Data from: Emsian Ammonoidea and the age of the Hunsrück Slate (Rhenish Mountains, Western Germany)

The ammonoids from the well-studied German Fossillagerstätte of the Hunsrück Slate have the reputation of being the oldest known representatives of this cephalopod group. This material is of great interest not only because of the global scarcity of the earliest ammonoids, but also because it includes the first record of stratigraphically-controlled specimens, which could be assigned to the middle Kaub Formation in the Bundenbach/Gemünden area. Accordingly, some of the Hunsrück Slate ammonoids are indeed the stratigraphically oldest ammonoids because they are associated with the index dacryoconarid Nowakia praecursor and thus derive from the Nowakia zlichovensis Biozone of the early Emsian (Zlíchovian), while younger dacryoconarids and other ammonoid samples (Mimagoniatites fecundus, Mimosphinctes tripartitus) indicate the Nowakia barrandei to N. elegans biozones. In spite of this special importance, these Early Devonian cephalopods have never been revised comprehensively.Our study includesmore than 300 Hunsrück Slate specimens from both public and private collections. For the first time, ammonoids from the Altlay Hunsrück Slate in the Northern Hunsrück/Mosel region are reported, while all the materials from older collections derive from the middle Kaub Formation of the Central Hunsrück Basin (central Hunsrück, Taunus). These early ammonoids thus prove to be a valuable source of information for biostratigraphic correlation within the Hunsrück Slate and with early Emsian occurrences in other regions. Based on conch characters (geometry, ornament, suture lines) and ontogenetic traits, we describe the species Metabactrites fuchsi n. sp., Ivoites hunsrueckianus (Erben 1960), Ivoites schindewolfi n. sp., ?Ivoites sp., ?Ivoites opitzi n. sp., Anetoceras mittmeyeri n. sp., Erbenoceras advolvens (Erben 1960), Erbenoceras solitarium (Barrande 1865), Chebbites sp., Mimosphinctes primigenitus (Erben 1965), Mimosphinctes tripartitus Eichenberg, 1931, Gyroceratites heinricherbeni n. sp., ?Teicherticeras sp., and Mimagoniatites fecundus (Barrande 1865). Supposedly endemic species of the Hunsrück Slate such as “Anetoceras recticostatum Erben, 1962” and “Mimagoniatites falcistria (Fuchs 1915)” are here synonymized with the widely distributed species Erbenoceras solitarium and Mimagoniatites fecundus, both known to occur also outside Europe. Furthermore, we studied their taphonomy and assigned them to sevengroups of preservation.Theresults of this taphonomic study corroborate previous interpretations of the depositional environment and diagenesis. We also discuss the evolution of the shell in the earliest ammonoids and their closest relatives as well as structures (“Opitzian pits”) possibly caused by parasitic infestations of these early Emsian ammonoids.产自研究程度较高的德国洪斯吕克板岩（Hunsrück Slate）化石产出地（Fossillagerstätte）的菊石类（ammonoids），素来被认为是该头足类（cephalopod）类群中已知最古老的代表类群。 这批化石材料之所以备受关注，不仅因为全球范围内最早的菊石类标本极为稀缺，还因为其中包含了首批具有地层控制信息的标本——这些标本可归属于本登巴赫/格明德地区的中考布组（middle Kaub Formation）。 据此，洪斯吕克板岩产出的部分菊石类确实是地层学意义上最古老的菊石类：它们与指相竹节石类（dacryoconarid）的模式种先今来克石（Nowakia praecursor）伴生，因而产自早艾姆斯期（Zlíchovian）的兹利乔夫期现克石生物带（Nowakia zlichovensis Biozone）；而时代更晚的竹节石类及其他菊石类标本（丰饶拟阿贡菊石Mimagoniatites fecundus、三分拟旋菊石Mimosphinctes tripartitus）则对应巴尔朗德现克石生物带至优雅现克石生物带（Nowakia barrandei to N. elegans biozones）。 尽管具有如此重要的科学价值，这批早泥盆世的头足类标本却从未得到过全面的修订研究。 本研究共收录了来自公共与私人馆藏的300余件洪斯吕克板岩标本。本次研究首次报道了北洪斯吕克/摩泽尔地区阿尔特莱伊洪斯吕克板岩产出的菊石类标本，而此前馆藏的所有材料均来自洪斯吕克中部盆地（洪斯吕克中部、陶努斯地区）的中考布组。 因此，这些早期菊石类成为洪斯吕克板岩内部，以及与其他地区早艾姆斯期产出化石进行生物地层对比（biostratigraphic correlation）的宝贵资料。 基于壳体特征（壳体形态、纹饰、缝合线（suture lines））及个体发育特征（ontogenetic traits），本研究描述了以下物种：富克斯后杆菊石（Metabactrites fuchsi）新种（n. sp.）、洪斯吕克伊沃菊石（Ivoites hunsrueckianus）（Erben 1960）、辛德沃尔夫伊沃菊石（Ivoites schindewolfi）新种（n. sp.）、？伊沃菊石未定种（?Ivoites sp.）、？奥皮茨伊沃菊石（Ivoites opitzi）新种（n. sp.）、米特迈耶网菊石（Anetoceras mittmeyeri）新种（n. sp.）、前伸厄尔本菊石（Erbenoceras advolvens）（Erben 1960）、独居厄尔本菊石（Erbenoceras solitarium）（Barrande 1865）、切布菊石未定种（Chebbites sp.）、原始拟旋菊石（Mimosphinctes primigenitus）（Erben 1965）、三分拟旋菊石（Mimosphinctes tripartitus）Eichenberg, 1931、海因里希厄尔本旋菊石（Gyroceratites heinricherbeni）新种（n. sp.）、？泰希特菊石未定种（?Teicherticeras sp.）以及丰饶拟阿贡菊石（Mimagoniatites fecundus）（Barrande 1865）。 此前被认为是洪斯吕克板岩特有种的"Anetoceras recticostatum Erben, 1962"与"Mimagoniatites falcistria (Fuchs 1915)"，本次研究将其归为广布种独居厄尔本菊石与丰饶拟阿贡菊石的同物异名，后二者在欧洲以外地区亦有发现记录。 此外，本研究还对这些标本的埋藏学（taphonomy）特征进行了研究，将其划分为7种保存类型。本次埋藏学研究结果验证了此前关于沉积环境与成岩作用（diagenesis）的相关解读。 本研究还探讨了最早期菊石类及其近缘类群的壳体演化，以及这些早艾姆斯期菊石可能因寄生侵染形成的"奥皮茨坑（Opitzian pits）"结构。