconger similis

Smith, David G. & Karmovskaya, Emma S., 2003, A new genus and two new species of congrid eels (Teleostei: Anguilliformes: Congridae) from the Indo­West Pacific, with a redescription and osteology of Chiloconger dentatus, Zootaxa 343, pp. 1-19 : 13-14

The status of Chiloconger similis

Chiloconger similis Wade, 1946 was described from a single individual collected off Cape San Lucas, Baja California, Mexico. Based on examination of this specimen and eight similar specimens from the Revillagigedo and Galapagos Islands, we conclude that C. similis should be placed in Paraconger rather than Chiloconger . Below, we compare the condition of seven character states among Chiloconger philippinensis , C. dentatus , C. similis , and Paraconger californiensis , the last three all sympatric in the eastern Pacific.

1). Labial flange. In Chiloconger dentatus , the flange ends anteriorly at about the level of the base of the anterior nostril. There is no superficial groove extending ventrally to the IO2 pore. In C. similis and P. californiensis the flange proper ends anteriorly about opposite the base of the anterior nostril, but a superficial groove continues ventrally, connecting with a depression containing the IO2 pore.

2) Adnasal (IO1) pore. In Chiloconger philippinensis , this pore is small and papillalike, just behind the upper edge of the base of the anterior nostril (in C. dentatus , the presence of the adnasal pore is problematical). In C. similis , this pore is moderately large, with a raised rim, just posterior to the base of the anterior nostril, in the space between the anterior nostril and the groove containing the IO2 pore. In P. californiensis , the condition is much like that of similis .

3) Second infraorbital (IO2) pore. In C. dentatus and philippinensis , this pore is located in an isolated depression, not a groove, on the outside of the lip, ventral and slightly anterior to the anterior end of the labial groove, and it has a raised rim. In C. similis , the pore is tubular and concealed in the labial groove, larger and more open, with a thin­walled rim. In P. californiensis , it is much like that of similis but smaller and more papilla­like, with thick walls and a smaller opening.

4) Fifth infraorbital (IO5) pore. In C. dentatus and philippinensis , this pore is located on the side of the head immediately above the posterior end of the labial flange (i.e., it is not on the flange itself). In C. similis and P. californiensis , the pore is on the dorsal edge of the flange, below the middle of the eye

5) Second supraorbital (SO2) pore. In C. dentatus and philippinensis , this is an open pore, slightly dorsal and distinctly anterior to the anterior nostril, by a distance substantially greater than the diameter of the pore. In C. similis , the pore is open, larger, and closer to the base of the anterior nostril, by a distance less than the diameter of the pore. In P. c a l ­ iforniensis, the pore has a raised rim and is in a slit or groove immediately dorsal to the base of the anterior nostril, the ventral rim of the pore touching the base of the nostril.

6) Upper end of gill opening. In C. dentatus and philippinensis , the upper end of the gill opening is located slightly below the upper end of the pectoral­fin base, at about the level of the third or fourth ray; the pectoral fin thus is not entirely enclosed by the gill opening. In both C. similis and P. californiensis , the upper end of the gill opening is above the top of the pectoral­fin base, enclosing the entire fin base.

7) Maxillary teeth. In C. dentatus and philippinensis , the maxillary teeth are in two to four series, conical, about equal size, and not forming a cutting edge. In P. californiensis , the teeth are in one or two rows, those of the outer row larger, compressed, their tips bladelike, closely spaced and forming a cutting edge. Chiloconger similis is somewhat intermediate in this respect. The teeth are mostly triserial, but those of the middle row are larger, pointed, and form a saw­like ridge.

Of the seven characters described above, Chiloconger similis resembles Paraconger californiensis in five of them (labial flange, adnasal pore, IO5 pore, SO2 pore, and pectoral fin/gill opening. In the other two characters (IO2 pore and maxillary teeth), C. similis is somewhat intermediate. In most if not all of these characters, the Paraconger condition is more derived. Indeed, the gill­opening/pectoral fin character is unique among congrids and has always been diagnostic for the genus Paraconger . We thus conclude that Chiloconger similis should be placed in Paraconger and henceforth known as Paraconger similis ( Wade, 1946) .

Comparative study material. Paraconger similis : CAS 86747 (2: 142–145), Galapagos Is., Genovesa Id., 24 November 1995, J. E. McCosker, et al.; LACM 21712 (holotype: 251), Inner Gorda Bank, Cape San Lucas, Lower California, Mexico, 23° 02' 30" N, 109° 03' 07" W, 59–78 fm (108–143 m), 17 February 1940; LACM 43616­1 (2: 395–423), Revillagigedo Is., near Clarion Id., 5–11 January 1984; SIO 87–128 (3: 311–345), Revillagigedo Is., 19° 03' N, 112° 08' W, by hook and line; USNM 362109 (1: 351), Galapagos Is., 1°23' 12" N, 91° 48' 36" W, 400 ft (122 m), 21 June 1998, J. E. McCosker. Paraconger californiensis : USNM 177696 (holotype: 505), Mexico, Sinaloa, Gulf of California, 25 miles southeast of Bahía Topolobampo, 22–27 fm (40–49 m), 7–13 June 1956, W. Baldwin.