Odontostilbe mitoptera (Fink & Weitzman 1974)

Cheirodon mitopterus

Compsura gorgonae (not Evermann and Goldsborough).—López, 1972:101 [listed from Rio Cocle del Norte, HL–172], 106 [discussion of lateral-line length].

MATERIAL EXAMINED

(All specimens from Panama)

*USNM 208539, holotype, a male 35.0 mm: Cocle Province, Rio Cocle del Norte basin, Rio Tucue at junction of river and road between Tucue and Tambo, coll. J. D. McPhail, 28 Aug. 1972.

*USNM 208513, paratypes, with same data as holotype; 7 specimens 28.5–36.8 mm (1 cleared and stained).

*ANSP 121987, paratype, with same data as holotype; 1 specimen 30.9 mm.

*BMNH 1973.2.16;1, paratype, with same data as holotype; 1 specimen 30.4 mm.

USNM 208540, Cocle Province, Rio Cocle del Norte basin, Rio Tucue, near village of Tucue in headwaters of Rio Cocle del Norte, H. Loftin and W. Kosan, 15 Sept. 1962; 12 specimens 25.7–33.4 mm (HL–171; A5–1).

USNM 208514, Cocle Province, Rio Cocle del Norte basin, Rio Tambo, near Tambo and Toabre, in headwaters of Rio Cocle del Norte, H. Loftin and W. Kupfer, 15 Sept. 1962; 14 specimens 24.6–33.1 mm (2 cleared and stained) (HL–172; A5–2).

USNM 208541, Cocle Province, Rio Cocle del Norte basin, stream near Toabre road (either the Rio Toabre or a small tributary of it) near Tambo, R. Dressier, Sept. 1972; 12 specimens 28.4–35.1 mm.

Tables include 10 specimens used in the description and 10 specimens each from USNM 208540 and USNM 208514.

DESCRIPTION.—Standard length of examined specimens 24.9–36.8 mm. Body elongate, compressed laterally; greatest body depth 23.6–38.3. Predorsal body profile somewhat convex, with a slight concavity at nape. Body profile nearly straight to slightly convex between posterior dorsal-fin base termination and anterior base of adipose fin. Posterior to adipose fin, body profile continuous as a straight line to procurrent caudal-fin rays. Distance from eye to dorsal-fin origin 29.8–49.7; distance from dorsal-fin origin to caudal-fin origin 44.0–74.3. Ventral body profile very gently rounded from jaws to anus, then with a slight ventral slope to anal-fin origin; steepest inclination of ventral profile ventral to jaws. Ventral body profile protrudes ventrally its greatest distance just anterior to pelvic-fin origin. Body profile along anal-fin base straight or very slightly convex; between posterior anal-fin termination and procurrent caudal rays body profile slightly concave. Caudal peduncle depth 8.5–14.7; peduncle length 13.1–21.0.

Head length 18.5–28.7. Eye diameter 7.9–12.9. Snout length 4.3–7.4. Least bony interorbital width 5.7–9.2. Maxillary moderate, sloping ventrally and posteriorly, forming an angle of about 50 degrees to longitudinal body axis; upper-jaw length 6.2–9.9. All teeth symmetrical, with 7–10 cusps (except the small posterior dentary teeth discussed below), with median cusps longest and at least 1 enlarged median cusp; all teeth in a single series (Figure 7). Maxillary with 2–3, usually 2, teeth; premaxillary with 5 teeth in all specimens. Dentary with 8 to 10 teeth, broader than those of maxillaries, becoming smaller toward rictus, row ending in a small conical tooth. No teeth on vomer, palatines, or pterygoids.

Fontanel moderate, that part anterior to epiphyseal bar about as long as greatest width of fontanel posterior to bar. Gill rakers moderate, 18–20, usually 19. Circumorbital bones well ossified, infraorbital 3 wide, contacting the preopercle ventrally, and with a narrow naked posterior area.

Scales moderately large, cycloid, with concentric circuli, and about 4–6 radii on exposed posterior field. Lateral line complete, with up to 37–38 perforated scales and a short fleshy tubular extension onto middle caudal-fin rays. Lateral line with a ventral curve on side of body, approaching midline at end of caudal peduncle. Lateral scales 34–36, usually 35 (often irregular and difficult to count with accuracy); scales above lateral line 5–6, usually 5; scales below lateral line 3–4, usually 4. Predorsal scales about 11–12. Scale sheath at base of anal fin of about 6 scales. Axillary scale present dorsal to pelvic-fin insertion. Caudal fin with scales arranged much as in C. dialepturus, that is, with approximately 2 rows of irregular scales caudad to the more regular scales of the caudal peduncle, extending slightly over caudal fin (some of those near midline attached to fin membrane). Usually with each of 2 or 3 posteriormost scales at midline longer than deep.

Dorsal fin with ii,9 in all specimens. Dorsal-fin origin anterior to anal-fin origin, posterior to pelvic-fin origin, nearer eye than caudal-fin base. Distance from tip of snout to dorsal-fin origin 40.6–68.4. In adult males second or third rays extend as a short filament, in females second or third ray of dorsal fin longest; in both sexes posterior rays shorter, forming a slightly rounded posterior margin to fin; length of longest ray 23.2–39.8, holotype damaged.

Anal fin with 4 unbranched rays and 17–19, usually 18, branched rays. First unbranched ray not always visible except in radiographs. Origin of anal fin posterior to midpoint of standard length 49.7–85.0. Fourth through eighth or ninth anal rays longer, with successive posterior rays shorter, forming an abruptly protruding fin margin anteriorly and a straight or slightly convex margin posteriorly. Dorsally recurved anal-fin hooks present in adult males only; these occur on posterior unbranched ray and on posterior branches of first through seventeenth (1 specimen, holotype), first through fifteenth (1 specimen not fully matured), first through fourteenth (1 specimen), and first through sixth (1 immature specimen) branched rays; only 1 hook or bilateral pair of hooks per bony ray segment; fin often fleshy around hooks. Posteriormost branched anal-fin rays straight, not bending anteriad.

Pectoral fin with 1 unbranched ray and 11–12, usually 11, branched rays. Pectoral fins of males reach slightly beyond pelvic-fin origin; in females pectoral fins reach just anterior to or to pelvic-fin origin. Distance from tip of snout to dorsal end of pectoral-fin base 18.7–30.2, and length of pectoral fin from base to tip of longest ray 15.0–32.5.

Pelvic fin with 1 unbranched ray and 7–8, usually 7, unbranched rays, distal tip in males reaching to fifth branched anal ray, in females distal tip reaching from anterior to or just to anal-fin origin. Distance from tip of snout to pelvic-fin origin 34.9–60.0; pelvic-fin length 15.3–30.1. In males, unbranched pelvic-fin ray extended as a filament. In males, unbranched ray without hooks, first through seventh (2 specimens, including holotype), first through sixth (1 specimen, immature), and second through sixth (1 specimen, immature) branched rays with antrorse hooks, usually on the ventral surface of the rays; only 1 hook present per bony ray segment.

Caudal fin with 10/9 principal caudal rays in all specimens; fin forked, not split to base. Caudal fin symmetrical and without hooks. Ventral procurrent rays of males often somewhat longer than dorsal procurrent rays.

Precaudal vertebrae 16–17, usually 17. Total vertebrae 34–36, usually 35.

Color in alcohol: Ground color light cream brown. No humeral spot; area at “pseudotympanum” darker than sides of body. Small melanophores present on head, tip of snout, and nape; also present on scale margins of back, more numerous dorsally, forming reticulate pattern above midline. Midline with groups of melanophores forming a diffuse lateral stripe internal to scales. In some specimens melanophores less numerous or absent along sides above and below melanophores of midline. Often a few melanophores, more numerous anteriorly, in a diffusely defined lateral stripe or stripes just below midline; in more heavily pigmented specimens there is a loose reticulate pattern instead of the diffuse lateral stripes. A few scattered melanophores present between anal-fin base and midline, sometimes following myomere junctions. Silvery lateral stripe present in recently preserved specimens. Caudal spot present as an elongate oval area of dense melanophores extending onto middle caudal-fin rays. On pectoral fins melanophores present along first through fifth rays, absent on others. A few melanophores present along first through fifth pelvic-fin rays. Anal-fin rays with small melanophores along rays (occasionally on interradial membrane), more numerous proximally and distally. Dorsal fin with small melanophores along fin rays. Caudal fin with melanophores along rays and on interradial membranes, concentrated on dorsal rays of dorsal lobe and ventral rays of ventral lobe, virtually absent from middle caudal-fin rays (excepting caudal spot). In some specimens preserved for a period of years, melanophores on fins no longer visible.

Color in life: The following description has been supplied to us by Dr. J. D. McPhail: Back light green shading to bright silver on sides and belly. Reticulate scale pattern of back not conspicuous. Between anal-fin base and midline, sides translucent with a silvery coat. Two bright silver areas (almost gold in some lights) on caudal fin above and below oval caudal spot. Fins, except for pectoral, with white tips, otherwise transparent. Anal fin with microscopic flecks of red in males.

Range: Cheirodon mitopterus is found only in the Rio Cocle del Norte basin, an Atlantic drainage of central Panama.

According to McPhail (personal communication), the Rio Cocle del Norte has a fauna somewhat differentiated from the rest of Panama. The taxonomy of the forms in this river needs to be examined in terms of broad-based studies of related forms throughout Central and South America. Whether or not other forms in the river system will prove to be as distinct as C. mitopterus remains to be seen.

COMPARISONS.—Cheirodon mitopterus is allopatric in regard to all known Central American cheirodontins. Based on tooth morphology, it seems closest to C. dialepturus and C. gorgonae but differs as described under those species. Cheirodon mitopterus differs from C. affinis and C. terrabae in caudal-peduncle squamation, in having symmetrical premaxillary teeth, an enlarged median cusp on each dentary tooth, fewer scales below the lateral line (usually 4 compared to 5 or 6 in those species), fewer branched anal-fin rays (usually 18 compared with as many as 21–23 in those species), and more vertebrae (usually 35–36 vs. 31–34). Cheirodon mitopterus differs from Carlana eigenmanni in numerous features including dentition, number of branched anal rays, gill rakers, and in caudal squamation. Cheirodon mitopterus differs from Phenagoniates macrolepis in having more than 3 cusps on the teeth and a shorter anal fin, in caudal squamation, and in numerous other characters listed under C. macrolepis.

ETYMOLOGY.—From the Greek mitos (thread) and pteros (fin), in reference to the threadlike extensions of the dorsal and pelvic fins.

Cheirodon gorgonae Evermann and Goldsborough

Cheirodon gorgonae Evermann and Goldsborough, 1909:99 [original description; Gorgona, Panama], fig. 1 [holotype figured], 100, fig. 3 [teeth figured].

Cheirodon insignis (not Stcindachncr).—Eigenmann, 1915:69 [Eigenmann placed Cheirodon gorgonae Evermann and Goldsborough in the synonymy of Cheirodon insignis Steindachner].

Compsura gorgonae..—Meek and Hildebrand, 1916:274 [description], fig. 2 (teeth figured) Eigenmann, 1922:128 [generic allocation].—Breder, 1927:117 [listed; variation, range], 163 [in key].—Jordan, Evermann, and Clark, 1930:96 [listed].—Hildebrand, 1938:250 [discussion; range].—Evans, 1952:44 [listed from Chilibre].—Gosse, 1966:8 [listed from Panama Province].—Miller, 1966:784 [listed].—Bussing, 1967: 211 [in part, listed], 214 [in part, compared with Pseudocheirodon].—López, 1972:93–129 [in part, confused with C. dialepturus and C. mitopterus], 119, fig. 4 [caudal squamation figured inaccurately].

MATERIAL EXAMINED

(All specimens from Panama)

*USNM 64094, holotype, a juvenile 22.1 mm, Canal Zone, Gorgona, from small seepage pool below reservoir. A. H. Jennings, 7 Feb. 1908.

*USNM 127086, paratypes, with same data as holotype; 3 specimens 19.4 to approximately 23.0 mm (specimen damaged). Previously Bureau of Fisheries No. 5421.

*USNM 64095, paratypes, with same data as holotype; 4 specimens 19.8–21.3 mm.

*USNM 78691, Rio Frijoles, Frijoles, S. E. Meek and S. F. Hildebrand, 14 Mar. 1911; 17 specimens 22.8–26.6 mm.

*USNM 78687, Gatun River at Monte Lirrio, S. E. Meek and S. F. Hildebrand, 27 Mar. 1911; 41 specimens 22.1–25.5 mm.

*USNM 208543, creek about 2 mi E of Nueva Emperador road, H. Loftin, E. Tyson, C. Kupfer, 17 Aug. 1962; 17 specimens 24.6–28.1 mm (HL–163; A7–2).

USNM 64773, sluggish stream emptying into dammed-up lake at Gatun, A. H. Jennings, 15 Aug. 1909; 1 specimen 21.8 mm.

USNM 109254, Madden Lake, Boqueron River (above lake in current), S. F. Hildebrand, 12 Feb. 1935; 4 specimens 26.0–29.0 mm.

USNM 109255, Rio Cocoli, Miraflores Lake, S. F. Hildebrand, 2 Apr. 1937; 5 specimens 24.0–26.3 mm.

USNM 208542, creek about 5 mi W of El Llano on road, H. Loftin and C. Kupfer, 17 Mar. 1962; 4 specimens 26.7–29.4 mm (HL–132; P6–2).

USNM 78694, Reservoir Creek, Gorgona, S. E. Meek and S. F. Hildebrand, 29 Mar. 1912; 4 specimens 28.0–28.4 mm (1 cleared and stained).

ANSP 99865, creek into Rio Caimito 8 mi from Chorrera on Nuevo Emperado road, H. Loftin, E. Tyson, C. Kupfer, 17 Aug. 1962; 87 specimens, 14.8–24.5 mm (HL–162; P8–4).

ANSP 104039, Rio Perequete at bridge on IAH E of Capira, H. Loftin, 24 Mar. 1962; 9 specimens 23.3–26.0 mm (HL–139; P8–6).

The type series of C. gorgonae includes only juveniles (designated as such in the morphometric tables). For this reason, the range for adults from several lots is given in the description and in the tables; adults are from USNM 78687, 5 males and 5 females; USNM 70691, 3 males and 1 female; and USNM 208543, 6 males and 4 females. In the description, the range for a given morphometric character is given first for juveniles, then for the adults.

Also, in stating number of “cotypes,” Evermann and Goldsborough (1909) made an error in indicating number of specimens in the USNM collections (now including the Bureau of Fisheries specimens). On subtracting 4 specimens sent to other institutions from the original 11, they indicate a remainder of 8 specimens—this should be 7.

DESCRIPTION.—Standard length of examined specimens 19.4–21.3; 22.9–28.4 mm. Body elongate, compressed laterally; greatest body depth 25.7–36.7; 33.4–37.8. Predorsal body profile somewhat convex with a slight concavity at nape; concavity deepest at posterior termination of supraoccipital spine. Body profile straight or slightly convex between posterior dorsal-fin base termination and anterior base of adipose fin. Between posterior adipose-fin base and dorsal procurrent caudal-fin rays, body profile slightly convex or straight. Distance from eye to dorsal-fin origin 36.2–39.8; 38.0–43.2; distance from dorsal-fin origin to end of caudal peduncle 49.3–54.6; 50.2–54.5. Ventral body profile gently rounded from jaws to anus; steepest inclination ventral to jaws. Ventral body profile protrudes its greatest distance just anterior to pelvic-fin origin. Body profile along anal-fin base straight or slightly convex. Between posterior termination of anal-fin base and ventral procurrent caudal-fin rays, body profile straight or slightly concave. Caudal peduncle depth 11.1–14.2; 12.0–14.3; peduncle length 14.0–15.1; 13.6–17.1.

Head length 25.3–27.3; 23.5–26.3. Eye diameter 10.4–11.9; 9.2–10.8. Snout length 5.4–5.8; 5.3–5.8. Least bony interorbital 7.0–8.3; 6.5–8.1. Maxillary relatively long, sloping ventrally and posteriorly, forming an angle of about 50–60 degrees to longitudinal body axis; upper-jaw length 7.6–8.3; 7.4–8.0. All jaw teeth in a single series; teeth usually with middle cusps enlarged, forming a rounded cutting edge. Maxillary teeth 1–3, usually 2, usually with about 8 cusps, teeth broader than premaxillary teeth. Premaxillary teeth 5 in all specimens (holotype damaged), usually with 9 cusps. Dentary with about 9 teeth, anterior 5 teeth larger (with 7–8, usually 8, cusps) and posterior teeth tapering in size (the smallest has 3–5 cusps). No teeth present on vomer, palatines, or pterygoids.

Fontanel moderate, that part anterior to epiphyseal bar about as wide posteriorly and about as long as width of fontanel immediately posterior to bar. Gill rakers moderate, 16–20, usually 18–19 (holotype and juveniles not counted). Circumorbital bones well ossified, infraorbital 3 wide, contacting the preopercle ventrally and with a narrow naked area posteriorly. Infraorbital 2 not contacting the preopercle as indicated by López (1972).

Scales moderately large, cycloid with concentric circuli and about 2–5 radii on the exposed posterior field. Perforated lateral-line scales 8–18, usually 11–13 (holotype with 10), lateral line with a slight ventral curve. Lateral scales 32–33 (holotype with 33); scales above lateral line 5 (in some other lots examined, there were 6 scales above lateral line); scales below lateral line 4 in all specimens. Scale sheath at base of anal fin of about 5–7 scales. Axillary scale present dorsal to pelvic-fin origin; caudal fin without scales except as described below.

Dorsal fin with ii,9 in all specimens. Dorsal-fin origin anterior to anal-fin origin, posterior to pelvic-fin insertion, nearer eye than caudal-fin base. Distance between tip of snout and dorsal-fin origin 49.5–53.9; 51.4–56.8. Second or third ray of dorsal fin longest with posterior rays shorter, forming a slightly rounded posterior margin to fin; length of longest ray, 29.8; 27.6–32.4 (holotype and all but 1 paratype damaged).

Anal fin with 4 unbranched rays and 15–19, usually 16–17, branched rays. First unbranched ray not always visible except in radiographs. Anal-fin origin posterior to midpoint of standard length 63.1–65.6; 62.2–67.2. Fourth through eighth anal rays longer than other anal-fin rays; each posterior successive ray somewhat shorter than its predecessor, forming a protruding fin margin anteriorly and a concave margin posteriorly. Adult males with dorsally recurved hooks present on posteriormost branched ray and posterior branches of first through eleventh (1 specimen), thirteenth (2 specimens), fourteenth (7 specimens), or fifteenth (4 specimens) branched rays. Hooks, single or, usually, in bilateral pairs; only 1 hook or pair of hooks per bony ray segment; fin often fleshy about hooks. Posterior 8 or 9 branched anal-fin rays straight or slightly curved caudad, not curved anteriorly.

Pectoral fin slightly pointed or rounded, with 1 unbranched ray and 9–11, usually 10, branched rays (holotype damaged). Pectoral fins extend from just anterior to slightly beyond pelvic-fin origin. Distance from tip of snout to dorsal end of pectoral-fin base 26.7–28.6; 24.2–28.8 and length of pectoral fin from base to tip of longest ray 21.8; 20.0–25.4 (holotype and all but one paratype damaged).

Pelvic fin with 1 unbranched ray and 7–8, usually 7, branched rays, distal tip reaching from just anterior to or to anal-fin origin. Distance from tip of snout to pelvic-fin origin 46.9–49.0; 45.0–49.8; pelvic-fin length 16.0–18.0; 16.5–21.4 (holotype damaged). In males first unbranched pelvic ray usually without hooks (hooks were present on 1 specimen), first through sixth (2 specimens) or seventh (12 specimens) branched rays with antrorse hooks on ventral surface of ray; only 1 hook present per bony ray segment.

Caudal fin with 10/9 principal caudal rays in all specimens (holotype damaged); fin forked, not split to base. Upper and lower lobes usually equal in size, occasionally a large male with slightly larger lower caudal lobe. Dorsal and ventral procurrent caudal-fin rays usually protrude abruptly from caudal peduncle and each ventral ray is equal in size to its dorsal counterpart. No hooks on caudal fin. Lower caudal lobe of both sexes with a series of modified scales forming 3 pouches (Figure 10). Holotype damaged and missing these scales but scale pockets indicate presence of pouch scales; all paratypes possess pouch scales.

Precaudal vertebrae 15–16, total vertebrae 33–34, usually 33.

Color in alcohol: Ground color pale brown or tan. Melanophores form a reticulate pattern on scale pockets along back and extend over nape and top of head; these melanophores more numerous in some populations, less in others. Melanophores less numerous below midline, a few scattered above anal-fin base, often along myomere junctions; belly usually unpigmented. Humeral spot absent, but some darkening of tissues in area of “pseudotympanum.” Melanophores concentrated at posterior termination of caudal peduncle, forming a caudal spot. Dorsal, caudal, anal and, usually, pelvic fins with few scattered melanophores along fin rays, pectoral fins without pigment; otherwise all fins hyaline.

Range: Existing collections of C. gorgonae indicate a limited distribution near the center of Panama, where it occurs in both the Pacific and Atlantic drainages, in Colon and western Panama Provinces.

COMPARISONS.—Cheirodon gorgonae can be distinguished from all other Central American cheirodontins by a combination of the following three characters: modified caudal-fin scales and peduncle scales, forming pouches; symmetrical dentary teeth with enlarged median cusps and absence of antrorse hooks on the caudal fin. In the past C. gorgonae has been confused with C. dialepturus (see the discussion above of the latter). Cheirodon gorgonae does seem close to C. dialepturus but differs in having caudal scale pouches, lacking caudal-fin hooks, and in having fewer maxillary teeth (usually 2, compared with a mode of 3 in C. dialepturus).

Cheirodon gorgonae differs from C. mitopterus in many ways, including caudal peduncle squamation, color pattern, and meristic characters, including number of pectoral-fin rays (9–11, usually 10, vs. 11–12, usually 11, in C. mitopterus) and total number of vertebrae (32–34, usually 33, vs. 34–36, usually 35, in C. mitopterus). Cheirodon gorgonae differs from C. affinis and C. terrabae in having symmetrical premaxillary teeth, enlarged median cusps on the dentary teeth, forming rounded cutting edges, and a relatively longer, more slender maxillary. Cheirodon gorgonae differs from Phenagoniates macrolepis and Carlana eigenmanni in dentition, caudal scale modifications, and numerous meristic characters as described.

Cheirodon gorgonae exhibits sexual dimorphism by having retrorse hooks on the anal and pelvic fins in males. We could find no geographical or seasonal variation in this character. There is some slight variation in the formation of the caudal-fin pouches regarding size and placement of individual scales.

Cheirodon affinis (Meek and Hildebrand)

Cheirodon insignis (not Steindachner).—Evermann and Goldsborough, 1909:98 [brief description], 100, fig. 2 [teeth figured].—Eigenmann, 1915:69 [in part].

Pseudocheirodon affinis Meek and Hildebrand, 1916:pl. XVIII [photograph], 275 [new genus and species; original description; Rio Gatun, Panama].—Eigenmann, 1922:129 [listed].—Breder, 1925:143 [listed from Rio Tapia, Panama].—Breder, 1927:118 [listed; variation; range], 163 [in key].—Jordan, Evermann, and Clark, 1930:96 [listed].—Grey, 1947: 179 [listing of types (see below)].—Hildebrand, 1938:251 [brief description; range].—Gosse, 1966:8 [listed from tributary of Rio Bayano].—Miller, 1966:784 [listed; range].—Bussing, 1967:214 [compared with C. terrabae and with “C gorgonae,” a mixture of C. gorgonae and C. dialepturus], 236 [listed], 241, fig. 1 [photograph].—Géry, 1972:73 [brief discussion in comparison with undescribed characid from Ecuador].—López, 1972:93–129 [compared with “C. gorgonae” (a mixture of C. dialepturus, C. mitopterus, and C. gorgonae) and C. terrabae; variation of several characters (discussed below); distribution], 119, fig. 3B [teeth figured].

MATERIAL EXAMINED

(All specimens from Panama)

*FMNH 8944, holotype, a male 29.5 mm: Rio Gatun, Monte Lirio, S. E. Meek and S. F. Hildebrand, 28 Mar. 1911.

*USNM 78668, Gatun River, Monte Lirio, S. E. Meek and S. F. Hildebrand, 28 Mar. 1911; 39 specimens 25.1–37.8 mm.

USNM 208519, Cocle Province, Rio Grande basin, Rio Churube at bridge on IAH 13 mi E of Nata, H. Loftin and C. Kupfer, 25 Feb. 1962; 34 specimens 22.3–32.1 mm (5 cleared and stained) (HL–118; P10–3).

USNM 208520, Panama Province, Rio Bayano Basin, creek about 5 mi W of El Llano on road, H. Loftin and C. Kupfer, 17 Mar. 1962; 36 specimens 27.2–39.2 mm (2 cleared and stained) (HL–132; P6–2).

USNM 62943, small ditch of “pure” running water at Tabernilla, Canal Zone, A. H. Jennings, 24 July 1908; 6 specimens 24.3–29.7 mm.

USNM 78667, Gatun River at Mitchelville, S. E. Meek and S. F. Hildebrand, 27 Mar. 1911; 36 specimens 28.3–37.9 mm.

USNM 208545, Canal Zone, small ditch of “pure” running water at Tabernilla, A. H. Jennings, 24 July 1908; 4 specimens 24.7–25.8 mm.

USNM 78657, Limon Creek, Alhajuela, S. E. Meek and S. F. Hildebrand, 26 Feb. 1911; 9 specimens 24.4–35.2 mm.

USNM 78664, Gorgona Reservoir Creek, Gorgona, Canal Zone, S. E. Meek and S. F. Hildebrand, 29 Mar. 1912; 8 specimens 34.8–42.8 mm.

USNM 78681, Rio Missimbi, Empire, Canal Zone, S. E. Meek and S. F. Hildebrand, 8 Feb. 1911; 12 specimens 28.4–34.9 mm.

USNM 78684, Trinidad River, Agua Clara, Canal Zone, S. E. Meek and S. F. Hildebrand, 10 Mar. 1911; 24 specimens 24.5–35.3 mm.

USNM 208544, Panama Province, Rio Bayano basin, creek about 2½ mi W of El Llano road, H. Loftin and C. Kupfer, 17 Mar. 1962; 10 specimens 29.3–34.0 mm (HL–131; P6–3).

USNM 208518, Veraguas Province, Rio San Pedro basin, creek at bridge 12 mi W of Santiago on road to Sona, H. Loftin, E. Tyson, R. Yerger, 28 Jan. 1962; 49 specimens 18.6–29.3 mm (2 cleared and stained) (HL–105; P16–9).

USNM 208548, Cocle Province, Rio Grande Basin, Rio Cocle at road just outside La Pintada, H. G. Loftin, 23 Mar. 1962; 59 specimens 22.2–35.0 mm (HL–135; P10–2).

USNM 208550, Rio Santa Maria Basin, Rio Estero Salado (coastal stream) on IAH about 5 mi W of Aguadulce, H. Loftin and E. Tyson, 15 Oct. 1961; 11 specimens 24.3–29.4 mm (HL–24; P11–2).

USNM 208549, Veraguas Province, Rio San Pedro basin, river at bridge about 17 mi W of Santiago on road to Sona, H. Loftin E. Tyson, R. Yerger, 28 Jan. 1962; 12 specimens 21.8–27.7 mm (HL–104; P16–10).

USNM 208551, Cocle Province, Rio Grande basin, Rio Anton at town of Anton on IAH, H. Loftin and E. Hcslop, 11 Mar. 1962; 2 specimens 29.9–31.2 mm (HL–I20; P9–21).

USNM 208515, Cocle Province, Rio Grande basin, swampy creek at IAH about 2 mi E of Nata. H. Loftin and E. Tyson, 15 Oct. 1961; 6 specimens 29.7–35.7 mm (2 cleared and stained) (HL–21; PI0–5).

MCZ 45827, “Jesus Christ Stream” trib. of Chagres River near Gamboa, 9°7′N, 79°42′W. I. Rubinoff, et al., 6 Apr. 1967; 1 specimen 30.0 mm.

USNM 210991, two collections mixed together, Cocle Province, stream at El Roble at IAH or Veraguas Province, Rio San Pedro at San Pedro on IAH, M. and W. Bussing, 27 January 1971; 3 specimens 26.5–32.2 mm.

Meek and Hildebrand (1916) listed the holotype number as FMNH 8941 and stated that it was “38 mm in length.” Grey (1957) stated that the above number is an error and that the actual number is 8944. Mr. Loren P. Woods has kindly reexamined the catalog and confirmed that FMNH 8944, the number in the bottle, is indeed correct. The holotype is 29.5 mm in SL.

Grey (1947) listed 261 paratypes from several areas in Panama. We do not accept type status for any of these fishes as Meek and Hildebrand (1916), although using more than 1 specimen for their description, listed only the holotype, adding that “numerous specimens were preserved.”

Tables include specimens used in the following description and 10 specimens each USNM 208519 and USNM 208520.

DESCRIPTION.—Standard length of examined specimens 22.5–38.8 mm. Body elongate, compressed laterally; greatest body depth 38.0–42.1. Predorsal body profile convex with a slight concavity at nape; concavity deepest at posterior termination of supraoccipital spine. Body profile slightly convex between posterior dorsal-fin base and adipose fin; posterior to adipose fin body profile with an upward slope to procurrent caudal-fin rays. Distance from eye to dorsal-fin origin 38.9–41.9; distance from dorsal fin to end of caudal peduncle 53.6–56.0. Ventral body profile rounded to anus; steepest inclination ventral to jaws. Ventral body profile protrudes ventrally its greatest distance just anterior to pelvic-fin insertion. Body profile straight or slightly curved along anal-fin base; at posterior anal-fin termination profile concave to procurrent caudal-fin rays. Caudal-peduncle depth 12.3–13.7; peduncle length 11.9–14.6.

Head length 23.4–25.4. Eye diameter 9.3–10.6. Snout 5.3–6.2. Least bony interorbital width 8.2–9.0. Maxillary short, sloping ventrally and posteriorly, forming an angle of 45–50 degrees to longitudinal body axis; upper-jaw length 6.2–7.1. All teeth with 7–8, usually 8, cusps (except smallest maxillary tooth, which has 5–6 cusps, and the smallest dentary teeth, which are quinquecuspid or conical); all in a single series. Maxillary teeth 3, with a rounded cutting edge and with outer cusps equidistant from tooth base. Premaxillary teeth 5 in all specimens with a rounded cutting edge, cusps on anterior cutting edge begin nearer to tooth base than cusps on posterior cutting edge. Dentary with 7–9, usually 7–8, teeth, anterior teeth larger, becoming smaller (usually conical) posteriorly; teeth with an even cutting edge, median cusp not elongate, long axis of anterior dentary teeth extending dorsoanteriorly. No teeth present on vomer, palatines, or pterygoids.

Fontanel moderate, length of that part anterior to epiphyseal bar slightly less than width of fontanel posterior to bar. Gill rakers moderate, 17–20, usually 18. Circumorbital bones well ossified, infraorbital 3 wide, contacting preopercle ventrally, and with a naked area posteriorly.

Scales moderately large, cycloid with concentric circuli and about 4–8 radii on exposed posterior field. Lateral lines of holotype and specimens from USNM 78668 incomplete, with a slight ventral curve with 7–11, usually 9 (10 in holotype), perforated scales. In some other lots examined lateral line variable (e.g., USNM 208520), with some specimens having 10–11 perforated scales and others in the same lot with as many as 33 perforated scales (a complete lateral line). This variation not present in all populations but occurs throughout range of this species (see discussion below). Lateral scales 32–33 (33 in holotype); scales above lateral line 5–6, usually 6; scales below lateral line 4–5, usually 5. Predorsal scales 9–12, usually 10–11. Scale sheath at base of anal fin of about 5–6 scales. Axillary scale present dorsal to pelvic-fin insertion; caudal fin without scales.

Dorsal fin ii,9 in all specimens. Dorsal-fin origin anterior to anal-fin origin, posterior to pelvic-fin insertion, nearer eye than caudal-fin base. Distance from tip of snout to dorsal-fin origin 51.7–54.5. Third or fourth ray of dorsal fin longest, with posterior rays shorter, forming a slightly rounded posterior margin to fin; length of longest ray 30.0–30.9.

Anal fin with 4 unbranched rays and 19–21, usually 20, branched rays. First unbranched ray not always visible except in radiographs. Anal-fin origin posterior to midpoint of standard length 63.6–67.5. Fourth through ninth or tenth anal-fin rays longer, with posterior rays shorter, forming a protruding fin margin anteriorly and a straight or slightly concave fin margin posteriorly. Dorsally recurved anal-fin hooks present in males only (see discussion below) on last unbranched ray and first through sixth or seventh (rarely to eleventh) branched rays (on first through sixth in holotype); usually only 1 hook or bilateral pair of hooks per bony ray segment (rarely with 2 hooks on same side of segment); fin often fleshy around hooks.

Pectoral fin with 1 unbranched ray and 10–11, usually 11, branched rays. Pectoral fins reach anterior to or just to pelvic-fin insertion. Distance from tip of snout to dorsal end of pectoral-fin base 24.5–26.4 and length of pectoral-fin base to tip of longest ray 20.1–21.8.

Pelvic fin with i,7 rays in all specimens, distal tip reaching well anterior to or just to anal-fin origin. Distance from tip of snout to pelvic-fin insertion 47.4–49.8; pelvic-fin length 16.9–19.1. In males, unbranched ray and first or second through sixth or seventh branched rays with antrorse hooks, usually on ventral surface of ray segment (unbranched ray often without hooks); 1 hook, rarely 2, present per bony ray segment (in holotype all pelvic rays with hooks). See below for further discussion.

Caudal fin with 10/9 principal rays; fin not deeply forked, not split to base; caudal-fin lobes symmetrical. Dorsal and ventral procurrent caudal rays of equal size; ventral procurrent rays not enlarged and extended. No hooks on caudal rays.

Precaudal vertebrae 15–16, usually 16. Total vertebrae 32–33, usually 33.

Color in alcohol: Ground color pale brown, back and nape darker brown. Small melanophores present on sides bordering scale pockets, more numerous dorsally, forming a reticulate pattern above midline and sparingly across belly (not as evident in type as in some other specimens) and loosely following myomere junctions below midline above anal fin. Melanophores sometimes slightly concentrated at “pseudotympanum,” forming a weak humeral spot. Melanophores usually concentrated just dorsal to midline, forming a lateral stripe which terminates in a large spot at end of caudal peduncle, extending to middle caudal rays. Lateral stripe not always pronounced but caudal spot always present. Type with silvery cheeks and with a broad, silvery lateral stripe; this silvery coloration more or less evident in other specimens examined. Dorsal fin with melanophores on interradial membranes, more concentrated distally. Caudal fin with melanophores on interradial membranes, often concentrated near middle caudal rays. Anal fin with melanophores on interradial membranes (occasionally on rays) proximally, but melanophores lacking on distal one-half to one-fourth of fin. Pectoral fin with melanophores ventrally on rays, lacking on interradial membranes. Pelvic fins with melanophores primarily on interradial membranes, concentrated distally.

Color in life: Based on 1 male and 3 females from USNM 210991 observed alive in our aquaria (with dark substrate), the color is as follows. Back light yellowish-green shading to bright silver on sides and belly. Burnished silver lateral stripe. Reticulate scale pattern of back conspicuous. Between anal-fin base and midline, side translucent yellowish green, with loose pattern of melanophores along myomere lines. Light yellowish areas on caudal fin above and below broad caudal spot. Dorsal, anal, and pelvic fins with small white tips; all fins but pectorals yellowish, pectoral fin translucent.

Range: Collections of C. affinis are most numerous from the Canal Zone, probably reflecting the extensive collecting in that area early in this century. Loftin (1965) extended the known range of this species from east-central Panama Province to central Veraguas Province. The species is now known in Pacific drainages throughout central Panama and in Atlantic drainages at least throughout the Canal Zone.

COMPARISONS.—Cheirodon afjinis is a common species in central Panama. It is sympatric with C. dialepturus and C. gorgonae and there has been some confusion among these three species. Cheirodon afjinis is distinguished from the other two by the combination of its lack of both caudal-fin hooks and modified caudal-peduncle scales, together with its possession of asymmetrical premaxillary teeth and dentary teeth without an enlarged median cusp. It differs from C. mitopterus in dentitional characters also, as well as caudal peduncle scalation, and other characters as described in the discussion of C. mitopterus.

Cheirodon affinis is closest to C. terrabae but apparently differs from that form in having fewer dentary and maxillary teeth, a smaller modal number of branched anal-fin rays, and gill rakers. Most populations of C. affinis have an incomplete lateral line, whereas terrabae has the lateral line complete.

VARIATION.—Previously, C. affinis has been described as lacking anal-fin hooks (Bussing, 1967). Our examination has shown that retrorse hooks are present on the anal and pelvic fins of males collected between the months of March and July and are absent in those specimens collected in the months of October and January. We were unable to obtain collections from every month, so our information on this variation is incomplete. Also we had no collections from the same locality from different seasons, and the presence or absence of hooks could be explained as population variation. However, numerous collections from different seasons are from adjacent localities in the Canal Zone and these showed seasonal variation. Other than the hooks on the fins of males, we could find no obvious sexual dimorphism.

Bussing (1967) and López (1972) discussed the length of the lateral line in C. affinis. We have essentially confirmed their findings, as we have found specimens from several localities with complete or nearly complete lateral lines. We could find no geographical or ecological correlation with the variation in this character.

López (1972) found a correlation in length of the maxillary and geographical distribution. We found no significant correlation with total upper-jaw length and distribution. See our comments on this character in the discussion of C. dialepturus.

Cheirodon mitopterus is a species of fish in the family Characidae.