Tilicrassatella torrens, Devries, 2016
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publication ID |
https://doi.org/ 10.4202/app.00228.2015 |
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persistent identifier |
https://treatment.plazi.org/id/AF5F87F5-FFE8-FF83-FF2F-FB6EFB17FA64 |
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treatment provided by |
Felipe |
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scientific name |
Tilicrassatella torrens |
| status |
sp. nov. |
Tilicrassatella torrens View in CoL sp. nov.
Fig. 8D− G, I.
Etymology: From Latin torrens , torrent; referring to episodic flooding of the Rio Grande near the type locality.
Type material: Holotype, adult left valve with exposed hinge and ventral margin mostly missing: UWBM 101846 About UWBM , B8354, L (97.0), H (78.6), T 23.2 . Paratypes: UWBM 101849 About UWBM , B8326, L (58.2), T 23.6; UWBM 101850 About UWBM , B8326, L (77.1), H (68.6), T 22.0; UWBM 101851 About UWBM , B8308, L (66.3), H 63.8, T 19.4; UWBM 101853 About UWBM , B8308, L (56.3); UWBM 101855 About UWBM , B8313, L (86.4), H 69.9, T 18.8; MUSM INV 217 , B8326, L (52.9), T 22.0; MUSM INV 230 , B8313, L (50.2). From Quebrada Gramonal (B8326), Carhuas-Comotrana road (B8308), Filudo depression (B8313). All material from the East Pisco Basin, Peru .
Type locality: B8354, east flank of Río Grande , across river from Cerro Terrestral, East Pisco Basin, Peru .
Type horizon: Chilcatay depositional sequence, lower Miocene .
Material.—UWBM 101847, B8330, L 55.9, H 45.9, T (15); UWBM 101848, B8330, H (44.1); UWBM 101852, B8324, L (74.1), H (55.9), T 19.8; UWBM 101854, B8304, H (55.4); UWBM 101856, B8305, H (39.9); MUSM INV 215, B8330, L (48.9), H (46.0); MUSM INV 216, B8330, L 57.2, H 46.3; MUSM INV 218, B8309, L (86.3), H 70.3. Other specimens from B8306, B8311, B8313, B8325, B8333, B8337. All material from the East Pisco Basin, Peru.
Diagnosis.—Shell trapezoidal, not inflated, nearly equilateral.
Description.—Shell to 100 mm long, trapezoidal, not inflated, beaks more than two-fifths of length from anterior end, L:H ratio 1.2, T:H ratio 0.2, maximum inflation ventral or posterior to beak. Anteriodorsal and posteriodorsal margins nearly straight, not steeply descending. Anterior and ventral margins broadly rounded, posterior margin broadly truncate, not produced. Primary posterior ridge rounded to obsolete, diverging 20−25° from posteriodorsal margin. Secondary posterior ridge usually obsolete. Lunule elongate-cordate, slightly wider than escutcheon, both about half the length of respective margins. Beak prosogyrate. Umbo slightly flattened, orthogyrate, with closely spaced commarginal ribs extending across primary posterior ridge. Remainder of exterior with irregular commarginal growth lines. Resilifer extending to vmHP. Left anterior cardinal tooth thick, elongate, wedge-shaped, inclined anteriorly 40–50°, separated from beak by lunule. Left posterior cardinal tooth narrow, straight, inclined anteriorly less than 20° or orthocline. Right anterior pseudocardinal tooth narrow, elongate, diverging from lunule margin and inclined anteriorly 70°. Right cardinal tooth thick, wedge-shaped, elongate, inclined anteriorly 20°. Right posterior pseudocardinal tooth lamellar, diverging 20° from cardinal tooth, passing resilifer anterioventrally. Inner ventral margin usually crenulate on large specimens.
Remarks.—Specimens of Tilicrassatella torrens are more equilateral than specimens of T. ponderosa and T. sanmartini and much less inflated than specimens of T. ponderosa . The presence of a crenulated inner ventral margin distinguishes specimens of T. ponderosa (and every species of Tilicrassatella ) from specimens of Hybolophus in Miocene and Pliocene strata of the East Pisco Basin and northern Peru.
Stratigraphic and geographic range.—Aquitanian to Langhian, Chilcatay and basal Pisco depositional sequences, East Pisco Basin, south-central Peru.
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