文章基本信息

标题：Lower jaw of Spathites (Ammonoidea, Acanthoceratoidea) from the Upper Cretaceous (Turonian) of New Mexico. (American Museum novitates, no. 3925)
本地全文：下载
作者：Landman, Neil H. ; Sealey, Paul L. ; Foley, Michael P. 等
期刊名称：American Museum Novitates
印刷版ISSN：0003-0082
电子版ISSN：1937-352X
出版年度：2019
卷号：2019
页码：1-12
出版社：American Museum of Natural History
摘要：A lower jaw was recently discovered in a limestone concretion in association with the Late Cretaceous (Turonian) ammonite Spathites puercoensis (Herrick and Johnson, 1900) from the Carlile Member of the Mancos Shale in Sandoval County, New Mexico. It is nearly complete and comprises the aptychus with a hinge along the midline. The better-preserved plate, the left (according to its position in life), is roughly triangular in shape with a broadly rounded lateral margin, a narrowly rounded posterior margin, and a weakly concave anterior margin. It is 26.2 mm wide and 33.0 mm long. Together, the left and right plates form an escutcheonlike shape that projects slightly forward at the apex. The ratio of jaw width to length (26.2 mm x 2 / 33.0 mm) equals 1.59. The aptychus consists of yellow-orange calcite and is covered with comarginal ribs that parallel the lateral and posterior margins and become more prominent toward the posterior end. It is likely that this jaw belongs to the associated ammonite and would have comfortably fit inside the body chamber, based on a comparison of the length of the jaw and the whorl height, suggesting that it functioned as a jaw, rather than as an operculum. It is the first report of an ammonite jaw in the genus Spathites and the first reported occurrence of an ammonite jaw from New Mexico.
关键词：Spathites puercoensis -- Anatomy.; Mandible.; Ammonoidea -- Anatomy.; Sandoval County (N.M.); New Mexico.; Mancos Shale.