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Ordovician ectocochleate cephalopods of the order Lituitida Starobogatov, 1983, mainly from erratics of the Orthoceratite Limestone embedded in Pleistocene glacio-fluvial sediments in Germany, Poland and the Kaliningrad Region of Russia are revised. In total, seven genera (Rhynchorthoceras, Ancistroceras, Angelinoceras, Holmiceras, Lituites, Trilacinoceras, Cyclolituites) and 28 species are identified. Eleven species are newly described: Rhynchorthoceras kranepuhlense sp. nov., R. rugium sp. nov., Holmiceras havelense sp. nov., Lituites baculus sp. nov., L. bottkei sp. nov., L. clavis sp. nov., L. dewitzi sp. nov., L. kruegeri sp. nov., L. nebeni sp. nov., Trilacinoceras filix sp. nov. and T. knoefleri sp. nov. The concept of several taxa described in the 19th century, including the ambiguous species L. lituus de Montfort, 1808 and L. perfectus Wahlenberg, 1818, is refined. Neotypes are proposed for the latter two species.
Lacewing larvae in the Cretaceous were more diverse in appearance than they are today, best documented by numerous fossils preserved in amber. One morphotype of an unusual larva from about 100 Ma old Kachin amber (Myanmar) was formally recognised as a distinct group called Ankyloleon. The original description erected a single formal species, Ankyloleon caudatus. Yet, it was indicated that among the five original specimens, more species were represented. We here report five new specimens. Among these is the so far largest as well as the so far smallest specimen. Based on this expanded material we can estimate certain aspects of the ontogenetic sequence and are able to recognise a second discrete species, Ankyloleon caroluspetrus sp. nov. We discuss aspects of the biology of Ankyloleon based on newly observed details such as serrations on the mandibles. Long and slender mouthparts, legs and body together with a weakly expressed outer trunk segmentation provide indications for a lifestyle hunting for prey in more confined spaces. Still many aspects of the biology of these larvae must remain unclear due to a lack of a well comparable modern counterpart, emphasising how different the fauna of the Cretaceous was.
Rhaptothyreus is arguably the most enigmatic nematode taxon due to a combination of unusual morphological features (e.g., large feather-like amphids, vestigial mouth, trophosome, single spicule), unclear phylogenetic relationships (possible affinities with the Enoplida, Mermithida and Benthimermithida) and a distribution restricted to the deep sea. Here I provide the first record of the genus in the Western Pacific Ocean and describe new morphological features of a moulting juvenile. This specimen is characterised by features that differ markedly from those of the adults, the most prominent being the absence of cephalic sensillae and amphids and the presence of a stylet-like structure in the buccal cavity. Similar contrasts in morphology are found between adults and juveniles of the order Benthimermithida, which is characterised by free-living adults and parasitic juveniles.
Other morphological (large body size, presence of trophosome) and distributional characteristics (predominantly deep-sea distribution, juveniles rare / absent in sediments) are also common to both groups. Published records show that Rhaptothyreus is commonly found in oligotrophic environments (e.g., abyssal plain) where organisms bearing symbiotic bacteria are not typically found, which makes the presence of endosymbiotic bacteria inside the trophosome unlikely. These observations are consistent with the existence of a parasitic juvenile life stage in Rhaptothyreus.