Vexillichthys Armbruster, 2024

Armbruster, Jonathan W., 2024, A new genus for the Blackfin Sucker, Thoburnia atripinnis (Cypriniformes: Catostomidae), Zootaxa 5536 (2), pp. 325-335 : 327-331

Vexillichthys Armbruster , new genus urn:lsid:zoobank.org:act:5CA3B8BF-1CC1-4C70-9433-1D35632AF249

Figs 1–2

Type species. Moxostoma (Thoburnia) atripinne Bailey 1959 .

Included species. Moxostoma (Thoburnia) atripinne Bailey 1959:7 , Pls. 1–2; Figs.1B–D , 2C , 3A–B Salt Lick Creek , at state highway 52 bridge, Red Boiling Springs, Macon County, Tennessee, U.S.A., elevation 765 feet. Holotype: UMMZ 169506 (image examined). Paratypes: UMMZ 165370 (6). Valid as Vexillichthys atripinnis .

Specimens examined. Specimens used for morphometrics in supplementary table 1 and those for the map ( Fig. 3 ) in supplementary table 2 available at Armbruster (2024) (AUM specimens were additionally used for morphological comparisons). Skeletal specimen examined AUM 86412.

Diagnosis. Vexillichthys can be separated from all other Catostomids by the presence of well-developed, thin, black stripes on the body and a large, black mark on the anterodistal portion of the dorsal fin. Members of Hypentelium and Thoburnia may have stripes, but the stripes are faint, and the dorsal saddles are darker than the stripes (vs. the stripes darker than the saddles in Vexillichthys ). Hypentelium does have dark marks in the dorsal fin, but the fin has bands or blotches instead of a single, large, black area at the anterodistal portion of the fin and the remainder of the fin hyaline. Vexillichthys can be further separated from Thoburnia by lacking a rust-colored, wide lateral stripe. Minytrema also has dark stripes, but these are composed of distinct spots (vs. continuous lines). Some of the species of Moxostoma formerly ascribed to Scartomyzon , also may have stripes, but they are not as intense as that of Vexillichthys and there is maximally some black just at the anterodistal edge of the dorsal fin (vs. a large area). Vexillichthys may also be unique in the development of pads on the distal ends of the anterior unbranched rays of the pectoral fin as well as the anterior portion of the first branched ray and occasionally the second branched ray (other suckers may have thickened skin in these regions, but not distinct pads; Fig. 5 ).

Osteologically, Vexillichthys can be diagnosed by two characteristics of the skull: lateral laminae of the dermethmoid angled anteriorly ( Fig. 4C ; vs. laterally in Thoburnia rhothoeca , Fig. 4B , or posteriorly as in Hypentelium and most Moxostoma , Fig. 4A ); narrowest portion of lateral ethmoid when viewed ventrally much less than length of anterolateral processes (vs. approximately equal in T. rhothoeca and Hypentelium , area of base shown in Fig. 4 ).

Description. Morphometrics in table 1. Body long and low, flattened ventrally to anal fin and then rising to caudal peduncle. Dorsal surface forms gentle arc from snout to dorsal fin and then slowly lowering to caudal peduncle. Head small and roughly conical. Eye large. Mouth inferior. Upper lip plicate, about half width of lower lip; lower lip plicate proximally and with cross furrows distally; lower lip with distal split between left and right lobes.

Dorsal fin roughly triangular in juveniles and females, becoming almost rectangular in nuptial males; located approximately mid body; ii,8–10 (usually 9). Anal fin rounded, broader in nuptial males; ii,6–7 (usually 6). Caudal fin emarginate with rounded lobes, i,8,8,i. Pectoral fin short and rounded with leading unbranched rays and anterior margin of first branched ray with fleshy pad; located at ventral margin of body; ii,12,i. Pelvic fins rounded, originating below middle of dorsal fin; i,6–8 (usually 7),i.

Lateral line complete. Scales small, 46–50 in lateral line, 16–20 predorsal scale rows, 9 caudal peduncle scale rows, 16 circumpeduncular scale rows, 31–32 circumferential scales. Scales of breast and nape deeply embedded. Vertebrae 43–45. 35 right and 39 left pharyngeal teeth; ventral most teeth with U -shaped cusps (shallowest in middle, longest edge medial) and dorsal most teeth thin and filelike; pharyngeal arch narrow, not much wider than teeth; single tooth present on neck of arch (portion of arch ventral to widened section).

Coloration. Body distinctly dark above (base color tan with overlying dark markings) and white below. Head with thick, diffuse stripe from tip of snout, through eye, to dorsal margin of opercle. Body with approximately seven black stripes running entire length separated by tan to cream interspaces. Faint dorsal saddles present below stripes, first behind head, second below origin of dorsal fin (slanted anteroventrally), third behind dorsal fin (slanted posteroventrally), fourth at middle of caudal peduncle (wedge-shaped, narrowest dorsally), and fifth at base of caudal fin; second and fourth saddles darkest. Dorsal fin clear to hyaline with large, black spot anterodistally on first five to six rays with spot continuing only on extreme distal portion of remaining rays. Other fins hyaline with caudal darker; caudal also with broad, dark stripe down middle and sometimes with dark edge. Nuptial specimens darker often with a dark mark over the pectoral girdle that extends medially behind opercular opening and interradial membranes of pectoral and/or anal fins pigmented (mainly in center third of length of fin). Color in life similar, but pectoral fins and dorsal and ventral margins of caudal fin rust-colored with lighter yellow to rust coloring on pelvic and anal fins.

Sexual Dimorphism. Males much smaller than females with larger anal fin (anal fin height to SL ratio 21.4– 33.7% vs. 7.9–17.2%) and a more rectangular dorsal fin with a greater depressed dorsal fin length to SL ratio 22.3–33.4% (vs. 20.0–22.3%). Tubercles found in both males and females. Tubercles in females small and present on anal fin and caudal peduncle ventral to lateral line. Nuptial males with large tubercles on the anal and caudal fins and small tubercles on much of body (particularly caudal peduncle head and throat). Males also with some small tubercles occasionally on ventral side of pectoral fin and dorsal side of pelvic fin. Body tubercles of males best developed on caudal peduncle.

Distribution. Found only in headwaters of the Barren River System of Kentucky and Tennessee, USA.

Ecology. The trematode, Dactylogyrus atripinnei was described from the gills of Vexillichthys ( Timmons & Rogers 1977) . Life history was described in Timmons et al. (1983) with V. atripinnis found in headwater streams (1.5–9 m wide) with alternating pools and riffles. Streams were clear with a substrate of limestone, shale, and siltstone. Young were found in pools (0.3–1m deep) often in schools over gravel. Adults were collected along the shore or in pools (1.0– 1.5 m deep) and would retreat into crevices in the bedrock.Adults are associated with bedrock ledges, boulders, slab rock, and rootwads (see also Stringfield 2013; Kentucky Ecological Services Field Office 2017). They feed mostly on chironomids but also on cladocerans, copepods, ostracods, simuliids, melgalopterans, and trichopterans. Males are tuberculate in year two, but Timmons et al. (1983) reported a young-of-the-year male that was emitting milt in December. Bailey (1959) reported spawning males in water eight centimeters deep from 6–10 April while Timmons et al. (1983) reported tuberculate males in March. Males gather in riffles weeks before spawning females arrive (females were normally in pools). Egg size is 1.7–2.5 mm and fecundity ranged from 1,070 to 1,755 eggs per female. Maximum reported age is five years.

Etymology. From the Latin vexillum for flag and the Greek ichthys for fish. The dorsal fin has a flaglike pattern and the approximately thirteen alternating dark and light stripes are like the flag of the United States of America. Gender masculine.

Figures

FIGURE 1. Live specimens of Vexillichthys n. gen. atripinnis. A. young in typical coloration (90 mm SL, Salt Lick Creek at Bugtussle Road crossing, Monroe Co., KY, 36.65654°, -85.92124°) and B. nuptial specimen, probably female (147 mm SL, Long Hungry Creek, at KY 1333 crossing, Allen Co., KY, 36.67412°, -86.04397°). Specimens uncataloged. Photos by M. Thomas.

FIGURE 2. Preserved nuptial male specimen of Vexillichthys n. gen. atripinnis in dorsal, lateral, and ventral views. AUM 12812, 71.6 mm SL. Photos by J.W. Armbruster. Scale = 1 cm.

FIGURE 3. Distribution of Vexillichthys n. gen. atripinnis.

FIGURE 4. Dorsal view of crania of A. Hypentelium nigricans, AUM 86410, 259.5 mm SL, B. Thoburnia rhothoecum, AUM 86411, and C. Vexillichthys n. gen. atripinnis, AUM 86412. 109.7 mm SL. DE—dermethmoid (lines are to a lateral lamina), F—frontal, FPF—frontoparietal fenestra, LE—lateral ethmoid (lines are to the base of the bone), and SOC—supraorbital crest (lines are to a lateral lamina). Photos by J.W. Armbruster. Scale = 1 cm.

FIGURE 5. Ventral view of right pectoral fins of A. Thoburnia rhothoeca, AUM 61433, 94.7 mm SL and B. Vexillichthys n. gen. atripinnis, AUM 12812, 133.7 mm SL. Unbranched pectoral fin rays numbered with lowercase Roman numerals and first two branched rays numbered with Arabic numerals. The specimen in B is a large, nuptial female and pads are present on all four of the numbered rays with even some thickening on the third branched ray (numbers are approximately in the center of the pads). Photos by J.W. Armbruster. Scale = 1 cm.