ABSTRACT

Early Mesozoic halecomorphs are highly diverse, but their taxonomy and phylogenetic relationships are still controversial. We describe here a new halecomorph taxon from the Late Jurassic (Kimmeridgian) Nusplingen Lithographic Limestone, southern Germany. Sanctusichthys rieteri, gen. et sp. nov., is characterized by the peculiar patterns of skull roofing bones and cephalic sensory canals, and a unique squamation made of tiny lepisosteoid-type scales with extremely or completely reduced ganoin layer. Very peculiarly, S. rieteri presents a series of bones placed between the frontals and the anamestic supraorbitals, one of them carrying a portion of the main supraorbital sensory canal between the frontal and nasal bones. These bones, here called parafrontals, are so far unknown in other actinopterygians. The new taxon resembles most closely several Late Jurassic Furo-like halecomorphs, which have been classified in the family Furidae and are currently placed in either of the controversial orders Ophiopsiformes or Ionoscopiformes. The close phylogenetic relationships between these taxa are confirmed in a cladistic analysis that retrieves Sanctusichthys within a broadly defined Ionoscopiformes, including the potentially independent Ophiopsiformes. Interestingly, these Furo-like halecomorphs are highly diverse in the Late Jurassic deposits of southern Germany, and they are especially well represented—with four species accounting for 15% of the actinopterygian taxa—in the Nusplingen quarry, which yields one of the three most diverse Jurassic assemblages of these fishes. The paleoecological significance of this high diversity can only be explored after solving the β-taxonomy and phylogenetic relationships of these Furo-like taxa.

摘要

早期的中生Halecomorphs高度多样化，但它们的分类学和系统发育关系仍存在争议。我们在这里描述了来自德国南部晚侏罗世（基默尼迪安河）努斯普林根平版印刷石灰岩的一种新的类晶分类单元。Sanctusichthys rieteri，根。等。nov。的特征是颅骨屋顶骨和头感觉管的奇特图案，以及由微小类鳞状类固醇类鳞片制成的独特鳞屑，其角蛋白层大大减少或完全减少。非常奇怪的是，S。rieteri提出了一系列位于额骨和无名的眶上之间的骨头，其中一个在额骨和鼻骨之间携带了部分眶上主感觉管。这些骨骼，这里称为副额叶，到目前为止在其他放线翅目鸟类中还未知。新分类群酷似关系最密切的几个晚侏罗世呋喃并般halecomorphs，已被归类在家庭Furidae，目前放置在任何有争议的订单Ophiopsiformes或Ionoscopiformes的。在分类分析中证实了这些分类单元之间的密切系统发育关系，该分析可在广泛定义的离子形表目（包括可能独立的蛇形目）中检索到Sanctusichthys。有趣的是，这些Furo状的类变体在德国南部的晚侏罗世沉积物中高度多样化，并且在努斯普林根采石场中尤为突出（其中四个物种占放线目类群的15％），产生了三种最多样化的侏罗纪组合之一这些鱼。这种高多样性的古生态意义只有在解决了这些类Furo类群的β分类和系统发育关系之后才能探索。