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In the region of In Amenas (south-eastern Algeria) Triassic deposits crop out, on top of Palaeozoic rocks under an angular unconformity. Astudy of their sedimentological and palaeoenvironmental characteristics has revealed asandy-clay unit with vertebrate remains, tree trunks and ichnofossils of Middle-Late Triassic age. This so-called Zarzaitine Formation, which reflects deposition in adeltaic environment, shows three facies associations. The first defines an upper and shallow intertidal mixed flat zone with in-situ temnospondyl capitosauroid remains, associated with Skolithos ichnofacies, while the second one defines alower intertidal delta plain zone, composed of sandstone, distributary channels and muddy interdistributary areas,which record daily tidal rhythmites and monthly tidal bundles. The third, and last, facies association represents an upper delta plain of the supratidal zone, characterised by coarse sandstone deposits of braided rivers and aCycadophyta palaeosol. Previous work, which led to considering these Triassic deposits as aseries composed of four formations, deposited in abraided rivers environment, whose lower floodplains constituted ecological niche for atemnospondyl fauna, under hot and dry climatic conditions and plants belonging to this same formation, for mushrooms and algae, will also be considered. [ABSTRACT FROM AUTHOR]

Abstract Distinct, new oviposition lesion types, Paleoovoidus pyriformis ichnosp. nov. and Variomorphonotatus sagittaeformis ichnogen. et ichnosp. nov., occurring on two fossil compression Cycadophyte leaves from the Lower Jurassic Shemshak Formation of western Alborz Ranges, northern Iran are documented and compared with the previously instituted morphologically analogous taxa. Comparison of the shape and configuration of the scars with those of the modern zygopteran Odonata suggests that any member of the Lestid-damselfly produced P. pyriformis ichnosp. nov. whereas any representative of Coenagrionid-damselflies (damselflies-dragonflies) induced formation of V. sagittaeformis ichnogen. et ichnosp. nov. In the absence, so far, of any entomofaunal evidence from the Shemshak Formation, the ichnotaxa documented herein offer unequivocal evidence to the presence of the Odonatan representatives in the Early Jurassic riparian ecosystems of northern Iran.

Distinct, new oviposition lesion types, Paleoovoidus pyriformis ichnosp. nov. and Variomorphonotatus sagittaeformis ichnogen. et ichnosp. nov., occurring on two fossil compression Cycadophyte leaves from the Lower Jurassic Shemshak Formation of western Alborz Ranges, northern Iran are documented and compared with the previously instituted morphologically analogous taxa. Comparison of the shape and configuration of the scars with those of the modern zygopteran Odonata suggests that any member of the Lestid-damselfly produced P. pyriformis ichnosp. nov. whereas any representative of Coenagrionid-damselflies (damselflies-dragonflies) induced formation of V. sagittaeformis ichnogen. et ichnosp. nov. In the absence, so far, of any entomofaunal evidence from the Shemshak Formation, the ichnotaxa documented herein offer unequivocal evidence to the presence of the Odonatan representatives in the Early Jurassic riparian ecosystems of northern Iran. [ABSTRACT FROM AUTHOR]

The extended phenotype of helical burrowing behavior in animals has evolved independently many times since the Cambrian explosion (~540 million years ago [MYA]). A number of hypotheses have been proposed to explain the evolution of helical burrowing in certain taxa, but no study has searched for a general explanation encompassing all taxa. We reviewed helical burrowing in both extant and extinct animals and from the trace fossil record and compiled 10 hypotheses for why animals construct helical burrows, including our own ideas. Of these, six are post‐construction hypotheses—benefits to the creator or offspring, realized after burrow construction—and four are construction hypotheses reflecting direct benefits to the creator during construction. We examine the fit of these hypotheses to a total of 21 extant taxa and ichnotaxa representing 59–184 possible species. Only two hypotheses, antipredator and biomechanical advantage, cannot be rejected for any species (possible in 100% of taxa), but six of the hypotheses cannot be rejected for most species (possible in 86%–100% of taxa): microclimate buffer, reduced falling sediment (soil), anticrowding, and vertical patch. Four of these six are construction hypotheses, raising the possibility that helical burrowing may have evolved without providing post‐construction benefits. Our analysis shows that increased drainage, deposit feeding, microbial farming, and offspring escape cannot explain helical burrowing behavior in the majority of taxa (5%–48%). Overall, the evidence does not support a general explanation for the evolution of helical burrowing in animals. The function and evolution of the helix as an extended phenotype seems to provide different advantages for different taxa in different environments under different physicochemical controls (some traces/tracemakers are discussed in more detail due to their association with body fossils and well‐constrained physicochemical parameters). Although direct tests of many of the hypotheses would be difficult, we nevertheless offer ways to test some of the hypotheses for selected taxa. [ABSTRACT FROM AUTHOR]

Ooids are abundant carbonate grains throughout much of Earth's history, but their formation is not well understood. Here, an in‐depth study of microbial bioerosion features of Holocene ooids from the Schooner Cays ooid shoals (Great Bahama Bank, Eleuthera, Bahamas) and the Shalil al Ud ooid shoals in the Arabian/Persian Gulf (Abu Dhabi, United Arab Emirates) is presented. No obvious differences were found in ooid size distribution, cortex layer thickness, the composition of nuclei or euendolithic community when comparing ooids from both locations. Microendolithic borings are present in most studied ooid surfaces, but the intensity of (micro‐)bioerosion varies significantly. Applying an epoxy vacuum cast‐embedding technique allowed the identification of ichnotaxa and their inferred producers (various genera of diatoms, cyanobacteria, coccolithophores and unspecified bacteria). Euendolithic taxa have specific low‐light tolerances and light optima. This implies that information about the relative bathymetry (seafloor versus burial within an ooid shoal) and ecology for ooid cortex formation can be obtained via the presence or absence of their respective ichnotaxa. The history of a statistically significant number of ooid cortices can be translated into dune dynamics and the temporal variations thereof by allocating the inferred index producer to a defined burial or light penetration zone. In this context, ooid formation can be divided into four stages: (i) an agitation stage in the water column, characterized by the colonization of grains by photoautotrophs; (ii) a resting stage, characterized by temporary burial of the ooid, leading to immobilization and a shift towards heterotrophs; (iii) a sleeping stage, characterized by prolonged burial and colonization by organotrophs; and (iv) a reactivation stage, characterized by a resurfacing of the ooid and a subsequent shift towards photoautotrophs. The sleeping stage is presumably a stage of ooid degradation where bioerosion, mainly by heterotrophic fungi and bacteria is particularly active. [ABSTRACT FROM AUTHOR]

Using modern ichnological and stratigraphic tools, we reinvestigate two iconic sauropodomorph-attributed tetradactyl ichnogenera, Pseudotetrasauropus and Tetrasauropus, and their stratigraphic occurrences in the middle Upper Triassic of Lesotho. These tracks have been reaffirmed and are stratigraphically well-constrained to the lower Elliot Formation (Stormberg Group, Karoo Basin) with a maximum depositional age range of <219-209 Ma (Norian). This represents the earliest record of basal sauropodomorph trackways in Gondwana, if not globally. Track and trackway morphology, the sedimentary context of the tracks, and unique features (e.g., drag traces) have enabled us to discuss the likely limb postures and gaits of the trackmakers. Pseudotetrasauropus has bipedal (P. bipedoida) and quadrupedal (P. jaquesi) trackway states, with the oldest quadrupedal Pseudotetrasauropus track and trackway parameters suggestive of a columnar, graviportal limb posture in the trackmaker. Moreover, an irregularity in the intermanus distance and manus orientation and morphology, in combination with drag traces, is indicative of a non-uniform locomotory suite or facultative quadrupedality. Contrastingly, Tetrasauropus, the youngest trackway, has distinctive medially deflected, robust pedal and manual claw traces and a wide and uniform intermanus distance relative to the interpedal. These traits suggest a quadrupedal trackmaker with clawed and fleshy feet and forelimbs held in a wide, flexed posture. Altogether, these trackways pinpoint the start of the southern African ichnological record of basal sauropodomorphs with bipedal and quadrupedal locomotory habits to, at least, c. 215 Ma in the middle Late Triassic. [ABSTRACT FROM AUTHOR]

Studies of marine microbioerosion in polar environments are scarce. They include our recent investigations of bioerosion traces preserved in sessile balanid skeletons from the Arctic Svalbard archipelago and the Antarctic Ross Sea. Here, we present results from a third study site, Frobisher Bay, in the eastern Canadian Arctic, together with a synthesis of our current knowledge of polar bioerosion in both hemispheres. Barnacles from 62 to 94 m water depth in Frobisher Bay were prepared using the cast-embedding technique to enable visualization of microboring traces by scanning electron microscopy. In total, six ichnotaxa of traces produced by organotrophic bioeroders were found. All recorded ichnotaxa were also present in Mosselbukta, Svalbard, and most in the Ross Sea. Frobisher Bay contrasts with Mosselbukta in that it is a siliciclastic-dominated environment and shows a lower ichnodiversity, which may be accounted for by the limited bathymetrical range and a high turbidity and sedimentation rate. We evaluate potential key ichnotaxa for the cold-temperate and polar regions, of which the most suitable are Flagrichnus baiulus and Saccomorpha guttulata, and propose adapted index ichnocoenoses for the interpretation of palaeobathymetry accordingly. Together, the three studies allow us to make provisional considerations about the biogeographical distribution of polar microbioerosion traces reflecting the ecophysiological limits of their makers.

Trace fossils of the ichnogenera Cruziana and Rusophycus are described for the first time from the Lower Ordovician of Baltica. These specimens were found from the upper Tremadocianâlower Floian glauconite sandstone of the Leetse Formation in the Leetse and Uuga cliffs on the Pakri Peninsula, North-West Estonia. The one from the Leetse locality was collected already in the 19th century but was hidden in museum collections. On this piece of rock, together with the Rusophycus, brachiopods Leptembolon lingulaeformis and Thysanotos siluricus occur. They indicate that the sample comes from the strata corresponding to the Thysanotossiluricus Brachiopod Biozone of the Hunneberg Stage. Different lithology of the two newly discovered loose slabs with trace fossils found under the Uuga cliff indicates that, most probably, they originate from different levels of the glauconite sandstone exposed in this section. One of them is heavily pyritized and yields a contact surface with the underlying beige argillite of the Varangu Stage with fragments of the graptolite Kiearograptus supremus and some undescribed acrotretid and other linguloid brachiopods. The second, less strongly lithified slab contains abundant fine debris of thin-shelled unidentifiable linguloid brachiopods and probably comes from a higher level. Earlier studies of conodonts revealed that the Prioniodus elegans Conodont Zone is missing in the Uuga section, thus narrowing down the possible interval of origin of these ichnotaxa to the Paroistodus proteus zone. Interestingly, these two slabs preserve the dissimilar pattern of grouping and orientation of the multiple Rusophycus/Cruziana traces giving some idea about the ethology of trilobites who probably left these traces. The earliest trilobites in the Ordovician succession of Estonia are recorded from the Mäeküla Member, the uppermost part of the Leetse Formation, from an interval where calcareous component first appears in the sediment and thus also the trilobites with their calcitic exoskeleton are preserved. The only trilobites recorded from the Mäeküla Member of the Leetse Formation in these two localities are specimens of Paramegistaspisleuchtenbergi who could have been the trace maker with its macropygidium being of similar size to its cephalon if the second slab would come from the same interval. However, there are more candidates, mainly isoteline trilobites with similar characteristics which are preserved in older but calcareous succession in Sweden and Norway.

Studies of marine microbioerosion in polar environments are scarce. They include our recent investigations of bioerosion traces preserved in sessile balanid skeletons from the Arctic Svalbard archipelago and the Antarctic Ross Sea. Here, we present results from a third study site, Frobisher Bay, in the eastern Canadian Arctic, together with a synthesis of our current knowledge of polar bioerosion in both hemispheres. Barnacles from 62 to 94 m water depth in Frobisher Bay were prepared using the cast-embedding technique to enable visualization of microboring traces by scanning electron microscopy. In total, six ichnotaxa of traces produced by organotrophic bioeroders were found. All recorded ichnotaxa were also present in Mosselbukta, Svalbard, and most in the Ross Sea. Frobisher Bay contrasts with Mosselbukta in that it is a siliciclastic-dominated environment and shows a lower ichnodiversity, which may be accounted for by the limited bathymetrical range and a high turbidity and sedimentation rate. We evaluate potential key ichnotaxa for the cold-temperate and polar regions, of which the most suitable are Flagrichnus baiulus and Saccomorpha guttulata, and propose adapted index ichnocoenoses for the interpretation of palaeobathymetry accordingly. Together, the three studies allow us to make provisional considerations about the biogeographical distribution of polar microbioerosion traces reflecting the ecophysiological limits of their makers. [ABSTRACT FROM AUTHOR]

Various ichnotaxa found in hard substrates are interpreted as "phoronid" trace fossils. Their records are briefly reviewed. An interpretation of Diorygma found in the shells of brachiopods is not compatible with phoronid morphology and anatomy. Criteria for the discrimination of phoronid burrows and borings from those of similar organisms from others are difficult to establish even when the evidence and conclusions made therefrom are sound.

Trace fossils of the ichnogenera Cruziana and Rusophycus are described for the first time from the Lower Ordovician of Baltica. These specimens were found from the upper Tremadocian−lower Floian glauconite sandstone of the Leetse Formation in the Leetse and Uuga cliffs on the Pakri Peninsula, North-West Estonia. The one from the Leetse locality was collected already in the 19th century but was hidden in museum collections. On this piece of rock, together with the Rusophycus, brachiopods Leptembolon lingulaeformis and Thysanotos siluricus occur. They indicate that the sample comes from the strata corresponding to the Thysanotossiluricus Brachiopod Biozone of the Hunneberg Stage. Different lithology of the two newly discovered loose slabs with trace fossils found under the Uuga cliff indicates that, most probably, they originate from different levels of the glauconite sandstone exposed in this section. One of them is heavily pyritized and yields a contact surface with the underlying beige argillite of the Varangu Stage with fragments of the graptolite Kiearograptus supremus and some undescribed acrotretid and other linguloid brachiopods. The second, less strongly lithified slab contains abundant fine debris of thin-shelled unidentifiable linguloid brachiopods and probably comes from a higher level. Earlier studies of conodonts revealed that the Prioniodus elegans Conodont Zone is missing in the Uuga section, thus narrowing down the possible interval of origin of these ichnotaxa to the Paroistodus proteus zone. Interestingly, these two slabs preserve the dissimilar pattern of grouping and orientation of the multiple Rusophycus/Cruziana traces giving some idea about the ethology of trilobites who probably left these traces. The earliest trilobites in the Ordovician succession of Estonia are recorded from the Mäeküla Member, the uppermost part of the Leetse Formation, from an interval where calcareous component first appears in the sediment and thus also the trilobites with their calcitic exoskeleton are preserved. The only trilobites recorded from the Mäeküla Member of the Leetse Formation in these two localities are specimens of Paramegistaspisleuchtenbergi who could have been the trace maker with its macropygidium being of similar size to its cephalon if the second slab would come from the same interval. However, there are more candidates, mainly isoteline trilobites with similar characteristics which are preserved in older but calcareous succession in Sweden and Norway. [ABSTRACT FROM AUTHOR]

The de‑oxygenation of marine environments is thought to have played a significant role in many of Earth's major mass extinction events. This includes the end-Triassic mass extinction event (ETME), which witnessed the disappearance of conodonts, the near extinction of ammonoids and the most significant reef crisis across the entirety of the Phanerozoic. However, there are few high-resolution redox studies across the ETME, including across the main pulse of marine extinction, and few studies that directly correlate marine redox conditions with the biotic record in the same sedimentary succession. Here we present a high-resolution multi-proxy redox record from an expanded Triassic–Jurassic boundary section (Carnduff-2 borehole) from the Larne Basin, Northern Ireland. Redox conditions within the Larne Basin during the latest Triassic and earliest Jurassic were oxic to suboxic with suboxia being mainly restricted to sedimentary pore fluids. Such conditions differ from the photic zone euxinia reported from this time in other basins. Despite the Larne Basin being relatively oxygenated during the latest Triassic (Rhaetian) to earliest Jurassic (Hettangian), subtle pulsed marine redox changes within the Larne Basin had a profound effect on infaunal marine organisms. Suboxia within the Larne Basin coincided with the disappearance of 62.5% of bivalve species, of which 90% were infaunal, and the temporary absence of bioturbation. • A high-resolution palaeo-redox record from an expanded Triassic–Jurassic boundary location. • The Larne Basin remained relatively oxygenated during the Latest Triassic and Earliest Jurassic. • Infauna were significantly affected by subtle redox changes in the Larne Basin during the TJB. • A local redox shift is observed at the base of the initial CIE, coinciding with the ETME. [ABSTRACT FROM AUTHOR]

Abstract: Ichnotaxonomy classify and name trace fossils, an heterogeneous set of sedimentary structures resulting from various animal activities. A uniform vocabulary is needed for palaeoichnology, a discipline now currently used for sedimentological, palaeoecological and palaeoethological studies. The rules of binominal nomenclature (ichnogenus–ichnospecies) established by the International Code of Zoological Nomenclature are followed. This artificial approach (parataxonomy) needs to be easy to use, but is rather hard to establish. This brief article deals with general considerations and underlines particularities and difficulties of ichnotaxonomy. It shows that, to be efficient, ichnotaxonomy especially, needs rigour and pragmatism. [Copyright &y& Elsevier]

The Late Jurassic–Lower Cretaceous microorganisms incertae sedis Lithocodium aggregatum Elliott and Bacinella irregularis Radoičić are taxonomically studied based on material from the Lower Aptian of the western Maestrat Basin (Spain). This study is supplemented with detailed photographs from Elliot’s type-material. Given that the original description of Lithocodium aggregatum is ambiguous, a detail from the holotype is chosen as an epitype to serve as an interpretative type (article 9.7 ICBN). Lithocodium is re-interpreted as a filamentous-septate heterotrichale ulvophycean alga (?order Ulotrichales) exhibiting a heteromorphic life cycle consisting of two phases: an epilithic gametophytic and a euendolithic sporophytic ( Gomontia stage). Bacinella irregularis is interpreted and redescribed as a purely euendolithic ulvophycean alga which bores into either Lithocodium aggregatum or the substrate below Lithocodium crusts. A small microendolith boring into Lithocodium crusts capable of cryptobiotically stretching within its filamentous network is tentatively assigned to the siphonal chlorophyte Ostreobium Bornet and Flahault. Another associated microfilamentous boring chlorophyte with characteristic long thin hairs (setae) is described as Phaeophila? sp. The euendolithic community comprises a variety of micro- and macroborings that affect the thalli of Lithocodium. Finally, the filaments of the outer zone of the Lithocodium crust are infested by calcimicrobes (cyanobacteria, ?fungi). The description made by Elliott in his original work of the “inner layer” of Lithocodium aggregatum as “confused” is explained here as a complex multitaxon chlorophyte-calcimicrobial assemblage overprinted by multiple bioerosion ichnofabrics. [ABSTRACT FROM AUTHOR]

The Late Jurassic–Lower Cretaceous microorganisms incertae sedis Lithocodium aggregatum Elliott and Bacinella irregularis Radoičić are taxonomically studied based on material from the Lower Aptian of the western Maestrat Basin (Spain). This study is supplemented with detailed photographs from Elliot’s type-material. Given that the original description of Lithocodium aggregatum is ambiguous, a detail from the holotype is chosen as an epitype to serve as an interpretative type (article 9.7 ICBN). Lithocodium is re-interpreted as a filamentous-septate heterotrichale ulvophycean alga (?order Ulotrichales) exhibiting a heteromorphic life cycle consisting of two phases: an epilithic gametophytic and a euendolithic sporophytic ( Gomontia stage). Bacinella irregularis is interpreted and redescribed as a purely euendolithic ulvophycean alga which bores into either Lithocodium aggregatum or the substrate below Lithocodium crusts. A small microendolith boring into Lithocodium crusts capable of cryptobiotically stretching within its filamentous network is tentatively assigned to the siphonal chlorophyte Ostreobium Bornet and Flahault. Another associated microfilamentous boring chlorophyte with characteristic long thin hairs (setae) is described as Phaeophila? sp. The euendolithic community comprises a variety of micro- and macroborings that affect the thalli of Lithocodium. Finally, the filaments of the outer zone of the Lithocodium crust are infested by calcimicrobes (cyanobacteria, ?fungi). The description made by Elliott in his original work of the “inner layer” of Lithocodium aggregatum as “confused” is explained here as a complex multitaxon chlorophyte-calcimicrobial assemblage overprinted by multiple bioerosion ichnofabrics. [ABSTRACT FROM AUTHOR]

Abstract: Aspects of texture and structure in a bed resulting from bioturbation can provide valuable information about the ecology and environment at the time of deposition. However, not only the degree of bioturbation, but the structure of the burrows is important for interpreting biogenic fabrics. Here, image analysis is applied to real and artificial images of biogenic sedimentary structures. Image segmentation was applied to images of Middle Ordovician biogenic sedimentary structures from Dixon, Illinois (Pecatonica Formation), isolating the biogenic sedimentary structures. A gray-level co-occurrence matrix (GLCM) is calculated from the segmented image and eight artificial images representing different levels of image noise. Texture measures were calculated from the GLCMs and compared with identify scale and directional structural differences between the images. Principal component analysis was used to statistically group the images. Artificial images were found to be distinguishable from the real images by GLCM texture measures, and the real images differed most significantly at the largest scales. [Copyright &y& Elsevier]

The taxonomic treatment of trace fossils needs a uniform approach, independent of the ethologic groups concerned. To this aim, trace fossils are rigorously defined with regard to biological taxa and physical sedimentary structures. Potential ichnotaxobases are evaluated, with morphology resulting as the most important criterion. For trace fossils related to bioerosion and herbivory, substrate plays a key role, as well as composition for coprolites. Size, producer, age, facies and preservation are rejected as ichnotaxobases. Separate names for undertracks and other poorly preserved material should gradually be replaced by ichnotaxa based on well-preserved specimens. Recent traces may be identified using established trace fossil taxa but new names can only be based on fossil material, even if the distinction between recent and fossil may frequently remain arbitrary. It is stressed that ichnotaxa must not be incorporated into biological taxa in systematics. Composite trace fossil structures (complex structures made by the combined activity of two or more species) have no ichnotaxonomic standing but compound traces (complex structures made by one individual tracemaker) may be named separately under certain provisions. The following emendations are proposed to the International Code of Zoological Nomenclature: The term ‘work of an animal’ should be deleted from the code, and ichnotaxa should be based solely on trace fossils as defined herein. [ABSTRACT FROM AUTHOR]

Otozoum moodii Hitchcock, 1847 is one of the classic Connecticut Valley ichnotaxa established by Edward Hitchcock between 1836 and 1865. The taxon is redescribed, and AC 4/1a re-established as the holotype specimen. Otozoum minus and O. caudatum are synonymised with O. moodii. The syntypes of Kalosauropus pollex (nomen nudum) are described as O. pollex sp. nov. Cladistic, quantitative, and comparative methods of trackmaker identification suggest that Otozoum was made by a prosauropod dinosaur. In quantitative analyses, only those phalanges likely to contribute to footprint morphology were considered; claws were also excluded due to their highly variable styles of impression. Several diagnostic characters distinguish Otozoum from Brachychirotherium, Chirotherium, Batrachopus, Tetrasauropus, and Pseudotetrasauropus; these ichnotaxa are probably attributable to crurotarsan archosaurs. Otozoum is found primarily in Hettangian strata of the Hartford, Deerfield, and Fundy rift basins of eastern North America; it is also present in the Early Jurassic Navajo Sandstone (Colorado Plateau, USA) and Clarens Formation (Lesotho). The taxon is unknown in older strata; Triassic material previously referred to Otozoum (including O. grandcombensis) instead belongs in Pseudotetrasauropus. Correlation of sediments and comparison of faunal assemblages, particularly within the Newark Supergroup, suggest that the Otozoum trackmakers were restricted to arid environments. [ABSTRACT FROM AUTHOR]