The phylogenetic affinities and morphological peculiarities of the bird-like dinosaur Borogovia gracilicrus from the Upper Cretaceous of Mongolia

Borogovia gracilicrus is a small-bodied theropod dinosaur from the Maastrichtian (Upper Cretaceous) Nemegt Formation of southern Mongolia. The taxon is based on a single fragmentary specimen preserving only the distal part of the hindlimbs. The morphology of Borogovia shows a peculiar combination of features, some of which are traditionally considered troodontid synapomorphies and others which are unusual for Troodontidae but are shared with other maniraptoran clades. In particular, the second toe of B. gracilicrus differs from other troodontids in lacking some of the features which contribute to the specialized ‘sickle-clawed’ second toe, here termed the ‘falciphoran condition’, shared with dromaeosaurids and some other paravians, such as the strongly compressed and falciform ungual. Phylogeny reconstructions intended to explore the affinities of Borogovia consistently support its referral within a subclade of troodontids including all Late Cretaceous taxa. The placement of Borogovia is not significantly affected by its unusual combinations of hindlimb features or by the homoplasy of the elements forming the falciphoran condition. Borogovia is supported as a valid taxon and is distinct from the other Nemegt troodontids, Tochisaurus and Zanabazar. The lack of a falciform ungual, and the distinctive morphology of the second toe in B. gracilicrus are interpreted as a derived specialization among Troodontidae and not as retention of the plesiomorphic condition of non-paravian theropods.

Pendraig milnerae , a new small-sized coelophysoid theropod from the Late Triassic of Wales

We describe a new small-bodied coelophysoid theropod dinosaur, Pendraig milnerae gen. et sp. nov, from the Late Triassic fissure fill deposits of Pant-y-ffynnon in southern Wales. The species is represented by the holotype, consisting of an articulated pelvic girdle, sacrum and posterior dorsal vertebrae, and an associated left femur, and by two referred specimens, comprising an isolated dorsal vertebra and a partial left ischium. Our phylogenetic analysis recovers P. milnerae as a non-coelophysid coelophysoid theropod, representing the first-named unambiguous theropod from the Triassic of the UK. Recently, it has been suggested that Pant-y-ffynnon and other nearby Late Triassic to Early Jurassic fissure fill faunas might have been subjected to insular dwarfism. To test this hypothesis for P. milnerae , we performed an ancestral state reconstruction analysis of body size in early neotheropods. Although our results indicate that a reduced body size is autapomorphic for P. milnerae , some other coelophysoid taxa show a similar size reduction, and there is, therefore, ambiguous evidence to indicate that this species was subjected to dwarfism. Our analyses further indicate that, in contrast with averostran-line neotheropods, which increased in body size during the Triassic, coelophysoids underwent a small body size decrease early in their evolution.

A new carcharodontosaurian theropod dinosaur occupies apex predator niche in the early Late Cretaceous of Uzbekistan

Carcharodontosauria is a group of medium to large-sized predatory theropods, distributed worldwide during the Cretaceous. These theropods were probably the apex predators of Asiamerica in the early Late Cretaceous prior to the ascent of tyrannosaurids, although few Laurasian species are known from this time due to a poor rock record. Here, we describe Ulughbegsaurus uzbekistanensis gen. et sp. nov. from the early Late Cretaceous (Turonian) of Central Asia, which represents the first record of a Late Cretaceous carcharodontosaurian from the region. This new taxon is represented by a large, isolated maxilla from the Bissekty Formation of the Kyzylkum Desert, the Republic of Uzbekistan, a formation yielding a rich and diverse assemblage of dinosaurs and other vertebrates from fragmentary remains. Comparison of the maxilla with that of other allosauroids indicates Ulughbegsaurus was 7.5–8 m in body length and greater than 1000 kg in body mass, suggesting it was the previously unrecognized apex predator of the Bissekty ecosystem while smaller known tryannosauroids and dromaeosaurids were probable mesopredators. The discovery of Ulughbegsaurus records the geologically latest stratigraphic co-occurrence of carcharodontosaurid and tyrannosauroid dinosaurs from Laurasia, and evidence indicates carcharodontosaurians remained the dominant predators relative to tyrannosauroids, at least in Asia, as late as the Turonian.

Theropod tracks from the Jurassic–Cretaceous boundary, Tuchengzi Formation, Chengde, China: Review and new observations

Previously known theropod dinosaur footprints preserved as natural casts in the Tuchengzi Formation, on a rock wall beside the railway in Nanshuangmiao Village, Shangbancheng Town, Chengde City, were originally assigned to ichnogenus Anchisauripus and tentatively attributed to oviraptosaurs. The assemblage was restudied in more detail by examining the entire assemblage of 55 tracks associated with two horizons. The size range of the 27 measured tracks suggests a more diverse grallatorid–eubrontid assemblage and potentially greater diversity of theropod trackmakers. The label Anchisauripus, which has fallen into disuse in some recent literature, implies trackmakers of medium shape and size in the grallatorid–eubrontid morphological spectrum. However, given the presence of other theropod ichnotaxa in the Jurassic to Early Cretaceous strata of the Tuchengzi Formation and time equivalent units we suggest that explicit reference to the Grallator-Anchisauripus-Eubrontes (GAE) plexus, or simply the term Grallator-Eubrontes plexus be confined to Lower Jurassic assemblages as originally defined and intended. Further study centered on the 16 known Tuchengzi assemblages and older theropod ichnfaunas is necessary to confirm or refute the degree to which grallatorid–eubrontid assemblages from these different epochs are similar or convergent. Even if the tracks are morphologically very similar inferences regarding trackmaker identity are problematic because the same theropodan trackmaker species, genera or even families were not present in both epochs.

Art, Anatomy, and the Stars: Russell and Séguin’s Dinosauroid

It takes a bold, innovative mind to publish an exercise in speculative evolution pertaining to an alternative timeline. Dale Russell’s studies of the troodontid Stenonychosaurus and of ornithomimid theropods, published in 1969 and 1972, inspired him to consider the possibility that some theropod dinosaur lineages might have given rise to big-brained species had they never died out. By late 1980, Russell had considered the invention of a hypothetical descendant of Stenonychosaurus dubbed the ‘dinosauroid’. There is likely no specific inspiration for the dinosauroid given Russell’s overlapping areas of interest, but his correspondence with Carl Sagan and his involvement in the SETI programme were likely of special influence. The early-1980s creation of a life-size Stenonychosaurus model with Ron Séguin gave Russell the impetus to bring the dinosauroid to life. Authors have disagreed on whether the dinosauroid’s creation was an exercise in scientific extrapolation or one of speculative fiction, and on whether its form reflects bias or an honest experiment: Russell justified his decisions on the basis of the dinosauroid’s anatomy being adaptive and linked to efficiency, but he also stated or implied that the human form may be considered a predictable evolutionary outcome among big-brained organisms, and expressed a preference for directionist views which posit humans as close to the pinnacle of evolution. Both derided and praised at the time of its construction, the dinosauroid is undergoing a resurgence of interest. Given that its aim was to spark discussion and invite alternative solutions, it can only be considered an extraordinary success.