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<jats:title>ABSTRACT</jats:title> <jats:p>This study assesses the foraminiferal morphogroup concept as a quantitative tool for interpreting environments of deposition in the geological record. This was achieved by first establishing a solid paleoenvironmental framework based on assessment of trace fossils (Zoophycos, Cruziana, and Phycosiphon ichnofacies, and the unnamed brackish-water association), sedimentology, and facies analysis of shallow-marine siliciclastic units of the upper Albian Viking Formation of the Western Interior Seaway, Canada. Foraminiferal morphogroups were integrated into a framework of six well-defined marine mudstone-dominated facies—estuarine, embayment, prodelta, upper offshore, lower offshore, and marine shelf. Seven morphogroups were recognized, quantified, and labeled using alphanumeric codes—A (tubular), B1 (globular), B2 (coiled, flat), B3 (lenticular), C1 (elongate), C2 (quinqueloculine), and D (trochospiral).</jats:p> <jats:p>Tubular forms (A, Bathysiphon) occur rarely in these shallow-marine facies. Globular forms (B1, Lagenammina) are common in estuarine (33%) and embayment (23%) facies, but also occur elsewhere in low numbers (7–14%). Coiled planar forms (B2, Ammodiscus) occur only rarely (1–8%), but have a minor presence in embayment facies (8%). Lenticular forms (B3, Haplophragmoides) are dominant in estuarine facies (43%) and occur commonly in other environments (9–29%) as well. Elongate forms (C1, Ammobaculites, Reophax, Verneuilinoides) dominate all shallow-marine facies (43–80%), except estuarine (10%). Quinqueloculine forms (C2, Miliammina) have a minor presence in prodelta and marine facies (5%) but are generally rare. Trochoid forms (D, Trochammina) occur rarely, but are relatively common in the prodeltaic facies (15%). Albian foraminiferal morphogroups of the Viking Formation are comparable to those of modern-day offshore environments from water depths of 13 to 160 meters. Foraminiferal morphogroups are objective entities independent of taxonomic determinations. Analysis of their form and function is applicable not only in the shallow-marine facies of the Albian Western Interior Seaway, but in similar facies throughout the geologic record.</jats:p>

<jats:title>ABSTRACT</jats:title> <jats:p>A large collection of vertebrate coprolites derives from a debris flow conglomerate in the Upper Triassic Irohalene Member (Carnian) of the Timezgadiouine Formation, northern Argana Basin, Morocco. The coprolites are classified into 14 different morphotypes (MA to MN) based on their size, shape, and surface texture that are divided into three groups: striated coprolites; spiral and scroll-like coprolites; and non-spiral coprolites lacking striations. The great variety of morphotypes suggests the coprolites correspond to a variety of terrestrial and aquatic carnivorous producers. The carnivore coprolites lithified rapidly and were deposited in a high-energy sheetflood. The majority of the coprolites were produced by semi-aquatic and terrestrial tetrapods, with a small percentage produced by fish.</jats:p> <jats:p>The occurrence of Dicynodontocopros, common Alococopros, and some heteropolar forms with affinities to Heteropolacopros, are consistent with a late Carnian age for the Irohalene Member. The Irohalene coprolites are mostly similar to those of the coprofaunas of late Carnian age (Otischalkian–Adamanian) in the lower Chinle Group of the western United States in the co-occurrence of Alococopros and Dicynodontocopros. Significantly, this Moroccan coprofauna from Gondwana has close Laurussian relationships.</jats:p>

<jats:title>ABSTRACT</jats:title> <jats:p>Taphonomic indicators are often used to assess time-since-death of skeletal remains. These indicators frequently have limited accuracy, resulting in the reliance of other methodologies to age remains. Arctica islandica, commonly known as the ocean quahog, is a relatively widespread bivalve in the North Atlantic, with an extended lifespan that often exceeds two hundred years; hence, their shells are often studied to evaluate climate change over time. This report evaluates taphonomic age using 117 A. islandica shells collected from the Mid-Atlantic Bight offshore of the Delmarva Peninsula with radiocarbon dates extending from 60–4,400 cal years BP. These shells had varying degrees of taphonomic alteration produced by discoloration and degradation of periostracum. To determine if a relationship exists between taphonomic condition and time-since-death, radiocarbon ages were compared with the amount of remaining periostracum and type of discoloration. Old shells (individuals that died long ago) were discolored orange with no periostracum while younger shells (individuals that died more recently) had their original color, with some periostracum. Both the disappearance of periostracum and appearance of discoloration followed a logistic process, with 50% of shells devoid of periostracum and 50% discolored in about 1,000 years. The logistic form of long-term taphonomic processes degrading shell condition is first reported here, as are the longest time series for taphonomic processes in death assemblages within the Holocene record. This relationship can be utilized for triage when deciding what shells to age from time-averaged assemblages, permitting more efficient application of expensive methods of aging such as radiocarbon dating.</jats:p>

<jats:title>ABSTRACT</jats:title> <jats:p>Molluscan death assemblages occurring on present-day beaches frequently consist of secondary-colored shells, with yellow to brown and gray to black colors. It is hypothesized that this secondary coloration can be related to postmortem age and to conditions in the taphonomically active zone, altering shells to black and gray tones in reducing conditions, and then becoming yellowish or brownish in oxidizing settings. In this study, we assessed whether the variability in the degree of shell discoloration of two species of the infaunal bivalve Mactra collected in beach death assemblages from a temperate siliciclastic beach in Uruguay is a function of postmortem age, and whether this variability in discoloration can be linked to differences in their elemental composition, microstructure, and provenance. Although we did not detect any differences in mineralogy or elemental composition among shells differing in discoloration, we show that modern (younger than a century) beach shells are not secondary-colored, but have remained white, but some white shells are also old (millennial). In contrast, yellow and gray shells are consistently older than 1,000 years, indicating that this degree of discoloration requires millennial residence times in the taphonomically active zone and suggesting that discoloration can be used as an indicator of time averaging. Discolored shells are derived from subtidal death assemblages.</jats:p>

<jats:title>ABSTRACT</jats:title> <jats:p>Scorpions are intermediate predators in numerous terrestrial environments, and many are temporarily to permanently fossorial. As a result, they play key roles in terrestrial food webs, in soil development, and as ecosystem engineers. However, scorpions have a poorly described ichnofossil record likely due to an inadequate understanding of their trace morphology. Critical to correcting this is assessing the variability of burrows constructed by phylogenetically, geographically, and environmentally distinct scorpions. Five extant scorpions, Heterometrus spinifer, Pandinus imperator, Pandipalpus viatoris, Hadrurus arizonensis, and Paravaejovis spinigerus were studied through neoichnological experiments under varying substrate conditions. Burrow casts produced were described and compared across species and different substrate conditions. Tropical scorpions excavated sediment and carried it away from the burrow to produce open, straight-to-sinuous, subvertical tunnels to branching tunnel systems with single to multiple entrances and often chambers. Arid scorpions excavated with rapid leg movements to throw sediment behind the body to produce single to linked networks of U-shaped burrows as well as subvertical tunnels to tunnel networks with single to multiple entrances and rarely chambers. Changes in sediment composition and moisture tended to reduce burrow production but did not significantly alter burrow morphology. All scorpion burrows, regardless of species, bore a moderate-to-high similarity despite differences in excavation styles and architecture suggesting that scorpions produce burrows of consistent form regardless of phylogenetic or environmental distance. The result of these studies provides key ichnotaxobases of scorpion burrows which can be used to identify them in the fossil record and improve interpretations of ancient terrestrial ecosystems.</jats:p>

<jats:title>ABSTRACT</jats:title> <jats:p>Microbes colonize sediment and alter its properties creating a bio-mineral medium. The microbially induced sedimentary structures (MISS) are the fossil record of an interaction between the physical environment and such a medium. The present report documents bedding surface structures from the Cisuralian (Asselian) Sandstone Building Member (BSM) of the Słupiec Formation, a unit that outcrops in the south-western Poland, in the Sudetes Mountains. The BSM represents likely continental (fluvial) sedimentary settings. The sedimentary structures on bedding surfaces in the BSM are interpreted as the MISS. The observations of the bedding structures are supplemented with thin section data that support the microbial interpretation of the bedding surface structures. The Słupiec Formation MISS record supplements the global patchy fossil record of the post-Cambrian (Paleozoic) MISS from the non-marine settings.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>A horizon of aperture-up, subvertically oriented shells of Tentaculites in the Middle Devonian Arkona Formation (Hamilton Group) near Arkona, Ontario, Canada, is investigated with respect to burial processes, tentaculitid life habits, and associated diagenetic features. Field observations of the horizon in situ confirm previous suspicions that thick-walled tentaculitoids were benthic and oriented aperture-up in life. In this biocoenosis, tentaculitids vary from low-density populations to dense clumps, the latter sometimes showing grid-like arrangements. The mutual spacing of individuals reflects space demands of a feeding apparatus. The limited size range of the shells suggest that tentaculitid colonization event was brief, involving no more than two generational growth cohorts. Sedimentary features associated with the subvertical shells indicate that the seafloor mud inhabited by the tentaculitids was soft, but sufficiently cohesive to preserve microtopographic features, and prone to disturbance by storms. Preservation of their shells in (subvertical) life position necessitated rapid burial (via mud blanketing) without significant scouring. The emanation of sulfidic decay products from the tentaculitid shell apertures led to the local inhibition of later-precipitated calcareous concretionary cement. Preferential erosion of this material resulted in the development of circular pockmarks on concretion surfaces. The concretions themselves formed along a thin zone of alkalinity that developed below the sediment-water interface at the sulfate-methane boundary during a depositional hiatus sometime after the burial of the subvertical tentaculitids. Variations in the vertical positions of radially tilted tentaculitid shells apertures show undulations that, in turn, imply tentaculitids mutually adjusted their growth directions to maximize living space and/or food acquisition.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Preservation of arthropod cuticles is of paramount importance for taphonomic interpretations in which the fossil record of the chitin-protein complex is considered a key molecular signature of the group studied. In this work, different specimens of clam shrimps and their surrounding sedimentary matrix recovered from four localities of the La Matilde Formation (Patagonia, Argentina) were chemically analyzed for the first time by Laser-induced breakdown spectroscopy (LIBS) and RAMAN spectroscopic techniques. The spectral data recorded from the fossils were processed and analyzed through multivariate statistics, including Principal Component Analysis (PCA), Nonmetric Multidimensional Scaling (NMDS), and Analysis of Similarities (ANOSIM). The correlation between the different colorations featured by the specimens and the atomic chemical composition of their carapaces was systematically investigated to gain a better understanding of the fossilization processes together with more detailed interpretations. We found that the carapaces featuring a yellow-brown color exhibited a similar chemical profile with iron predominance, while those with the same color as the sedimentary matrix presented a distinctive composition. Considering the volcanic influence to which the different localities studied and carapaces were exposed, we propose that the clam shrimps from the four localities were preserved in at least three ways, namely, (1) pyritization; (2) admixed preservation; and (3) impression, each with distinctive characteristics of the taphonomic processes involved. Overall, results obtained provide useful information to achieve a more comprehensive knowledge about the taphonomy of fossils in a Jurassic lacustrine paleo-environment, as the La Matilde Formation.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>A complex system of three-dimensional cameral membranes is known from the phragmocones of several ammonoid genera—both Paleozoic and Mesozoic. The origin and functions of these membranes remain mysterious, and their study is complicated by the absence of identical structures in modern cephalopods. Current hypotheses about the origin of cameral membranes and other organic structures of the phragmocone are mainly based on the study of Paleozoic, Triassic, and Cretaceous ammonoids. This paper examines the membranes of Subboreal Jurassic ammonites. The spatial arrangement and complexity of these membranes differ from those described earlier. It was previously assumed that three-dimensional membranes only appeared late in ammonoid ontogeny, at the end of the neanic stage. However, in the ammonites studied herein, such membranes are present starting from the second phragmocone chamber. In addition to membranes, we report other initially organic phragmocone structures of Jurassic ammonites: pseudosutures and drag lines. The discovery of a unique structure in the last phragmocone chamber of one specimen, which likely represents a fossilized set of pseudosepta, has led to a new hypothesis, that can explain the formation of all types of membranes and other initially organic phragmocone structures. According to this idea, all types of cameral sheets despite their different shapes, were formed during merging and subsequent dehydration of organic pseudosepta. Pseudosutures and drag lines are imprints of the pseudosepta margins.</jats:p>