Sample Detail of
Sample: Sample No. 65ATr73.5 -- USGS No. Mesozoic loc. 29280
Locality: Field No. 65ATr73.5
Description: (=64 Snelson 321 and 64T305). Howard Pass quad. at 68o 37'30" N., 156o 42'30" W; sec. 36, T. 9 S., R. 21 W.; south of Lisburne Ridges. Same locality as 64T305 and 64 Shell. Additional fossils from Otapiria zone. [I.L. Tailleur, 1965, Same locality data as Mesozoic loc. M2451. (description from Imlay, 1967, p. B6)-*NOTE by R.B. Blodgett lat.long date slightly different here: lat 68o 37.62' N., long 156o 43.05' W]
Location: Alaska Quadrangle: Howard Pass C-2
Township&Range: T9S R21W Section: Sec.36
Lat.: 68o37'30 " Long.: 156o42'30 "
Reference
Title: Report on Referred Fossils ,  1965 (12/06)
The common pelecypod in these collections from northern Alaska belongs to the genus Otapiria (see memos of Oct. 26, 1964 and Jan. 29, 1965 to N.J. Silberling) and is similar in size, shape and ribbing to O. limaeformis Zakharov from northeastern Siberia. It differs by having distinct ribbing on its right valve, whereas the right valve of the species from Siberia is smooth.

The two ammonites from locs. 65ATr123B and 65ATr149.4 are highly evolute and have strong, straight radial trending, widely spaced ribs. The specimen from loc. 65ATr123B may have a low keel on its venter. These ammonites resemble genera that are fairly common in Lower Jurassic beds and in basal Middle Jurassic beds. In side view they resemble such genera as Tmetoceras from the basal Bajocian and Catulloceras and Dumortieria from the upper Toarcian, which genus has a sulcus on its venter.

One bit of evidence against an early Bajocian age for the Otapiria-bearing beds is the presence of a well preserved specimen of Oxytoma (loc. 65ATr73.5) that does not belong to O. jackonsoni (Pompeckj). That species occurs in basal Bajocian beds on Prince Patrick Island (Frebold, 1957, Geol. Survey Canada Bull. 41, p. 14, 23, pl. 6, figs. 1-3) and on the Canning River (Mes. loc. 24035).

One bit of evidence against a Toarcian age for the Otapiria beds is the presence of Inoceramus similar to I. lucifer Eichwald, which species at Wide Bay in the Alaska Peninsula and in the Cook Inlet region ranges through beds that are correlated with the early Bajocian and early middle Bajocian of Europe on the basis of ammonites. Similarly in Japan Inoceramus similar to I. lucifer occurs in beds of Bajocian age (Hayami, 1960, Jour. Fac. Sci., Univ. Tokyo, Sec. II, vol. 12, pt. 2, p. 292.)

An age not older than Toarcian for the Otapiria beds is shown by the fact that true Inoceramus is present. This genus according to Hayami (1960, p. 292, 294) originated near the end of the Early Jurassic time and became common in the Bajocian.

In summation, the ammonites present in the Otapiria beds indicate an Early Jurassic or early Middle Jurassic age. The specimens remind me of genera that occur near the Toarcian-Bajocian boundary. The presence of true Inoceramus shows that the beds are not older than Toarcian. This resemblance of the Inoceramus to I. lucifer Eichwald favors an early Bajocian age. Possibly the Otapiria-beds span the Toarcian-Bajocian boundary.
Report by: Ralph W. Imlay
Referred by: Irv L. Tailleur
Age: Toarcian-Bajocian
Comment:The common pelecypod in these collections from northern Alaska belongs to the genus Otapiria (see memos of Oct. 26, 1964 and Jan. 29, 1965 to N.J. Silberling) and is similar in size, shape and ribbing to O. limaeformis Zakharov from northeastern Siberia. It differs by having distinct ribbing on its right valve, whereas the right valve of the species from Siberia is smooth.

One bit of evidence against an early Bajocian age for the Otapiria-bearing beds is the presence of a well preserved specimen of Oxytoma (loc. 65ATr73.5) that does not belong to O. jackonsoni (Pompeckj). That species occurs in basal Bajocian beds on Prince Patrick Island (Frebold, 1957, Geol. Survey Canada Bull. 41, p. 14, 23, pl. 6, figs. 1-3) and on the Canning River (Mes. loc. 24035).

One bit of evidence against a Toarcian age for the Otapiria beds is the presence of Inoceramus similar to I. lucifer Eichwald, which species at Wide Bay in the Alaska Peninsula and in the Cook Inlet region ranges through beds that are correlated with the early Bajocian and early middle Bajocian of Europe on the basis of ammonites. Similarly in Japan Inoceramus similar to I. lucifer occurs in beds of Bajocian age (Hayami, 1960, Jour. Fac. Sci., Univ. Tokyo, Sec. II, vol. 12, pt. 2, p. 292.)

An age not older than Toarcian for the Otapiria beds is shown by the fact that true Inoceramus is present. This genus according to Hayami (1960, p. 292, 294) originated near the end of the Early Jurassic time and became common in the Bajocian.

In summation, the ammonites present in the Otapiria beds indicate an Early Jurassic or early Middle Jurassic age. The specimens remind me of genera that occur near the Toarcian-Bajocian boundary. The presence of true Inoceramus shows that the beds are not older than Toarcian. This resemblance of the Inoceramus to I. lucifer Eichwald favors an early Bajocian age. Possibly the Otapiria-beds span the Toarcian-Bajocian boundary.

Occurrence(s)
No. Group Name Qty Notes
1 Bivalves Otapiria sp.
2 Bivalves Inoceramus sp.
3 Bivalves Oxytoma sp.
4 Ammonoids ammonite fragment
5 Vertebrates fish scales

Title: The Mesozoic Pelecypods Otapiria Marwick and Lupherella Imlay, New Genus, in the United States ,  1967
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
Age: Toarcian-Bajocian (Toarcian - early Bajocian)
Formation: Unnamed (Unnamed organic shale)
Occurrence(s)
No. Group Name Qty Notes
1 Bivalves Otapiria tailleuri Imlay n. sp.