The Salazac locality (Gard, southeastern France) is renowned for the richness of its cephalopod fauna (especially ammonites) from the Mortoniceras fallax Zone (uppermost Albian, Lower Cretaceous). However, most ammonite species have paradoxically been scarcely illustrated up to now. Furthermore, the rare assessments of ammonite taxonomic diversity are presumably inaccurate, as they either result from a drastic typological approach or could not benefit from the most recent advances in modern concepts of ammonoid intraspecific and ontogenetic variations. In this work, we document an original cephalopod assemblage from Salazac represented by abundant, well-preserved specimens (564 studied ammonites, including ca. 50% of heteromorphs) constituting a high diversity. The sample size and quality of this new material allowed some extensive morphological and biometric analyses whenever possible (i.e., for subdatasets in which a significant number of measurements is available) and to thoroughly assess intraspecific and ontogenetic variations for a few species. This led to determine the diagnostic value of various shell characters commonly used to characterize both well-documented and poorly-defined species. In particular, we show that a significant part of the variation in the number of ribs per whorl within the heteromorphic genera Mariella and Turrilitoides is directly related to shell size and that the strength of tubercles covaries negatively with the number of ribs in Mariella, therefore challenging the diagnostic value of these characters. We further suggest that rib density covaries with whorl shape in Mariella, following Buckman’s first rule of covariation. In total, one species of nautilid and 38 taxa (25 genera) of ammonites are described, among which five species are documented from Salazac for the first time. In turn, this study provides valuable data for future phylogenetic, biostratigraphical, biogeographical and broad-scale diversity studies.

Salazac地区（法国东南部的Gard）因其Mortoniceras落叶小虫的头足类动物（尤其是am虫）的丰富性而闻名。区域（最高的阿尔比山脉，下白垩统）。然而，到目前为止，几乎没有说明大多数亚铁矿物种。此外，对氨铁矿分类学多样性的罕见评估可能是不准确的，因为它们要么是从严峻的类型学方法得出的结果，要么就无法从现代的氨类内部和种源变异概念的最新进展中受益。在这项工作中，我们记录了Salazac的原始头足类动物组合，它们由数量丰富且保存完好的标本（564个研究过的炸药，包括大约50％的异形体）构成，具有很高的多样性。这种新材料的样品大小和质量允许在可能的情况下进行一些广泛的形态和生物特征分析（即，（其中有大量测量可用的子数据集），并彻底评估少数物种的种内和个体发育变异。这导致确定通常用于表征有据可查和定义不清的物种的各种外壳特征的诊断价值。特别是，我们表明异形属中每个螺纹的肋骨数量变化的很大一部分Mariella和Turrilitoides与蛋壳大小直接相关，而结节的强度与Mariella中肋骨的数量呈负相关，因此挑战了这些字符的诊断价值。我们进一步建议，遵循巴克曼的第一个协变规则，Mariella中肋骨密度随螺纹形状而协变。总共描述了一种鹦鹉螺和38个分类单元（25属）的炸药，其中首次从Salazac记录了五种。反过来，这项研究为将来的系统发育，生物地层学，生物地理学和大规模多样性研究提供了有价值的数据。