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The Cretaceous outcrops of Haqel, Hjoula (Cenomanian) and Sahel Aalma (Santonian) in Lebanon are renowned for their exceptional preservation of coleoid soft tissue in coeval shallow carbonate mud deposits and provide an unmatched opportunity to study many specimens of a single species, Dorateuthis syriaca. Despite being the most abundant coleoid from these localities, the taxon lacks clear, unambiguous diagnostic characteristics of both the gladius, and soft tissue anatomy. The absence of a defined character complex for the species has led to inconsistencies in the literature and the need for a reappraisal. This investigation represents the largest sample of D. syriaca studied with high-resolution, multi-imaging techniques, and has obtained a comprehensive morphological dataset of measurements on this key taxon. This has allowed us to refine some of the character states used to understand the phylogeny of coleoids. Furthermore, we have identified morphological characters that were previously undescribed for the genus, including suckers, axial nerves, and possible retractor muscles, as well as provided confirmation of the circulatory and excretory systems, and an Octobrachia-type digestive system. We also discount the presence of tentacles, tentacular pockets, and hooks within the arm crown, and we show that the species definition of D. syriaca is more complex than expected as our sample suggests intraspecific variability is present in the gladius. We strongly support the hypothesis that it was an 8-armed coleoid that was likely an active visual predator. [ABSTRACT FROM AUTHOR]

The fossil record of gladius-bearing coleoids is scarce and based only on a few localities with geological horizons particularly favourable to their preservation (the so-called Konservat-Lagerstätten), which naturally leads to strongly limited data on geographical distributions. This emphasizes the importance of every new locality providing gladius-bearing coleoids. Here, we assess for the first time the gladius-bearing coleoid taxonomic diversity within the lower Toarcian "Schistes Cartons" of the Causses Basin (southeastern France). The material includes two fragmentary gladii, identified as Paraplesioteuthis sagittata and "Loligosepia sp. indet. Just with these two specimens, two (Prototeuthina and Loligosepiina) of the three (Prototeuthina, Loligosepiina and Teudopseina) suborders of Mesozoic gladius-bearing coleoids are represented. Thus, our results hint at a rich early Toarcian gladius-bearing coleoid diversity in the Causses Basin and point out the need for further field investigations in the lower Toarcian "Schistes Cartons" in this area. This new record of Paraplesioteuthis sagittata is only the second one in Europe and the third in the world (western Canada, Germany and now France). Based on these occurrences, we tentatively suggest that P. sagittata originated in the Mediterranean domain and moved to the Arctic realm through the Viking Corridor to eventually move even farther to North America. [ABSTRACT FROM AUTHOR]

Palaeontological data are key elements for inferring ancestral character states and the assembly of character complexes, but cephalopod fossils preserving soft tissues are very rare. The exceptionally well-preserved, unique specimen of Jurassic Proteroctopus ribeti Fischer & Riou from the Lagerstätte of La-Voulte-sur-Rhône ( c. 165 Ma, France) is one of the few fossil octopod related taxa, but is rarely considered in evolutionary studies. In this paper, we used synchrotron microtomography to reappraise its external characters and for the first time, to reveal its internal structures. A unique character association is found with two fins, head fused to the body, eight well-developed arms with cirri and two rows of oblique suckers, a gladius and absence of an ink sac. The phylogenetic analysis indicates that Proteroctopus is a basal member of the Vampyropoda. However, this result should be interpreted with caution due to the number of unknown character states in the matrix. Contrary to previous assumptions, the phylogenetic position of Proteroctopus, as well as its stratigraphic occurrence, suggest that the arrangement of biserial suckers may be the ancestral condition in Vampyropoda. [ABSTRACT FROM AUTHOR]

Radular teeth occur between the jaws in two specimens of the Late Cretaceous scaphitid ammonite Rhaeboceras halli (Meek and Hayden, 1856) from the Western Interior of the United States. The detailed morphology of the teeth has been revealed by propagation phase contrast X-ray synchrotron microtomography. Each row of the radula of R. halli consists of a total of seven teeth (a central rachidian, two pairs of lateral and one pair of marginal teeth), as in other known ammonoid radulae, although the central tooth could not be confirmed in the specimens examined. The lateral teeth are multicuspid and robust, and the marginal teeth are long (4.6 mm) and slender. In overall morphology, the heterodont and ctenoglossan radula of R. halli is similar that of Jurassic and Cretaceous ammonites with the same aptychus-type lower jaw, that is, the Aptychophora. This discovery reveals the range of variation in radular morphology, which could be related to ecological or phylogenetic factors. It also invalidates the hypothesis that the hook-like structures in R. halli previously described are radular elements. [ABSTRACT FROM AUTHOR]