Associated and isolated teeth of the extinct elasmobranch Ptychodus latissimus Agassiz, 1835 from the Upper Cretaceous Scaglia Rossa pelagic limestone of northern Italy are described and discussed here in detail for the first time. The dentition of this widely distributed species consists of low-crowned molariform teeth that exhibit marked and strong occlusal ornamentations suitable for crushing hard-shelled prey. The associated tooth sets and isolated teeth analyzed here are heterogeneous in size and crown outline, but unambiguously belong to a single species. Re-examination of this Italian material consisting of ca. 30 specimens mostly coming from historical collections allows for a rigorous assessment of the intraspecific variability of P. latissimus, including the identification of three different tooth “morphotypes” based on their positions within the jaws. The relatively flat crowns and occlusal sharp and thick ridges indicate a high adaptation for crushing hard-shelled prey in P. latissimus indicating that the durophagous adaptations of this species were certainly more pronounced than in all other species of Ptychodus. We hypothesize that P. latissimus was a third-level predator occupying habitats with abundant thick-shelled prey, such as inoceramid bivalves and ammonites.

中文翻译：

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白垩纪鲨鱼 Ptychodus latissimus Agassiz 的意大利记录，1835 年（软骨鱼目；Elasmobranchii）


本文首次详细描述和讨论了 1835 年产自意大利北部上白垩统 Scaglia Rossa 中上层石灰岩的已灭绝软骨鱼 Ptychodus latissimus Agassiz 的相关牙齿和孤立牙齿。这种分布广泛的物种的牙列由低冠磨牙状牙齿组成，具有明显而强烈的咬合装饰，适合压碎硬壳猎物。这里分析的相关牙齿组和孤立的牙齿在大小和牙冠轮廓上是不同的，但明确属于单一物种。重新检查这份意大利材料，其中包含约。 30 个标本主要来自历史收藏，可以对阔齿松种内的变异性进行严格评估，包括根据牙齿在颌骨内的位置识别三种不同的牙齿“形态类型”。相对平坦的冠和咬合锋利且厚的脊表明P. latissimus对粉碎硬壳猎物的高度适应，这表明该物种的硬食适应肯定比所有其他Ptychodus物种更明显。我们假设 P. latissimus 是一种三级捕食者，栖息地有丰富的厚壳猎物，例如双壳类和菊石。