1983 01 15: The conodont animal.A unique specimen of a small, elongate, soft-bodied animal from the Lower Carhoniferous of the Edinburgh district, Scotland, is described. The head expands anteriorly into two lohate 5tructures flanking a central lumen; behind this lies a conodont apparatus, apparently in situ. consisting of an aligned set of ramiform elements followed by a pair of ozarkodiniform elements and one of platform elements. From the morphology of the platform elements the animal has been identified as CIydagnathus? cf. cavusformis. Repeated structures which may represent segments are evident in the posterior part of the trunk, which bears a posterior and a caudal fin, each supported hy rays. The animal shows similarities to both chordates and chaetognaths, but the evidence supports its assignment to a separate phylum, the Conodonta. The function of the conodonts remains equivocal, but it seems more likely that they served as teeth than as internal supports.

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Three new specimens which preserve the soft parts of conodonts are described from the Lower Carboniferous of Granton, Edinburgh. The animal was apparently laterally flattened in life and the somites were V‐shaped. The nature of the preserved axial lines is equivocal; some may represent the walls of the gut. The elements of one of the new specimens show that it does not belong to Clydagnathus, to which the other soft‐bodied specimen from Granton was tentatively assigned. The possibility of a relationship between the euconodonts and the Chaetognatha is discounted. Nor do the conodonts constitute a phylum, but are a separate group of primitive jawless craniates.

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.

The thick lenses in the aggregate eyes of a group of trilobites were double structures designed to eliminate spherical aberration. The shape of the optically correcting interface is in accord with constructions by Des Cartes and Huygens and is dictated by a fundamental law of physics. Trilobites may have evolved such sophisticated eye-lenses to maximise optic neurone response in a dimly lit environment.

Vision has revolutionized the way animals explore their environment and interact with each other and rapidly became a major driving force in animal evolution. However, direct evidence of how ancient animals could perceive their environment is extremely difficult to obtain because internal eye structures are almost never fossilized. Here, we reconstruct with unprecedented resolution the three-dimensional structure of the huge compound eye of a 160-million-year-old thylacocephalan arthropod from the La Voulte exceptional fossil biota in SE France. This arthropod had about 18,000 lenses on each eye, which is a record among extinct and extant arthropods and is surpassed only by modern dragonflies. Combined information about its eyes, internal organs and gut contents obtained by X-ray microtomography lead to the conclusion that this thylacocephalan arthropod was a visual hunter probably adapted to illuminated environments, thus contradicting the hypothesis that La Voulte was a deep-water environment.

Clarkson, E. N. K. & Henry, J. L.: Structures coaptatives et enroulement chez quelques Trilobites ordoviciens et siluriens. [Coaptative structures and enrollment in some Ordovician and Silurian trilobites.] Certain trilobites possessed highly adapted structures on the cephalon and pygidium, and sometimes also the thorar, which ensured very close interlocking of opposing surfaces during enrollment. Different kinds of structures are described in detail in selected Ordovician and Silurian genera. There is a simple ‘press‐stud’ mechanism axially situated on the opposing cephalic and pygidial doublures of Kloucekia micheli, whereas in various species of Crozonaspis and in Kloucekia dujardini a projecting cephalic beak fits into an excavation under the caudal spine. The cephalic beak and corresponding pygidial excavation seemingly evolve towards a more pronounced form in successive species throughout time. Colpocoryphe rouaulti, by contrast, has a pygidial protuberance interlocking with a cephalic excavation. Complete specimens of Encrinurus tuberculatus and E. variolaris have very complex contact surfaces along opposing doublures, with various kinds of interlocking structures.

Several thousand disarticulated remains together with a few complete enrolled specimens of the lower Cambrian eodiscoid trilobite Calodiscus lobatus (Hall, 1847) have been collected at two outcrop areas in Sweden. The material reveals new details of morphology and morphogenesis during ontogenetic development. Size-frequency analyses show that the material from the Fånån rivulet in Jämtland, central Sweden, represents a natural population dominated by juveniles, whereas the material from Gislövshammar in Scania, southern Sweden, has been sorted during postmortem transport. Three stages of protaspid development can be traced and defined as well as all subsequent ontogenetic stages for the cephalon, hypostome and pygidium. The early meraspid pygidium has a pronounced larval notch, which persists, though becoming progressively less distinct in later meraspides. The number of axial rings in the transitory pygidium increases throughout meraspid development until a third and final thoracic segment is liberated. During ontogeny the articulating half-rings are strongly developed, and both meraspides and holaspides were capable of full sphaeroidal enrollment and outstretched postures. The hypostome undergoes some dramatic modifications; in M0 the anterior margin is axe-shaped, by M1 the area of attachment greatly decreases and the hypostome becomes more elongated and pear-shaped, before attaining its adult form, which has an overall resemblance to that of polymerid trilobites. During ontogeny, the hypostome changes from a conterminant attachment to a natant condition, thereby mirroring hypostomal evolution within trilobites generally. The morphology, ontogeny, enrollment, hypostomal development and the presence of calcified protaspides suggest polymerid rather than agnostoid affinities of the eodiscoids.