Published in Journal of Vertebrate Paleontology, Volume 21, Issue 1, March 1, 2001, pages 24-33. Copyright © 2005 Society of Vertebrate Paleontology. Journal webpage: http://vertpaleo.org/publications/JVPContent.cfm.
A partial fish skull with a nearly complete rostrum, a cup-shaped sclerotic hone, and cycloid scales (UCMP 123170) from the Yaquina Formation (late Oligocene, Oregon) is described and identified as Aglyptorhynchus maxillaris, sp. nov. Unusual features of the rostrum include a fused premaxillary segment with a low dorsal keel, and a maxilla with both a flat flange on its postero-ventral margin and a large condyle that presumably allowed dorsoventral movement of the rostrum to increase the gape. The Yaquina Formation was estimated to have been deposited at a water depth of over 100m and a sea surface temperature of at least 20°C, conditions that are similar to the preferred habitats of extant billfish and postulated paleoenvironments of blochiids from the Ashley River Formation, Belgian Basin, London Clay, and Monte Bolea. This is the first record of a blochiid from a deposit bordering the Pacific Ocean. It is hypothesized that A. maxilmaris or its ancestor emigrated from the warm Gulf Stream of the Atlantic into the Pacific via the Panama Seaway.