Polyodontes texanus Pettibone 1989

Polyodontes texanus

MATERIAL EXAMINED.—GULF OF MEXICO. Northwestern part, 27°50′N, 95°12.5′W, 183 m, Alaminos sta 68A 13–17, 19 Nov 1968, L.H. Pequegnat, holotype (USNM 98807).

DESCRIPTION.—Holotype incomplete, with 49 segments, 112 mm long, 34 mm wide with setae. Dorsum rusty brown, also brownish on upper, lateral, and lower lips of mouth, enclosed in segments 3–7. Elytra oval, with eccentric attachment on lateral sides, leaving middorsum uncovered; reddish brown on medial part and with shallow lateral pockets on more posterior elytra (Figure 93B–D).

Prostomium and tentacular segment pulled back into anterior segments and enclosed in parapodia of segment 2. Prostomium bilobed, with large black oval ommatophores occupying anterior border, with white domes on tips, without distinct necks; median antenna with oval ceratophore, papillate laterally, with style extending slightly beyond tips of ommatophores; posterior pair of small eyes lateral to ceratophore, plus some extra pigment spots; lateral antennae inserted ventrally on bases of ommatophores, with tips extending slightly beyond ommatophores; palps long, tapered, smooth (Figure 93A). Tentacular segment distinct dorsally; tentaculophores lateral to prostomium, each with 2 acicula, 2 groups of capillary setae and pair of dorsal and ventral tentacular cirri, ventral cirri slightly longer than dorsal ones (Figure 93A,E).

Second segment with first pair of elytrophores, ventral buccal cirri much longer than following ventral cirri, and biramous parapodia; notopodium short digitiform lobe with bundle of long capillary notosetae; neuropodium larger, with rounded presetal acicular and postsetal lobes, upper and middle neurosetae stouter, tapering to fine tips; lower neurosetae more slender (Figure 93F,G). Pharynx not extended and not examined.

Third segment with first pair of dorsal cirri with short cirrophores and tapering styles extending beyond setae; notopodium and notosetae similar to those of segment 2; upper and middle neurosetae stout, tapering to spinous tips; lower neurosetae more slender, curved, with larger spinous rows more basally and close–set spinous rows on tapering tips, similar to lower neurosetae of following segments (Figure 93H–J).

Parapodia of segments 4–8 becoming larger, with stout neurosetae changing gradually, becoming smooth basally, and forming transitional aristae distally (Figure 93K–M). Beginning with segment 9, notopodium wide, rounded, flattened, on anterodorsal half of larger neuropodium, with notoaciculum, spinning gland, and short row of notosetae emerging from lower side of notopodium; neuropodium with presetal acicular and postsetal lobes and more or less distinct anteroventral bract; lower neurosetae numerous, within anteroventral bract, similar to more anterior parapodia; middle row of stout smooth acicular neurosetae with spinous aristae; upper group of neurosetae, emerging from low dorsoanterior bract, hidden by notopodium, of 2 types: (a) wider basally, with long spinous tips; (b) shorter, slender, with widely spaced spines (Figures 93N, 94C–E).

Middle parapodia becoming larger, with more numerous neurosetae of same types; dorsal cirri with inflated cirrophores and short, wide styles extending to tips of neuropodia (Figure 94A–H). Numerous round branchiae on anterior, dorsal and posterior sides of parapodia, beginning on segment 10 and continuing to about segment 36; ventrally, bulbous extensions between ventral cirri and bases of parapodia, beginning on about segment 10 (Figure 94A,B,F,G).

ETYMOLOGY.—The species is named for the collection site, off Texas.

DISTRIBUTION.—Gulf of Mexico. In 183 meters.