Large Ornithopod Research Articles

Systematic of a Massively Constructed Specimen of Iguanodon galvensis (Ornithopoda, Iguanodontidae) from the Early Barremian (Early Cretaceous) of Eastern Spain

Styracosternan ornithopods are plenty abundant in the Lower Cretaceous fossil record of Europe. In particular, Iguanodon, the second genus of dinosaurs described worldwide, has been found in UK, Belgium, France, Germany, and Spain, evidencing a wide geographical distribution. Currently, the genus Iguanodon comprises two species, the type species I. bernissartensis from the late Barremian–Aptian of Europe and I. galvensis from the early Barremian of Teruel, Spain. The latter species is well known mainly from perinate and juvenile specimens. Here, axial and appendicular fossils of an adult, large and massively constructed ornithopod from the lower Barremian (Lower Cretaceous) Camarillas Formation of Galve (province of Teruel, Spain) are described. Fossil dimensions and some osteological evidence reveal that the specimen was a large (roughly 10 m long) ornithopod. An autapomorphic feature in the ischium and other characters allow us to ascribe this specimen to I. galvensis. In addition, postcranial co-ossification and fusion of the neurocentral suture indicate that the specimen was skeletally mature. Part of the material studied here was unknown in adults of I. galvensis, providing a better knowledge of the axial and appendicular region of this species.

Diversity and discrimination of large ornithopods revealed through their tracks (Lower Cretaceous, Spain): A phenetic correlation approach

Large ornithopods were frequent in the alluvial-to-coastal sedimentary systems developed during the Barremian in the Iberian Peninsula. Here, several pes track casts of large ornithopods from the Barremian Camarillas Formation of the southwestern sector of the Maestrazgo Basin (Iberian Basin, Spain) are analyzed. Two morphotypes of tracks from three different size classes are differentiated based on some morphological features, such as length of digits, the width of the “heel” pad impression, and width of the proximal part of digit III. These casts are assigned to Caririchnium isp. Morphotype 1 is represented by small to large-sized tracks, whereas Morphotype 2 by medium-sized tracks. Morphological variation seen among tracks of Morphotype 1 is interpreted to be possibly an ontogenetic variation. On the contrary, the differences seen between Morphotype 1 and 2 cannot be explained only by extramorphological causes, so might represent different trackmakers, especially when taking into account the considerable Barremian ornithopod diversity. A modified phenetic correlation is carried out between several well-preserved casts and the identified feet of Barremian ornithopods from Iberia, in order to infer the putative trackmakers. Morphotype 1 fits with the foot skeletal structure of the large styracosternan Iguanodon, including small-sized tracks that are perfectly accommodated to that of perinates of I. galvensis. Morphotype 2 matches better to the pes skeletal structure of the medium-sized Mantellisaurus. Similar two morphotypes can be also identified in other areas of the Lower Cretaceous of Europe, so, they could be tentatively produced by the two sized groups of styracosternans typical in the Early Cretaceous of Europe. Therefore, the ichnological analysis may allow differentiation of the diversity known through the direct record. In addition, the paleoecological analysis indicates a spatial niche partitioning between two size groups of styracosternans, because large-sized tracks and bones of these dinosaurs are the most common in such sediments.

Classification of large ornithopod dinosaur footprints using Xception transfer learning.

Large ornithopod dinosaur footprints have been confirmed on all continents except Antarctica since the 19th century. However, oversplitting problems in ichnotaxa have historically been observed in these footprints. To address these issues and distinguish between validated ichnotaxa, this study employed convolutional neural network-based Xception transfer learning to automatically classify ornithopod dinosaur tracks. The machine learning model was trained for 162 epochs (i.e., the number of full cycles of all training data through the model) using 274 data images, excluding horizontally flipped images. The trained model accuracy was 96.36%, and the validation accuracy was 92.59%. We demonstrate the performance of the machine learning model using footprint illustrations that are not included in the training dataset. These results show that the machine learning model developed in this study can properly classify footprint illustration data for large ornithopod dinosaurs. However, the quality of footprint illustration data (or images) inherently affects the performance of our machine learning model, which performs better on well-preserved footprints. In addition, because the developed machine-learning model is a typical supervised learning model, it is not possible to introduce a new label or class. Although this study used illustrations rather than photos or 3D data, it is the first application of machine-learning techniques at the academic level for verifying the ichnotaxonic assignments of large ornithopod dinosaur footprints. Furthermore, the machine learning model will likely aid researchers to classify the large ornithopod dinosaur footprint ichnotaxa, thereby safeguarding against the oversplitting problem.

The largest ornithopod (Dinosauria: Ornithischia) from the Upper Jurassic of Europe sheds light on the evolutionary history of basal ankylopollexians

Abstract Ankylopollexia was an abundant and diverse clade of ornithopods present in North America, Europe, Africa, and Asia from the Late Jurassic to the Late Cretaceous. However, the relationships between the basal ankylopollexians are poorly understood. A new ankylopollexian ornithopod genus and species is described here, based on a dentary tooth, an ungual pollex of the manus, and an almost complete left hindlimb. The fossils come from deposits of the Villar del Arzobispo Formation (upper Kimmeridgian–Tithonian). Phylogenetic analysis revealed that Oblitosaurus bunnueli gen. et sp. nov. is the basalmost member of Ankylopollexia, together with Draconyx loureiroi. Furthermore, these results have relevant taxonomic implications for the genus Camptosaurus, being the first phylogenetic analysis to support the monophyly of Camptosaurus species. The estimated size of Oblitosaurus bunnueli suggests that it is the largest ornithopod described in the Upper Jurassic of Europe and one of the largest around the world, and could be the trackmaker of large ornithopod tracks found in the Upper Jurassic of the Iberian Peninsula. This discovery increases the known ankylopollexian diversity in Iberia, revealing the presence of an Iberian basal ankylopollexian clade that does not appear to be present in the contemporaneous outcrops of North America.

Ornithopod tracks and bones: Paleoecology and an unusual evidence of quadrupedal locomotion in the Lower Cretaceous of eastern Iberia (Teruel, Spain)

Dinosaur tracks and osteological remains in the El Castellar Formation (upper Hauterivian–lower Barremian) in the Peñagolosa subbasin, southwest sector of the Maestrazgo Basin (Teruel Province, Spain), are scarce and fragmentary, respectively. Here, we report several unexpected, well-defined natural casts of large ornithopods from several sites of the El Castellar Formation. Moreover, an unusual manus-pes track set preserved as convex hyporelief has been found in the lowermost sandstone level of the Camarillas Formation, the first evidence of dinosaur for the base of this unit at the Peñagolosa subbasin. The ichnological comparison allows us to ascribe the studied tracks to Caririchnium. Their trackmakers were large styracosternans related to Iguanodon, and the presence of a manus-pes track set verifies that some of them may have a quadrupedal locomotion. This associated manus-pes track set constitutes one of the oldest ichnological pieces of evidence of quadrupedalism in large ornithopods from the Lower Cretaceous of Iberia and increases the limited record of this kind of track in the Lower Cretaceous of Europe. In addition, we describe some osteological fossils of these dinosaurs from the El Castellar Formation. These skeletal remains are related to medium to large-sized styracosternans, some of which closely resemble those of other European styracosternans such as Iguanodon. The evidence provided here verifies that these dinosaurs were frequent components in the coastal wetland, and fluvial to deltaic systems developed, during the late Hauterivian–early Barremian, in the Peñagolosa subbasin, possibly because these may have had a source of fresh vegetation and may have provided protection.

Abundance of large ornithopod dinosaurs in the El Castellar Formation (Hauterivian-Barremian, Lower Cretaceous) of the Peñagolosa sub-basin (Teruel, Spain)

Abundance of large ornithopod dinosaurs in the El Castellar Formation (Hauterivian-Barremian, Lower Cretaceous) of the Peñagolosa sub-basin (Teruel, Spain)

A juvenile ornithopod tracksite from the Lower Cretaceous Haman Formation, South Korea

A new dinosaur tracksite with footprints of non-adult ornithopods was discovered from the Lower Cretaceous Haman Formation (Albian), Gunbuk District, Haman County, South Gyeongsang Province of South Korea in 2018. The tracksite consists of 58 ornithopod footprints (seven short trackways and 26 isolated footprints) within three track-bearing horizons partially exposed on the small creek bottom. Lithofacies and sedimentary structures of the track-bearing horizons and overlying strata suggest a marginal lacustrine environment. All tracks are sub-symmetrical tridactyl and small- to medium-sized pes prints. They have wide, blunt, short digital impressions with a large, rounded heel pad impression. No manus print is observable in the tracksite. Tracks are generally longer than their width with a distinctly developed digit III. Trackways show the inward (negative) rotation of footprints. The morphological characteristics of the footprints are most likely attributable to ichnogenus Caririchnium. A relatively small pes size (lengths range from 13 to 27 cm) indicates that the trackmakers were juvenile to subadult ornithopods when compared with the contemporary large ornithopods in South Korea. The majority of the trackways show preferred orientations with trends of parallel to subparallel groupings on each surface, suggesting gregarious behavior. Notably, the tracksite consists exclusively of juvenile ornithopod dinosaurs, which is an uncommon phenomenon when compared to other ornithopod tracksites with age-mixed or large ornithopod footprints reported from other localities around the world. The absence of the adult ornithopod tracks may be interpreted as the spatial segregation of an ornithopod population based on their ages and the formation of juvenile-only communities without parental care.

Diversity of large ornithopod dinosaurs in the upper Hauterivian-lower Barremian (Lower Cretaceous) of Teruel (Spain): a morphometric approach

We report some large ornithopod vertebrae from two upper Hauterivian-lower Barremian (Lower Cretaceous) localities in El Castellar (Maestrazgo Basin, Teruel,Spain).These fossils have been studied systematically as well as morphometrically using a multivariate analysis in order to analyse the diversity of the sample. In fact, principal component analysis has been demonstrated as a useful tool for establishing affinities in isolated iguanodontian vertebrae, at least when size effect is not removed from the analysed dataset. As result of this study, twolarge indeterminate styracosternans are distinguished in the sample: a large one with platycoelus anterior caudal vertebrae related to the genera Magnamanusand Iguanodon, and a middle-sized one with longer-than-high dorsal vertebrae and amphicoelus anterior caudal vertebrae related to Morelladon. Such diversity of large ornithopods observed in the upper Hauterivian-lower Barremian of the Maestrazgo Basin is similar to that previously observed in Western Cameros Basin and it demonstrates the presence of at least two different forms of styracosternan in this stratigraphic range of the Iberian Peninsula.

Systematics and paleobiology of a new articulated axial specimen referred to Iguanodon cf. galvensis (Ornithopoda, Iguanodontoidea)

ABSTRACT The early Barremian Iberian ornithopod Iguanodon galvensis was described for the first time in 2015. However, much of its anatomy, such as the axial skeleton in mature specimens, remains unknown. Here, the partially articulated presacral vertebrae and ribs belonging to a large adult ornithopod (DS-1 ornithopod) from the lower Barremian (Lower Cretaceous) that were found in Teruel Province (northeast of the Iberian Peninsula, Spain) are investigated by a systematic study and a phylogenetic analysis. The only cervical vertebra preserved is strongly opisthocoelus, as is typical of styracosternans. In fact, the phylogenetic analysis resolves DS-1 ornithopod as an hadrosauriform styracosternan. The assemblage also includes ten anterior-to-posterior dorsal vertebrae that strongly resemble those of the contemporary European iguanodontoid Iguanodon, particularly in having amphiplatyan and higher-than-long centra and dorsal neural spines two times the lateral height of their centra and slightly sigmoid in the posterior vertebrae. In addition, the dorsal centra are moderately compressed between the articular faces and lack a ventral keel, unlike the late Barremian type species I. bernissartensis but resembling the sympatric I. galvensis. For these reasons, DS-1 ornithopod is ascribed here as I. cf. galvensis. Moreover, this specimen has costovertebral ankyloses likely related to the specimen’s maturity. Finally, the fossils of I. galvensis including those referred to it as DS-1 ornithopod, as well as evidence provided by bones and tracks in other places, indicate that the genus Iguanodon frequently occupied areas around rivers, lakes, estuaries, or lagoons.

A Reexamination of Dinosaur Trackmakers Based on Three-Dimensional Quantitative Data from the Lower Cretaceous Tetori Group of the Oshirakawa Area, Gifu Prefecture (Japan)

Researchers disagree on the identity of dinosaurs that left footprints in the Lower Cretaceous Tetori Group of the Oshirakawa area (Japan). To clarify these identities, we quantitatively analyzed footprint data obtained from three-dimensional laser scanning technology. From these data, we identified six tracks belonging to dinosaurs. These six tracks were bipedal with a tridactyl morphology, which we could differentiate into large theropods (the ichnofamily Eubrontidae) and large ornithopods (similar to Amblydactylus-type). Our results indicate that the ichnofauna of the Oshirakawa site is richer than previously thought. Additionally, the cooccurrence of large theropod and Amblydactylus-type ornithopod footprints in the Oshirakawa area is the oldest in the Tetori Group (although a similar assemblage was identified in the Kitadani Formation, which is the uppermost part of the Tetori Group). Thus, quantitatively assessing dinosaur footprints using 3D digital data is an effective approach to identify dinosaur footprints.

A new dinosaur tracksite from the Lower Cretaceous Sanbukdong Formation of Gunsan City, South Korea

South Korea has become globally famous for various tetrapod footprints from Upper Cretaceous strata. Here we report the first Early Cretaceous “large” tracksite from the Sanbukdong Formation of an unnamed small basin in the west of Gunsan City, North Jeolla Province. The tracksite (720 m2) produced 425 tracks. Among them, eleven ornithopod and three theropod trackways (189 tracks) were measured and mapped in detail. Most of ornithopod tracks are large (32 cm–51 cm in length) and very similar to pes imprints of Caririchnium lotus from China in that the general track dimensions and large heel pad impressions are typically longer than wide. They are attributable to basal hadrosauroids based on their stratigraphic and palaeogeographic occurrence as well as skeletal evidence in Korea. Eleven ornithopod trackways show gregarious behaviour and two main directions of movements along a lake margin. One movement is that of a group that went back and forth along the lacustrine margin and the other movement showing dinosaurs that came to the lakeshore probably to drink water or any other purposes. One trackway consists of 39 consecutive tracks with the distance of 39 m, representing the longest Early Cretaceous ornithopod trackway ever found in Korea. Sanbukdong ornithopod tracks suggest that basal hadorsauroids had the same growth pattern as derived hadrosaurids such as a brief period where it was very rapid. They also support independently that the majority of Early Cretaceous basal hadrosauroids were smaller than Late Cretaceous hadrosaurids in body size. Two theropod trackways consist of large tracks (more than 40 cm in length) and closely resemble Irenesauripus glenrosensis from the Lower Cretaceous of Texas which was inferred to be of Acrocanthosaurus origin. It is reasonable that they are attributable to carcharodontosaurids because their skeletal materials were already reported from the Lower Cretaceous strata in China and Korea. This new tracksite indicates that large ornithopod and theropod dinosaurs lived in the Early Cretaceous in Korea and strengthens previous hypotheses of their existence based on only isolated teeth.

Complex In-Substrate Dinosaur (Sauropoda, Ornithopoda) Foot Pathways Revealed by Deep Natural Track Casts from the Lower Cretaceous Xiagou and Zhonggou Formations, Gansu Province, China

ABSTRACTSeveral new Early Cretaceous tracksites from the Lower Cretaceous Xiagou Formation of Gansu Province (China) with tracks of large sauropods and ornithopods are described. Previously reported bird tracks were missing due to human negligence. The studied specimens are preserved as impressions and shallow and deep natural track casts. These dinosaur tracks are first reported from the Jiuquan area in the Changma Basin, matching well with the skeletal record of diverse non-avian dinosaur-bird faunas of this region. Moreover, they add new data to the dinosaur ichnofaunas of the Lanzhou-Minhe Basin (Gansu Province) and indicate a wide distribution of dinosaur-bird assemblages in the Early Cretaceous. Regarding morphology, sauropod, and ornithopod tracks from the Lanzhou-Minhe Basin and the Jiuquan area are very similar to each other. Titanosauriform trackmakers are assumed for the sauropod tracks and possibly iguanodontids have left the large, tridactyl ornithopod tracks. Of particular interest are well-preserved, deep natural track casts of large ornithopods and sauropods preserving ridges and grooves as well as striation marks on the lateral sides of the casts that allow the reconstruction of complex pathways of the foot within the substrate. One particular sauropod pes–manus track cast even indicates lateral and vertical sliding within the sediment because of the presence of “double impressions of digits” on the bottom.

First Record of Gregarious Behavior in Robust Medium-Sized Jurassic Ornithopods: Evidence from the Kimmeridgian Trackways of Asturias (N. Spain) and Some General Considerations on Other Medium-Large Ornithopod Tracks in the Mesozoic Record

ABSTRACTAt least four parallel trackways of medium-sized and robust ornithopods are described from the Upper Jurassic Tereñes tracksite in Asturias (N. Spain). While the tracks and trackways of small and gracile ornithopods are common in the Jurassic record, large ornithopods are very rare in this period. Ornithopod gregarious behavior has been recorded from many Cretaceous ichnoassemblages, but there are few examples from the Jurassic, and these always relate to small individuals. The Asturian tracks are quite different from known ichnogenera, but they are not sufficiently well preserved to propose a new one. Medium-large Jurassic ornithopods with robust feet such as Draconyx or Cumnoria are the best candidates to be the trackmakers.

First evidence of Hadrosauropodus in Gondwana (Yacoraite Formation, Maastrichtian-Danian), northwestern Argentina

Uppermost Cretaceous (Campanian-Maastrichtian) large ornithopod tracks are scarce in Gondwana. This record is limited to few citations in the northern Argentina, Peru and possibly Bolivia, although their ichnological affinities are still under discussion. Recently, a new vertebrate tracksite with large ornithopod tracks has been found in the Maimará locality, Jujuy province, Argentina, from the Yacoraite Formation (Maastrichtian-Danian). The best preserved track is characterized by having large and bilobed heel impression and wide and short digit impressions with blunt claw marks. This record represents the unambiguous record of large ornithopod tracks in Gondwana in the Uppermost Cretaceous, and its features allow classifying it as Hadrosauropodus. Previously, this ichnotaxon had exclusively Laurasian distribution. Therefore, this record is the first evidence of Hadrosauropodus from Gondwana expanding the geographic range of this ichnogenus. A member of Hadrosauridae is reinforced as possible trackmaker of the Hadrosauropodus tracks. Uppermost Cretaceous hadrosaurid dinosaurs are scarce in Gondwana, being the record limited to Patagonia, La Pampa province and Antarctica. Therefore, the Maimará tracks increase the knowledge of this kind of dinosaur from Gondwana.

Contribution to knowledge of the last dinosaur footprints in Europe. Persistence of ornithopods in the upper Maastrichtian of SE Spain

In the locality of Rambla de los Gavilanes (Betic Chain Murcia, Spain), six new outcrops with dinosaur footprints are reported from an uppermost Cretaceous succession of coastal marine deposits. Four of these sites are found in the upper part of the lower Maastrichtian and the other two in the upper Maastrichtian, these latter located only a few meters below the Cretaceous-Paleocene boundary (K/Pg). Traces appear as impressions or as natural casts, on tabular limestone beds consisting of micritic carbonate facies, these deposited in coastal marine areas that include a variety of environments (coastal lakes, tidal flats, salt marshes, and shallow coastal lakes). Two main types of traces have been recognized, respectively attributed to sauropod footprints and large ornithopod footprints with remarkable pointed hoof marks. The Maastrichtian sites with large ornithopod footprints in Europe are reported from Spain, Poland and Romania. Sauropod (titanosaurian), theropod (Irenesauripus and other undetermined theropods), and ornithopod footprints have been found at sites located up to 20 m below the K/Pg boundary. The Spanish dinosaur ichnites known closest to the K/Pg boundary are in the Pyrenean upper Maastrichtian, and are tridactyl, theropod and ornithopod (Hadrosauropodus and Amblydactylus) footprints. In this work, the assignation of the Rambla de los Gavilanes ornithopod footprints has been made following the recommended synthesis in several recent papers which reduce the large ornithopod ichnogenus to four.

Ichnotaxonomic review of large ornithopod dinosaur tracks: temporal and geographic implications.

BackgroundLarge ornithopod tracks are known from the Upper Jurassic to the uppermost Cretaceous rocks of all continents but Antarctica. They include the tracks historically called Iguanodon footprints, iguanodontid footprints, hadrosaur/hadrosaurid footprints, and other large ornithopod tracks that have been used to define ichnotaxa. More than 40 ichnospecies based on large ornithopod tracks have been defined, but the validity of many of them is questionable.Methodology/Principal Findings34 ichnogenera and 44 ichnospecies have been analysed in this work. Many of them are considered to be invalid because they have been defined on the basis of poorly preserved tracks without diagnostic features, have an inadequate diagnosis, or are based on temporal and/or geographical criteria. Only eight ichnospecies belonging to the ichnogenera Caririchnium, Iguanodontipus and Hadrosauropodus are here regarded as valid.Conclusions/SignificanceThe monospecific ichnogenus Iguanodontipus (I. burreyi) is characterized by a small, rounded heel and elongate, narrow digit impressions. Its distribution is limited to the Berriasian-Valanginian of Europe. Caririchnium consists of four ichnospecies (C. magnificum [type ichnospecies], C. kortmeyeri, C. billsarjeanti and C. lotus) with a large, rounded heel and short, wide digit impressions. This ichnogenus ranges from the Berriasian-Hauterivian to the Aptian-Albian of South America, North America, Asia and Europe. Finally, Hadrosauropodus (three ichnospecies: H. langstoni [type ichnospecies], H. leonardii and H. kyoungsookimi) shows a large, bilobed heel and short, wide digit impressions. It is known from the Aptian-Albian to the Maastrichtian of North America, Asia and Europe. The ichnofamily Iguanodontipodidae includes large iguanodontian tracks characterized mainly by mesaxonic, tridactyl and subsymmetrical pes tracks that are as wide as (or wider than) long and have one pad impression in each digit and one in the heel. Its distribution is confidently limited to the Cretaceous of Europe, Asia, North America and South America.

On the history, osteology, and systematic position of the Wealden (Hastings group) dinosaurHypselospinus fittoni(Iguanodontia: Styracosterna)

The history of discovery and interpretation of several dinosaurs collected from quarries near the town of Hastings during the latter half of the 19th century is more complicated than it should be. Samuel Husbands Beckles and Charles Dawson collected several large ornithopod skeletons from this area, but just a few bones from these skeletons were subsequently described and interpreted (principally) by Richard Owen and Richard Lydekker. All these specimens merited recognition because they had the potential to contribute to an on-going debate about the anatomical structure and relationships of the iconic Wealden dinosaur Iguanodon. Unfortunately, no detailed description of these important skeletons was published in later years. Furthermore, previously known associations of bones and even provenance information, linked to the specimens that were gradually acquired by the Natural History Museum, are unclear. Confusion may have arisen because Richard Lydekker used the private collector Charles Dawson as a voluntary curatorial assistant. This account documents the past work on the osteology of material that can be attributed to Hypselospinus fittoni. Nearly all such material is described here for the first time, and every effort has been made to re-establish associations between bones as well as provenance information. A skeletal reconstruction of Hypselospinus is attempted on the basis of the hypodigm. Most of the on-going confusion concerning the affinity of this material with either Hy. fittoni or its sympatric contemporary Barilium dawsoni has been resolved. Hypselospinus fittoni (Lydekker, 1889) is rediagnosed on the basis of this new and relatively comprehensive anatomical description, and this animal is compared with known contemporary and closely related taxa. Some recently published accounts claiming to be revisions of the taxonomy of Wealden ‘iguanodonts’, including material belonging to the hypodigm of Hy. fittoni, have failed to adhere to basic taxonomic principles and have caused more confusion than was strictly necessary. The systematic position of Hypselospinus is reassessed cladistically. The cladistic analysis forms the basis for a revised hierarchical classification of derived ornithopods. The consensus topology generated by the systematic analysis has been used to explore the phylogenetic history of these dinosaurs and create an internally consistent classificatory hierarchy (phylogenetic definitions and Linnaean diagnoses are given for critical positions in the topology). This analysis suggests that there is a fundamental split amongst the more derived (clypeodontan) ornithopod ornithischians into the clades Hypsilophodontia and Iguanodontia. There is evidence for anatomical parallelism and convergence (homoplasy) particularly between large-bodied representatives of both clades. Hypselospinus is one of the earliest known styracosternan iguanodontians and displays anatomical characteristics that presage the evolution of the extraordinarily abundant and diverse hadrosaurs of the latest Cretaceous (Campanian−Maastrichtian). These observations cast fresh light on the phylogeny, classification, diversity, and biology of derived ornithopods. There is little doubt that Hy. fittoni could have been understood far better more than a century ago. That this statement is undoubtedly true is reflected in the century of doubt and confusion that has surrounded this taxon and its original incarnation as Iguanodon fittoni.

A review of footprints from the Wessex Formation (Wealden Group, Lower Cretaceous) at Hanover Point, the Isle of Wight, southern England

Hanover Point on the Isle of Wight, England, is a Lower Cretaceous (Barremian) site yielding a large number of dinosaur footprints from the Wessex Formation. These footprints, hitherto often referred to as ‘Iguanodon’ tracks, have generated interest and speculation since the beginning of the Victorian era. Today, Hanover Point largely yields sandstone casts (convex hyporeliefs) of footprints but also includes some impressions (concave epireliefs), a few of which form short trackways. The majority belongs to large ornithopods, many with foot lengths in excess of 50?cm. Theropods and the occasional thyreophoran track are also represented. The site represents the Wessex Formation within the Wealden Group and can be described ichnologically as a category 3a deposit. Most of the large ornithopod footprints have a distinctive quadripartite morphology and are best assigned to the ichnogenus Caririchnium or in some cases Amblydactylus. Few are morphologically compatible with Iguanodontipus which was described from pre-Wealden deposits and appears to be little represented in the Wealden ichnofaunas.

A review of large Cretaceous ornithopod tracks, with special reference to their ichnotaxonomy

Trackways of ornithopods are well-known from the Lower Cretaceous of Europe, North America, and East Asia. For historical reasons, most large ornithopod footprints are associated with the genus Iguanodon or, more generally, with the family Iguanodontidae. Moreover, this general category of footprints is considered to be sufficiently dominant at this time as to characterize a global Early Cretaceous biochron. However, six valid ornithopod ichnogenera have been named from the Cretaceous, including several that are represented by multiple ichnospecies: these are Amblydactylus (two ichnospecies); Caririchnium (four ichnospecies); Iguanodontipus, Ornithopodichnus originally named from Lower Cretaceous deposits and Hadrosauropodus (two ichnospecies); and Jiayinosauropus based on Upper Cretaceous tracks. It has recently been suggested that ornithopod ichnotaxonomy is oversplit and that Caririchnium is a senior subjective synonym of Hadrosauropodus and Amblydactylus is a senior subjective synonym of Iguanodontipus. Although it is agreed that many ornithopod tracks are difficult to differentiate, this proposed synonymy is questionable because it was not based on a detailed study of the holotypes, and did not consider all valid ornithopod ichnotaxa or the variation reported within the six named ichnogenera and 11 named ichnospecies reviewed here. We therefore emphasize the need to base comparisons between ichnotaxa on type material, and not on selected referred material. It is concluded that there is considerable variation in the morphology of the holotypes, as well as variation in size and quality of the samples and the mode of preservation. Conversely, there is considerable overlap in morphology among other tracks that have been informally attributed to these ichnotaxa. These factors make it difficult to synonymize any of the existing ichnotaxa without detailed revision of the samples from which the type material originates. Nevertheless, a review of the type material of all ichnotaxa is presented as a basis for further discussion and, as a first step, the ichnofamily Iguanodontipodidae is proposed to accommodate Amblydactylus, Caririchnium and Iguanodontipus.

Re-description of the partially collapsed Early Cretaceous Zhaojue dinosaur tracksite (Sichuan Province, China) by using previously registered video coverage

A re-description of the Early Cretaceous Zhaojue dinosaur tracksite (Sichuan Province, China) is the major focus of the present work. The tracksite is located in an active copper mine, and a dinosaur track-bearing surface of about 1500 m2 (named tracksite I) initially discovered in 1991, has since almost completely collapsed due to ongoing quarry activities. Only about 5% of the initial surface still remains in place (named “remaining tracksite”), while due to the collapse a few new but rather poorly-preserved tracks were unearthed on an underlying level. While the tracks still in place were studied using common field techniques, a schematic tracksite map of the collapsed surface was drawn based on a “corrected orthophotograph” that was generated from overview photographs and from video frames. Fortunately, the resolution of some of the close-up video frames is sufficiently high to observe general track morphology, and to re-interpret previously wrongly identified trackways. Here, we report a quite diverse ichnocoenosis consisting of sauropod, ornithopod, theropod, and pterosaur trackways and isolated tracks. The sauropod trackways belong to the Brontopodus-type and were possibly left by medium-sized titanosaurs. One of the sauropod trackways turns around and makes an astonishingly narrow turn of more than 180° with very pronounced “off-tracking” of the manus with respect to the pes. Such unusual trackways are important for the reconstruction of sauropod locomotion. The theropod trackways were left by small and medium-sized animals with the imprint morphology being similar to that of the ichnogenera Grallator and Eubrontes. Large tridactyl tracks with blunt toes are tentatively identified as ornithopod tracks and may be described as Caririchnium-type tracks. Pterosaur tracks can be assigned to Pteraichnus. The association of pterosaur with small theropod tracks is rather unusual, and this tracksite further corroborates the frequent presence of large ornithopods in inland environmental settings.