Lituyapecten poulcreekensis (MacNeil, 1961)
MACNEIL, F. S. 1961. Lituyapecten (new subgenus of Patinopecten) from Alaska and California and Stratigraphic occurrence of Lituyapecten in Alaska. United States Geological Survey Professional Paper, 354-J, K [p. 229, pl. 36, fig. 5; pl. 38, fig. 5]
1961 Lituyapecten poulcreekensis MacNeil, 1961
F. S. MacNeil, 1961, plate 36.
F. S. MacNeil, 1961, plate 38.
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«Two incomplete specimens from near the Poul Creek- Yakataga formation boundary, but whose exact formational position is not known, are unique in having some sculptural details like P. (L.) poulcreekensis, some sculpture intermediate between P. (L.) poulcreekensis and P. (L.) yakatagensis, and narrower and more numerous ribs, agreeing in this respect more with P. (L.) yakatagensis. They could well represent linear intermediates between the two species, but at the same time they are typical of neither. The earliest growth stage on one fragment shows it to have concentric raised growth lines like juveniles of poulcreekensis and yakatagensis. Interstitial ribs with moderately strong flanges are present in some of the interspaces, agreeing in this respect with poulcreekensis.
The prevalence in this form of single strong flanges completely crossing the ribs suggests that it may be ancestral to the P. (L.) dilleri group, of which group a fragment obtained high in the section in the Lituya Bay district is believed to be a member (pl. 45, fig. 4; right valves on pl. 41, figs. 4, 5). This form is not being named at present, although with better preserved material it probably would be. It seems likely that this form and typical P. (L.) poulcreekensis had a common ancestry but are at least subspecifically distinct. If this form and the one from the Suckling Hills (pl. 35, fig. 6) were end members of the same population it would be variable indeed. The largest fragment figured (GAS 29285) has a diameter of 118 mm, a fraction of the whole dimension. Distribution.— Early Miocene, uppermost part of the Paul Creek formation or the lowermost part of the Yakataga formation, Yakataga district, Alaska. Localities.— CAS 29285; USGS D341 (T).» FRANCIS STEARNS MACNEIL, 1961
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