OCCASIONAL PAPERS OF THE California Academy of Sciences No. 73, 4 pages, 1 figure. June 6, 1969 A New Pipefish from the Virgin Islands, Micro gnathus dawsoni By Earl S. Herald Steinhart Aquarium, California Academy of Sciences San Francisco, California 94118 SAN FRANCISCO PUBLISHED BY THE ACADEMY 1969 LiBRARY OCCASIONAL PAPERS OF THE CALIFORNIA ACADEMY OF SCIENCES No. 73, 4 pages, 1 figure. J""t' 6, 1969 A New Pipefish from the Virgin Islands, Micrognathus dawsoni By Earl S. Herald Steinhart Aquarium, Californio Academy of Sciences San Francisco, California 94118 Twenty-five species of Atlantic American pipefishes have previously been recognized (Herald, 1965), and the addition of an intriguing new species from St. John brings the total to 26. It can be expected that deepwater pipefishes will be discovered in the future, but it is quite startling that this shallow water form should have escaped notice until this time. The syngnathid genus Micrognathus is one of the intermediates on the evolutionary line believed to lead from the Parasyngnathus-type pipefishes with everted brood pouch closure (E-BPC) to the Hippocampus-iype seahorse (Herald, 1959). There are 12 species in Micrognathus, four in the Atlantic including the new one described herein, and eight in the Pacific. Two sub- genera are recognized: Anarchopterus Hubbs with only two species, both Atlantic, has smooth body ridges and lacks the anal fin. The subgenus Micrognathus Duncker with two Atlantic and eight Pacific species has sharp body ridges and does have the anal fin. Micrognathus (Micrognathus) dawsoni Herald, new species. HoLOTYPE. USNM 203148, female 134.5 mm. standard length (139 mm. total length); Fish Bay, St. John, U.S.V.I.; depth 5 feet, sand bottom with some Thalassia and scattered algae. Chemfish ichthyocide ; 16 November 1966. C. E. Dawson and A. Damman, collectors. Diagnosis. Dorsal fin rays 30; pectoral 13-13; anal 3; caudal 10; dorsal fin covering 7 rings: iVi trunk rings and V-2A tail rings; trunk rings W/-2] tail rings ^35 (see discussion below); snout 9.2 mm.; head 16.9 mm.; dorsal fin base 12.9 mm.; trunk 39.6 mm.; tail 78.0 mm.; pectoral base 1.7 CALIFORNIA ACADEMY OF SCIENCES [Occ. Papers Micrognathus dawsoni Herald. Holotype, USNM 203148, 139 mm female; Fish Bay, St. John, U. S. V. I. Figure 1. Micrognathus dawsoni Herald, new species. mm.; pectoral length 2.3 mm.; head-in-standard length 7.95; snout-in-head 1.84; dorsal fin-base-in head 1.31; head-in-dorsal fin base 0.76; brood pouch details unknown; body ridge pattern typical of Micrognathus, i.e., lateral trunk ridge deflected ventrally at anal ring, then continuous with inferior tail ridge; superior tail ridge deflected ventrally at dorsal fin becoming lateral tail ridge, and ending free at anal ring. Belly flat. Color: light tan; slightly darker above lateral trunk ridge; scutella dark-rimmed; caudal dark. Description. ^Median snout ridge smooth, beginning at interorbital area and extending forward one-half length of snout. Superior ocular ridge extends forward for one-half eye diameter, and posteriorly one-third of an eye diameter. Mid opercular ridge equal to one-third length of opercle. Pectoral cover plate with distinct median ridge and indistinct superior ridge. Nuchal ridge tri-lobed. Body ridges well developed but without sharp edges. Comparison. Among the eight species of Atlantic American pipefishes that have the lateral trunk ridge continuous with the inferior tail ridge, two species only, i.e., Ichthyocampus pawneii and Penetoptcryx nanus, lack the lateral tail ridge. The remaining six species, including the four Micrognathus, have this ridge well developed. The seahorse pipefish, Amphclikturus dcn- driticus, as well as the true seahorses, Hippocampus species, can be identified by their prehensile tails. Oostethus and Micrognathus may be separated by the short tail of the former with number of rings being only 4-7 more than number of trunk rings; by contrast, Micrognathus has about twice as many tail rings as trunk rings. Micrognathus dawsoni has 30 dorsal fin rays, whereas the other three Atlantic American members of the genus have only 16 22 dorsal rays. Comments. In most pipefishes, the normal position of the anus is at the posterior end of the last trunk ring with the anal fin on the anterior end of the first tail ring. This relationship does not hold for M. dawsoni, since the anus is far enough forward on the anal ring so that there is room for the anal fin on the posterior portion of the ring. Hence to be thoroughly accurate in the ring counts they should be shown as 17'/-> + 'l>35. This could be in- terpreted as 18 + 35 or 17 -J- 36; the writer prefers the latter. No. 73] HERALD: XEW PIPEFISH FROM VIRGIX ISLANDS 3 Named in honor of C. E. Dawson, who collected and recognized this pipefish as different from the other Atlantic syngnathids. LITERATURE CITED Herald, Earl S. 1959. From pipefish to seahorse — a study of phylogenetic relationships. Proceedings of the California Academy of Sciences, 4th ser., vol. 29, no. 13, pp. 465-473, 3 figs. 1965. Studies on the Atlantic American pipefishes with descriptions of new species. Proceedings of the CaHfornia Academy of Sciences, 4th ser., vol. 32, no. 12, pp. 363-375; 2 tables. 'K \l: ■) ^^ lifliJ K fl i i 3 1 t