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Reference
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| Title: |
Letter
,
1964
(10/26)
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[letter to N. J. Silberling and D. L. Jones. Subject: Pelecypods from USGS Mes. locs. M2317, M2318 and 24060 in northern Alaska] |
| Report by: |
Ralph W. Imlay
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| Referred by: |
William W. Patton
, Jr.
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| | Age: | Early Jurassic |
| Formation: | Shublik Formation |
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| Comment: | The Inoceramus from loc. 24060 resembles some of the smoother forms of I. lucifer Eichwald found at the base of the Middle Jurassic at Wide Bay.
The pelecypod assigned to Meleagrinella differs from any species of Meleagrinella in our Jurassic collections from Alaska by being more elongate posteriorly, by having a fairly long posterior wing and by its ribs being more wavy. However, some of the immature specimens and some of the umbonal portions of large specimens do resemble Meleagrinella.
To me the pelecypod species from northern Alaska is very similar to Otapiria marshalli (Trechmann) from the basal Jurassic (Hettangian and Sinemurian) of New Zealand and the Hettangian of New Caledonia. It differs from O. marshalli mainly by being a little smaller.
Otapiria was defined by Marwick in 1935 and "Pseudomonotis" marshalli Trechmann was selected as the genotype. It was reillustrated by Marwick in 1950 along with Otapiria dissimilies Cox from the Rhaetic and O. masoni Marwick from beds of middle Kimmeridgian age.
The genus Meleagrinella has been described in great detail by Cox (1940). It differs from Otapiria by being orbicular to subquadrate in outline instead of obliquely elongate, by having a short posterior wing, by having much less wavy ribbing, and by the right valve instead of the left being smooth or bearing weaker radial threads.
In a recent monograph by some Russian paleontologists (Saks and others, 1963), the pelecypod Otapiria limaeformis Tuchkov is listed as occurring in beds of Hettangian and Sinemurian ages. I have not found descriptions and illustrations of the species, but in a paper published by I.I. Tuchkov in 1957 he mentions that species under the genus Psuedomonotis (Anaucella). New Anaucella was described by Pchelintseva in 1962 for some Jurassic forms of Buchia and some other species as old as Upper Triassic. Apparently Tuchkov now considers that his species limaeformis belongs to Otapiria rather than to Pseudomonotis or to Anaucella.
In summary, the pelecypod species from Alaska shows more resemblance ot Otapiria than to Meleagrinella and it is closely similar to the genotype species O. marshalli (Trechmann). The association with an Inoceramus similar to I. lucifer shows that it is of Jurassic age not younger (higher) than middle Bejocian. |
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| Title: |
The Mesozoic Pelecypods Otapiria Marwick and Lupherella Imlay, New Genus, in the United States
,
1967
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Abstract: The pelecypod genera Otapiria Marwick and Lupherella Imlay, n. gen., both resembling the late Triassic genus Monotis, are recorded for the first time from Mesozoic beds in the United States. Lupherella is represented by L. bocchiformis (Hyatt) from beds of Pliensbachian age in eastern Oregon and California. It has not been found elsewhere. One species of Otapiria, named O. tailleuri Imlay, n. sp., has been found in northern Alaska associated with or directly underlying Inoceramus cf. I. lucifer Eichwald, whose presence indicates an early Middle Jurassic or late Early Jurassic age not older than Toarcian. Another species, referred to as O. sp. undet., has been found as float in the upper Yukon Valley in east-central Alaska. Its age is unknown, but the presence of the crinoid Pentacrinus subangularis var. alaska Springer in the same float indicates that beds of Early Jurassic age are present in the area. Otapiria has been found previously in Upper Triassic to Upper Jurassic beds in New Zealand, Lower Jurassic beds in New Caledonia, and Upper Triassic to Lower Jurassic beds in northeastern Siberia. |
| Report by: |
Ralph W. Imlay
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| | Age: | Toarcian-Bajocian (Toarcian - early Bajocian) |
| Formation: | Unnamed |
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| Title: |
Report on Referred Fossils
,
1964
(09/10)
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| Report by: |
Norman J. Silberling
,
David L. Jones
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| Referred by: |
William W. Patton
, Jr.
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| | Age: | Middle Jurassic (Middle? Jurassic) |
| Formation: | Shublik Formation |
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| Comment: | Both of these collections [64APa206 and 64APa224] contain a distinctive pteriid pelecypod identical to that associated with the Middle Jurassic pelecypod Inoceramus lucifer Eichwald in a collection from USGS Mesozoic loc. 24060 (= 51ATr94) on Ipnavik Creek. In this collection from the Ipnavik River, the pteriid in question is not preserved on the same slabs that bear the Inoceramus, but Inoceramus shell prisms are abundant in thin sections of the slabs with the pteriids and their presence argues against this collection being a mixed lot. Thin sections of material from 64APa224 also contain some Inoceramus prisms along with abundant radiolaria in a noticeably petroliferous matrix.
The pteriid in common to these three collections in evidently an undescribed species best assigned to Meleagrinella, a genus typical of the Jurassic but ranging down into the Upper Triassic. The structure of its dorsal margin clearly precludes assigning it to either Halobia or Monotis (sensu stricto). |
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