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New Directions in the Study of Vertebrate Trace Fossils
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New Directions in the Study of Vertebrate Trace Fossils

A special issue of Fossil Studies (ISSN 2813-6284).

Deadline for manuscript submissions: 31 October 2026 | Viewed by 7467

Editors

Dr. Adrian P. Hunt

E-Mail Website
Guest Editor
Flying Heritage and Combat Armor Museum, 3407 109th St. SW, Everett, WA 98204, USA
Interests: vertebrate paleontology, ichnology and stratigraphy of the late Paleozoic through late Mesozoic
Prof. Dr. Spencer G. Lucas

E-Mail Website
Guest Editor
New Mexico Museum of Natural History and Science, 1801 Mountain Road N. W., Albuquerque, NM 87104-1375, USA
Interests: paleontology, biostratigraphy and stratigraphy, especially of nonmarine deposits; vertebrate paleontology and ichnology, particularly of the late Paleozoic, Mesozoic and Cenozoic
Dr. Lida Xing

E-Mail Website
Guest Editor
State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Beijing 100190, China
Interests: archosaur track; palaeovertebrates morphology; paleopathology; amber with vertebrate inclusions

Special Issue Information

Dear Colleagues,

The study of ichnofossils dates back two centuries. Ichnology has broad significance in many fields of the geosciences, including paleoecology, taphonomy, biochronology, sedimentology, facies analysis, and evolutionary biology. There has been a renaissance of the study of trace fossils across the past decades, both ichnotaxonomically and conceptually. Notably, most recently, there have been synoptic reviews of all groups of vertebrate trace fossils. Therefore, there are now large databases for synthetic studies. In addition, new methodologies are being developed and are gaining more widespread use (e.g., 3D modelling, micro CT, AI) and changing the nature of the study of traces. Terminology is experiencing some flux, not only because of methodological advances but also because of the increasing interdisciplinarity of the field. Thus, ichnology is at a juncture of consolidated databases and new methodologies that will lead the field in new directions. The purpose of this volume is to discuss opportunities for new avenues of research and to review previous models. This volume will include ichnological case studies, methodological discussions, and critical reviews of models and concepts. Thus, this volume will both highlight new directions of study in ichnology and provide suggestions for future developments in the field.

Dr. Adrian P. Hunt
Prof. Dr. Spencer G. Lucas
Dr. Lida Xing
Guest Editors

Manuscript Submission Information

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Keywords

  • ichnofossils
  • vertebrate
  • trace fossils

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Published Papers (7 papers)

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Research

Jump to: Review

19 pages, 724 KB  
Article
Classical Hypotheses and New Tools in Dinosaur Ichnology: A Review of Footprints with Geometric Morphometrics, Machine Learning and Biomechanics
by Ancheng Peng and Lida Xing
Foss. Stud. 2026, 4(3), 18; https://doi.org/10.3390/fossils4030018 - 9 Jul 2026
Abstract
Dinosaur footprints are among the most abundant trace fossils, but they are not direct records of anatomy, behaviour or faunal composition. They preserve locomotion, substrate interaction and occurrence data only after those signals have been filtered by foot anatomy, movement, sediment properties and [...] Read more.
Dinosaur footprints are among the most abundant trace fossils, but they are not direct records of anatomy, behaviour or faunal composition. They preserve locomotion, substrate interaction and occurrence data only after those signals have been filtered by foot anatomy, movement, sediment properties and preservation. Classical dinosaur ichnology has relied on two-dimensional outlines, linear and angular measurements, qualitative ichnotaxonomy and influential hypotheses about trackmaker identity, speed, social behaviour and evolutionary timing. Here we review how these hypotheses are being reassessed with three-dimensional digitisation, geometric morphometrics, supervised and unsupervised machine learning, and biomechanical simulation. We first consider how different footprint representations, including interpretive outlines, landmarks, silhouettes, depth maps and three-dimensional models, shape the questions that track data can answer. We then assess analytical approaches ranging from multivariate statistics and landmark-based classifiers to convolutional neural networks and β-variational autoencoders. Against this methodological background, we revisit four linked problem domains: ornithopod–theropod discrimination and the Grallator–Anchisauripus–Eubrontes plexus; speed and gait reconstruction; ecological and behavioural interpretations of track abundance, sauropod gauge and trackway arrangement; and macroevolutionary claims about body-size trends, functional morphotypes and avian-like pedal morphologies. Across these cases, newer methods rarely remove ambiguity. They more often show where classical interpretations are robust, where they depend on representation or prior labels, and where competing explanations remain hard to separate. We argue that footprint-based inference is strongest when tracks are treated as preservationally filtered products of anatomy, motion and substrate mechanics, and when they are integrated with skeletal data, experimental analogues and forward models in explicit, uncertainty-aware frameworks. Full article
(This article belongs to the Special Issue New Directions in the Study of Vertebrate Trace Fossils)
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13 pages, 4855 KB  
Article
Polygons or Points? A Polygon-Based Approach to the Morphometrics of Fossil Human Footprints
by Matthew R. Bennett, Marcin Budka, Michael Everett, Hannah Strehlau and Sally C. Reynolds
Foss. Stud. 2026, 4(3), 17; https://doi.org/10.3390/fossils4030017 - 1 Jul 2026
Viewed by 124
Abstract
Quantitative analysis of footprint shape is central to ichnology, yet the application of geometric morphometrics is often limited by the difficulty of defining homologous landmarks on irregular or variably preserved impressions. Here we present a polygon-based approach to footprint morphometrics in which the [...] Read more.
Quantitative analysis of footprint shape is central to ichnology, yet the application of geometric morphometrics is often limited by the difficulty of defining homologous landmarks on irregular or variably preserved impressions. Here we present a polygon-based approach to footprint morphometrics in which the footprint margin is digitised as a continuous outline and resampled into a standardised set of boundary points for analysis. Using a combination of simulated perturbation experiments and empirical datasets, we assess the sensitivity of this method to annotation uncertainty and compare it to natural variation within and between trackways. The results demonstrate a clear hierarchy of variance, in which annotation noise is lower than inter-observer variability, intra-trackway variation, and between-trackway differences. These findings suggest that polygon-based representations of footprint shape are robust to realistic levels of digitisation uncertainty. Application of the method to modern and fossil trackways, including the Laetoli footprints, shows that resampled polygon outlines retain meaningful morphological structure and can be used effectively in comparative analyses. Full article
(This article belongs to the Special Issue New Directions in the Study of Vertebrate Trace Fossils)
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10 pages, 1742 KB  
Article
Micro-CT Scanning Tracks: A Means for Non-Destructively Exploring Volumetric Track Formation
by Tash L. Prescott, Benjamin W. Griffin, Andréas Jannel and Peter L. Falkingham
Foss. Stud. 2026, 4(2), 14; https://doi.org/10.3390/fossils4020014 - 1 Jun 2026
Viewed by 393
Abstract
Animals frequently traverse a range of deformable substrates, leaving tracks. Track morphology is controlled by anatomy and motions of the foot, and substrate consistency, resulting in complex, three-dimensional structures that record dynamic foot-substrate interactions. Understanding such interactions can provide valuable biological and environmental [...] Read more.
Animals frequently traverse a range of deformable substrates, leaving tracks. Track morphology is controlled by anatomy and motions of the foot, and substrate consistency, resulting in complex, three-dimensional structures that record dynamic foot-substrate interactions. Understanding such interactions can provide valuable biological and environmental insights, but visualising them remains challenging. Prior physical experiments explored track formation using various indenters impressed into a range of substrate types and consistencies. However, to visualise the deformation below the surface, destructive methods such as physical sectioning are often used, typically resulting in the sample being destroyed. Here, we present the methodology and challenges involved in experimentally generating tracks and introduce micro-CT scanning as a non-destructive approach to visualising sub-surface sediment movement during track formation. Two separate track volumes were produced using different substrate consistencies (‘soft’ and ‘very soft’) whereby sand and clay were alternately layered and then scanned during indentation by a cadaveric pheasant (Phasianus colchicus) foot. Across the two substrate consistencies, the CT reconstructions revealed differences in sub-surface sediment displacement, and in complex sub-surface features. Although there are challenges attributed to experimentally producing and visualising tracks, micro-CT offers a novel approach to viewing sub-surface sediment movement during experimental track formation in the lab. Full article
(This article belongs to the Special Issue New Directions in the Study of Vertebrate Trace Fossils)
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20 pages, 36496 KB  
Article
Review of Tridactyl Avian Footprints (Ichnofamily Avipedidae) with Emphasis on Type Material from the Miocene of the Carpathians (Ukraine, Hungary and Romania)
by Ricardo Melchor, Viktória Káposztás and Yaryna Tuzyak
Foss. Stud. 2026, 4(2), 13; https://doi.org/10.3390/fossils4020013 - 26 May 2026
Viewed by 469
Abstract
Numerous ichnotaxa (about 21 ichnogenera and 39 ichnospecies) have been proposed for fossil tridactyl avian footprints. The purpose of this contribution is to analyze type material from Ukraine of the first proposed tridactyl avian ichnogenus, Avipeda, and related ichnogenera from the Carpathians [...] Read more.
Numerous ichnotaxa (about 21 ichnogenera and 39 ichnospecies) have been proposed for fossil tridactyl avian footprints. The purpose of this contribution is to analyze type material from Ukraine of the first proposed tridactyl avian ichnogenus, Avipeda, and related ichnogenera from the Carpathians of Hungary and Romania (Aviadactyla, Ornithotarnocia, Passeripedia, and Carpathipeda). The criteria for erection of ichnofamilies, ichnogenera and ichnospecies of avian footprints are discussed. It is proposed that trackway features only be used for ichnospecies. The ichnofamily Avipedidae comprises essentially small leptodactylous avian footprints showing three digits directed forward, with digits united or separate proximally, and lacking web imprint. The type material of Avipeda is represented by small footprints (less than 30 mm in length) that are wider than they are long, showing large total divarication and near symmetry with respect to digit III. Examined material from the type series of Avipeda from the Miocene of Ukraine also contains tetradactyl bird footprints that are better compared with Gruipeda. Aviadactyla and Ornithotarnocia (from the Lower Miocene of Ipolytarnóc, Hungary) are considered potentially available, whereas Passeripedia is deemed unavailable. Carpathipeda (erected for material from the Miocene of Romania) is indistinguishable from Avipeda. Additional comparisons are necessary to evaluate the status of other tridactyl avian ichnotaxa. Full article
(This article belongs to the Special Issue New Directions in the Study of Vertebrate Trace Fossils)
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12 pages, 2910 KB  
Article
A New Regurgitalite from the Early Eocene of Wyoming (USA) Provides Evidence for Predation on “Armored” Glyptosaurid Lizards and Diurnal Behavior of Early Owls
by Adrian P. Hunt, Spencer G. Lucas and Krister T. Smith
Foss. Stud. 2026, 4(2), 12; https://doi.org/10.3390/fossils4020012 - 19 May 2026
Viewed by 1304
Abstract
Bromalites (trace fossils produced by food processing) from the early Eocene Willwood Formation of Wyoming contain abundant glyptosaurid lizard skeletal elements. They clearly represent bromalites as they are discrete, three-dimensional, disarticulated accumulations of biological materials. Furthermore, they contain abundant skeletal elements, principally osteoderms, [...] Read more.
Bromalites (trace fossils produced by food processing) from the early Eocene Willwood Formation of Wyoming contain abundant glyptosaurid lizard skeletal elements. They clearly represent bromalites as they are discrete, three-dimensional, disarticulated accumulations of biological materials. Furthermore, they contain abundant skeletal elements, principally osteoderms, that exhibit no indication of digestion, so they can be identified as regurgitalites. The Willwood specimens represent orniothoregurgitalites, specifically strigilites, the regurgitalites of owls. These strigilites are assigned to Sauresus osteodermus igen. et isp. nov. This ichnotaxon is characterized by an elongate, sub-cylindrical or sub-ovoid bromalite pellet with irregular surface texture that is composed of a micritic matrix and contains abundant, well-preserved skeletal elements of glyptosaurids, principally osteoderms. The strigilites were probably produced by Primoptynx poliotauros that used its feet to kill glyptosaurids. The lizard, rather than rodent, content of the strigilite supports the hypothesis that Eocene owls were diurnal in habit and only became nocturnal in the Oligocene. Full article
(This article belongs to the Special Issue New Directions in the Study of Vertebrate Trace Fossils)
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11 pages, 1616 KB  
Article
A Quantitative Framework for Assessing Locomotor Asymmetry in Dinosaur Trackways: Testing the Evidence for Limping and Lateral Preference
by Anthony Romilio
Foss. Stud. 2026, 4(2), 9; https://doi.org/10.3390/fossils4020009 - 24 Apr 2026
Cited by 1 | Viewed by 1434
Abstract
Trackways preserve sequential records of animal locomotion and provide some of the most direct evidence of locomotor behaviour in the vertebrate fossil record. Alternating short–long pace lengths have historically been used to infer gait irregularities such as limping or lateral limb preference, but [...] Read more.
Trackways preserve sequential records of animal locomotion and provide some of the most direct evidence of locomotor behaviour in the vertebrate fossil record. Alternating short–long pace lengths have historically been used to infer gait irregularities such as limping or lateral limb preference, but these interpretations typically lack statistical validation, treating mean asymmetry as sufficient grounds for behavioural conclusions without first establishing whether observed differences exceed normal locomotor variability. This study introduces a quantitative framework that addresses this gap by applying Welch’s t-test to pace and stride length measurements, establishing statistical confirmation of asymmetry as a prerequisite for behavioural interpretation. The framework is demonstrated on nine dinosaurian trackways drawn from published data. While all had previously been interpreted as asymmetric, seven exhibited statistically significant pace asymmetry (p < 0.05) and two did not exceed the range of normal variation. Stride length showed no significant asymmetry in any trackway, confirming that pace-level metrics are more sensitive to limb bias than stride-based measures. This framework provides an objective, reproducible standard for evaluating asymmetry claims—a necessary and feasible methodological advance for vertebrate ichnology. Full article
(This article belongs to the Special Issue New Directions in the Study of Vertebrate Trace Fossils)
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Review

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36 pages, 9092 KB  
Review
A Review of Vertebrate Footprints from the Mesozoic of Thailand and Their Palaeobiogeographical Significance
by Tida Liard, Romain Liard and Eric Buffetaut
Foss. Stud. 2026, 4(2), 10; https://doi.org/10.3390/fossils4020010 - 30 Apr 2026
Viewed by 1824
Abstract
Thailand preserves one of the most extensive records of Mesozoic vertebrate tracks in Tropical Asia, yet these ichnological data have never been comprehensively synthesized. This review compiles and reassesses all known Triassic to Cretaceous vertebrate tracksites in Thailand to clarify their stratigraphic distribution, [...] Read more.
Thailand preserves one of the most extensive records of Mesozoic vertebrate tracks in Tropical Asia, yet these ichnological data have never been comprehensively synthesized. This review compiles and reassesses all known Triassic to Cretaceous vertebrate tracksites in Thailand to clarify their stratigraphic distribution, taxonomic diversity, and palaeobiogeographical significance. Published records, new field observations, and updated stratigraphic correlations are integrated to evaluate trackmaker attributions and temporal patterns. The Thai record documents diverse assemblages including chirotheriids, early theropods, sauropodomorphs, ornithopods, sauropods, and crocodilians. Late Triassic–Early Jurassic assemblages capture a major faunal transition, revealing the co-occurrence of non-dinosaurian archosaurs and some of the earliest dinosaurs in the region, whereas Lower Cretaceous sites are dominated by theropods, sauropods and diverse ornithopods. Comparison with other Asian ichnofaunas indicates faunal continuity across eastern Asia and supports early dinosaur dispersal into equatorial low latitudes. This synthesis also evaluates site conservation, highlighting the vulnerability of several Triassic localities and a positive trend of community-led discoveries since 2009, underscoring the need for proactive management and standardized digital documentation. Overall, the Thai ichnological succession represents the most complete Mesozoic track record presently known from Tropical Asia and provides key insights into vertebrate evolution, palaeoecology, and regional biogeography. Full article
(This article belongs to the Special Issue New Directions in the Study of Vertebrate Trace Fossils)
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