阿门角石（学名Armenoceras）是阿门角石科下一个主要的属，生存于奥陶纪中期至上希留利亚纪。

阿门角石的壳笔直，中至大型，横砌面呈圆形或亚圆形。连室细管很大，位于近中央的腹面。每节的阔度较长，渐向住室扩阔。隔颈很短。连室细管的大部份管道都是呈双孤型。很少有气室沉积。阿门角石是衍生自五顶角石，其连接环较薄，内连室细管系统也较简单。

最早期的阿门角石分布在中国北部及韩国，直至到了奥陶纪末才在北美洲出现。另外，在北欧、俄罗斯及澳洲也有它们的踪影。

阿门角石相信是尼氏角石（虽然有另一相反的意见）及塞耳扣克角石的祖先。

Armenoceras is the principal genus of the Armenoceratidae, ranging from the late Whiterockian Stage in the early Middle Ordovician, through the remainder of the period and on into the Upper Silurian.

The shells of Armenoceras are straight and medium to large in size with a circular to subcircular cross section. The siphuncle is large, located subcentrally to resting on the ventral margin. Segments are wider than long, broadly expanded into the camerae. Septal necks short with wide brings that may be in contact with posterior surface of septa. In most the canal system within the siphuncle in is of the double arc type. Cameral deposits are rare.