PaleoBios, Volume 14, Number 1, Pages 1-2, April 24, 1992 Reworked Cleiotkyridina sp. in the Seymour Canal Formation (Jurassic-Cretaceous), Southeastern Alaska Rex Alan Hanger1 and Harvey A. Cohen2 1 Museum of Paleontology & Dept. of Integrative Biology University of California, Berkeley, CA 94720; 2Dept. of Geological and Geophysical Sciences Princeton University, Princeton, NJ 08544 A single, fragmentary specimen of the Late Paleozoic (Pennsylvanian - Permian) brachiopod, Cleiotkyridina sp., was found within a reworked cherty limestone clast within the Jurassic- Cretaceous Seymour Canal Formation on Marsh Island, southeastern Alaska. The Seymour Canal Formation is a part of the Gravina Belt volcanic arc terrane, consisting mostly of deep-water flysch sedimentary rocks and andesitic volcanics (Berg et al., 1972). The occurrence of a late Paleozoic (probably Permian) fossil within the Seymour Canal Formation is important for three reasons: 1) Analysis of sedimentary lithofacies and petrology (Cohen and Lundberg, 1990) indicates that sediments of the Gravina basin were derived primarily from a contemporaneous Jurassic- Cretaceous arc. Positive identification of Cleiothyridina sp. provides concrete evidence for the existence of an additional (older) source terrane, and is consistent with other inherited Paleozoic fossils found in the Seymour Canal Formation (Brew and Karl, 1988). 2) Although the (Jurassic-Cretaceous) Gravina Belt is considered to depositionally overlie the (Paleozoic-Triassic) Alexander terrane (Berg et al., 1972), no unmodified depositional contacts between the Gravina Belt and older rocks have been found (Brew and Karl, 1988). Any reworked Paleozoic or Triassic fossils within the Gravina Belt that show a particular affinity with the undescribed (but see faunal lists in Buddington and Chapin, 1929, and Loney, 1964) faunas of the Alexander terrane would provide evidence in support of the hypothesized Gravina-Alexander association. 3) Finally, the discovery of Cleiothyridina sp. in the Seymour Canal Formation augments the global Permian brachiopod paleobiogeography (Hanger, 1990, in prep.) which has as one goal the determination of original relative positions of circum-Pacific terranes. Of particular importance is the relation of the Alexander terrane to the Wrangellia terrane (Jones, 1991) which requires the complete description/comparison of all southeastern Alaska fauna, of which this is a part. A detailed description of UCMP hypotype 39668 is provided to facilitate future taxonomic and paleobiogeographic comparisons. SYSTEMATIC PALEONTOLOGY Family Athyrididae McCoy, 1844 Subfamily Athyridinae McCoy, 1844 Genus Cleiothyridina Buckman, 1906 Cleiothyridina sp. (Fig. 1, a-c) Specimen: UCMP hypotype 39668. Location: From UCMP Locality 11086, which is on the southeast corner of Marsh Island, at 56° 06' 50" N and 132° 42' 48" W, on the Petersburg (A-3), Alaska, 15-minute U. S. Geological Survey quadrangle, 1953 version. Description: Large size for genus; strongly biconvex; subelliptical outline; anterior commissure uniplicate; fold moderately prominent; foramen small, incomplete and subcircular; maximum width anterior to midlength; strong concentric lamellae, closely spaced; spines up to 2mm length preserved only anterior to midlength. Dorsal valve with swollen, pointed beak. Dorsal interior with strong cardinalia and deep sockets; large three-element hinge plate; lateral elements wide, flat and lobate; medial element slightly depressed with deep, subtrigonal perforation; anterior ends of lateral elements with pointed projections to crura; deeply Hanger and Cohen Cleiothyridina sp. Page 2 Figure 1. All UCMP 39668. a) dorsal exterior, X 1.3. b) brachial valve interior, X 1.3. c) close-up of anterior margin, showing spines, X 4.6. impressed posterior adductor scars; low midline; radial lines, weakening anteriorly. Measurements: length (broken) = 36.05mm, curved length (broken) = 46.30mm, half-width (x2) = 44.00mm, foramen diameter = 2.80mm, hinge- plate width = 7.35mm. Discussion: UCMP hypotype 39668 is one of the largest individuals of Cleiothyridina ever described from any Permian rocks worldwide. North American species of this genus typically are small in size, less than 20mm total length. Large species typify Asian Tethyan deposits (Cooper and Grant, 1976; Grant, 1976). The Asian species, C. accola (Reed, 1944, pp. 266-267) from the Middle and Upper Productus Limestone of the Salt Range in Pakistan and C. excavata (Grabau, 1931, p. 117) from the Jisu Honguer Limestone in Mongolia, are most similar in both overall size and exterior features to UCMP 39668. Interior characters of the two Asian species are not known and so cannot be directly compared to UCMP 39668. REFERENCES Berg, H.C., D.L. Jones and D.H. Richter. 1972. Gravina- Nutzotin Belt - tectonic significance of an Upper Mesozoic sedimentary and volcanic sequence in southern and southeastern Alaska. United States Geological Survey, Professional Paper, 880D: Dl- D24. Brew, D.A. and S.M. Karl. 1988. A reexamination of the contacts and other features of the Gravina Belt, southeastern Alaska. United States Geological Survey, Circular, 1016:143-146. Buddington, A.F. and T. Chapin. 1929. Geology and mineral deposits of southeastern Alaska. United States Geological Survey, Bulletin, 800:1-398. Cohen, H.A. and N. Lundberg. 1990. Jura-Cretaceous sedimentation on the eastern slope of the Wrangellian microcontinent: lithofacies of the Seymour Canal Fm., Gravina Belt of Northern Southeast Alaska. GSA Abstracts With Programs, 22(3): 3. Cooper, G.A. and R.E. Grant. 1976. Permian brachiopods of West Texas, IV. Smithsonian Contributions to Paleobiology, 22:1923-2608. Grabau, A.W. 1931. The Permian of Mongolia. Natural History of Central Asia, Volume 4:1-665. Grant, R.E. 1976. Permian brachiopods of Southern Thailand. Paleontological Society, Memoir 9 (Journal of Paleontology, 50(3) suppl.): 1-269. Hanger, R.A. 1990. A probabilistic global paleobiogeography for Permian brachiopods with implications for North America terrane analysis. GSA Abstracts With Programs, 22(7): 304. Loney, R.A. 1964. Stratigraphy and petrography of the Pybus-Gambier Bay area, Admiralty Island, Alaska. United States Geological Survey, Bulletin, 1181R: R1-R48. Reed, F.R.C. 1944. Brachiopoda and Mollusca from the Productus Limestones of the Salt Range. Palaeontologia Indica, 23(2, new series): 1-679.