New holostean (Actinopterygii, Neopterygii) from the Nusplingen Lithographic Limestone (Upper Jurassic, Late Kimmeridgian), Germany
Final Report Abstract
The project was meant to study a new fossil fish (SMNS 96921/5) discovered during the 2015 excavations led by Dr. Günther Schweigert (State Museum of Natural History Stuttgart) in the Upper Kimmeridgian limestones of Nusplingen. The detailed anatomical study of SMNS 96921/5 led to the discovery of some anatomical features, which are completely novel among ray-finned fishes. These and other morphological peculiarities clearly distinguish the specimen as a new taxon. The placement of the new taxon in the Neopterygii is granted by diagnostic anatomical characteristics. Within Neopterygii, several morphological features indicate affinities within the Halecomorphi. Each of these morphologic features are synapomorphic at different levels on the stem to Amiiformes. Among halecomorphs, SMNS 96921/5 resembles most closely several Triassic and some Jurassic taxa of still controversial phylogenetic relationships. Among the Triassic taxa, SMNS 96921/5 is most similar to the genera Panxianichthys, Subortichthys, Asialepidotus, Eoeugnathus and Allolepidotus, which form a monophyletic group representing an independent lineage, the Panxianichthyformes. However, the monophyly of the order Panxianichthyformes has been rejected in other cladistic analyses. The same morphologival similarities are also shared between SMNS 96921/5 and the Early Jurassic Furo orthostomus and Heterolepidotus latus from Lyme Regis, UK, and ‘Furo’ normandica from La Caine, France, and the Late Jurassic Ophiopsis muensteri and ‘Furo’ elongatus from the Solnhofen limestones, Germany. In the so far most complete cladistic analysis of non-amiiform halecomorphs, F. orthostomus, H. latus, and O. muensteri are more closely related to the ophiopsids (Ophiopsiella and closely related genera) than to any other halecomorph within an independent clade Ophiopsiformes. The Panxianichthyformes are confirmed as a separate clade in this analysis. However, the morphological features shared by SMNS 96921/5 and these Triassic and Jurassic taxa have not been included as characters in previous cladistic analyses and, thus, whether they have a phylogenetic significance remains to be solved. Differences between previous phylogenetic hypotheses concerning the validity of Panxianichthyformes and Ophiopsiformes as clades might be due to the different taxonomic composition of the data matrices and, thus, a more comprehensive study including all the taxa is necessary to disentangle these conflicts and the relationships of SMNS 96921/5. Furthermore, those analyses are largely based on characters taken from previous authors, without revision of hypotheses of primary homology and the data sets contain numerous cases of problematic character coding, including unspecified character states, pseudo-ordering, and compound characters. In a recent paper resulted from one of my previous projects, a colleague and I critically revised these issues and compiled a data set, including 339 morphological characters after revision of all hypotheses of homology and the consequent redefinition of many characters and character states. However, the important characters shared by SMNS 96921/5 and panxianichthyforms and ophiopsiforms and various taxa (most of the putative members of these two orders) need to be added to this revised data set in order to solve the relationships of SMNS 96921/5. This work is in progress.
