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A symbiotic association of a boring polychaete and an echinoid from the Late Cretaceous of Germany

100%
Wisshak M., Neumann C.
Acta Palaeontologica Polonica
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2006
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tom 51
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nr 3
From the Early Maastrichtian white chalk of Rügen Island (N Germany), a specimen of the echinoid Echinocorys ovata featuring 27 boring traces of the ichnogenus Caulostrepsis is described. Individual traces are shallow to moderately deep U−shaped depressions and show distinct regeneration textures evidencing a syn−vivo infestation. All traces are located on the plastron between the peristome and periproct of the host echinoid, indicating an adaptation of the trace maker by choosing the most advantageous position of the specific host. The traces are attributed to the work of boring spionid polychaetes (Polydora complex), grounded on the close morphological resemblance with initial borings of Recent polydorids. This is the first evidence for a possible association of a boring polychaete not only with an echinoid but with an echinoderm in general. The symbiotic relationship was commensalistic in nature with the spionid probably taking advantage of organic matter resuspended by the echinoids locomotion and feeding activity and benefiting from effective shelter. For the host echinoid, the association was moderately harmful. The soft bottom environment of the chalk sea provided very limited hard substrate ecospace for settlers and bioeroders, available only in form of biogenic structures. Echinocorys was a dominant component of this benthic community and can be considered as a suitable host for symbiotic interactions because of its size and assumed longevity.
2
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Acanthodian fish trace fossils from the Early Devonian of Spitsbergen

80%
Wisshak M., Volohonsky E., Blomeier D.
Acta Palaeontologica Polonica
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2004
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tom 49
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nr 4
We describe and interpret Undichna septemsulcata isp. nov., from the fluvial Old Red Sandstone deposits of the Early Devonian Wood Bay Formation, of Northern Spitsbergen (Svalbard). Its delicate scratch pattern, comprising one unpaired median groove and three pairs of lateral grooves, all with a regular in−phase sinusoidal wave pattern of equal wavelength, allow the reconstruction of the number, position and relative spacing of the fins. The comparatively high−amplitude median groove is attributed to the main propelling action of the tail or caudal fin, the inner pair of the lateral grooves to the action of the pelvic fins, and the low−amplitude outer set of duplicate grooves to bifurcated pectoral fins, respectively. The in−phase geometric pattern is explained by a distance between the unpaired fin (caudal or anal fin) to the pectoral fins corresponding to one wavelength and a position of the pelvic fins half way in between. The direction of movement and the mode of locomotion of the trace maker (a carangiform to ostraciiform type) are deduced. This analysis is leading to an acanthodian (possibly Diplacanthus) as the most probable trace maker. By being Pragian or early Emsian (Early Devonian) in age, according to vertebrate and palynomorph biostratigraphy, these specimens are among the world’s oldest trace fossils made by a vertebrate.
3
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A giant boring in a Silurian stromatoporoid analysed by computer tomography

80%
Beuck L., Wisshak M., Munnecke A., Freiwald A.
Acta Palaeontologica Polonica
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2008
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tom 53
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nr 1
This study describes the largest known Palaeozoic boring trace, Osprioneides kampto igen. et isp. nov., found within a stromatoporoid Densastroma pexisum from the Upper Visby Formation (lower Wenlock, Silurian) on the island of Gotland, Sweden. Differences between the physical properties of the stromatoporoid and the dense micritic infilling of the borings allowed the application of the CT−scan technology for the 2D and 3D−visualisation of this rare trace. The additional application of a stereoscopic technique on these CT images and movies enhances its value for unravelling spatial orientations. This non−destructive method has a great potential for future macroas well as microboring analyses. The trace maker, most likely a worm, infested the hosting colony post−mortem with up to 120 mm long borings measuring 5–17 mm in diameter. Smaller forms of Trypanites and Palaeosabella within the same stromatoporoid preferentially occur in the outer coenosteum and occasionally in abandoned borings of O. kampto. The stratigraphic position of O. kampto follows the “Great Ordovician Biodiversification Event” in time, and reflects the increase in diversity of boring species. Borings with penetration depths of 120 mm are, however, unique findings for the Palaeozoic and were not exceeded until some 260 million years later (Bajocian, Middle Jurassic) when the “Mesozoic Marine Revolution” led to convergent reinventions as a result of enhanced predation, grazing pressure, and ecospace competition.
4
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Centrichnus eccentricus revisited: a new view on anomiid bivalve bioerosion

61%
Neumann C., Wisshak M., Aberhan M., Girod P., Rosner T., Bromley R. G.
Acta Palaeontologica Polonica
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2015
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tom 60
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nr 3
Saddle oysters (Anomiidae) attach themselves to calcareous hard substrates by means of a calcified byssus that etches an attachment structure, referred to as ichnospecies Centrichnus eccentricus. Examination of rich material from the Late Cretaceous of central Europe extends the fossil record of this ichnotaxon and revealed a set of previously unrecognised morphological features which appear to be typical for this time period and the respective anomiid trace maker. Excellent preservation of a large number of trace fossil specimens with a complete set of morphological characters allowed a biometrical analysis and additional observations indicating a distinct substrate preference for belemnite rostra, a strong intra- and interspecific competition for settlement space, as well as interactions with durophaguous predators. Further implications for anomiid palaeobiology and palaeoecology arise from allometric shell growth and an etched outline suture in the substrate along the dorsal, lateral and ventral shell margins. These features enhanced a firm attachment and increased shear resistance, and thus are interpreted as an effective defence mechanism against shell-crushing enemies under the intensified predation pressure in marine environments in the Late Cretaceous.
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