Crenella porterensis, WEAVER, 1912

Hickman, Carole S., 2023, Paleogene marine bivalves of the deep-water Keasey Formation in Oregon, Part II: The pteriomorphs, PaleoBios 40 (5), pp. 1-51 : 6-8

publication ID

https://doi.org/ 10.5070/P940561331

publication LSID

lsid:zoobank.org:pub:1756B24A-813B-423F-896F-91B21FF58A79

DOI

https://doi.org/10.5281/zenodo.11505085

persistent identifier

https://treatment.plazi.org/id/C23987DD-FFFF-2935-FF44-F9FDEBF4BC6F

treatment provided by

Felipe

scientific name

Crenella porterensis
status

 

CRENELLA PORTERENSIS WEAVER , 1912

FIGS. 3A–C, E View Figure 3 ; 4A View Figure 4

Crenella porterensis Weaver (1912) . p. 15; pl. 14, fig. 115.

Crenella porterensis Weaver, Weaver (1916) . pp. 36–37; figs. 41, 42.

Crenella porterensis Weaver, Weaver (1943) . p. 115; figs. 3, 4.

Crenella porterensis Weaver, Durham (1944) . p. 140. (unfigured hypotype UCMP 35163).

Crenella porterensis Weaver, Vokes in Warren, Norbisrath and Grivetti (1945).(checklist)

Crenella porterensis Weaver, R.C. Moore and Vokes (1953) . p. 119.

Crenella porterensis Weaver, Kanno (1971) . p. 47. pl. 1, fig. 27.

Crenella porterensis Weaver, Armentrout (1973) . pp. 387–389; pl. 8, fig. 23.

Crenella porterensis Weaver, E.J. Moore (1976) . p. 45; pl. 12, fig. 12.

Solamen porterensis (Weaver) , Addicott (1976b). p. 29; pl. 4, figs. 3,11.

Crenella porterensis Weaver, Allison and Marincovich (1981) . pp. 4, 8; pl. 1, figs. 5, 6.

? Crenella View in CoL cf. C. porterensis Weaver, E.J. Moore (1963) . p. 63; pl. 25, fig. 6.

? Crenella sp. ? Hickman (1969). pp. 33-34.

? Solamen snavelyi Addicott (1976b) . p. 29; pl. 4, figs. 6,9. not Crenella porterensis Weaver , Tegland (1933). p. 112; pl. 6, fig. 2.

Discussion — Crenella porterensis is distinguished by its thin and strongly inflated shell, ovate-elongate shape, prominent prosogyrous umbones, external elongate posterior ligament groove, and sculpture of numerous (>100) very fine radial ribs with distinct narrow interspaces and weaker commarginal ribs. Ribs terminate at the ventral margin to produce fine interlocking crenulations. Increase in the number of radial ribs is primarily by intercalation ( Fig. 4A View Figure 4 , black arrows) of new ribs, although bifurcation also occurs ( Fig. 4A View Figure 4 , yellow arrow). Both modes of rib numerical increase may occur on a single specimen. Rib increase is most prominent late in growth on the medial portion of the shell. Shell growth is strongly allometric with an initially ovate shape increasing to elongate and clearly visible at growth checks on a single adult shell ( Fig. 2A View Figure 2 ).

The finely decussate shell surface layer is translucent, and the thin underlying (middle) nacreous layer is visible as a pattern that is enhanced as light passes through fine interruptions of crossing radial and concentric elements of surface sculpture. A third non-nacreous layer is present interior to the middle nacreous layer in some of the Keasey shells. This is consistent with observations of complex crossed lamellar aragonite and other aragonitic microstructures in the interior layer of crenellids ( Carter 1990). The interior of well-preserved dry shells of living Crenella decussata (Hickman, personal observation) suggests a patchy, discontinuous distribution of mineralogy and microstructure that includes some nacre.

Although none of the specimens examined are sufficiently well preserved for excavation of the hinge, offset of the valves below the beaks reveals part of a thickened denticulate plate ( Fig. 3A View Figure 3 ). A denticulate hinge plate is characteristic of type Crenella , distinguishing it from edentulous living species assigned to the genus Solamen . This is probably a long-ranging species complex that includes the Miocene crenellid described by Addicott (1976b) as Solamen snavelyi . Armentrout (1973) reported it from six molluscan zones extending from the late Eocene into the early Miocene. The Miocene specimen from the Astoria Formation, illustrated by E.J. Moore (1963, pl. 25, fig. 6) has a denticulate hinge, and the mode of duplication of radial sculpture is consistent with the two modes documented here in Crenella porterensis .

Geographically, this is a high-latitude, cool-water species complex, occurring from the Keasey Formation in Oregon to the Poul Creek and Narrow Cape Formations in the Gulf of Alaska ( Kanno 1971, Allison and Marincovich 1981). The fauna of the Narrow Cape Formation is noted for its mixture of Asiatic, North American, and endemic high-latitude North Pacific taxa ( Allison and Marincovich 1981).

The Danian Crenella kannoi Marincovich (1993) from the Prince Creek Formation on the Arctic coastal plain of Alaska is strikingly similar in size and ovate-elongate shape to C. porterensis , but differs in a distinctive pattern of concentric undulations and wavy radial threads. As noted above, Arctic and Northeastern Pacific faunas were not connected at this time.

Material examined — 13 specimens.

Figured Keasey hypotypes — UCMP 110725 (in matrix), length 7.9 mm, height 10.8 mm, Loc. UCMP IP7984 (= USGS 25031); UCMP 110726 (in matrix), length 7.9 mm, height 9.8 mm, Loc. UCMP IP2286 (= USGS 15265); USNM 561803, length 8.9 mm, height 9.5 mm. Loc. USGS 15282.

Figured Lincoln Creek hypotypes — UCMP 32410, length 10.18 mm, height 18.2 mm, Loc. UCMP A9 (= UW 256, Weaver’s type locality); UCMP 35163, length 11.7 mm, height 18.0 mm, Loc. UCMP A1811.

Keasey Formation localities —Lower member: UCMP IP2286, USGS 15265. Middle member: UCMP IP7984, USGS 15282, 15276, 15277, 15279, 15525. Upper member: USGS 13515, 15518.

Other occurrences —In Oregon this species also occurs stratigraphically higher in the overlying Pittsburg Bluff Formation and Miocene Astoria Formation. In Washington it occurs in the Eo-Oligocene Lincoln Creek Formation, Quimper Sandstone, and Blakeley Formation .

UCMP

University of California Museum of Paleontology

USGS

U.S. Geological Survey

USNM

Smithsonian Institution, National Museum of Natural History

UW

University of Washington Fish Collection

Kingdom

Animalia

Phylum

Mollusca

Class

Bivalvia

Order

Mytilida

Family

Mytilidae

Genus

Crenella

Loc

Crenella porterensis

Hickman, Carole S. 2023
2023
Loc

Crenella

Hickman 2023
2023
Loc

Crenella porterensis

Weaver, Allison and Marincovich 1981
1981
Loc

Crenella porterensis Weaver, E.J. Moore (1976)

Weaver, E. J. Moore 1976
1976
Loc

Solamen snavelyi

Addicott 1976
1976
Loc

Crenella porterensis

Weaver, Armentrout 1973
1973
Loc

Crenella porterensis

Weaver, Kanno 1971
1971
Loc

C. porterensis Weaver, E.J. Moore (1963)

Weaver, E. J. Moore 1963
1963
Loc

Crenella porterensis

Weaver, Durham 1944
1944
Loc

Crenella porterensis

Weaver, Vokes 1912
1912
Loc

Crenella porterensis Weaver

Weaver, Vokes 1912
1912
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