ABSTRACT. The heteromorphic ammonite Chesapeakiceras nodatum Kennedy and Cobban, 1993, has been known only from the late Santonian to early Campanian Merchantville Formation of the Atlantic Coastal Plain of the United States. Prior to this report, only three fragmentary specimens have been recovered from the Chesapeake and Delaware Canal in the state of Delaware, U.S.A. Here we describe a fourth specimen, NJSM GP23099, that is the most complete known fragment of C. nodatum and is the only existing specimen that has been recovered “in situ”. This demonstrates that the stratigraphic range of C. nodatum extends into the upper Merchantville Formation.

中文翻译：

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重新描述来自美国切萨皮克和特拉华运河的罕见晚白垩世菊石 Chesapeakiceras nodatum

摘要。异形菊石 Chesapeakiceras nodatum Kennedy 和 Cobban，1993 年，仅在美国大西洋沿岸平原的桑托阶晚期至坎帕阶早期的 Merchantville 组中被发现。在本报告之前，仅从美国特拉华州的切萨皮克和特拉华运河中发现了三个碎片标本。这里我们描述了第四个标本 NJSM GP23099，它是已知最完整的 C. nodatum 碎片，也是唯一的已“原位”回收的现有标本。这表明 C. nodatum 的地层范围延伸到上部 Merchantville 组。