A new genus and species of pycnodontiform fishes, Grimmenodon aureum, from marginal marine, marine-brackish lower Toarcian (Harpoceras exaratum ammonite subzone) clay deposits of Grimmen in northeastern Germany is described. The single specimen represents a diagnostic left prearticular dentition characterized by unique tooth arrangement and ornamentation patterns. Grimmenodon aureum, gen. et sp. nov., is the second unambiguously identified pycnodontiform species from the Early Jurassic, in addition to Eomesodon liassicus from the early Lower Jurassic of western Europe. We also report an indeterminate pycnodontiform tooth crown from the upper Pliensbachian (Pleuroceras apyrenum ammonite subzone) of the same site. The material expands the Early Jurassic range of pycnodontiforms significantly northwards and confirms their presence before and immediately following the onset of the Toarcian Oceanic Anoxic Event (T-OAE) in the marginal marine ecosystems south of the Fennoscandian Shield. Moreover, the new records indicate that the Early Jurassic diversity of pycnodontiform fishes was greater than previously assumed and probably equaled that of the Late Triassic. Therefore, it is hypothesized that the Triassic-Jurassic mass extinction event did not affect pycnodontiform fishes significantly. Micro-computed tomography was used to study the internal anatomy of the prearticular of Grimmenodon aureum, gen. et sp. nov. Our results show that no replacement teeth were formed within the tooth-bearing bone but rather were added posteriorly to functional teeth.

一个新属和pycnodontiform鱼类物种，Grimmenodon萝，从边缘海相，海洋微咸水降低托尔阶（Harpoceras exaratum菊子区）在德国东北部格里门的粘土矿床进行说明。单个标本代表诊断性左关节前牙列，其特征是独特的牙齿排列和装饰图案。Grimmenodon aureum , gen. 等 sp. nov.，是除了来自西欧早下侏罗世的Eomesodon liassicus之外，第二个明确确定的早侏罗世 pycnodontiform 物种。我们还报告了来自上 Pliensbachian ( Pleuroceras apyrenum菊石亚区）的同一地点。该材料显着向北扩展了早侏罗世的 pycnodontiforms 范围，并证实了它们在 Fennoscandian 地盾以南的边缘海洋生态系统中的 Toarcian 海洋缺氧事件 (T-OAE) 发生之前和之后立即存在。此外，新记录表明，早侏罗世鱼类的多样性比以前假设的要大，可能与晚三叠世相同。因此，假设三叠纪-侏罗纪大灭绝事件对齿形鱼类没有显着影响。微型计算机断层扫描来研究的prearticular的内部解剖Grimmenodon萝，将军。等 sp. 十一月 我们的结果表明，在带牙骨内没有形成替代牙齿，而是在功能牙齿的后面添加。