Abstract:We redescribe the morphology of Yohoia tenuis (Chelicerata sensu lato) from the Cambrian Burgess Shale Lagerstätte. The morphology of the most anterior, prominent, so-called great appendage changes throughout ontogeny. While its principal morphology remains unaltered, the length ratios of certain parts of the great appendage change significantly. Furthermore, it possesses a special jack-knifing mechanism, i.e. an elbow joint: the articulation between the distal one of the two peduncle elements and the most proximal of the four spine-bearing claw elements. This morphology might have enabled the animal to hunt like a modern spearer-type mantis shrimp, an analogy enhanced by the similarly large and protruding eyes. For comparison, details of specimens of selected other great-appendage arthropods from the Lower Cambrian Chengjiang Lagerstätte have been investigated using fluorescence microscopy. This revealed that the morphology of the great appendage of Y. tenuis is much like that of the Chengjiang species Fortiforceps foliosa and Jianfengia multisegmentalis. The morphology of the great appendage of the latter is even more similar to the morphology developed in early developmental stages of Y. tenuis, while the morphology of the great appendage of F. foliosa is more similar to that of later developmental stages of Y. tenuis. The arrangement of the elbow joint supports the view that the great appendage evolved into the chelicera of Chelicerata sensu stricto, as similar joints are found in various ingroup taxa such as Xiphosura, Opiliones or Palpigradi. With this, it also supports the interpretation of the great appendage to be homologous with the first appendage of other arthropods.

BackgroundLeanchoilia superlata is one of the best known arthropods from the middle Cambrian Burgess Shale of British Columbia. Here we re-describe the morphology of L. superlata and discuss its possible autecology. The re-description follows a standardized scheme, the descriptive matrix approach, designed to provide a template for descriptions of other megacheiran species.ResultsOur findings differ in several respects from previous interpretations. Examples include a more slender body; a possible hypostome; a small specialised second appendage, bringing the number of pairs of head appendages to four; a further sub-division of the great appendage, making it more similar to that of other megacheirans; and a complex joint of the exopod reflecting the arthropod’s swimming capabilities.ConclusionsDifferent aspects of the morphology, for example, the morphology of the great appendage and the presence of a basipod with strong median armature on the biramous appendages indicate that L. superlata was an active and agile necto-benthic predator (not a scavenger or deposit feeder as previously interpreted).

Summary Here we present a set of methods for documenting (exo‐)morphology by applying autofluorescence imaging. For arthropods, but also for other taxa, autofluorescence imaging combined with composite imaging is a fast documentation method with high‐resolution capacities. Compared to conventional micro‐ and macrophotography, the illumination is much more homogenous, and structures are often better contrasted. Applying different wavelengths to the same object can additionally be used to enhance distinct structures. Autofluorescence imaging can be applied to dried and embedded specimens, but also directly on specimens within their storage liquid. This has an enormous potential for the documentation of rare specimens and especially type specimens without the need of preparation. Also for various fossils, autofluorescence can be used to enhance the contrast between the fossil and the matrix significantly, making even smallest details visible. ‘Life‐colour’ fluorescence especially is identified as a technique with great potential. It provides additional information for which otherwise more complex methods would have to be applied. The complete range of differences and variations between fluorescence macrophotography and different types of fluorescence microscopy techniques are here explored and evaluated in detail. Also future improvements are suggested. In summary, autofluorescence imaging is a powerful, easy and fast‐to‐apply tool for morphological studies.

Psychopsidae (silky lacewings) is a species-poor ingroup of Neuroptera. Silky lacewings show a distinct relic distribution, indicating that the group was more speciesrich and diverse in the past. Silky lacewings have distinct larvae that resemble antlion larvae but differ from these in lacking teeth on their mouth parts, and in having a projecting labrum, which makes them "long-nosed antlion larvae". These larvae are well known from Myanmar amber (about 100 mya) and Baltic amber (mostly 34-38 mya, possibly 23-48 mya), as well as from the extant fauna. We report and figure numerous additional specimens from both amber types and from ca. 100 mya old French Charentese amber, expanding the known record of well-illustrated extant and fossil specimens from 26 to 52 specimens. We compare the diversity of head shape among these larvae through time by outline analysis. Results indicate that morphological diversity was pronouncedly higher in the Cretaceous, even after sample size correction. Eocene representatives are more diverse than modern representatives, but less diverse than Cretaceous ones, in one shape aspect that explains most of the overall variation (55.7%). Eocene representatives are less diverse in another shape aspect that explains the second-most variation (26.9%), but this might reflect a lack of first larval stage specimens. There seems to be no strong correlation between size and shape. This type of analysis enables a test for the loss of diversity over time, based on morphological diversity as a proxy, without the requirement of identifying fossil larvae down to a narrow taxonomical range.