The Upper Cretaceous (Cenomanian) limestone quarry of Haqel, Lebanon, is home to one of the largest diversities of fossil actinopterygians in the Mesozoic, particularly of pycnodontiform fishes. Here, we describe a pycnodontiform fish, Flagellipinna rhomboides, gen. et sp. nov., from this locality based on four specimens. It is considered a member of the derived family Pycnodontidae due to the presence of a postparietal process. This taxon is distinct from other pycnodontids due to its diamond-shaped body, whip-like dorsal fin, postcloacal scales with forward-pointing spines, and acute anterior profile with a concave slope, giving it a ‘hunchback’ appearance. The prognathous snout armed with molariform teeth suggests that this pycnodont preyed on a variety of shelled animals from crevices. The smallest specimen is distinct in that it has a larger orbit size, no spines on the contour scales, poorly ossified skull roof bones, a notochord partially covered by arcocentra, and lacks whip-like filament on the dorsal fin, which suggest that it is a juvenile/subadult. The differences between the juvenile/subadult and other larger specimens suggest a change in ecological niche occupation during ontogeny, going from a generalized forager that lived in complex, reef habitats to moving into deeper waters to feed from crevices on the reef edge. These findings provide a more complete picture of the possible life history strategies that pycnodontiforms may have used in order to exploit different resources throughout their lives.

位于黎巴嫩 Haqel 的上白垩统（Cenomanian）石灰岩采石场是中生代放线鱼化石种类最多的地区之一，尤其是齿形鱼类。在这里，我们描述了一种 pycnodontiform 鱼，Flagellipinna rhomboides，将军。等 sp. 11 月，来自当地的基于四个标本。由于后顶叶过程的存在，它被认为是派生的 Pycnodontidae 家族的成员。由于其菱形身体、鞭状背鳍、带有向前指向的刺的泄殖腔后鳞片以及带有凹斜度的尖锐前部轮廓，使其具有“驼背”的外观，该分类群与其他斑齿龙科不同。长有磨牙状牙齿的前突口鼻表明，这种门齿兽从缝隙中捕食各种带壳动物。最小的标本的独特之处在于它的眼眶较大，轮廓鳞片上没有刺，头骨骨化程度差，脊索部分被弧中心覆盖，背鳍上没有鞭状细丝，这表明它是青少年/亚成人。幼鱼/亚成鱼和其他大型标本之间的差异表明，个体发育过程中生态位占据的变化发生了变化，从生活在复杂的珊瑚礁栖息地中的普遍觅食者转移到更深的水域以从珊瑚礁边缘的裂缝中觅食。这些发现提供了一个更完整的图景，说明了齿形目可能使用的可能的生活史策略，以便在其一生中利用不同的资源。