Andrew K. Rindsberg

Carboniferous Psammichnites: Systematic Re-Evaluation, Taphonomy and Autecology

The ichnogenus Psammichnites Torell 1870 includes a wide variety of predominantly horizontal, sinuous to looped, backfilled traces, characterized by a distinctive median dorsal structure. Though commonly preserved in full relief on upper bedding surfaces, some ichnospecies of Psammichnites may be preserved in negative hyporelief. Psammichnites records the feeding activities of a subsurface animal using a siphon-like device. Several ichnogenera reflect this general behavioral pattern, including Plagiogmus Roedel 1929 and the Carboniferous ichnogenera Olivellites Fenton and Fenton 1937a and Aulichnites Fenton and Fenton 1937b. Based on analysis of specimens from the United States, Spain, and the United Kingdom, three Carboniferous ichnospecies of Psammichnites are reviewed in this paper: P. plummeri (Fenton and Fenton, 1937a), P. grumula (Romano and Meléndez 1979), and P. implexus (Rindsberg 1994). Psammichnites plummeri is the most common Carboniferous ichnospecies and is characterized by a relatively straight, continuous dorsal ridge/groove, fine transverse ridges, larger size range, and non-looping geometric pattern. It represents a grazing trace of deposit feeders. Psammichnites grumula differs from the other ichnospecies of Psammichnites by having median dorsal holes or protruding mounds. The presence of mounds or holes in P. grumula suggests a siphon that was regularly connected to the sediment-water interface. This ichnospecies is interpreted as produced by a deposit feeder using the siphon for respiration or as a device for a chemosymbiotic strategy. Psammichnites implexus is characterized by its consistently smaller size range, subtle backfill structure, and tendency to scribble. Although displaying similarities with Dictyodora scotica, P. implexus is a very shallow-tier, grazing trace. Changes in behavioral pattern, preservational style, and bedform morphology suggest a complex interplay of ecological and taphonomic controls in Carboniferous tidal-flat Psammichnites. A first distributional pattern consists of guided meandering specimens preserved in ripple troughs, probably reflecting food-searching of buried organic matter concentrated in troughs. A second is recorded by concentration of Psammichnites on ripple crests and slopes. In some cases, the course is almost straight to slightly sinuous and closely follows topographic highs, suggesting a direct control of bedform morphology on trace pattern. Occurrences of Carboniferous Psammichnites most likely represent an opportunistic strategy in marginal-marine settings. Analysis of Carboniferous Psammichnites indicates the presence of a siphon-like device in the producer and reestablishes the possibility of a molluscan tracemaker.

The paleoenvironmental significance of the nearshore Curvolithus ichnofacies

Newly discovered Curvolithus-rich trace-fossil assemblages in fan-delta deposits of the Pennsylvanian Minturn Formation of Colorado are remarkably similar to several other Carboniferous deltaic ichnofaunas, as well as those from Jurassic fan-delta environments and other marginal-marine deposits with freshwater influence. The Minturn trace fossils comprise the type assemblage of the Curvolithus ichnofacies, dominated by infaunal locomotion-feeding activity in environments characterized by relatively rapid deposition of sandy sediment exceeding physical reworking. The ichnofacies also occurs in sandy, low-energy, open-shelf environments. Thus, the ichnofacies is a paleo-energy and paleo-depositional rate indicator, and we predict that its occurrence in strongly localized deltaic and nearshore sandy facies recurs throughout the Phanerozoic.

Arthrophycus in the Silurian of Alabama (USA) and the problem of compound trace fossils

Arthrophycus brongniartii (Harlan, 1832) is common in marginal-marine deposits in the Silurian Red Mountain Formation of Alabama. The ichnospecies, the second to be named in North America, is revived and emended after long disuse. Transitional forms to Rusophycus isp. and other morphologic evidence indicate that the maker of Arthrophycus was an arthropod, perhaps a trinucleine (raphiophorid?) trilobite. Interconnection of Arthrophycus and Nereites biserialis, as well as intergradation of Arthrophycus with Cruziana aff. quadrata, Phycodes flabellum, and Asterosoma ludwigae, indicate that these Red Mountain trace fossils were made by the same species of arthropod. Possible relationships with Arthrophycus alleghaniensis (Harlan, 1831) in the Silurian belt from Ontario to Tennessee are also explored. Ichnofamily Arthrophycidae Schimper, 1879 is emended. The ichnofamily is interpreted as chiefly the work of arthropods. Arthrophycus and other trace fossils from the Silurian of Alabama constitute a test case to build criteria for recognizing the members of complexes of trace fossils. In general, criteria such as interconnection of different forms, intergradation among unconnected forms, similarity of size, similarity of morphologic elements, and co-occurrence should be examined in order to determine the biologic and ethologic interrelationships of trace fossils. 7 2003 Elsevier Science B.V. All rights reserved.

Identification of 'extinct' freshwater mussel species using DNA barcoding

Freshwater mollusks are highly imperiled, with 70% of the North American species extinct, endangered, or at risk of extinction. Impoundments and other human impacts on the Coosa River of Alabama, Georgia and Tennessee of the southeastern USA alone are believed to have caused 50 mollusk species extinctions, but uncertainty over boundaries among several putatively closely related species makes this number preliminary. Our examination of freshwater mussels collected during an extensive survey of the upper‐drainage basin, DNA barcoding and molecular phylogenetic analyses confirm the rediscovery of four morphospecies in the genus Pleurobema (Unionidae) previously thought to be extinct from the upper Coosa basin. A fifth ‘extinct’ form was found in an adjoining basin. Molecular data show that the Coosa morphologies represent at least three species‐level taxa: Pleurobema decisum, P. hanleyianum and P. stabile. Endemism is higher than currently recognized, both at the species level and for multispecies clades. Prompt conservation efforts may preserve some of these taxa and their ecosystem.

Ichnotaxonomy: Finding Patterns in a Welter of Information

Abstract Naming trace fossils is necessary if we are to communicate ideas about them. In the absence of DNA-based molecular analysis, ichnologists must rely on morphologic characters to classify trace fossils. Careful observation and description of trace fossils are therefore essential to nomenclature in ichnology. Since 1953, trace fossils have been classified simultaneously according to several systems based on stratinomic, biologic, ethologic, and binominal systematic approaches. Each of these approaches has its uses, for example, the ethologic approach is the basis of the archetypical ichnofacies model, and the systematic (Linnean) approach, with ichnogenera and ichnospecies, is the one that is most commonly used for information retrieval. The best classifications are those that are the most objective and that allow the generation of new hypotheses and predictions, reflecting patterns in the data rather than in the mind of the observer.

Arthropod Tracemakers of Nereites? Neoichnological Observations of Juvenile Limulids and their Paleoichnological Applications

SUMMARY: To get the most out of the paleoichnological record, the behavior and resultant traces of extant animals must be studied carefully, even if this upsets long-established ideas about the makers of trace fossils. Observations of modern juvenile limulids ( Limulus polyphemus ) show that they make modern traces similar to the ichnogenus Nereites on sandy tidal flats of Sapelo Island (Georgia, USA)—with the understanding that ichnogenera are morphologically based groups of trace fossils with no implication as to the maker. Our results confirm earlier work that suggests various arthropod makers as the makers of some Paleozoic Nereites —while throwing into question the established interpretation of Nereites as a burrow of vermiform tracemakers. Accordingly, Nereites -like traces should be reinvestigated on a case-by-case basis with regard to their characteristic bioprint , i.e., the set of morphologic features that allows the identification of the maker of a trace.

An updated classification of animal behaviour preserved in substrates

During the last few decades, many new ethological categories for trace fossils have been proposed in addition to the original five given by Seilacher. In this article, we review these new groups and present a version of the scheme of fossil animal behaviour originally published by Bromley updated with regard to modern ethological concepts, especially those of Tinbergen. Because some behaviours are more common in certain environments than others, they are useful in palaeoecological reconstructions, forming the original basis of the ichnofacies concept. To simplify, we summarise some ethological categories as previously done by others. However, the tracemaker’s behaviour in some cases is so distinctive that subcategories should be employed, especially in ecological interpretations of certain environments where a special behaviour may be dominant.

A History of Ideas in Ichnology

Abstract Although the concept of ichnology as a single coherent field arose in the nineteenth century, the endeavor of understanding traces is old as civilization and involved cultural areas worldwide. In fact, fossil and recent traces were recognized since prehistoric times and their study emerged from the European Renaissance. This progression, from empirical knowledge toward the modern concepts of ichnology, formed a major research field which developed on a global scale. This report outlines the history of ichnology by (1) exploring the individual cultural areas, (2) tracing a comprehensive bibliographic database, and (3) analyzing the evolution of ichnology semiquantitatively and in a graphical form (“tree of ichnology”). The results form a review and synthesis of the history of ichnology, establishing the individual and integrated importance of the different ichnological schools in the world.

Bioirrigation in Alph n. igen., arthropod cubichnia from the Mississippian Hartselle Sandstone of Alabama (USA)

Cubichnia from the Hartselle Sandstone, described as Rusophycus hartselleanus and herein renamed Alph hartselleanus n. igen., includes specimens with well-defined, terminal cylindrical structures. We interpret these oblique shaft-like structures as having a respiratory function based on: (1) exact placement of cylindrical structures on the cubichnial axis; (2) unique sculpture with both transverse and longitudinal striation, absent elsewhere in the assemblage despite excellent preservation of trace fossils; (3) associated features in the trace such as bubbly structure that also could be caused by bioirrigation. Alph hartselleanus is much larger than known Carboniferous trilobites. While similar to Rusophycus, the Hartselle cubichnia has a complex morphology suggesting a crustacean tracemaker. The trace is quadrilobate, with distinct anterior and posterior regions. The posterior region has 5 or 6 pairs of coarse, obliquely transverse striae corresponding to digging appendages, crosscut by fine, obliquely longitudinal striae that may record bioirrigation. The anterior region has a bubbly structure suggestive of thixotropic movement of sand, again, possible evidence for bioirrigation. The axial shafts do not match known trilobite appendages, but could have been made by crustaceans. Were the cubichnia merely resting traces, or did they have additional functions such as nesting or protection during moulting? In a broader context, the physical evidence for bioirrigation represents a nearly untapped opportunity for understanding the Cambrian Substrate Revolution as well as Phanerozoic ecosystems. Where preserved, the apertures of burrows should be investigated for evidence of bioirrigation.

Arthrodendron maguricum n. sp., a New Larger Agglutinated Foraminifer from the Eocene Magura Flysch of the Polish Carpathians and its Relationship to Komokiaceans and Trace Fossils

Abstract Arthrodendron maguricum n. sp. is described from deep-sea flysch of the lower Eocene Życzanów Conglomerate Member of the Szczawnica Formation (Magura Unit) in the Polish Carpathians. Arthrodendron maguricum is a larger agglutinated foraminifer showing regular, tubular chambers that may branch dichotomously. Its wall is tripartite and composed of an outer organic-rich layer, a main agglutinated layer, and an internal organic-rich layer. The organism evidently lived as epibenthos on the muddy sea floor. Because of their branching morphology and comparatively large dimensions, larger agglutinated foraminifera of the genus Arthrodendron have previously been confused with algae and trace fossils. Care should be taken in such cases to resolve the agglutinated wall and chambers of this deep-water agglutinated foraminifer. Arthrodendron maguricum displays superficial similarities to some modern komokiaceans, especially to Septuma. Further investigations are needed for clarification of their affinities and possible taxonomic consequences.