Xylodiscula okutanii, Kiel & Goedert, 2007
publication ID |
https://doi.org/ 10.5281/zenodo.13271709 |
persistent identifier |
https://treatment.plazi.org/id/6713F503-FFB1-5E60-0F43-3C87FE790212 |
treatment provided by |
Felipe |
scientific name |
Xylodiscula okutanii |
status |
sp. nov. |
Xylodiscula okutanii sp. nov.
Fig. 4 View Fig .
2006 Hyalogyrina View in CoL n. sp.; Kiel and Goedert 2006a: 2626, fig. 2j, l.
Derivation of the name: After Takashi Okutani, Kanagawa.
Holotype: USNM 531406 About USNM . Well−preserved specimen with lower half of aperture and base concealed by matrix.
Type locality: USGS loc. 26897−A, Merrick's Bay , Clallam County, Washington State, USA .
Type horizon: Uppermost Oligocene to lowermost Miocene, Pysht Formation.
Material.— Holotype only.
Diagnosis.—A Xylodiscula with almost three whorls, protoconch made of one and one−fifth whorls, 211 ̊m wide, initial part with fine polygonal pattern; teleoconch made of one and three−quarter well−rounded whorls, growth lines sinuous and well−visible near suture.
Description.—Embryonic part of protoconch heterostrophic, one−half whorl, 102 ̊m wide; larval shell smooth except for occasional broad, sinuous wrinkles. Teleoconch skeneiform, one and three−quarter whorls, smooth, growth lines sinuous near suture, otherwise prosocline. Shell composed of an inner and an outer layer of simple prismatic structure, and an intersected crossed−acicular layer in between. Diameter 1.03 mm. Discussion.—We assigned this species earlier to the genus Hyalogyrina Marshall, 1988 because it resembles some low−spired species of this genus, like the Japanese H. depressa Hasegawa, 1997 . But we are now convinced that this species rather belongs to Xylodiscula , because Hyalogyrina has a different type of protoconch, which usually consists of half or three−quarters of a whorl only, and has a larger whorl expansion rate than the protoconchs of Xylodiscula . Most Recent species of Xylodiscula differ from X. okutanii by having a more−or−less well developed shoulder. This includes the type species which has a strong shoulder. An additional difference to X. okutanii is the more pronounced transition from protoconch to teleoconch. X. eximia Marshall, 1988 is somewhat shouldered, although much weaker than X. vitrea , and the shoulder may be indicated by a spiral ridge only. Another species with slightly angular whorls is the vent−inhabiting X. analoga Warén and Bouchet, 2001 . The shell microstructure of X. okutanii is very similar to that of X. analoga ( Kiel 2004) .
A somewhat similar heterobranch from the uppermost Eocene of western Washington, but with a planispiral shell is Cyclostremella (?) chimaera Hickman, 1980. That species has an entirely sinistrally coiled protoconch ( Hickman 1980b), whereas in Xylodiscula okutanii only the embryonic shell is sinistral.
Stratigraphic and geographic range.—Uppermost Oligocene to lowermost Miocene, upper part of the Pysht Formation, Washington State, USA.
USGS |
U.S. Geological Survey |
No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.
Kingdom |
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Phylum |
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Genus |
Xylodiscula okutanii
Kiel, Steffen & Goedert, James L. 2007 |
Hyalogyrina
Kiel, S. & Goedert, J. L. 2006: 2626 |