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Dinosaur Tracks: The Next Steps

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The latest advances in dinosaur ichnology are showcased in this comprehensive and timely volume, in which leading researchers and research groups cover the most essential topics in the study of dinosaur tracks. Some assess and demonstrate state-of-the-art approaches and techniques, such as experimental ichnology, photogrammetry, biplanar X-rays, and a numerical scale for quantifying the quality of track preservation. The high diversity of these up-to-date studies underlines that dinosaur ichnological research is a vibrant field, that important discoveries are continuously made, and that new methods are being developed, applied, and refined. This indispensable volume unequivocally demonstrates that ichnology has an important contribution to make toward a better understanding of dinosaur paleobiology. Tracks and trackways are one of the best sources of evidence to understand and reconstruct the daily life of dinosaurs. They are windows on past lives, dynamic structures produced by living, breathing, moving animals now long extinct, and they are every bit as exciting and captivating as the skeletons of their makers.

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1 Experimental and Comparative Ichnology


1.1. The morphological changes in a tridactyl track exposed to different degrees of erosion. The example is a plaster cast of an emu track emplaced in soft mud and afterward sectioned horizontally to simulate erosion of a track with the sedimentary infill still in place. (A) Section cut just below the tracking surface. (B) Section cut 14 mm below the tracking surface. (C) Section cut 25 mm below the tracking surface. (D) Section cut 38 mm below the tracking surface. Notice how the overall dimensions of the track become smaller with depth and that the individual parts of the track become separated with depth, until only the most deeply impressed parts are present, in this case, the distal part of the impression of the middle digit and the pad covering the metatarsal joint. Figure based on experimental data from Milàn and Bromley (2006).

Experimental and Comparative Ichnology


Jesper Milàn and Peter L. Falkingham

ONE OF THE MAIN PROBLEMS FACED IN PALEOICHNOLogy is the delicate relationship between the organism and the sediments it leaves its tracks and traces in. Since the first scientific report of comparisons between fossil and modern tracks, researchers have turned to making experiments and comparing tracks and trackways of modern animals in order to interpret fossil tracks and traces. The easiest experimental approach is simply to make living analogues to the fossil animals walk through soft sediment and directly study the tracks they produce. Modern, more sophisticated experimental procedures include laboratory-controlled settings with sediments of different properties and model feet and indenters impressed into the sediment to various degrees. When cement or plaster is used as a tracking medium in laboratory settings, it is possible to cut vertical sections through the tracks after hardening and to study the formation and morphology of undertracks along the subjacent horizons below the foot. Complementing physical experimentation is computer simulation, in which both substrate- and indenter-specific variables can be precisely, independently, and systematically controlled. Resultant virtual tracks can be visualized completely in three dimensions, together with a time component. Experimental ichnology is an important tool for people working with tracks because the experimental settings are able to provide important data about the variations in track morphologies that can occur as a result of erosion, gait, undertrack formation, ontogeny, and individual behavior of the track maker.


2 Close-Range Photogrammetry for 3-D Ichnology: The Basics of Photogrammetric Ichnology


2.1. (A) Placing photogrammetric control on the track surface at the Red Gulch Dinosaur Tracksite (RGDT), Wyoming, summer 1998. (B) Compiling topographic contour maps using an analytical stereoplotter, fall 1998. (C): Topographic contour map of single, Middle Jurassic theropod track from RGDT (right) and depth map (left) interpolated from the contour elevations. (D) Digital Softcopy Photogrammetric workstation circa 2001. See Breithaupt and Matthews (2001) and Breithaupt et al. (2001).

Close-Range Photogrammetry for 3-D Ichnology: The Basics of Photogrammetric Ichnology


Neffra Matthews, Tommy Noble, and Brent Breithaupt


VERTEBRATE TRACE FOSSILS REFLECT THE COMPLEX interrelationship between an animal’s activities and the substrate (Manning, 2004; Falkingham, 2014), which is well represented in the ichnofaunal record of Mesozoic dinosaurs (Thulborn, 1990; Lockley, 1991; Lockley and Meyer, 2000; Wright and Breithaupt, 2002). As such, these unique three-dimensional (3-D) fossils warrant detailed recordation that captures their multidimensional features to fully understand formation and preservation of the ichnofossils, as well as dinosaur community dynamics (Lockley, 1986; Falkingham, 2014). Currently, the most cost-efficient and high-resolution mechanism to collect 3-D digital data of trace fossils is through the proper use of photogrammetry. Digital ichnological and spatial data capture a large portion of the incredible wealth of information provided at tracksites and are the basis for photogrammetric ichnology. As such, close-range photogrammetry (CRP) can assist in the proper documentation, preservation, and assessment of ichnological resources of any size at any location no matter the orientation of the track surface. A properly executed ichnological photogrammetric project has the quality, reliability, and authenticity necessary for scientific use. Three-dimensional image data sets created from stereoscopic digital photography provide permanent digital records of fossil tracks, including the creation of digital type specimens, or “Digitypes” (Adams et al., 2010). CRP is a noninvasive, objective recording and analysis method, which provides a visual, quantifiable baseline to evaluate track-bearing surfaces. The CRP data sets support accurate visualization of the fossils and can be used to create a digital archive from tracksites worldwide, allowing researchers to conduct detailed scientific studies on these paleontological resources. Imagery that is correctly taken now can be used in software developments and remain relevant into the future. Fortunately, the tools to conduct photogrammetric documentation (e.g., digital camera, scale bar) are already part of any good ichnologist’s tool kit. Although conducting photogrammetric documentation need not be difficult, there are concepts and complexities that exist. A better understanding of these concepts may be reached by briefly reviewing the history of photogrammetry.


3 The Early Cretaceous Dinosaur Trackways in Münchehagen (Lower Saxony, Germany): 3-D Photogrammetry as Basis for Geometric Morphometric Analysis of Shape Variation and Evaluation of Material Loss during Excavation


3.1. The Münchehagen locality in Lower Saxony, Germany.

The Early Cretaceous Dinosaur Trackways in Münchehagen (Lower Saxony, Germany): 3-D Photogrammetry as Basis for Geometric Morphometric Analysis of Shape Variation and Evaluation of Material Loss during Excavation


Oliver Wings, Jens N. Lallensack, and Heinrich Mallison

LOWER CRETACEOUS SANDSTONES IN LOWER SAXONY, northern Germany, are well known for their abundant fossil dinosaur tracks. One of the most productive sites is Münchehagen, which is well known for the only German Cretaceous sauropod trackways and hundreds of tracks of ornithopods and theropods, often forming long individual trackways with dozens of consecutive footprints. The largest theropod trackway T3 from the layer that has produced the best preserved true tracks (Lower Level) shows variations in the footprint morphology that allow use of this data as an example for studying the variability of tridactyl dinosaur track measurements.


4 Applying Objective Methods to Subjective Track Outlines


4.1. Various methods of defining track edges and recording track length. Question marks indicate where it is particularly difficult to define track extents according to the method.

Applying Objective Methods to Subjective Track Outlines


Peter L. Falkingham

FORMALLY COMMUNICATING THE MORPHOLOGY OF A track generally occurs via a two-dimensional (2-D) medium (i.e., paper). For this reason, track outlines are often used to convey the geometry and morphology of a track. However, these track outlines are routinely subjective, based on the interpreter’s opinion of where the track ends and the surrounding undeformed substrate begins. Although such outlines are not a problem themselves, any subsequent application of numerical objective methods such as multivariate analyses or equations using track parameters can be strongly influenced by the subjective nature of the outline. This effect is compounded in deeper tracks with sloping sides. However, although there are numerous ways in which to define track extents objectively (horizontal plane intercept, maximum inflexion, direct track impression, etc.), none are applicable to all tracks and there is no universally “correct” objective definition of a track outline.


5 Beyond Surfaces: A Particle-Based Perspective on Track Formation


5.1. Tracks as surfaces. Computer renderings of a shallow true track (based on a photogrammetric reconstruction of a natural track cast SS.00 in Gatesy, 2001) (A) from above and (B) in perspective views. Grayscale is mapped from white (highest) to black (lowest) depth. Scale bar for A = 5 cm.

Beyond Surfaces: A Particle-Based Perspective on Track Formation


Stephen M. Gatesy and Richard G. Ellis

FOSSIL FOOTPRINTS RECORD UNRIVALED EVIDENCE OF behavior in long extinct species. For students of dinosaur locomotion, tracks offer clues about gait, speed, limb posture, foot motion (kinematics), foot loading (kinetics), and social behavior (e.g., Ostrom, 1972; Alexander, 1976; Thulborn and Wade, 1984, 1989; Padian and Olsen, 1989; Gatesy et al., 1999; Milàn, 2006; Graversen, Milàn, and Loope, 2007; Pérez-Lorente and Herrero Gascón, 2007; Ishigaki and Lockley, 2010; Avanzini, Piñuela, and Garcia-Ramos, 2011; Falkingham, 2014). Yet tracks must be studied differently from body fossils. Although complementary to skeletal remains, footprints are purely sedimentary structures that preserve traces of anatomy only indirectly. Tracks are thus neither organism nor environment but emergent features documenting their dynamic, coupled interaction (e.g., Baird, 1980; Padian and Olsen, 1984a; Allen, 1997; Falkingham and Gatesy, 2014).


6 A Numerical Scale for Quantifying the Quality of Preservation of Vertebrate Tracks


6.1. Photos of the emu tracks used to define Farlow’s (unpubl.) preservation scale. (A) Grade 1; (B) grade 2; (C) grade 3; (D) grade 4.

A Numerical Scale for Quantifying the Quality of Preservation of Vertebrate Tracks


Matteo Belvedere and James O. Farlow

FROM ITS BEGINNING, VERTEBRATE ICHNOLOGY HAS described fossilized footprints in a qualitative, descriptive way. At the same time, considerable effort has gone into illustrating footprint morphology. In recent years, new technologies (e.g., laser-scanning and close-range photogrammetry) and methods (e.g., geometric morphometrics) have allowed more objective, quantitative approaches to vertebrate ichnology. However, quantitative shape analyses need to be based on data of high quality, and comparisons are best made between tracks comparable in quality of preservation. Thus, determining which footprints constitute the most reliable sample for quantitative analyses is fundamental for the progress of ichnology.


7 Evaluating the Dinosaur Track Record: An Integrative Approach to Understanding the Regional and Global Distribution, Scientific Importance, Preservation, and Management of Tracksites


7.1. The Dinosaur Track Road in Teruel (Spain) footprint sites.

Evaluating the Dinosaur Track Record: An Integrative Approach to Understanding the Regional and Global Distribution, Scientific Importance, Preservation, and Management of Tracksites


Luis Alcalá, Martin G. Lockley, Alberto Cobos, Luis Mampel, and Rafael Royo-Torres

MANY PAPERS ON FOSSIL TRACKS, FROM MANY REGIONS of the world have been published in the last two decades, and this rapid increase in documentation has itself generated the idea of a dinosaur “footprint renaissance” marked by a landslide of new discoveries and documentation. Many of these papers mention the significance of these sites in terms of selected variables such as size of site, number of tracks, new or unknown ichnotaxa, new stratigraphic or geographic occurrence, trackmaker behavioral implications, and so forth. However, the significance of fossil tracksites is often not comprehensively discussed or evaluated in such a way as to address all relevant criteria and facilitate comparison with other sites. In this chapter we describe an approach for evaluating tracksites.


8 Iberian Sauropod Tracks through Time: Variations in Sauropod Manus and Pes Morphologies


8.1. Geographical and geological setting of the main sauropod tracksites of the Iberian Peninsula located in four broad areas: Lusitanian Basin, Cantabrian Range, Iberian Range, and the Pyrenees.

Iberian Sauropod Tracks through Time: Variations in Sauropod Manus and Pes Track Morphologies


Diego Castanera, Vanda F. Santos, Laura Piñuela, Carlos Pascual, Bernat Vila, José I. Canudo, and José Joaquin Moratalla

THE IBERIAN SAUROPOD TRACK RECORD HAS YIELDED more than 100 sauropod tracksites ranging in age from the Middle Jurassic (Bathonian) to the Late Cretaceous (Maastrichtian). During this wide range of time, four different types of manus prints can be differentiated, changing in morphology from (1) speech-bubble–shaped with a prominent claw mark in digit I (Middle Jurassic), (2) kidney-shaped with a claw mark in digit I or (3) without a claw mark in digit I (Late Jurassic and Early Cretaceous), to (4) horseshoe-shaped (Cretaceous). Pes prints are slightly more conservative in morphology through the Mesozoic and are generally subtriangular. They can mainly be differentiated on the basis of the number and orientation of the claw marks, although the presence of a lateral notch behind digit V and the heel can be useful as well. There seems to be a lateralization of the claw marks after the Middle Jurassic, where the pes have four claw marks, two of them oriented anteriorly and two laterally. Subsequently, pes prints have three (Late Jurassic–Early Cretaceous) or four (Late Cretaceous) claw marks oriented anterolaterally and decreasing in size. The variation in the manus and pes morphology in the Iberian sauropod tracks is a reflection of the changes in the sauropod faunas over time. The different types of manus prints suggest that the forelimbs should play a major role in sauropod ichnotaxonomy.


9 The Flexion of Sauropod Pedal Unguals and Testing the Substrate Grip Hypothesis Using the Trackway Fossil Record


9.1. (A) Mounted diplodocid right pes. Note the deep, laterally compressed unguals and en-echelon arrangement. Morrison Formation, Late Jurassic. Currently on display at New Mexico Museum of Natural History and Science. (B–D) Feet of the specialized scratch-digging tortoise, Gopherus. Note the curvature of the flattened unguals and their similarly en-echelon arrangement. (B) Left manus of Gopherus canyonensis, from Bramble (1982); (C) left manus and (D) pes of Gopherus polyphemus, from Auffenberg (1976). (E) Phylogenetic distribution of sauropod manual morphology (right manus depicted). Manual phalanges exhibit a phylogenetic trend toward reduction and loss, retaining only digit I; derived titanosauriforms take this even further, losing all manual phalanges. Reproduced from Figure 3, Fowler and Hall (2011).

The Flexion of Sauropod Pedal Unguals and Testing the Substrate Grip Hypothesis Using the Trackway Fossil Record



10 Dinosaur Swim Track Assemblages: Characteristics, 10 Contexts, and Ichnofacies Implications


10.1. Pedal kinematics model of dinosaur swim track formation from left to right. Distal track to the right displays a posterior overhang. Modified from Romilio, Tucker, and Salisbury. (2013).

Dinosaur Swim Track Assemblages: Characteristics, Contexts, and Ichnofacies Implications


Andrew R. C. Milner and Martin G. Lockley

TRACES MADE BY SWIMMING TETRAPODS ARE SIMPLY known as “swim tracks.” These trace fossils are of interest to paleontologists because they provide insight into the behavior of past vertebrates in aquatic environments. However, swim tracks have always been a controversial subject for several reasons. Often swim tracks show irregular morphologies and are incomplete, so interpretation of them can be problematic. Unlike tracks made by animals walking on firm ground, which supports most or all of their weight, swimming tetrapods are fully or partially buoyant, and if their feet or hands come into contact with the subaqueous substrate, they will register swim tracks, sometimes preserving elite swim tracks. It has been suggested that swim tracks rarely display regular step and stride patterns as observed in a walking trackway (Milner, Lockley, and Kirkland, 2006), although clear swim trackway patterns are sometimes distinguishable (McAllister, 1989a; Ezquerra et al., 2007; Romilio, Tucker, and Salisbury, 2013; Xing et al., 2013). Because swim tracks are sometimes incomplete and are often found to have irregular and confusing configurations, it is sometimes difficult to identify the trackmaker or to distinguish between manus and pes tracks if the producer was quadrupedal. Surprisingly, under closer examination of a variety of swim track types from different localities and of different ages, it is most often the case that a clear swim trackway pattern can be observed where there are large enough surfaces exposed and not too high a density of tracks, although these trackways can display considerable variation in overall morphology.


11 Two-Toed Tracks through Time: On the Trail of “Raptors” and Their Allies


11.1. Map showing the localities of Cretaceous, didactyl tracks worldwide. The star indicates Early-“middle” Cretaceous and the diamond u, Late Cretaceous tracks. Abbreviations: Dh, Dromaeosauripus hamanensis; Di, Dromaeosauripus isp.; Dj, Dromaeosauripus jinjuensis; Ds, Dromaeopodus shandongensis; Du, Dromaeopodus isp.; Dy, Dromaeosauripus yongjingensis; Ms, Menglongipus sinensis; U, unnamed/unattributed; Vi, Velociraptorichnus isp.; Vs, Velociraptorichnus sichuanensis; Vz, Velociraptorichnus zhangi.

Two-Toed Tracks through Time: On the Trail of “Raptors” and Their Allies


Martin G. Lockley, Jerald D. Harris, Rihui Li, Lida Xing, and Torsten van der Lubbe

THE TWO-TOED, OR DIDACTYL, TRACKS OF DEINONYCHOsaurian dinosaurs, popularly known as “raptors,” are among the most distinctive theropod tracks known. Including the first confirmed report from China in 1994, a total of 16 track-sites have been recognized, all from Cretaceous strata. These include nine Chinese, two Korean, three North American, and two European occurrences. Many of these tracks have been assigned to four ichnogenera: Velociraptorichnus (two ichnospecies), Dromaeopodus, Menglongipus, and Dromaeosauripus (three ichnospecies). Most of the tracks have been attributed to dromaeosaurid theropods, but in the case of the largest sample, from Germany, a troodontid trackmaker is inferred.


12 Diversity, Ontogeny, or Both? A Morphometric Approach to Iguanodontian Ornithopod (Dinosauria: Ornithischia) Track Assemblages from the Berriasian (Lower Cretaceous) of Northwestern Germany


12.1. (A) Locality map and (B) stratigraphic position of the material studied herein.

Diversity, Ontogeny, or Both?: A Morphometric Approach to Iguanodontian Ornithopod (Dinosauria: Ornithischia) Track Assemblages from the Berriasian (Lower Cretaceous) of Northwestern Germany


Jahn J. Hornung, Annina Böhme, Nils Schlüter, and Mike Reich

IDENTIFYING THE CAUSES OF MORPHOLOGICAL VARIAtion (including taxonomic diversity, ontogeny, sexual dimorphism, and individual variation) observed in a set of vertebrate tracks – especially from different closely related trackmaker species – is difficult and often not straightforward due to imperfect knowledge of biological variation in the autopodia of the trackmakers, and a number of ethological, preservational, and taphonomical influences. Here we use multivariate data sets obtained from 14 homologous two-dimensional (2-D) landmarks to evaluate the range and potential causes of variation in iguanodontian ornithopod pes tracks from the Berriasian of northwestern Germany.


13 Uncertainty and Ambiguity in the Interpretation of Sauropod Trackways


13.1. This small sample of three distinct trackways shows the wealth of information in the placement of the steps (and seeming missteps) of the trackmakers at the A16 tracksites. Derived from the Courtedoux – Béchat Bovais tracksite (level 515). Note that the elliptical manus (light gray) and pes (dark gray) track markers schematically represent the dimensions and orientation of each track. The triangle on each indicates the anterior direction of the manus or pes. Blue disks indicate tracks that were not definitely associated with any trackway.

Uncertainty and Ambiguity in the Interpretation of Sauropod Trackways


Kent A. Stevens, Scott Ernst, and Daniel Marty

TRACKWAY INTERPRETATION, THE DRAWING OF INFERences about a trackmaker and its movements from a pattern of trace impressions, is examined from the perspective of the information in the pattern of individual tracks along a trackway, with emphasis here on sauropod trackways. Although trackways are commonly regarded as direct records of locomotion behavior, their interpretation is in fact less straightforward than is often expected. Even the basic estimation of trackmaker size (e.g., glenoacetabular distance, a common proxy for trackmaker size) is not generally valid. Moreover, without knowledge of trackmaker size, any observed pattern of manus and pes tracks has arbitrarily many possible solutions in terms of limb phase and duty factor, the primary components of gait. An analysis of the relationship between trackmaker size, stride length, and limb phase (i.e., gait) reveals a previously unappreciated interdependence among these parameters. A new approach is introduced to address the problem of supporting inferences in the presence of ambiguity and uncertainty.


14 Dinosaur Tracks as “Four-Dimensional Phenomena” Reveal How Different Species Moved


14.1. (A) Tethyan paleogeography for southwestern Europe during the Early Aptian (modified from Skelton, Granier, and Moullade, 2013). (B) Paleogeographic map showing the evolution of Iberia during the Late Barremian to earliest Aptian (modified from Salas et al., 2001). (C) Simplified structural map of the Maestrazgo Basin during the Early Cretaceous (modified from Salas et al., 2001). (D) General stratigraphic column in the area of Río Alcalá tracksite. Abbreviations: AS-1, Rio Alcalá tracksite; BB, Betic Basin; BC, Basque-Cantabrian Basin; EH, Ebro High; FM, formation; IB, Iberian Meseta.

Dinosaur Tracks as “Four-Dimensional Phenomena” Reveal How Different Species Moved


Alberto Cobos, Francisco Gascó, Rafael Royo-Torres, Martin G. Lockley, and Luis Alcalá

ALTHOUGH THOUSANDS OF DINOSAUR TRACKS HAVE been found worldwide, three-dimensional (3-D) natural track casts are still relatively poorly documented. Those few that have been published, however, sometimes show impressions of reticulated skin, toe pads, and scratch marks made by scales and may even record how the sole of the foot bore the trackmaker’s weight. In very exceptional circumstances, such casts can even preserve evidence of distal limb kinematics of the trackmaker by recording the movement of the feet during track-making: in other words, footfall or footfall registration dynamics. Here we present a description of natural track casts that show all the features just outlined, allowing the contemplation of a new concept: “four-dimensional (4-D) tracks.” Highly informative and representative examples of such tracks casts come from a new and exceptional Early Cretaceous tracksite in the Province of Teruel (Spain), as well as from selected North American sites. 4-D tracks are defined as true tracks or their infillings showing slide marks or grooves that reveal the trajectory of the trackmaker’s foot within the sediment more completely than do most tracks. Each one of these tracks therefore reflects the time and motion involved in their registration: that is, they more obviously fossilize the fourth dimension of motion and time than typical 3-D tracks do. The Teruel track casts were made by large theropods and ornithopods, possibly spinosaurids and basal hadrosauriforms, walking on deep, firm mud. The infilling sediment responsible for this exceptional preservation consists of fine-grained sandstones with a high proportion of quartz. These were deposited in an estuarine shallow-water carbonate platform with freshwater discharges during the beginning of the Barremian-Aptian transgression of the Tethys Sea in southwestern Europe. Tracks with 4-D characteristics are probably more common than previously thought. Thus, the 4-D track concept has great potential to shed light on foot and distal limb kinematics.


15 Analyzing and Resolving Cretaceous Avian Ichnotaxonomy Using Multivariate Statistical Analyses: Approaches and Results


15.1. Ichnofamilies considered in this study. (A) Magnoavipes, a previously contentious ichnogenus originally described as the trace of a large avian but now considered to be that of a nonavian theropod (Matsukawa et al., 2014). (B) Avipedidae and Limiavipedidae: (upper left) Avipeda (modified from Vialov, 1965); (upper right) Aquatilavipes swiboldae, scale = 1.0 cm (modified from Currie, 1981); (lower right) Aquatilavipes izumiensis, scale = 1.0 cm (modified from Azuma et al., 2002); (lower left) Limiavipes curriei, scale = 5.0 cm (reassigned from Aquatilavipes curriei, McCrea and Sarjeant, 2001; McCrea et al., 2014). L. curriei is much larger than any Mesozoic ichnospecies of Aquatilavipes. (C) Ignotornidae: (top) Ignotornis mcconnelli, holotype (Lockley et al., 2009); (lower left) Goseongornipes markjonesi (Lockley, Houck, et al., 2006); (bottom center) Ignotornis yangi (Kim et al., 2006); (lower right) Hwangsanipes choughi (Yang et al., 1995). Scale divisions in centimeters. (D) Koreanaornipodidae: (top) Koreanaornis hamanensis (Kim, 1969); (lower left) Pullornipes aureus (Lockley, Matsukawa, et al., 2006); (lower right) Koreanaornis dodsoni (Xing et al., 2011). Scale bar = 5.0 cm. (E) Jindongornipodidae. Jindongornipes kimi (Lockley and Rainforth, 2002). Scale = 5.0 cm. (F) Shandongornipodidae. Shandongornipes muxiai (Lockley et al., 2007): (left) left track LRH-DZ70 and (right) right track LRH-DZ67 (from the Qingdao Institute of Marine Geology). Both tracks from S. muxiai holotype trackway LRH-DH01. Scale = 2.0 cm.


16 Elusive Ornithischian Tracks in the Famous Berriasian (Lower Cretaceous) “Chicken Yard” Tracksite of Northern Germany: Quantitative Differentiation between Small Tridactyl Trackmakers


16.1. Sketch of track 1/3 showing locations of the measured distances taken for quantitative analyses. Abbreviations: LII, length along second digit; LIII, length along third digit, the same as total track length; LIV, length along fourth digit; B, total track width; LIIoM, length of second digit without metatarsal; LIIIoM, length of third digit without metatarsal; LIVoM, length of fourth digit without metatarsal; BbII, width at proximal third or base of second digit; BbIII, width at proximal third or base of third digit; BbIV, width at proximal third or base of fourth digit; BmII, width at mid length of second digit; BmIII, width at mid length of third digit; BmIV, width at mid length of fourth digit; II–III°, divarication angle between digits II and III; III–IV°, divarication angle between digits III and IV; II–IV°, divarication angle between digits II and IV.

Elusive Ornithischian Tracks in the Famous Berriasian (Lower Cretaceous) “Chicken Yard” Tracksite of Northern Germany: Quantitative Differentiation between Small Tridactyl Trackmakers


17 Too Many Tracks: Preliminary Description and Interpretation of the Diverse and Heavily Dinoturbated Early Cretaceous “Chicken Yard” Ichnoassemblage (Obernkirchen Tracksite, Northern Germany)


17.1. The Chicken Yard level at night, photograph from a higher layer on the east side; artificial low-angle light from the northern margin. The surface is moderately to heavily dinoturbated. Courtesy Tobias Landmann/Schaumburger Zeitung, 2011.

Too Many Tracks: Preliminary Description and Interpretation of the Diverse and Heavily Dinoturbated Early Cretaceous “Chicken Yard” Ichnoassemblage (Obernkirchen Tracksite, Northern Germany)


Annette Richter and Annina Böhme

THE MODERATELY TO HEAVILY DINOTURBATED BERRIAsian Chicken Yard level from the Obernkirchen tracksite (Lower Saxony, northern Germany) is preliminarily described and analyzed. Its ichnoassemblage is characterized by an extraordinary high track density composed of several different morphotypes and size classes of theropod and ornithopod true tracks with an overall similar preservation quality. The occurrence of didactyl tracks of a new, so far unnamed ichnotaxon that can be attributed to deinonychosaurian dinosaurs is particularly remarkable. Despite the high track density and associated frequent overprinting of tracks, several trackways were identified. Their orientation analysis tends toward a primarily bimodal orientation pattern despite the overall chaotic appearance. Also, the history and development of the term “dinoturbation” and its application to Mesozoic dinosaur tracksites are reviewed, and the different factors and scenarios that may have led to high dinoturbation in general and at the Chicken Yard level in particular are discussed together with some recommendations for the analysis of heavily dinoturbated paleosurfaces.


18 Dinosaur Tracks in Eolian Strata: New Insights into Track Formation, Walking Kinetics, and Trackmaker Behavior


18.1. Dinosaur tracks in the Navajo Sandstone at Coyote Buttes, Utah. (A) Tracks of small theropod dinosaurs on the upper surface of an eolian grain flow (layer deposited by avalanching dry sand on the steep, downwind slope of a sand dune). (B) Close-up of dinosaur tracks in cross-section. Notice how the sharp digits have penetrated several layers of sand. Strata slope downward away from viewer. (C) Trackway of a crouching theropod on a dune slope, with interpretative drawing inset (from Milàn, Loope, and Bromley, 2008). (D) Otozoum trackway on a firm, wind-rippled interdune surface. (E) Trackway of sauropodomorph dinosaur adopting a sideways walking gait for the first part of the trackway. The later (upper) part shows that the animal then started moving directly up the slope. The solid arrow shows the direction of progression and the dashed arrow indicates the orientation of the animal’s body.

Dinosaur Tracks in Eolian Strata: New Insights into Track Formation, Walking Kinetics, and Trackmaker Behavior


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