Iowa Devonian ammonoids, biostratigraphy, paleogeography
Recovery of rare, well-preserved representatives of Manticoceras from Upper Devonian (Frasnian) strata of north and east-central Iowa allows clarification of the poorly understood species Manticoceras regulare Fenton & Fenton, and marks the first recorded North American occurrence of Manticoceras lindneri Glenister. The faunal horizons correlate with the upper Manticoceas cordatum (1-y) ammonoid zone and the Palmatolepis gigas conodont zone. M. regulare can be recognized by its narrowly discoidal conch, relatively broad sutural elements, and mature conch diameter of approximately 11 cm. Occurrences of M. regulare have been restricted to the "Amana Beds" of the Independence Shale and Cerro Gordo Member of the Lime Creek Formation. The larger M. lindneri (mature diameter of approximately 19 cm) possesses a moderately wide conch and narrow sutural elements. All known Iowa representatives are from the Owen Member of the Lime Creek Formation in the north-central portion of the state. The only other known occurrence of M. lindneri is from the lower Virgin Hills Formation, Fitzroy Basin, Western Australia. Recently proposed Devonian paleogeographic reconstructions suggest that such a wide distribution may be attributed to the dispersal effects of warm, equatorial currents.
Proceedings of the Iowa Academy of Science
© Copyright 1986 by the Iowa Academy of Science, Inc.
Baker, Cathy; Glenister, Brian F.; and Levorson, Calvin O.
"Devonian Ammonoid Manticoceras From Iowa,"
Proceedings of the Iowa Academy of Science: Vol. 93:
, Article 4.
Available at: http://scholarworks.uni.edu/pias/vol93/iss1/4