Archierato Schilder 1933

Fehse, Dirk & Simone, Luiz Ricardo L., 2020, Contributions to the knowledge of the Eratoidae. X. Revision of the genus Archierato Schilder, 1933 (Mollusca: Gastropoda), Zootaxa 4851 (1), pp. 81-110 : 82-84

Genus Archierato Schilder 1933

Archierato Schilder, 1932: 82 ; 1933: 246; 1935: 328; 1936: 79; 1968: 265; Wenz, 1941: 959; Korobkov, 1955: 244.

Proterato (Archierato) : Schilder, 1939: 171.

Type species. Erato pyrulata Tate, 1890 , by monotypy. Ypresian, late Eocene of Adelaide , South Australia .

Original description by Schilder (1933: 246). “Dorsum smooth or granulate, fossula and columella smooth. Fossula distinctly concave though often very narrow. Terminal ridge coarse, bordering the outlet, the subsequent columellar teeth small, distinctly remote.” Later (1935: 328) he added, “Terminal ridge consisting of one coarse rib, which borders the outlet and the anterior edge of the fossula; the subsequent columellar teeth are distinctly remote from this ridge, small and close.”

Redescription. Shells simple, marginal, terminal ridge sometimes bisected; mostly bulbously pear-shaped. Dorsum smooth or barely granulated. Spire slightly elevated, covered by thin callus. Aperture fairly narrow, siphonal canal broad and indented, anal canal less developed. Labrum narrow, outer margin calloused, somewhat shouldered; inner edge cutting. Peristome dentition often coarse, irregular; denticles rarely elongated, as delicate folds onto labrum, much less than ventrum. Columellar denticles and parietal lip often obscured. Fossula weakly developed, concave, ad narrow. Both fossula and columella smooth.

Remarks. Similar to Cypraeerato . Schilder (1932) introduced the genus Archierato lacking a description, but he designated Erato pyrulata Tate, 1890 as type species and listed names of taxa. The valid description followed almost one year later (1933: 82) in a descriptive key. Additionally six years later Schilder (1939: 171) assigned Archierato as subgenus to Proterato and mentioned, “ Archierato … bauchig birnförmig, Sp. [Spira] kürzer, E. [Enden] mehr gerandet, AL. [Aussenlippe] vorn mehr dekliv, AZ. [Aussenzähne] gröber, TZ. [Terminalzahn] aus 1 abgesonderten, randständigen Rippe bestehend, hintere IZ. [Innenzähne] obsolet, Fo.-IR. [Fossula-Innenrand] eingeschnürt, Farbe unbekannt.” [“ Archierato … bulbously pear-shaped, spire shorter, terminals more edged, labrum anteriorly more declivous, labral teeth coarser, terminal ridge consists of one separate, marginal fold, anterior columellar teeth obscured, inner fossular margin indented, color unknown.”]. However, Archierato has nothing in common with Proterato and seems to be more closely related to Hespererato Schilder, 1933 . Archierato and Hespererato share features including the simple or bisected terminal ridge, the anterior most columellar denticles rarely extended as folds onto the ventrum and the coarse dentition relative to the other genera.

Schilder (1933: 246) mentioned a ‘smooth or granulate dorsum’ for Archierato . It is mysterious what caused Schilder to describe a granulate dorsum for Archierato because he did not explain where he has observed such a feature. He assigned only five smooth taxa to his genus: Erato antiqua Marshall, 1919 from the Bartonian, M Eocene of New Zealand; Erato pyrulata Tate, 1890 from the Ypresian, late Eocene of South Australia; Erato morningtonensis Tate, 1890 from the Balcombian, M Miocene of Victoria, Australia; Erato obesula Chapman, 1922 from the Balcombian, M Miocene of Victoria, Australia; Erato duplicata Johnston in Tate, 1890 from the Aquitanian, early Miocene of Table Cape, Tasmania. He already mentioned a smooth dorsum for all the species in his list (1933: 253—“D sculpture of the dorsum:– = smooth, …”).

The fundamental resemblance (compare Schilder, 1933, text figs. 1, 4, 5) of the overall shell morphology between the type species of Archierato and the recent taxa of the Caribbean and East Pacific cannot be denied. The number of distinguishing features is limited in the genus but the anterior terminal fold (terminal ridge), the shell outline, the labral dentition, the shape of the labrum and the obscured columellar denticles are found in all of them.

In contrast, the appearance of the type species ( Fig. 2 ) of the genus Hespererato Schilder 1933 — Marginella vitellina Hinds, 1844 —is sufficiently different to indicate a different genus. It is difficult to understand why Schilder (1933) assigned so many species to Hespererato , although the shell morphology of most taxa has scanty resemblance. Species in the genus Hespererato are rather overall, with well-developed and widely spaced dentition, with denticles extended often as short folds onto labrum and columella, as well as ventrum, widened aperture and the more ovate instead of pyriform shell outline.

Figures

FIGURES 1–3. Eratoid shells. 1. Archierato pyrulata (Tate, 1890), topotype, CS 36. L 6.3 mm, W 4.8 mm, H 3.8 mm, Ypresian, late Eocene of Adelaide, South Australia. 2. Hespererato vitellina (Hinds, 1844), lectotype, NHMUK 1966236/1. L 12.3 mm, W 9.5 mm, H 8.0 mm, ‘Bay of Magdalena’, W Baja California, W Mexico (photo: Harry Taylor, NHMUK; © Natural History Museum of London 2014). 3. Hespererato scabriuscula (Gray in Sowerby I, 1832), lectotype, NHMUK 1966363/1. L 10.3 mm, W 6.2 mm, H 5.1 mm, “Santa Elena, Colombia” (photo: Harry Taylor, NHMUK; © Natural History Museum of London 2014).