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Martin introduces readers to the world of ichnology, the study of traces and trace fossils -- such as tracks, trails, burrows, nests, toothmarks, and other vestiges of behavior -- and how through these remarkable clues, help scientists explore and intuit the rich and complicated lives of dinosaurs during the Mesozoic era.

Analysis of modern animals and Ediacaran trace fossils predicts that the oldest bilaterians were simple and small. Such organisms would be difficult to recognize in the fossil record, but should have been part of the Ediacara Biota, the earliest preserved macroscopic, complex animal communities. Here, we describe Ikaria wariootia gen. et sp. nov. from the Ediacara Member, South Australia, a small, simple organism with anterior/posterior differentiation. We find that the size and morphology of Ikaria match predictions for the progenitor of the trace fossil Helminthoidichnites—indicative of mobility and sediment displacement. In the Ediacara Member, Helminthoidichnites occurs stratigraphically below classic Ediacara body fossils. Together, these suggest that Ikaria represents one of the oldest total group bilaterians identified from South Australia, with little deviation from the characters predicted for their last common ancestor. Further, these trace fossils persist into the Phanerozoic, providing a critical link between Ediacaran and Cambrian animals.

A remarkable diversity of bioerosion trace fossils is reflected by the plethora of ichnotaxa that has been proposed for these structures during the past two centuries. Bioerosion traces include microborings, macroborings, grazing traces, attachment etchings, and predation traces. They occur in calcareous, siliceous, osteic, and xylic substrates, and are known or interpreted to be produced by tracemakers as diverse as bacteria, fungi, algae, invertebrates, and vertebrates. This review presents the status quo of an inventory of all bioerosion ichnotaxa currently recognized as valid, comprising 123 ichnogenera and 339 ichnospecies, including 45 combinationes novae, the majority of which on account of fossil sponge bioerosion traces formerly grouped within the sponge biotaxon Cliona. In addition, the spelling of several ichnotaxa has to be corrected, leading to eight nomina corrigenda, and three cases of primary or secondary homonymy require establishing nomina nova, i.e., the new ichnogenus name Irhopalia replacing Rhopalia Radtke, 1991, as well as the new ichnospecies names Entobia morrisi replacing E. glomerata (Morris, 1851) and Entobia tuberculata replacing E. mammillata Bromley and D’Alessandro, 1984, respectively. Ichnotaxa of dubious or invalid nomenclatural status currently include an additional 76 ichnogenera and 157 ichnospecies. The invalid ichnogenus Ipites is herein reinstated as new ichnogenus. Considering that only four valid (and one invalid) ichnofamilies had previously been established for bioerosion ichnotaxa, we here introduce a suite of 14 additional ichnofamilies: Gastrochaenolitidae, Talpinidae, Entobiaidae, Planobulidae, Ichnoreticulinidae, Saccomorphidae, Centrichnidae, Renichnidae, Podichnidae, Gnathichnidae, Circolitidae, Oichnidae, Belichnidae, and Machichnidae. During the past five decades, the number of valid bioerosion ichnotaxa has more than quadrupled, reflecting a boost in bioerosion research, but also indicating the need for ichnotaxonomic consolidation in concert with a revision of key ichnogenera. In this context, the aim of this overview is to call for feedback from the research community in order to foster completeness of this list and to provide ichnotaxonomic stability. Furthermore, we want to raise awareness of the existence of the listed ichnotaxa, many of which obviously have remained unconsidered or forgotten for a long time.

For about 60 years, the ichnofacies model has been used to identify trace fossil assemblages associated with sedimentary environments. However, the ichnofacies model faces many problems, including: (1) how ichnofacies are defined; (2) non-environmental controls of trace fossil distribution; (3) trace fossil homeomorphy; (4) lack of autecology; (5) facies-crossing ichnotaxa; (6) non-uniformitarian aspects of trace fossil history; (7) monotaxial and other low-diversity ichnoassemblages; (8) ichnoassemblages that do not fit into established ichnofacies; and (9) taphonomic biases. Because of these problems, ichnofacies have become an over-generalized, assumption-ridden, exception-laden model that relies on diverse ad hocisms to explain away many of its shortfalls. Ichnofacies should be abandoned, and the relationship of trace fossils to sedimentary environments should be analyzed in a more granular and precise manner, focused on individual trace fossils or ichnoassemblages in conjunction with analysis of lithofacies and other biofacies data. Fossilized behavior is the conceptual paradigm of ichnology, not ichnofacies.

This study integrates ichnological and sedimentological data to interpret depositional environments of the carbonate sediments of the Tirgan Formation (Lower Cretaceous) in the eastern Kopet-Dagh Basin, north-east Iran. Lithofacies analysis shows that these sediments were deposited in inner ramp, middle ramp and offshore (outer ramp) environments. Five ichnoassemblages are identified in the sediments that consist of Thalassinoides, Thalassinoides–Rhizocorallium, Planolites–Rhizocorallium, Arenicolites–Diplocraterion, and Arenicolites. Th, Th-Rh and Pl-Rh with low diversity and abundance of the trace fossils formed during waning phase of storms in a predominantly medium to high-energy hydrodynamic regime. High sedimentation rate and mobile substrate condition featuring a shallow-marine setting. Ar–Di ichnoassemblage, consisting of horizontal and vertical traces of deposit and suspension feeders, respectively, portray two different phases. A predominantly high energy phase with instable substrate is displayed by the vertical traces, while a minor omission phase, associated with a decrease in sedimentation rate or non-deposition, is indicated by the horizontal structures. Arenicolites ichnoassemblage with low bioturbation index and low ichnodiversity is related to a semi-sheltered area of lagoon environments with periodically marine water circulation. The study of the ichnological attributes in the studied successions indicates the presence of a shallowing up-ward trend in the storm‒tide-dominated ramp sequence. Ichnoassemblage development is largely controlled by depositional and ecological conditions, e.g., the stability of substrate, hydrodynamic regime (wave and tide), and food abundance, which altogether control the substrate colonization. Based on an integrated ichnological and sedimentological approach, we characterize the depositional environment, deciphering allogenic and autogenic environmental controls on the trace fossil distribution on a passive margin depositional setting.

This study records the four ichnotaxa of burrowing activity of bivalves ascribed to Ptychoplasma excelsum , Ptychoplasma vagans , Lockeia siliquaria , and Lockeia cunctator from the Kuldhar Member of the Jaisalmer Formation of the Jaisalmer Basin, western India. These trace fossils have been recovered from the exposed road-cut section on the Jaisalmer–Sam Road near Kuldhara village. Here, Ptychoplasma excelsum is the first report from the Jaisalmer Basin. The Ptychoplasma excelsum are discovered as epichnial convex discontinuous ridges that connect through welding of the host rock strata, whereas the Ptychoplasma vagans are almond-shaped bodies that appear erratically, are oriented serially, and form looping or meandering patterns. The Lockeia siliquaria are almond-shaped traces with a tapering end and are found in isolated forms, while Lockeia cunctator are almond-shaped traces that are found in serially connecting forms or club-shaped structures. These trace fossils represent the repichnia and cubichnia behaviours of the burrowing bivalves. This study implies the shallow-water depositional settings for the Kuldhar Member of the Jaisalmer Formation.

The sandstone-shale-coal succession of the Barakar Formation (early Permian) of the Raniganj Basin, India hosts low-diversity ichnoassemblages, containing ichnogenera Arenicolites , Chondrites , Diplocraterion , Monocraterion , Ophiomorpha , Palaeophycus , Planolites , Skolithos , Taenidium, and Thalassinoides , produced by shallow marine infaunal invertebrates. Sedimentary facies architecture depicts a transgressive, fluvio-tidal (with a minor wave) interactive estuarine depositional setting. The fluvial deposits, lying beyond the zone of tidal encroachments, record absence of trace fossils, which is attributed to a low colonization window caused by high fluvial discharge and frequent channel migrations. Tidal interactions with high fluvial discharge led to bay-head deltas in the inner-middle estuary with the dominance of suspension-feeding and deposit-feeding ichnotaxa in coarser- and finer-dominated sediments, respectively, suggesting a mixed Skolithos–Cruziana ichnofacies. Increasing tidal influence with very less fluvial input allowed opportunistic colonizers and deposit feeders of the Cruziana ichnofacies to flourish in the central estuarine setting. Intermittent low-oxygenated restricted conditions marked by the chemosymbiotic ichnoassemblages of the Zoophycos ichnofacies indicate very low energy conditions. The outer estuary with increasing wave dominance is inhabited by suspension-feeding, domicile ichnotaxa of Skolithos ichnofacies, frequently mixed with the ichnotaxa of the Cruziana ichnofacies. The recurrent juxtaposition and lateral distribution of the Seilacherian marginal marine ichnofacies is attributed to complex sediment–organism interaction patterns in response to prevalent energy conditions, sediment discharge and substrate conditions in different zones of the fluvio-tidal estuarine setting. The integrated sedimentological-ichnological model signifies marine transgressions that affected the palaeogeography of the Permian continental Gondwanaland. Research Highlights Sedimentological–ichnological analysis signifies marine encroachment in Barakar Formation in peninsular India. Ichnoassemblages point to complex pattern of sediment–organism interactions with gross energy distribution. Sustained marine transgression event within the continental Gondwanaland during early Permian is visualized.

New invertebrate trace fossils from the Lower Jurassic Moenave Formation at the St. George Dinosaur Discovery Site at Johnson Farm (SGDS) continue to expand the ichnofauna at the site. A previously unstudied arthropod locomotory trace, SGDS 1290, comprises two widely spaced, thick, gently undulating paramedial impressions flanked externally by small, tapered to elongate tracks with a staggered to alternating arrangement. The specimen is not a variant of any existing ichnospecies, but bears a striking resemblance to modern, experimentally generated crayfish walking traces, suggesting a crayfish or crayfish-like maker for the fossil. Because of its uniqueness, we place it in a new ichnospecies, Siskemia eurypyge . It is the first fossil crayfish or crayfish-like locomotion trace ever recorded.

Globally Cenozoic interval witnessed recurrent climatic change of warming and cooling episodes of various magnitudes. The geological archives of the western part of the Kutch Basin are bestowed with spectacular igneous structures formed during the Deccan Trap volcanism. Overlying, Cenozoic successions of the Kutch Basin also get affected by the global climatic perturbations, which get registered in their impressive stratigraphic successions. Sedimentation in the basin was primarily controlled by the rate of relative sea-level fluctuations vs. background siliciclastic supply. Combined effect of climatic perturbations and relative sea-level fluctuation along passive-margin setting resulted in the occurence of variety of fossils, lithology and sedimentary structures, available all over the Cenozoic outcrops. To conserve and protect endangered geological features, geoscientists around the world have recognized several geosites, which can serve as standard reference section for further research and sustainable development for generations. In this study, we identify some spectacular outcrops from the western parts of the Kutch Basin (Cenozoic outcrops and Deccan Trap exposures) and document their properties to be recognized as potential geosites. These sites preserve exclusive geological features and provide template to understand the geological processes, however, needs conservation and protection. We propose the following assorted geosites viz. (1) Entablature geosite, (2) Pillow lava geosite, (3) Taphonomy geosite, (4) Fossil crab geosite, (5) Trace fossil geosite and (6) Soft sediment deformation (SSD) geosite. These sites may serve as exclusive locations for students field excursion, field-training for diverse professionals, social outreach activities and future reference section; indeed helps to achieve the implementation of some of the geoheritage goals. Diverse and unique geological features can be easily approached by thoroughly connected rail network and metalled roads.

Three main facies associations FA-1 to FA-3 occur in the Oxfordian Argiles rouges de Kheneg Formation in northwestern Algeria. They correspond respectively to the deeper part of a mixed siliciclastic-carbonate shelf, upper shoreface and offshore transition-lower offshore. The trace fossil association of the Argiles rouges de Kheneg Formation contains fifteen ichnogenera and is moderately diverse for the Upper Jurassic. The formation contains diverse and abundant deep water or dominantly deep water trace fossils (i.e. Belorhaphe, Chondrites, Helminthopsis, Nereites, Megagrapton). They indicate that a part of the formation was deposited in offshore transition to lower offshore environments.