Learning from time

With the rise of deep learning, computer vision systems have been highly successful at understanding images. However, understanding the dynamic visual world we live in requires both understanding the appearances of individual image frames, and the temporal relationships between them. This thesis aims to understand videos through the lens of time, by learning from the temporal relationships within image sequences, both instantaneously and over a period of time. In the first half, we focus on using instantaneous motion – temporal changes between neighbouring video frames – to discover moving objects, based on the intuition that the subject in the video usually moves independently from the background. We propose two methods that can solve this task: first, for a single object in a self-supervised manner by grouping motion into layers, and second, for multiple objects over time in a supervised manner using a vision foundation model. We show applications towards general videos, as well as discovering objects with minimal visibility such as camouflages, where we also present the largest video camouflage dataset to date. In the second half, we go beyond instantaneous changes and learn from patterns of changes over time, from seconds (natural videos) to days (time-lapse videos) to years (longitudinal images). We leverage the properties of time as a direct supervisory signal, and introduce applications that were previously unachievable in computer vision. We first exploit “uniformity” – that time flows at a constant rate, to read analog clocks in unconstrained scenes. We then relax this constraint to “monotonicity” – that certain changes are consistently unidirectional over a period of time, to discover monotonic changes in a sequence of images. For both cases, we also contribute datasets to foster further research

The postcranial skeleton of Monolophosaurus jiangi (Dinosauria: Theropoda) from the Middle Jurassic of Xinjiang, China, and a review of Middle Jurassic Chinese theropods

The Middle Jurassic was a critical time in the evolution of theropod dinosaurs, highlighted by the origination and radiation of the large-bodied and morphologically diverse Tetanurae. Middle Jurassic tetanurans are rare but have been described from Europe, South America and China. In particular, China has yielded a number of potential basal tetanurans, but these have received little detailed treatment in the literature. Here we redescribe the postcranial skeleton of one of the most complete Chinese Middle Jurassic theropods, Monolophosaurus. Several features confirmthe tetanuran affinities of Monolophosaurus, but the possession of ‘primitive’ traits such as a double-faceted pubic peduncle of the ilium and a hood-like supracetabular crest suggest a basal position within Tetanurae. This conflicts with most published cladistic analyses that place Monolophosaurus in a more derived position within Allosauroidea.We review the Middle Jurassic record of Chinese theropods and compare Monolophosaurus to other Middle Jurassic theropods globally. These comparisons suggest that Monolophosaurus and Chuandongocoelurus formed an endemic theropod clade limited to the Middle Jurassic of Asia. Other Middle Jurassic Chinese theropods deserve further study

Mother Me, Tennessee

Man standing by tree with fence and field in backgroundhttps://scholarsjunction.msstate.edu/cht-sheet-music/9315/thumbnail.jp

You Came Along

Title onlyhttps://scholarsjunction.msstate.edu/cht-sheet-music/11042/thumbnail.jp

The anatomy and systematic position of the theropod dinosaur Chilantaisaurus tashuikouensis Hu, 1964 from the Early Cretaceous of Alanshan, People's Republic of China

There is little consensus on the systematic position of the colossal theropod dinosaur Chilantaisaurus tashuikouensis from the Cretaceous (Aptian–?Albian or Upper Cretaceous) Ulansuhai Formation of Inner Mongolia, which has been recovered as a derived member of both Allosauroidea and Spinosauroidea by numerical phylogenetic analyses. Redescription of the type material of C. tashuikouensis reveals an unusual combination of morphological features that render determination of its systematic position problematic. It possesses anatomical features that have been proposed as synapomorphies of Neotetanurae: a preacetabular fossa on the ilium, and a wedge-shaped cross-section of the shaft of the third metatarsal. It also shares some features with specific allosauroid taxa: a pronounced ulnar epicondyle on the humerus, and a prominent medial shelf bounding the preacetabular fossa on the ilium (also present in tyrannosauroids). However, it lacks some features that are present in all other allosauroids: a marked depression on the anterior surface of the distal humerus adjacent to the ulnar condyle, and a humerus that is less than 0.4 times the length of the femur; it furthermore possesses a tibial astragalar facet that is approximately 10% of the tibial length, which suggests a more basal position within Tetanurae. Chilantaisaurus shares certain features with some spinosauroids: an enlarged and elongated first manual ungual, and a suprastragalar buttress that has been modified to a vertical ridge, but these characters are not unique to spinosauroids. A highly reduced fourth trochanter may be an autapomorphy of Chilantaisaurus, as has previously been suggested, or unite the taxon with Coelurosauria in an entirely novel grouping. On the basis of these observations it is likely that Chilantaisaurus is a neotetanuran, but unlikely that it is an allosauroid. Chilantaisaurus may belong to an alternative lineage of very large theropods that continued into the Cretaceous from the diversification of basal neotetanurans during the Middle Jurassic

Craving

Oval picture of man with flowers around him and bird to his righthttps://scholarsjunction.msstate.edu/cht-sheet-music/9112/thumbnail.jp

The higher-level phylogeny of Archosauria (Tetrapoda:Diapsida)

Crown group Archosauria, which includes birds, dinosaurs, crocodylomorphs, and several extinct Mesozoic groups, is a primary division of the vertebrate tree of life. However, the higher-level phylogenetic relationships within Archosauria are poorly resolved and controversial, despite years of study. The phylogeny of crocodile-line archosaurs (Crurotarsi) is particularly contentious, and has been plagued by problematic taxon and character sampling. Recent discoveries and renewed focus on archosaur anatomy enable the compilation of a new dataset, which assimilates and standardizes character data pertinent to higher-level archosaur phylogeny, and is scored across the largest group of taxa yet analysed. This dataset includes 47 new characters (25% of total) and eight taxa that have yet to be included in an analysis, and total taxonomic sampling is more than twice that of any previous study. This analysis produces a well-resolved phylogeny, which recovers mostly traditional relationships within Avemetatarsalia, places Phytosauria as a basal crurotarsan clade, finds a close relationship between Aetosauria and Crocodylomorpha, and recovers a monophyletic Rauisuchia comprised of two major subclades. Support values are low, suggesting rampant homoplasy and missing data within Archosauria, but the phylogeny is highly congruent with stratigraphy. Comparison with alternative analyses identifies numerous scoring differences, but indicates that character sampling is the main source of incongruence. The phylogeny implies major missing lineages in the Early Triassic and may support a Carnian-Norian extinction event.Marshall Scholarship for study in the United KingdomJurassic FoundationUniversity of BristolPaleontological Societ