Verruca sorrellae 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 sorrellae Perreault & Buckeridge , sp. nov..

Pl. 3, figs a–q

urn:lsid:zoobank.org:act:3C3CEFE3-916E-4DC7-8D84-B8E34D9A53FA

“new species of Verruca ” Zullo & Newman, 1964: 355.

Diagnosis. Shell with low, irregular ribbing crossed by fine growth lines; all plates perforated by fine punctae; second articulating rib on movable tergum almost twice width of first; rostrum and carina articulating with up to six ribs; movable scutum with second articular rib bilobed; fixed scutal radio-alar wing extending out at distance of up to 1.5x basal width of fixed scutum.

Type material.

Holotype. LACMIP 14760, a movable tergum (pl. 3, fig e, f).

Paratypes. NMV P332711 , a movable scutum (pl. 3, fig. a, b) ; NMV P332712 , a movable scutum (pl. 3, figs c, d) ; NMV P332713 , fixed tergum (pl. 3, figs l, m) ; NMV P332714 , a fixed scutum (pl. 3, figs n, o) ; NMV P332715 , a rostrum (pl. 3, figs h, i) .

Type locality. LACMIP locality 16935, Porter Creek.

Stratigraphic range. Upper Eocene (Priabonian), (Global Cycle TA 4.3 transgressive tract) to?lower Oligocene.

Distribution. Basal Lincoln Creek Formation, LACMIP localities 16934 (Oakville) and 16935 (Porter Creek), Grays Harbor County, Washington. Abundant in the Gries Ranch Formation; verrucid plates from the Gries Ranch locality were first mentioned by Zullo & Newman (1964: 355). The fauna from the Gries Ranch Formation ( Effinger, 1938) represents an inner shelf environment laterally equivalent to the two Lincoln Creek Formation intertidal sites.

Material. In addition to the types (above), LACMIP 16935 included four fixed scuta, four fixed terga, one movable scutum, one movable tergum, one carina, three rostra and seven indeterminate plates. LACMIP 16935 included more than 50 loose plates.

Description. Wall plates moderately thick, with weak, irregular ribbing crossed by distinct growth lines; all plates perforated by fine punctae. Carina asymmetrical with sharply pointed apex, rostral radio-alar area about one half length of basal margin with up to six articular ribs; tergal radio-alar area about one fourth length of basal margin with up to three narrow articular ribs; sheath well developed, high, dependent, with shallow furrow curved toward fixed side; ornamented by fine horizontal growth lines, interior otherwise featureless.

Rostrum gently curved, carinal margin with up to six articular ribs, highest two separated from rest by larger, deeper articular furrow; fixed scutal margin with one or two coarse articular ribs; interior smooth with sheath highly recurved, dependent only on carinal margin, coincident with first articular rib.

Fixed scutum with triangular radio-alar wing, twice as long as high, extending beyond plate by up to 1.5 x basal margin of plate, with two narrow articular ridges below; wing more than twice as long as high; movable scutal margin slightly concave; fixed tergal margin straight to slightly concave, with incised scalloped area along margin exterior; exterior ornamented by closely spaced growth ridges on articular ridges, widely spaced on plate, sometimes alternating with irregular rows of very small pits; sharply pointed apex slightly removed from plate; adductor plate prominent, erect, with a myophore.

Fixed tergum narrow, strongly convex, apex removed from movable tergal margin, radio-alar extensions well developed, blunt, carinal radio-alae usually longer than fixed scutal; carinal margin with one well-developed articular rib below ala, fixed scutal margin slightly convex or sinuous, with a weakly developed ridge below radio-ala, in subapical groove to receive fixed scutum; interior strongly concave, occludent plate wide, with deep apical cavity one third to one half height of plate, with low raised margin at apex.

Scutum narrow, length slightly greater than twice width, flat; occludent margin convex, apex pointed, basi-occludent angle acute, sharp; basal margin angled at shallow furrow paralleling apico-basal rib; apico-basal rib sharp, slightly elevated, close to movable tergal margin; second articular rib slightly wider than first, may bifurcate in larger plates; exterior with regularly spaced growth ridges; interior slightly concave, occludent margin broadening towards apex, with low narrow bordering ridge; no longitudinal ridge; adductor scar not visible.

Movable tergum subrhomboidal, height and width nearly equal; apico-basal ridge flat, sides overhanging, slightly curved toward movable scutal margin, as wide as or slightly narrower than second articular ridge, protruding below carinal margin; carinal portion bowed, with vague sulcus parallel to apico-basal ridge, marked by slight downturn in growth lines; fixed tergal margin smoothly convex, fixed scutal margin straight to slightly convex, carinal margin straight; fixed tergal/fixed scutal angle slightly less than 90˚; first articular ridge twice width of sec- ond, with deep articular furrow between, extending beyond second articular ridge nearly as far as apico-basal ridge; second articular ridge with shallow sulcus in lower part, with corresponding indentation in movable scutal margin; exterior ornamented by prominent, fine, regularly spaced growth lines, without intercalating rows of pits; interior smooth, all articular surfaces wide, with fine longitudinal ridges.

Discussion. Verruca sorrellae sp. nov. is closest in appearance to V. tasmanica chatheca Buckeridge, 1983 , differing in the movable scutum and in proportions of the movable tergum and fixed scutum. The movable scutum of V. sorrellae sp. nov. is narrower than that of V. tasmanica chatheca , the occludent margin is straighter with a sharp basioccludent angle and the basal margin is angled. In addition, the second articular rib is wider and better developed than that of V. tasmanica chatheca . The movable tergum most closely resembles that of V. tasmanica chatheca in the apico-basal ridge and characters of the carinal section. However, V. tasmanica chatheca possesses a second articular ridge twice the width of the apico-basal ridge, with a narrow first articular ridge. Verruca sorrellae sp. nov. possesses a second articular ridge of variable width, but usually much less than twice the width of the apico-basal ridge. Further, the second articular ridge possesses a nearly median sulcus and corresponding indentation in the movable scutal margin, features absent in V. tasmanica tasmanica or V. tasmanica chatheca . This rib corresponds with bifurcating second articular ribs of the movable scutum. The fixed scutum is closer to V. tasmanica chatheca in the form of the adductor late. The fixed scutal/fixed tergal articulation of V. sorrellae sp. nov. is more derived than the earlier species in having the weak rib in the articular furrow of the fixed tergum, and in the incised scalloped area on the fixed scutum. This rib is best seen from the interior of the plate. The articulation of both of the V. tasmanica subspecies is unelaborated.

Verruca sorrellae sp. nov. differs from V. cookei Pilsbry, 1927 , in its fixed scutal adductor ridge, which is near the apex, instead of basally. The beaded ornament characteristic of V. cookei is less developed in V. sorrellae sp. nov. Verruca alaskana Pilsbry, 1943 is poorly known, the movable opercula being absent, but the rostrum is narrower than the carina, with up to 7 articular ribs, as opposed to 5–6 in V. sorrellae sp. nov. The rostrum and carina of the latter are more similar. Verruca sorrellae sp. nov. may be ancestral to both other species, and possibly the extant V. stroemia and V. laevigata .

This species is a representative of a mostly shallow-water lineage beginning in the Late Cretaceous of Western Australia. The only living representatives in shallow waters of the Pacific Basin are Verruca cookei of Hawaii, and V. laevigata (Patagonia to Peru). Verruca laevigata differs primarily in having a movable tergum that is wider than high, continuing a trend begun with V. tasmanica tasmanica .

Etymology. Named in honor of Sorrelle Benson, daughter of Jeremy Benson, owner of the type locality.

Type repositories. Holotype LACMIP 14760 held by the Natural History Museum of Los Angeles County, CA; illustrated paratypes NMV P332711-15 held by Museum Victoria, Melbourne, Australia.