/pdf/fossil-calibrations-for-the-arthropod-tree-of-life-4ite4o70cy.pdf

Fossil calibrations for the arthropod Tree of Life

Histoire naturelle, generale et particuliere (一般と個別の博物誌)

We redescribe the morphology of Yohoia tenuis (Chelicerata sensu lato) from the Cambrian Burgess Shale Lagerstatte. The morphology of the most anterior, promi- nent, so-called great appendage changes throughout ontog- eny. 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 proxi- mal of the four spine-bearing claw elements. This morphol- ogy might have enabled the animal to hunt like a modern spearer-type mantis shrimp, an analogy enhanced by the sim- ilarly large and protruding eyes. For comparison, details of specimens of selected other great-appendage arthropods from the Lower Cambrian Chengjiang Lagerstatte have been inves- tigated 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 Jianfen- gia multisegmentalis. The morphology of the great appendage of the latter is even more similar to the morphology devel- oped in early developmental stages of Y. tenuis, while the morphology of the great appendage of F. foliosa is more sim- ilar 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.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1475-4983.2011.01124.x

Functional morphology, ontogeny and evolution of mantis shrimp‐like predators in the Cambrian

Leanchoilia 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 Our 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 Different 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)

/pdf/morphology-and-function-in-the-cambrian-burgess-shale-4bu2ohnh3l.pdf

Morphology and function in the Cambrian Burgess Shale megacheiran arthropod Leanchoilia superlata and the application of a descriptive matrix

We give an overview of available techniques for imaging and documenting applied to gammarideans and discuss their advantages and disadvantages. Although recent techniques, such as confocal laser scanning microscopy (cLSM), focused ion beam scanning electron microscopy (FIB SEM), or computed microtomography (μCT), provide new possibilities to detect and document structures, these high-tech devices are expensive, and access to them is often limited. Alternatively, there are many possibilities to enhance the capabilities of established techniques such as macrophotography and light microscopy. We discuss improvements of the illumination with polarized light and the possibilities of utilizing the autofluorescence of animals such as the gammarideans. In addition, we present software-based enhancing tools such as image fusion and image stitching.

/pdf/imaging-and-documenting-gammarideans-3gblf2c2id.pdf

Imaging and Documenting Gammarideans

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.

Autofluorescence imaging, an excellent tool for comparative morphology.

We describe new specimens of Mesozoic mantis shrimps (Stomatopoda, Malacostraca) that exhibit morphological and developmental information previously unknown. Specimens assigned to the taxon Sculda exhibit preserved pleopods, thoracopods including all four raptorial limbs as well as details of antennae and antennulae. The pleopods and the antennulae resemble those of the modern mantis shrimps, but the raptorial limbs are not as differentiated as in the modern species. In some specimens, the first raptorial limb (second thoracopod) is not significantly larger than the similar-sized posterior three pairs (as in extant species), but instead these appendages become progressively smaller along the series. In this respect they resemble certain Palaeozoic stomatopods. Another specimen, most likely belonging to another species, has one pair of large anterior raptorial thoracopods, a median-sized pair and two more pairs of small-sized raptorial appendages and, thus, shows a new, previously unknown type of morphology. A single specimen of Pseudosculda laevis also exhibits the size of the raptorial limbs; they are differentiated as in modern species, one large pair and three small pairs. Furthermore, we report additional larval specimens and show also post-larval changes, e.g., of the tail fan. These new data are used to reconsider the phylogeny of Stomatopoda. We still need a strict taxonomical revision of the Mesozoic mantis shrimps, but this first examination already demonstrates the importance of these fossils for understanding mantis shrimp evolution and the interpretation of evolutionary pathways of particular features.

/pdf/evolution-of-mantis-shrimps-stomatopoda-malacostraca-in-the-17t6o7nmw6.pdf

Evolution of mantis shrimps (Stomatopoda, Malacostraca) in the light of new Mesozoic fossils

We describe the tagmatization pattern of the anterior region of the extant stomatopod Erugosquilla massavensis. For documentation we used the autofluorescence capacities of the specimens, resulting in a significant contrast between sclerotized and membranous areas. The anterior body region of E. massavensis can be grouped into three tagmata. Tagma I, the sensorial unit, comprises the segments of the eyes, antennules and antennae. This unit is set-off anteriorly from the posterior head region. Ventrally this unit surrounds a large medial sclerite, interpreted as the anterior part of the hypostome. Dorsally the antennular and antennal segments each bear a well-developed tergite. The dorsal shield is part of tagma II, most of the ventral part of which is occupied in the midline by the large, partly sclerotized posterior part of a complex combining hypostome and labrum. Tagma II includes three more segments behind the labrum, the mandibular, maxillulary and maxillary segments. Tagma III includes the maxillipedal segments, bearing five pairs of sub-chelate appendages. The dorsal sclerite of the first of these tagma-III segments, the segment of the first maxillipeds, is not included in the shield, so this segment is not part of tagma II as generally thought. The second and third segments of tagma III form a unit dorsally and ventrally. The tergites of the segments of tagma III become progressively larger from the anterior to the posterior, possibly resulting from a paedomorphic effect during evolution, which caused this reversed enlargement. The described pattern of tagmosis differs from current textbook knowledge. Therefore, our re-description of the anterior body area of stomatopods is of considerable impact for understanding the head evolution of Stomatopoda. Likewise, it has a bearing upon any comparisons with fossil stomatopods, as mainly sclerotized areas are fossilized, and, on a wider scale, upon larger-scale comparisons with other malacostracans and eucrustaceans in general.

/pdf/tagmatization-in-stomatopoda-reconsidering-functional-units-2vwuxmqnob.pdf

Tagmatization in Stomatopoda – reconsidering functional units of modern-day mantis shrimps (Verunipeltata, Hoplocarida) and implications for the interpretation of fossils

We re-evaluate the Mesozoic mantis shrimp Ursquilla yehoachi, based on the original four specimens and a new exquisitely preserved one. All specimens were documented by application of a new technique, which is introduced here and termed the virtual peel technique. This technique includes two steps: 1) Documentation of lowrelief fossils including their 3D information with the aid of a standard flat-bed scanner. 2) Virtual inversion of the negative relief of fossils; the resulting positive relief facilitates a better understanding of the fossil. Unlike the previously known specimens, the new specimen of U. yehoachi preserved most details of the uropod including the exopod, an important feature in stomatopod phylogeny. Remarkably, this exopod bears striking similarities to that of modern stomatopods in being bipartite and having a paddleshaped distal part, supporting earlier assumptions about the systematic position of U. yehoachi within Squilloidea. Observable morphological differences among the available material of U. yehoachi can now be identified as ontogenetic variation. The telson, for example, attains a proportionally broader shape with increasing size, a result of allometric growth. Carolin Haug. Department of Cytology and Evolutionary Biology, Zoological Institute and Museum, University of Greifswald, Soldmannstrasse 23, 17487 Greifswald, Germany carolin.haug@palaeo-evodevo.info Verena Kutschera. Biosystematic Documentation, University of Ulm, Helmholtzstrasse 20, 89081 Ulm, Germany verena.kutschera@uni-ulm.de Shane T. Ahyong. Australian Museum, 6 College Street, Sydney, NSW 2010, Australia Shane.Ahyong@austmus.gov.au Francisco J. Vega. Instituto de Geología, UNAM, Ciudad Universitaria, Coyoacán, México DF 04510, Mexico vegver@unam.mx Andreas Maas. Biosystematic Documentation, University of Ulm, Helmholtzstrasse 20, 89081 Ulm, Germany andreas.maas@uni-ulm.de Dieter Waloszek. Biosystematic Documentation, University of Ulm, Helmholtzstrasse 20, 89081 Ulm, Germany dieter.waloszek@uni-ulm.de HAUG ET AL.: URSQUILLA AND VIRTUAL PEEL 2 Joachim T. Haug. Department of Cytology and Evolutionary Biology, Zoological Institute and Museum, University of Greifswald, Soldmannstrasse 23, 17487 Greifswald, Germany joachim.haug@palaeo-evodevo.info

/pdf/re-evaluation-of-the-mesozoic-mantis-shrimp-ursquilla-mczxm6a9hf.pdf

Verena Kutschera

Papers

Autofluorescence imaging, an excellent tool for comparative morphology.

Imaging and Documenting Gammarideans

Evolution of mantis shrimps (Stomatopoda, Malacostraca) in the light of new Mesozoic fossils

Tagmatization in Stomatopoda – reconsidering functional units of modern-day mantis shrimps (Verunipeltata, Hoplocarida) and implications for the interpretation of fossils

Re-evaluation of the Mesozoic mantis shrimp Ursquilla yehoachi based on new material and the virtual peel technique