Apterichtus Duméril 1806

Hibino, Yusuke, 2015, A review of the finless snake eels of the genus Apterichtus (Anguilliformes: Ophichthidae), with the description of five new species, Zootaxa 3941 (1), pp. 49-78 : 50-52

Apterichtus Duméril 1806

Caecilia Lacepède 1800:134 (type species Caecilia branderiana Lacepède 1800 = Muraena caeca Linnaeus 1758 , by monotypy; preoccupied by Caecilia Linnaeus 1758 , a genus of Amphibia).

Apterichtus Duméril 1806:331 (type species Muraena caeca Linnaeus 1758 , by monotypy). Also spelled Apterichthys, Apterichthe , and Apterichtes , by other authors.

Typhlotes Fischer 1813:81 (replacement name for Caecilia Lacepéde , preoccupied).

Branderius Rafinesque 1815:93 (replacement name for Caecilia Lacepède , preoccupied).

Ophisurapus Kaup 1856a:52 (type species Ophisurapus gracilis Kaup 1856 , by monotypy).

Ophisuraphis Kaup 1856b:29 (emendation for Ophisurapus Kaup 1856a ).

Verma Jordan and Evermann 1896:374 (type species Sphagebranchus kendalli Gilbert 1891 , by original designation).

Diagnosis. Subfamily Ophichthinae , tribe Sphagebranchini . Body elongate, cylindrical, pointed at both ends; head and trunk nearly equal to or slightly shorter than tail. All fins absent. Snout sub-conical, flat on underside. Anterior nostrils either in a short tube or flush with the snout; posterior nostrils outside of mouth. 3 or 4 preopercular pores, 3 to 9 supratemporal pores. Gill openings ventral, converging forward, their isthmus narrow. Teeth conical and uniserial on jaws and typically on vomer, becoming biserial on vomer in larger specimens of some species.

Remarks. Blache and Bauchot (1972) considered monodi Roux 1966 , kendalli ( Gilbert 1891) , and anguiformis ( Peters 1877) to belong to Verma , rather than Apterichtus (which they thought to contain caecus and gracilis ). McCosker (1977), on the basis of adults, and Leiby (1981), on the basis of larvae, recognized Verma as a junior synonym of Apterichtus . The characters which Blache and Bauchot used to separate species of Verma from those of Apterichtus included: posterior nostril above the upper lip and outside of the mouth (vs. on the ridge of the upper lip); mandibular symphysis under the level of the eye or near the snout tip (vs. beneath the eye or closer to the snout); and the anterior nostril inserted in advance of the level of the intermaxillary teeth (vs. well in advance of the intermaxillary teeth). After our examination of many additional specimens and the discovery of several new species we conclude that there is considerable overlap in those characters, thereby disallowing the recognition of Verma and Apterichtus as separate genera or subgenera within the complex.

Prior to our study, all species of Apterichtus were known to possess a tubular anterior nostril, a diagnostic character used to separate them from those of Ichthyapus Brisout de Barneville 1847, whose anterior nostrils lack or have a short tube. We have discovered and herein describe 2 new species of Apterichtus which lack an anterior nostril tube. We include them within Apterichtus on the basis of their eye size and location (moderate in size and located along the side of the head, vs. small and dorsolaterally located in Ichthyapus ) and the posterior nostril condition (outside vs. inside the mouth). “ Apterichtus ” keramanus Machida, Hashimoto & Yamakawa 1997 has a tube-like nostril, however we conclude that it is a species of Ichthyapus (see The Status of “ Apterichtus ” keramanus in this paper).

The western Pacific genus Cirricaecula Schultz 1953 is the only additional ophichthine with entirely finless species. Its two species, C. johnsoni Schultz 1953 and C. macdowelli McCosker & Randall 1993 , differ from those of Apterichtus in possessing conspicuous labial cirri and a posterior nostril within the mouth. The anterior nostril, like that of nearly all Apterichtus , is within a tube.

Etymology. From the Greek απτερόν (apteron), without fins, and ίχθύς (ichtus, more correctly written ichthys; masculine), fish.