Michael E. Burns

A redescription of the ankylosaurid dinosaur Dyoplosaurus acutosquameus Parks, 1924 (Ornithischia: Ankylosauria) and a revision of the genus

ABSTRACT The holotype of Dyoplosaurus acutosquameus Parks, 1924 (=Euoplocephalus tutus Lambe, 1910), represents one of the most complete ankylosaurid specimens collected to date. It consists of a partial skull roof, four mandible fragments with two teeth in situ, portions of postcranial armor (some in situ), skin impressions, articulated post-thoracic vertebrae, ten partial thoracic ribs, a partial left ilium, both ischia, and tail club, and associated right radius, left metacarpal IV, femur, tibia, fibula, and pes. We provide a detailed redescription of this material as well as comparisons with other ankylosaurid specimens referred to E. tutus. The synonymy of the genus with Euoplocephalus is not supported, and Dyoplosaurus is a valid taxon. It is possible that the fragmentary nature of the holotype of Euoplocephalus leads to the inference that the diversity of Late Cretaceous North American ankylosaurids is lower than it actually is. As such, it might be necessary to look beyond traditional cranial characters in order to accurately appraise the number and nature of various ankylosaurid taxa.

Taxonomic Utility of Ankylosaur (Dinosauria, Ornithischia) Osteoderms: Glyptodontopelta mimus Ford, 2000: A Test Case

Abstract A new nodosaurid specimen from the Upper Cretaceous Naashoibito Member of the Ojo Alamo Formation in the San Juan Basin, New Mexico is assigned to Glyptodontopelta mimus Ford, 2000 based on characters of internal (histological) and external osteoderm morphology. This specimen is from the same stratigraphic horizon as the holotype (USNM 8610), and because it displays a wide range of osteoderm morphotypes, it can be used as a basis for comparison of osteoderm shape and sculpturing among different ankylosaur taxa. Its unique surface texture differentiates it from other Upper Cretaceous ankylosaurids and nodosaurids (Ankylosaurus, Nodocephalosaurus, Edmontonia, Euoplocephalus, and Panoplosaurus) and demonstrates that G. mimus is a valid taxon. The nodosaurid Edmontonia australis Ford, 2000 is considered a subjective junior synonym of G. mimus based on having the same surface texture and shape of the medial cervical osteoderms. Ankylosaur osteoderms are distinctive to at least the genus level and are commonly found in Upper Cretaceous strata, thus they have great biostratigraphic utility.

External and internal structure of ankylosaur (Dinosauria, Ornithischia) osteoderms and their systematic relevance

ABSTRACT Ankylosaurian systematics can be assessed using morphological, textural, and histological characters of osteoderms. Archosaur osteoderms have cortices surrounding cancellous cores. Ankylosaurs are united by an external cortex distinguishable from the core and by the presence of mineralized structural fibers. Nodosaurid osteoderms lack a well-developed basal cortex and have dense external cortical fibers. Ankylosaurid osteoderms are thinner than those of other ankylosaurs. Polacanthine osteoderms have a cancellous core, but share this feature with other derived and primitive taxa. Cortical thickness overlaps among groups, so a thick cortex is not diagnostic for polacanthines. Specialized elements diverge histologically from the primitive condition to suit their specific functions. Some shapes and external textures are diagnostic for specific taxa, such as Ankylosaurus and Glyptodontopelta. Parsimony analyses suggest osteodermal support for a monophyletic Polacanthinae (excluding Mymoorapelta) and Shamosaurinae.

Histological variability in fossil and recent alligatoroid osteoderms: Systematic and functional implications

Statements about morphological variation in extinct taxa often suffer from insufficient sampling that can be remedied by taking advantage of larger sample sizes provided by related, extant taxa. This analysis quantitatively and qualitatively examines histological and morphological variation of osteoderms from extant and extinct alligatoroid specimens. Statistically significant differences were correlated with changes in osteoderm size and shape. These differences are independent of position on the body, taxonomy, or evolution. Histological variation in alligatoroid osteoderms is due to morphological constraints on the elements themselves, and not taxonomic differences. This has implications for the recognition of histological characters in the osteoderms of extinct archosaur groups that lack extant representatives. J. Morphol., 2013.

The Folklore of Dinosaur Trackways in China: Impact on Paleontology

Fossilized footprints made by extinct creatures have captured the attention of humans worldwide. Many different prescientific cultures have attempted to identify the trackmakers and account for the tracks of unfamiliar species. In China, local folklore about dinosaur footprints is preserved in oral traditions of great antiquity, which persist today in at least five regions with conspicuous tracksites. Although folk explanations are expressed in mythological terms, they are based on careful observation over many generations. Ichnological myths often contain details that reveal attention to size, morphology, and sedimentology of tracks. Chinese folklore identified dinosaur tracks as those of divine or fantastic birds of various sizes, legendary large mammals, sacred plants, and deities or heroes. Popular knowledge of dinosaur tracksites and myth-based descriptions of mysterious footprints in stone could serve as a guide for paleontologists in East Asia, leading them to identify new trackways previously unknown to science.

New Elmisaurine Specimens from North America and Their Relationship to the Mongolian Elmisaurus rarus

New specimens from Canada confirm the presence of elmisaurines in North America and shed light on the relationship of Leptorhynchos elegans to Mongolian forms. These specimens have hindlimb elements previously unknown from elmisaurines in the Dinosaur Park Formation, including tibiae and pedal phalanges. Metatarsal anatomy is sufficiently different to merit a generic distinction from Elmisaurus rarus, and both can be distinguished from Caenagnathus collinsi and Chirostenotes pergracilis. Differences between these taxa include body size, degree of coossification of the tarsometatarsus, and development of cruciate ridges of the metatarsal III. Histological analysis confirms that these differences are not correlated with ontogenetic age of the specimens. The results support the informal separation of caenagnathids based on metatarsal structure, and allow comments on paleobiological differences between caenagnathids and oviraptorids.

Abdominal Contents from Two Large Early Cretaceous Compsognathids (Dinosauria: Theropoda) Demonstrate Feeding on Confuciusornithids and Dromaeosaurids

Two skeletons of the large compsognathid Sinocalliopteryx gigas include intact abdominal contents. Both specimens come from the Jianshangou Beds of the lower Yixian Formation (Neocomian), Liaoning, China. The holotype of S. gigas preserves a partial dromaeosaurid leg in the abdominal cavity, here attributed to Sinornithosaurus. A second, newly-discovered specimen preserves the remains of at least two individuals of the primitive avialan, Confuciusornis sanctus, in addition to acid-etched bones from a possible ornithischian. Although it cannot be stated whether such prey items were scavenged or actively hunted, the presence of two Confuciusornis in a grossly similar state of digestion suggests they were consumed in rapid succession. Given the lack of clear arboreal adaptations in Sinocalliopteryx, we suggest it may have been an adept stealth hunter.

A Review of Pelvic Shield Morphology in Ankylosaurs (Dinosauria: Ornithischia)

Abstract The pelvic shield of ankylosaurian dinosaurs refers to an area of osteoderms lacking differentiated transverse bands over the pelvic region and it is used as a diagnostic character for various ankylosaur groups. The pelvic shield character varies across ankylosaur taxa but is typically coded as a binary character or is excluded from phylogenetic analyses, which obscures evolutionary trends and relationships. This study investigates for the first time pelvic shield morphology in a stratigraphic and geographic context. This paper comprehensively reviews pelvic shield morphology with firsthand observations of specimens, and proposes three categories of pelvic shield morphology. Category 1 pelvic shields have un-fused but tightly interlocking osteoderms. Category 2 pelvic shields have fused osteoderms forming rosettes and are restricted to the Late Jurassic to mid Cretaceous of North America and Europe. Category 3 pelvic shields have fused polygonal osteoderms of similar size, and are found in the mid- to Late Cretaceous of North America. Although the pelvic shield is used to characterize the Polacanthidae, an interpretation supported by this review, the validity of such a clade is dependent upon a global parsimony analysis incorporating this character. Future analyses of the Ankylosauria should incorporate a more detailed treatment of the pelvic shield to determine its diagnostic value within the group.

The earliest fossil evidence of bone boring by terrestrial invertebrates, examples from China and South Africa

Abstract We report the oldest fossil evidence of osteophagia by terrestrial invertebrates on both the Asian and African continents. Bones attributable to the Middle Jurassic dinosaur Chuanjiesaurus (Dinosauria: Sauropoda) were found with post-mortem insect modification in the Chuanjie Formation, Yunnan Province, China. The morphology of the borings closely matches the ichnogenus Cubiculum. Based on the lack of bioglyphs observed in Cubiculum ornatus, a new ichnospecies is proposed here. The new trace fossil, Cubiculum inornatus isp. nov., is interpreted to have been constructed for pupation by an unknown taxon of insect. Additionally, we report even older borings from Early Jurassic dinosaur bones of the Elliott Formation in the Karoo Basin, which represent the second oldest occurrence of insect traces in bone from continental settings. Both trace fossils sites have palaeogeographic implications for the origins and dispersal of osteophagia amongst terrestrial invertebrates during the Mesozoic. These discoveries push back the antiquity of pupation in animal bones by more than 100 million years to the Middle Jurassic, indicating that this behaviour, and osteophagy more generally, originated early in the Mesozoic, roughly comparable with the origination of insect pupation in woody substrates (Late Triassic).

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.