Eunice megabranchia Fauchald 1970

Eunice megabranchia Fauchald, 1970

Eunice megabranchia Fauchald, 1970:33–36, pl. 4: figs. a–e.

MATERIAL EXAMINED.—Holotype, AHF Poly 1056, Gulf of California, Mexico, 27°03′N, 112°18″W, 894 m, coll. S. Calvert, sta L-184.

DESCRIPTION.—Holotype incomplete mature female with large eggs in body cavity with 74 setigers; length 68 mm; maximal width 7 mm; length through setiger 10, 12 mm. Anterior end of body cylindrical, becoming dorsally and ventrally flattened towards posterior end of fragment; crosssection nearly quadrangular posteriorly.

Prostomium (Figure 71f) distinctly shorter and narrower than peristomium, as deep as of peristomium. Prostomial lobes frontally obliquely rounded; median sulcus shallow, separation continued as distinct ridge to base of A-III. Surface of prostomium rugose, palps distinctly marked frontolaterally by shallow grooves. Eyes posterior to bases of A-I, hidden under peristomial fold, purple. Antennae in a horseshoe, evenly spaced, similar in thickness. Ceratophores ring-shaped in all antennae, without articulations. Ceratostyles slender and tapering, without articulations. A-I to setiger 1; A–II to setiger 6; A-III to setiger 9. Peristomium cylindrical. Lower lip scalloped. Separation between rings distinct on all sides; anterior ring of total peristomial length. Peristomial cirri to slightly beyond tip of prostomium slender and tapering, without articulations.

Jaws not examined.

Branchiae (Figure 71m) present, pectinate, distinctly longer than notopodial cirri, not reduced in mid-body region, erect. Branchiae from setiger 3 to setiger 54. Branchiae terminating well before posterior end, present on less than 55% of total number of setigers. Last 7 pairs single filaments; all other branchiae strongly pectinate with 47 or more filaments where best developed, at setigers 15–20. Branchial stems erect, strong, tapering to very narrow tips, and outreaching notopodial cirri in all but last 7 branchial segments. Filaments filiform, forming tangled masses on sides of specimen; some filaments longer than notopodial cirri, but most distinctly shorter than notopodial cirri.

Anterior neuropodial acicular lobes obliquely truncate with aciculae emerging dorsal to midline. Posteriormost neuropodial acicular lobes present (Figure 71i) symmetrically rounded with aciculae emerging medially. Pre- and postsetal lobes low, transverse folds. Pre- and postbranchial ventral cirri tapering. Ventral cirri modestly basally inflated in branchial region. Inflated bases ovate; narrow tips tapering. Anterior notopodial cirri, slightly inflated basally, becoming tapering with long, slender, filiform tips in branchial region; postbranchial notopodial cirri slender, tapering, very much shorter than in branchial region. All notopodial cirri with distinct cirrophores; anterior notopodial cirri with 3 to 4 irregular articulations; articulations lost in first few branchial setigers.

Limbate setae narrow, marginally smooth. Shafts of pectinate setae (Figure 71h,l) wide, flattened. Blades slightly flaring, flat or gently furled. One marginal tooth distinctly longer than other teeth; 16 teeth present. Shafts of anterior compound falcigers (Figure 71g) distally inflated, becoming tapering in posterior setigers (Figure 71j), marginally smooth; internal striation distinct, with distinct, narrow beaks. Appendages tapering from base to very small distal heads, bidentate. Proximal teeth smaller than distal teeth, forming low, triangular lateral projections. Distal teeth erect, slender in anterior setigers and thick in posterior setigers. Guards tapering to slender, distinct mucros, marginally serrated. Pseudocompound falcigers and compound spinigers absent. Aciculae single in anterior setigers, up to 3 in posterior setigers, honey-colored, tapering to blunt tips, straight; cross-sections round. Subacicular hooks (Figure 71k) honey-colored, bidentate. Hooks first present from setiger 35, present in all setigers thereafter, always single (except for replacements). Hooks tapering to small heads. Proximal teeth much larger than distal teeth; both teeth directed distally.

UNKNOWN MORPHOLOGICAL FEATURES.—Jaw structure; features associated with posterior parapodia; pygidium and anal cirri.

EXPECTED STATES OF UNKNOWN MORPHOLOGICAL FEATURES.—None.

CHARACTERS USED IN PREPARATION OF KEY NOT SCORED.—Inappropriate Characters: 22, 56, 58, 59. Unknown Characters: 1, 2,4, 6, 47, 50, 63, 74, 78.

ASSUMED STATES FOR PURPOSE OF PREPARING KEY.—None.