Euspira, LOUIEMARINCOVICHI, AGASSIZ, 1837

Powell, II, Charles L. & Dineen, Ashley A., 2023, A new fossil Euspira? (Mollusca: Gastropoda: Naticidae) from the Gubik Formation on the North Slope of Arctic Alaska, PaleoBios 40 (1904), pp. 1-28 : 2-3

EUSPIRA ? LOUIEMARINCOVICHI

POWELL AND DINEEN, N. SP.

FIGURES 1–4

Zoobank ID — urn:lsid:zoobank.org:act:2969452C-D99E-45B3-8851-D726958FB5C9

Diagnosis —The fine, closely spaced, narrow radial, and spiral sculpture forming a faint checkerboard pattern set this species apart from all northeastern Pacific and Arctic Naticidae .

Holotype — UCMP 123663 from UCMP locality- IP23235.

Paratypes — UCMP 123666 from UCMP locality IP23232 and UCMP 123677 from UCMP locality IP 23248.

Referred Collections —The number of specimens and partial specimens in each collection are documented as follows: complete or nearly complete specimens followed in square brackets by partial specimens or larger identifi- able fragments – i.e., 5[4] = 5 complete or nearly complete specimens (4 significantly broken or fragmented speci- mens). UCMP localities IP22958 (3[3]), IP23232 (5[1]), IP23233 (0[1]), IP23235 (3[0]), IP23238 (3[0]), IP23239 (3[0]), IP23248 (1[2]), IP23264 (4[0]), IP23266 (1[0]), IP23272 (2[0]), IP23279 (1[0]), IP23280 (7[0]), IP23316 (1[0]), IP23511 (3[3]), IP23555 (1[0]), IP23559 (12[3]), IP23561 (1[1]), IP23574 (7[0]), IP23576 (4[0]), IP23577 (8[0]), IP23588 (1[2]), IP23589 (6[2]), IP23590 (16[5]), IP23593 (9[1]), IP23596 (4[1]), IP23597 (1[0]), IP23602 (1[0]), IP23607 (1[0]), IP23721 (2[0]), IP23722 (5[0]), IP23724 (6[1]), IP23812 (1[0]), IP23856 (4[3]), IP23857 (3[0]), IP23868 (1[2]), IP23870 (6[1]), IP23879 (1[0]), IP23884 (5[0]), IP24104 (7[0]).

Additional collections observed: USGS localities M8151 and M8997. These collections could not be locat- ed at UCMP, but were identified for internal USGS E&R’s (Evaluation and Report documents). The information is added here for completeness as either Louie Marincovich or the senior author ( CPII) identified the specimens.

Locality information for all collections can be found in Appendix 1.

Occurrence — Known only from the Gubik Formation along the northwestern part of the Arctic Coastal Plain (North Slope) of Alaska from Skull Cliff south of Barrow in the west to along the Colville River and Kogru River/ Teshekpuk Lake areas in the east, North Slope Borough, Alaska ( Figure 6 and Appendix 1). Early Pleistocene in age (see discussion for details).

Etymology — This new species is named for Louie Marincovich, Jr. who first introduced this species to the senior author and for his work on unraveling many mysteries of Paleogene–Neogene Arctic geology and paleontology.

Description — This new species has a naticiform shell about as high as wide and with a moderate thick, substantial shell. The spire is very short and consists of about four whorls and is less than a tenth the height of the entire shell. The protoconch is worn on all specimens and not available for description.With a generally smooth shell profile the whorls show a slight indentation or suture and a very fine, channel at the top of its whorls. The exterior of the shell shows very fine, closely spaced, irregular, spiral threads crossed by very fine, closely spaced, mostly continuous, radial threads forming a microscopic crosshatch pattern covering the exterior of the shell ( Figure 5 ). The aperture is large, near–tear–drop shape and is about three–quarters of the shell's height with a parental callus that mirrors the inner margin of the aperture a few millimeters wide. The posterior apertural

Figures

Figure 5. Close–up of spiral and radial sculpture on the body whorl of the holotype specimen. Field of view approximately 0.5 cm. Blue arrow indicates radial sculpture, red arrow indicates spiral sculpture. angle of the aperture is acute and points towards the apex. A deep, partially open umbilicus is present, but is obscured in part by the umbilical callus making it tear– drop shaped.

Figure 6. Map showing generalized occurrences of Euspira? louiemarincovichi along the northern coastal plain of Alaska. These occurrences are concentrated in three areas: adjacent to the Colville River (southern eastern occurrences), near and along the Kogru River/Teshekpuk Lake (northern eastern occurrences), and along Skull Cliff (occurrences southwest of Barrow to the west). Not all collections are represented in this figure, just enough to determine the general geographic areas where this new species occurs. Some addition geographic names are mentioned to help interpret the geographic ranges of some gastropods.

Figures 1–4. Euspira? louiemarincovichi n. sp. UCMP holotype 123663, UCMP locality IP23235 (USGS M7346). Bar = 1 cm. 1. Aperical view, 2. Apical view, 3. Umbilical view, 4. Inclined side view. Photographs by Dave Strauss, UCMP.