Atetrapachylasma, Newman, William A. & Jones, William J., 2011

Newman, William A. & Jones, William J., 2011, Two Northeast Pacific deep-water barnacle populations (Cirripedia: Calanticidae and Pachylasmatidae) from seamounts of the Juan de Fuca Ridge; " insular " endemics stemming from Tethys, or by subsequent dispersal from the Western Pacific center of distribution?, Zootaxa 2789, pp. 49-68 : 60

Atetrapachylasma gen. nov.

Diagnosis. Wall of female of four plates ( Figs 11 , 12 ), compound rostrum (RLRRL), paired compound carinolatals (CL1CL2s) and carina (C); compound plates apparently without sutural traces in dwarf males as well as females. Wall low conical, wider than high; overall round plan constricted at sutures giving the four parietal parts a somewhat lobed appearance ( Figs 5 , 11 ). Opercular plates simple, triangular in outline, articular ridges and furrows weakly developed; tergum without depressor muscles crests; scutum with strong occludent ridge visible externally and internally, adductor pit and ridge absent.

Etymology. “A-” not, in preference to “Para-“ beside or near “, since despite also being four-plated and without traces of vestigial sutures, it is otherwise evidently not closely related to the type, Tetrapachylasma trigonum Foster, 1988: 225 , much less to Tetrapachylasma s.l.

Figures

FIGURE 5. Atetrapachylasma dijonesae gen. et sp. nov. in situ on pillow basalt from 2080 m of depth Vance B Seamount, with nozzle of suction sampler of ROV Tiburon largely to their right. A, the remains of several walls broken away by the nozzle can be seen to the right of “ 1 ” leaving membranous bases exposed. B, the barnacles seen between “ 2 ” and “ 3 ” and to the right of “ 4 ” in A have been collected. N. B.: Inspection of MPEGs taken by ROV Tiburon during collection of the barnacles seen removed in these frames detected no loss of material in the process. Therefore, it can be said with confidence that the shell fragments at the base of the basalt below the barnacles (cf. Fig. 4) represent natural postmortem accumulations.

FIGURE 11. Atetrapachylasma dijonesae gen. et sp. nov. holotype: A, exterior view of female with males; note largely exposed alae and the pair of males on each side of the tight fitting occludent ridges of the scuta. B, interior view of the same female, note the tight fit of the bearing surfaces of the alae on the adjacent plates, and the close fit of the sutures between plates, especially between the opercular plates and the interior of the orifice.

FIGURE 12. Atetrapachylasma dijonesae gen. et sp. nov., exploded four-plated wall arranged from loose plates, type lot: A, exterior of a rostrum; B and D, left and right carinolaterals; C, a carina; and E, the interior of a portion of a rostrum. Note the variably pronounced depression in the sheath of rostrum (E), which, together with the edges of the carinolateral alae, receives the rostral ends of the occludent ridges of the scuta (Figs 9 A; 11 C, D).