Well-preserved Tracks Research Articles

First discovery of a deinonychosaur trackway from the lower Upper Cretaceous of southeastern China

The new deinonychosaur trackway was recovered from the lower Upper Cretaceous Jinhua Formation of Zhejiang Province, southeastern China. This trackway includes nine well-preserved tracks characterized by elongate and didactyl morphology, and thus is assigned to the ichnospecies Velociraptorichnus sichuanensis. This trackway enables more accurate estimations of the speed and gait of the trackmaker for the ichnogenus Velociraptorichnus than the previous studies because the latter is based only on two consecutive tracks. Due to substantial differences in hindlimb proportions between the two clades assignable to the trackmaker of Velociraptorichnus, namely Dromaeosauridae and Troodontidae, we calculated the speed of trackmaker for each pattern. The estimated speeds resulted in 6.1 km/h for dromaeosaurids and 4.6 km/h for troodontids, both of which indicate that this trackway was made by a walking gait. This is the first record of a deinonychosaur trackway from the Cretaceous of southeastern China and extends the known distribution of didactyl theropod ichnotaxa. In combination with previous studies, it also suggests that a diverse ichnoassemblage of non-avian theropods was widely distributed in East Asia during that time.

Diverse preserved dinosaur footprint assemblage from Jurassic–Cretaceous transition eolian dune deposits of western Shandong Province, China

Ancient desert, characterized by low biotic diversity as well as low preservation potential, has long been assumed as devoid of biotic activity. However, recent works from Mesozoic trace fossils preserved in the eolianites in North America, South America and East Asia indicate that the ancient desert can also have diverse inhabitants. This paper presents a diversified preserved dinosaur track assemblage from the Jurassic-Cretaceous transition eolian dune deposits in western Shandong Province, China. Based on the ichnological analysis, tracks are assigned to ichnogenus Anomoepus, Eubrontes-like and Ornithopodichnus-like forms, representing the oldest and second example of the Chelichnus ichnofacies reported from China as well as Asia. Sedimentological analysis of the tracksites indicates that tracks occurred in linear dunes under arid climatic conditions. Well-preserved tracks with detailed anatomical information are more likely to be preserved in moist sands, contrary to the dry cohesionless sands. Anomoepus and Ornithopodichnus-like tracks cooccurring with northwestward winds were made during summer wet season, while Eubrontes-like track was present during winter dry season characterized by strong northeastward wind, implying different habits between ornithopod and theropod dinosaurs. The preserved Jurassic-Cretaceous transition dinosaur tracks in eolian dune deposits not only expand the spatial-temporal distribution of dinosaur fauna in North China, but also greatly improve our understanding of the adaptive capacity of dinosaurs in severe living conditions, such as the desert environment.

Multi-aged social behaviour based on artiodactyl tracks in an early Miocene palustrine wetland (Ebro Basin, Spain)

We present a new locality with at least 880 vertebrate tracks found at the top of a limestone bed from the lower Miocene Tudela Formation (Spain). The trampled surface was formed by artiodactyls that crossed a muddy carbonate accumulated under the influence of water level variations in a palustrine environment. The tracks reflect different types of morphological preservation. The well-preserved tracks have tetradactyl digit impressions caused by both manus and pes, and are the type series of a new artiodactyl ichnotaxon, Fustinianapodus arriazui ichnogen. nov. and ichnosp. nov. The rest of the tracks, which are not as well preserved, are didactyl and were classified as undetermined artiodactyl tracks. According to their preservation, morphology, size, arrangement and orientation, we propose that this tracksite is the product of a social behaviour, particularly gregariousness, of a multi-age group of artiodactyls ~19 Ma ago. The morphologic and palaeoecologic data presented here suggest that the trackmakers were a group of anthracotheres with a livelihood similar to current hippos. They crossed, periodically, a fresh water palustrine area along some preferential pathways (trails).

An unusual sauropod turning trackway from the Early Cretaceous of Shandong Province, China

An unusual turning and a regular, straight sauropod trackway both left by small trackmakers, as well as additional isolated medium-sized to large sauropod tracks are described from the Early Cretaceous Dasheng Group of the Zhucheng Basin, Shandong Province, China. Based mainly on well-preserved tracks exhibiting three forwardly-directed digit/claw impressions and a pronounced heteropody, and to a lesser degree due to a predominantly narrow to medium trackway gauge, the two small trackways are assigned to the Parabrontopodus ichnotaxon. As there is no clear trackway and no well-preserved tracks amongst the medium-sized to large sauropod tracks, these tracks can only be identified as of sauropod origin but they cannot be assigned to an ichnotaxon. The unusual turning trackway is characterized by a highly variable trackway configuration (pes and manus outward rotation, gauge, pace, stride) and pattern (different degree of manus overprinting by pes tracks) along its course, evidently related to the narrow, semicircular turn to the left that the animal made. This is also associated with a pronounced change from a narrow–medium (in the straight part at the beginning) to a (very) wide (within the turn) gauge. This demonstrates that these two stances could have been used by one and the same sauropod trackmaker, even if in the present case associated with turning and not simply during straight progression, as it was already reported from a Late Jurassic tracksite from NW Switzerland and an Early Cretaceous tracksite from Spain. Such ‘untypical’ trackways provide important constraints for the reconstruction of locomotor characteristics of sauropods such as unsteady locomotion and changes in locomotor behavior, and they will be of particular interest in the future to model and understand the different ‘locomotor styles/capabilities’ sauropods were engaged in.

Hints of the early Jehol Biota: important dinosaur footprint assemblages from the Jurassic-Cretaceous boundary Tuchengzi Formation in Beijing, China.

New reports of dinosaur tracksites in the Tuchengzi Formation in the newly established Yanqing Global Geopark, Beijing, China, support previous inferences that the track assemblages from this formation are saurischian-dominated. More specifically, the assemblages appear theropod-dominated, with the majority of well-preserved tracks conforming to the Grallator type (sensus lato), thus representing relatively small trackmakers. Such ichnofaunas supplement the skeletal record from this unit that lacks theropods thus far, proving a larger diversity of dinosaur faunas in that region. Sauropods are represented by medium to large sized and narrow and wide-gauge groups, respectively. The latter correspond with earlier discoveries of titanosauriform skeletons in the same unit. Previous records of ornithischian tracks cannot be positively confirmed. Purported occurrences are re-evaluated here, the trackways and imprints, except of a single possible specimen, re-assigned to theropods. Palecologically the Tuchengzi ichnofauna is characteristic of semi-arid fluvio-lacustrine inland basins with Upper Jurassic-Lower Cretaceous deposits in northern China that all show assemblages with abundant theropod and sauropod tracks and minor components of ornithopod, pterosaur and bird tracks.

Asianopodus-type footprints from the Hekou Group of Honggu District, Lanzhou City, Gansu, China and the “heel” of large theropod tracks

An increasing number of dinosaur tracksites have been reported from the Cretaceous Hekou Group deposits of the Lanzhou-Minhe Basin in the Gansu Province region. These include small sites such as the Huazhuang tracksite, from the Honggu District reported here, the Zhongpu tracksite with multiple track levels but few well-preserved tracks, other small tracksites currently under investigation, and the large and diverse Liujixia National Dinosaur Geopark site at Yanguoxia, where intensive study is ongoing. Collectively these sites reveal that ichnofaunas in the Hekou Group are widespread and diverse. The Huazhuang tracksite yields a small assemblage of moderately well-preserved theropod tracks assigned to Asianopodus. This is the first report of Asianopodus from the Hekou Group. Huazhuang Asianopodus belongs to the Eubrontes morphotype. The large theropod tracks from Lanzhou-Minhe Basin were left by large theropod trackmakers with the same general foot morphology. The specimens are described in detail and compared with other theropod track morphotypes from the Lower Cretaceous of China and elsewhere. In general, although the metatarsophalangeal pads of some Jurassic Eubrontes-type tracks are aligned with the axis of digit III, this feature appears most common in the Early Cretaceous theropod (Eubrontes-type) tracks.

The Smallest Dinosaur Tracks in the World: Occurrences and Significance of Minisauripus from East Asia

We review the status of the distinctive ichnogenus Minisauripus based on more than 80 well-preserved tracks comprising a minimum of 50 trackways from two localities in China and five in Korea. The tracks, attributed to theropod dinosaurs, have been assigned to two ichnospecies, M. chuanzhuensis and M. zhenshounani, based on Chinese specimens. Until recently, the known range of foot lengths was 1.5–6.0 cm, indicating a diminutive track-making species. However, newly discovered Minisauripus tracks from the Haman Formation in the Changseon region of Korea are as short as 1.0 cm. Most remarkably, a few, provisionally also labeled cf. Minisauripus, are reported as large as 16–20 cm, potentially adding unprecedented new data to the previous record. The larger tracks suggest that all the small tracks pertain to juveniles and not a small, distinct species as previously inferred. Tracks with foot lengths of only ∼1 cm suggest that individuals hatched from very small eggs. The fact that such tracks are abundant in fine-grained, lake-margin facies argues for the importance of suitable preservational conditions in recording the activity of small trackmakers. Thus, inferences about dinosaur population structure, growth rates, and other biological and ecological phenomena, based on the absence of small dinosaur tracks, should be made with caution.

Diverse tetrapod trackways in the Lower Pennsylvanian Tynemouth Creek Formation, near St. Martins, southern New Brunswick, Canada

Newly discovered tetrapod trackways are reported from eight sites in the Lower Pennsylvanian Tynemouth Creek Formation of southern New Brunswick, Canada. By far the most abundant and well-preserved tracks comprise pentadactyl footprints of medium size (32–53 mm long) with slender digits and a narrow splay (mostly < 55°). Digit lengths typically approximate a phalangeal formula of 23453 (manus) and 23454 (pes), but this may vary due to extramorphology. These tracks are referred to Pseudobradypus and they are attributed to early amniotes. A second type of track (rare) comprises very small (5–8 mm long) tetradactyl manus, and incompletely preserved pedes. Referred to Batrachichnus, these are attributed to temnospondyl amphibians. A third type (also rare) comprises small pentadactyl pedes (20–25 mm long) showing stubby, widely splayed (152°) digits with a terminal bulge. Manus are probably pentadactyl (preservation incomplete) with a narrower digit splay. These footprints, classified as Baropezia, are attributed to anthracosaurs. Facies analysis at the most prolific site (179 footprints documented) suggests that the tetrapods lived amongst small alethopterid trees colonizing the abandoned floor of a seasonally active fixed-channel river and a similar dryland context is probable for the seven other sites. The dominance of amniotes in these dryland alluvial facies contrasts markedly with coeval wetland facies in the nearby Joggins Formation, where skeletal and trackway assemblages are amphibian-dominated. This may imply that amniotes were better adapted to seasonally dry settings and sheds new light on the community ecology of tetrapods during a key evolutionary phase.

A new Isochirotherium trackway from the Triassic of Vieux Emosson, SW Switzerland: stratigraphic implications

The footprint assemblage of Vieux Emosson, located at 2400 m altitude in the Swiss Alps, was first described in 1982. The assemblage was regarded as Late Ladinian or Carnian in age, but the dating was questioned because the taxa show few affinities with other Triassic assemblages. Here we describe a short trackway with shallow but well-preserved tracks referred to the ichnogenus Isochirotherium, showing affinities with Isochirotherium soergeli and Isochirotherium lomasi. The trackway is present on a piece of slab ex situ lying on a mass of fallen rocks, but the slab can be attributed with confidence to the same level as the main one previously mapped. Preliminary observations in situ and of the footprint casts made in 1979 and deposited in the Natural History Museum of Geneva suggest that none of these are attributable to dinosaurs and that the Vieux Emosson footprints are mainly “track preservation variations” of chirotherian tracks. The occurrence of the ichnogenus Isochirotherium favours an older age, probably Early or Middle Triassic, than previously suggested for the Vieux Emosson tracksite.