Verruca alabamensis Perreault & Buckeridge, 2019

Perreault, Ray T. & Buckeridge, John S., 2019, Paleogene Verrucidae (Cirripedia: Verrucomorpha) of North America, with descriptions of three new species, Zootaxa 4712 (1), pp. 34-50 : 34-50

Verruca alabamensis Perreault & Buckeridge , sp. nov.

Pl. 2, figs a–q

urn:lsid:zoobank.org:act:FD071DD7-1907-416A-81ED-6C5F4AAC8273

Diagnosis. All plates non-punctate; wall plates with ribbing prominent near plate margins, crossed with fine growth lines; rostral-carinal articulation with five ridges; movable scutum with one distinct articular rib; first and second articular ridges of movable tergum indistinct, about equal width; fixed scutal radio-alar wing extending one-third basal width of fixed scutum.

Type material.

Holotype. LSUMG I-10727 , a movable scutum (pl. 2, figs o, p).

Paratypes. Figured paratypes: LSUMG I-10723 , a fixed scutum (pl. 2, figs a,b) ; LSUMG I-10724 , a fixed tergum (pl. 2, figs c, d) ; LSUMG I-10725 , a rostrum (pl. 2, figs i, j) ; LSUMG I-10726 , a carina (pl. 2, figs k, l) ; LSUMG I-10728 , a movable tergum (pl. 2, fig g, h) ; LSUMG I-10729 , an articulated carina-rostrum pair (pl. 2, figs m, n) ; LSUMG I-10730 , a juvenile movable scutum (pl. 2, figs e, f) .

Type locality. LSUMG locality IL 1974K (= HVH locality 319-6).

Stratigraphic range. Late Eocene (Priabonian).

Distribution. Alabama, USA.

Additional material. 8 carinae, 10 rostra, 4 fixed scuta, 4 fixed terga. 2 movable scuta, 2 movable terga (LSUMG IL 1974K); 1 carina, 1 rostrum, 1 fixed scutum (Shubuta Member, UF locality ZA039) (Cat. No. UF- 70252).

Description. Shell ovate, elongated carino-rostrally with D-shaped orifice; all plates without ribbing or punctae, with fine growth lines; some wall plates provided with thickened base and calcareous internal rim, clearly shown in plate 2, fig. m.

Carina strongly asymmetrical, with tilt toward fixed tergal side; fixed tergal margin with three articular ribs, distinct, with lowermost very small; rostral margin with five articular ribs, evenly lengthening apically; interior provided with dependent sheath widest at apex.

Rostrum strongly asymmetrical, with three articular ribs on fixed scutal margin, five ribs on carinal margin; ornamented by fine growth lines only; interior provided with narrow sheath, dependent, with furrow to receive free opercular plates.

Fixed scutum convex, smooth, wider than high, with narrow, crescentic radio-alar wing extending about onethird its own distance from rostral margin, ornamented with fine, transverse growth lines only; rostral articulation with two articulating ribs; fixed tergal margin convex with node one third to base, with two ribs below; interior with bordering ridge on fixed tergal margin; straight broad articular ridge extending almost to apex with one rib, tilting basally; myophore absent.

Fixed tergum convex, smooth, higher than wide, flared basally, ornamented by fine growth lines only; fixed scutal margin straight or slightly convex, with wide internal border ridge; protruding ala short, curved with small indentation at base; carinal margin with two coarse, vague articular ribs and prominent upward curving ala slightly protruding from carinal margin and prominent indentation below; interior strongly concave, apical shelf dependent, strongly sloping basally.

Movable scutum slightly bowed, plate moderately curved tergally; exterior ornamented by regularly spaced incised growth lines, each forming very low tooth on highly convex occludent margin; tergal margin strongly concave, less curved than occludent margin; margin provided with low, rounded border ridge, fading basally; one prominent, wide articular ridge extending three-quarters to basal margin; ridge protruding from tergal margin and separated from plate by shallow, distinct furrow with incised borders; basal margin very slightly convex, basi-tergal angle nearly 90˚, basi-occludent angle broadly rounded. Interior smooth, all margins provided with low, rounded ridge; adductor scar large, sub-rounded, vaguely defined, placed close to occludent margin well apically of center; apex with prominent overfold for articulation with movable tergum, marked by distinct bordering ridge.

Movable tergum flat, rhomboidal, with wide, prominent apico-basal ridge; ridge raised, demarked by incised edges, slightly overhanging, protruding slightly more than its own width from basiscutal angle, merging into plate near apex; basal margin nearly straight, carinal margin gently convex, meeting at nearly right angle; basi-scutal angle acute, scutal margin undulating; carinal portion triangular, with prominent growth ridges at nearly right angles to carinal margin basally, sloping basally in apical half; growth ridges converging slightly towards apico-basal ridge; two articular ridges, vague, coarse; interior featureless.

Discussion. The lack of punctae and ribbing differentiates this species from Verruca gailgoedertae sp. nov. and V. sorrellae sp. nov.

Verruca alabamensis sp. nov. may be distinguished from other known North American Paleogene Verrucidae by its inturned calcareous rim on some plates. This feature does not seem to be related to size or ontogeny. All of these in-turned rims, and most basal margins, show a preferred attachment to ribbed substrates. Most likely, plicatulid bivalves are candidates, by the shape of the ribbing.

Verruca alabamensis sp. nov. is uncommon, and must have occurred under restricted environmental conditions. Both known localities are characterized by abundant branching bryozoans, crinoids, gorgonian axes and brachiopods (dominantly Terebratulina lachryma ). In both localities, aragonitic remains are completely leached, and phosphate is present. At the type locality, phosphate occurs as internal molds of molluscs and solitary corals. Corals may be identified to genus on the basis of these internal molds. At the Shubuta locality, phosphate occurs additionally as small nodules. These nodules are sometimes encrusted with bryozoan colonies, indicating nodule formation was contemporaneous with deposition.

Boring traces are common at the type locality. Several wall plates show naticoid drill holes, some fully penetrating the shell. The holotype scutum features a minute, spearhead-shaped boring of unknown origin (Pl. 2, fig. q).

Etymology. Named after the state of Alabama.

Type Repositories. Holotype LSUMG I-10727 , paratypes LSUMG I-10723-10726 , 10728-10730 ; topotypes LSUMG I-10731-10737 . All held by Collection of Fossil Protists and Invertebrates , Louisiana State University , Museum of Natural History , Baton Rouge, LA.