Hybolophus terrestris, 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-FFEB-FF9E-FC90-FD11FEE6FE77 |
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treatment provided by |
Felipe |
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scientific name |
Hybolophus terrestris |
| status |
sp. nov. |
Hybolophus terrestris View in CoL sp. nov.
Fig. 9E− J View Fig .
Etymology: Referring to Cerro Terrestral, the type locality.
Type material: Holotype, complete adult left valve with hinge exposed: UWBM 101871 About UWBM , L 57.3, H 51.0, T 15.4 . Paratypes (all B8320): UWBM 101872 About UWBM , L (45.6), H 43.3, T 14.2; UWBM 101873 About UWBM , L 56.6, H 46.5, T 15.5; UWBM 101874 About UWBM , L 69.7, H 63.9, T 26.6; UWBM 101875 About UWBM , L 63.2, H 56.5, T 17.5; UWBM 101876 About UWBM , L 69.0, H 59.1, T 20.0; UWBM 101877 About UWBM , L 60.4, H 46.0, T 16.0; MUSM INV 224 , L 58.3, H 47.6, T 16.5; MUSM INV 225 , L (52.8), H (44.5), T 15.0; MUSM INV 226 , L (68.9), H 58.9, T 18.5; MUSM INV 227 , L 54.3, H 47.6, T 14.4; MUSM INV 228 , L 64.1, H 51.7, T 17.3; MUSM INV 229 , L 61.8, H 48.0, T 16.9.
Type locality: B8320, Cerro Terrestral , East Pisco Basin, Peru .
Type horizon: Upper Pisco depositional sequence, Tortonian or Messinian .
Material.—UWBM 101878, B8355, L 43.7, H 36.6, T 10.5; UWBM 101879, B8355, L 55.4, H 47.4, T 15.5. Other specimens from B8317 (molds) and B8319. All from material from the East Pisco Basin, Peru.
Diagnosis.— Hybolophus with shell veneriform, nearly circular, inflated, with irregular commarginal growth lines beyond the umbones.
Description.—Shell to 80 mm long, veneriform and nearly circular, rarely posteriorly produced, L: H ratio usually 1.0−1.1, T: H ratio 0.3, maximum inflation ventral or posterior to beak. Anteriodorsal and posteriodorsal margins straight to slightly convex, rarely slightly concave, anterior and ventral margins broadly rounded, posterior margin rounded to broadly truncate. Weakly angular primary posterior ridge diverging less than 20° from posteriodorsal margin, secondary posterior ridge bordering escutcheon. Lunule elongate-cordate, 60% length of anteriodorsal margin. Escutcheon 70−80% length of posteriodorsal margin, narrower than lunule. Beak prosogyrate. Umbo flattened, orthogyrate, rarely opisthogyrate, with widely spaced commarginal ribs. Remainder of exterior with irregular commarginal growth lines. Left anterior cardinal tooth narrow, wedge-shaped, inclined anteriorly 30–40°, extending from vmHP to beak. Left posterior cardinal tooth bladelike, straight, nearly orthocline. Right anterior pseudocardinal tooth narrow, diverging anteriorly from midpoint of lunule margin. Right cardinal tooth narrow, wedge-shaped, inclined anteriorly 30°. Right posterior pseudocardinal tooth lamellar, diverging 10–20° posteriorly from midpoint of right cardinal tooth, passing resilifer anteriorly. Inner ventral margin smooth.
Remarks.—Most specimens of Hybolophus terrestris have convex anteriodorsal and posteriodorsal margins, imparting a veneriform profile, yet individuals can be either trigonal or as elongate as some Miocene specimens of H. gibbosus and H. nelsoni , a pattern of variability also illustrated by Marks (1951) in H. carrizalensis . Like specimens of H. gibbosus , those of H. terrestris are inflated, thick, and have a flattened umbo, but the umbo is rarely as opisthogyrate. Also, specimens of H. terrestris lack the angular secondary posterior ridge of H. gibbosus .
Stratigraphic and geographic range.—Tortonian to Messinian, Pisco depositional sequence, East Pisco Basin, south-central Peru.
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