Ashinkailepas indica Gale, 2020

Gale, Andy S., Little, Crispin T. S., Johnson, Joel E. & Giosan, Liviu, 2020, A new neolepadid cirripede from a Pleistocene cold seep, Krishna-Godavari Basin, offshore India, Acta Palaeontologica Polonica 65 (2), pp. 351-362 : 354-358

Ashinkailepas indica Gale sp. nov.

Figs. 3A–F , 4A–M .

Zoobank LSID: urn:lsid:zoobank.org:act:18AA3E40-1B2E-44EE-9588-109780A3A74C

Etymology: Indica, latinised form of India, the country adjacent to the discovery site.

Type material: Holotype: tergum ( NHMUK IC1409 ) . Paratypes: carinae, scuta, rostra, upper latera, peduncular plates ( NHMUK IC 1402– 1408 ; 1410–1420) from the type locality and horizon .

Type locality: Krishna-Godavari Basin , offshore east coast of India . Type horizon: Late Pleistocene, 52.6 ka.

Material.— Over 100 capitular plates and peduncular scales (NHMUK) from the Late Pleistocene (52.6 ka) of the Krishna-Godavari Basin, offshore east coast of India.

Diagnosis.— Ashinkailepas in which radial ribbing is weakly developed, and restricted to the apical, occludent portion of the scutum; the terga possess a smooth, triangular region on the ventral side of the apicobasal ridge which bears only growth lines.

Description. —Terga ( Figs. 3A–C , 4A–C ) flat, rhomboidal, slightly asymmetrical, as the occludent margin is longer than the upper carinal margin. The umbo is slightly inclined towards the dorsal margin, and a weak, narrow ridge for scutal contact is present. A raised apicobasal ridge runs from the umbo to the basal angle; this is either straight, curved or slightly sinuous. A minor secondary ridge is present on the ventral side of the apicobasal ridge, and the two define a slightly raised, triangular region dominated by growth increments. The sculpture of the terga comprises evenly spaced, weakly terraced growth increments, and a variably developed radial element, which forms small nodes where ridges intersect with growth lines. The scuta ( Figs. 3E , 4E, F ) are rhomboidal and strongly dorsally inclined, with a concave tergal margin and a convex occludent margin; the rostral and inner margins are short and straight. A sharply defined, raised apicobasal ridge is present. The sculpture comprises evenly spaced terracing, parallel with growth increments, and weak radial ridges, concentrated in the apical region adjacent to the occludent margin. On small scuta, the radial sculpture forms discrete, short nodes on each growth increment.

The outline of the upper latera ( Figs. 3C , 4I ) forms an isosceles triangle, twice as tall as broad; the sculpture comprises irregular transverse grooves which are inflected towards the basal margin. The rostra ( Figs. 3F , 4J ) are triangular in ventral aspect, 2–3 times taller than broad, and carry a raised central ridge which strengthens apically, and the lateral margins are slightly swollen on larger plates. The carinae ( Figs. 3D , 4D ) are very tall (4 times width) and taper gradually to the apex; they carry a rounded central ridge, and raised lateral margins. Regularly spaced, terraced, growth increments flare slightly on the lateral margins and central ridge. A few (2–4) radial elements form irregular, narrow ridges, subparallel with the central axis. The peduncular plates ( Fig. 4 G, H, K, L, M ) have a slightly asymmetrically triangular form, and are robust. They possess two lateral processes and a tall, outwardly curved central spine. The interior face is flat to weakly concave and smooth; the external surface bears short, coarse ridges.

Remarks. —The fossil material of dissociated plates can be referred confidently to Ashinkailepas , from comparison of the shape of the capitular and peduncular plates with illustrations of A. seepiophila ( Yamaguchi et al. 2004) and A. kermadecensis Buckeridge, 2009 . The capitular plates lack the numerous, fine radial ribs of A. seepiophila , which also lacks conspicuous growth increments, and are more closely comparable with those of A. kermadecensis . Detailed comparison is difficult, because the photographic illustrations of that species ( Buckeridge 2009: pl. 1) are wet with alcohol and the surface sculpture is rather difficult to make out. Differences include the very narrow, sharply defined apicobasal ridge on the terga of A. kermadecensis , whereas this is blunter and broader, with an accessory ridge, in the material described herein as A. indica Gale sp. nov. Additionally, in A. kermadecensis , very fine radial ridges, interrupted by growth increments, cover the entire terga and scuta (e.g., Buckeridge 2009: pl. 1: 3); in A. indica Gale sp. nov. the radial sculpture is weakly developed, and concentrated in the apical region of the scuta and terga.

Stratigraphic and geographic occurrence.—Late Pleistocene of Krishna-Godavari Basin, offshore east coast of India.

Figures

Fig. 3. Capitular plates of neolepadid cirripede Ashinkailepas indica Gale sp. nov. from Late Pleistocene (52.6 ka), Krishna-Godavari Basin, offshore India (A–G) and living species of the genus (H, I). A–F. Capitular plates of paratypes. A. NHMUK IC 1402, tergum in external (A1) and internal (A2) views. B. NHMUK IC 1403 small tergum in external view. C. NHMUK IC 1404, upper latus in external view. D. NHMUK IC 1405, carina in dorsal (D1) and lateral (D2) views. E. NHMUK IC 1406, small scutum in internal (E1) and external (E2) views. F. NHMUK IC1407, rostrum in ventral view. G. Recent Ashinkailepas seepiophila Yamaguchi, Newman, and Hashimoto, 2004 from near Sagami Bay, Japan. USNM 1018131, paratype in lateral (right side) view (based on Yamaguchi et al. 2004: fig. 4). H. Recent Ashinkailepas kermadecensis Buckeridge, 2009 from Kermadec Ridge, northeast of North Island, New Zealand. NIWA 44722, holotype in lateral view (based on Buckeridge 2009: pl. 1: 5).

Fig. 4. Plates of neolepadid cirripede Ashinkailepas indica Gale sp. nov. from Late Pleistocene, 52.6 ka) Krishna-Godavari Basin, offshore India. A–C. External views of terga. A. NHMUK IC 1408. B. NHMUK IC 1409, holotype. C. NHMUK IC 1410. D. NHMUK IC 1411, carina in dorsal view. E. NHMUK IC 1412, scutum external (E1) and internal (E2) views. F. NHMUK IC 1413, small scutum in external view, with predatory gastropod drillhole Oichnus paraboloides Bromley, 1981. I. NHMUK IC 1416, upper latus in external view, with predatory boring made by gastropod. J. NHMUK IC 1417, rostrum in ventral view. G, H, K–M. NHMUK IC 1414, 1415, 1417–1419, respectively, peduncular plates in external (G, L, K) and internal (H, M) views.