Glossary

Dromaeosauridae is a family of feathered coelurosaurian theropod dinosaurs that ranged in size from crow-sized to polar-bear-sized, spanning the Middle Jurassic (based on isolated teeth, approximately 167 million years ago) to the end-Cretaceous mass extinction (66 million years ago), with the earliest definitive body fossils dating to the Early Cretaceous. Found across Asia, North America, South America, Europe, and Africa, these bipedal carnivores are characterized by a hypertrophied, sickle-shaped claw on the second pedal digit that was held retracted off the ground during locomotion, a semi-lunate carpal bone in the wrist enabling lateral flexion of the hands (a motion homologous to the avian flight stroke), and a long tail stiffened by overlapping bony extensions of the caudal vertebral arches. Musculoskeletal modelling studies indicate the sickle claw was better suited for piercing and pinning prey in a manner analogous to extant raptorial birds rather than for disembowelling, supporting the 'raptor prey restraint' (RPR) hypothesis. Within the clade Paraves, Dromaeosauridae and Troodontidae together form Deinonychosauria, which is widely recovered as the sister group to Avialae (the clade containing all birds). This phylogenetic position makes dromaeosaurids central to understanding feather evolution, the origin of flight, and the reassessment of dinosaurian activity levels that defined the Dinosaur Renaissance of the late twentieth century.

Maniraptora is a stem-based clade of coelurosaurian theropod dinosaurs defined as all dinosaurs closer to modern birds than to *Ornithomimus velox*. First named by Jacques Gauthier in 1986, the clade first appears in the fossil record during the Jurassic period (with the alvarezsaur *Haplocheirus* from the late Middle Jurassic, approximately 160 million years ago) and persists to the present day in the form of birds—the only surviving dinosaur lineage. Its non-avian members went extinct at the end-Cretaceous mass extinction (66 million years ago). Maniraptorans are united by a suite of shared derived characters including a semilunate carpal bone enabling lateral wrist flexion (later co-opted for the avian flight stroke), a fused furcula (wishbone), elongated forelimbs, and in many lineages a retroverted pubis. The clade encompasses Therizinosauria, Alvarezsauria, Oviraptorosauria, and Paraves (which includes Dromaeosauridae, Troodontidae, and Avialae), representing an extraordinary range of body plans and ecological niches. Dietary diversification was a major trend: at least six independent shifts toward herbivory occurred within Maniraptora, with only Dromaeosauridae maintaining primarily carnivorous habits. The lineage leading directly to birds underwent sustained miniaturization across approximately 50 million years and at least 12 consecutive branches, during which key avian features—pennaceous feathers, flight-related limb modifications, brooding behaviour—evolved progressively. Maniraptora thus constitutes the evolutionary framework within which the origin of birds and powered flight is understood.

**Oviraptorosauria** is a clade of feathered maniraptoran theropod dinosaurs from the Cretaceous period (approximately 125–66 million years ago), known from Asia and North America. Positioned within Pennaraptora—the group uniting oviraptorosaurs and paravians—they are characterized by short, deep, highly pneumatized skulls bearing toothless beaks in derived forms (or reduced dentition in basal members) and, in many species, prominent cranial crests. The two major derived lineages, Caenagnathidae and Oviraptoridae, differ markedly in mandibular morphology, geographic distribution, and inferred feeding ecology: caenagnathid jaws were generally slender and adapted for shearing, whereas oviraptorid jaws were robust and suited for powerful crushing bites. Oviraptorosaurs provide some of the most compelling fossil evidence for avian-style brooding behavior in non-avian dinosaurs, with multiple specimens preserved sitting atop egg clutches in postures closely resembling those of modern nesting birds. This brooding evidence, combined with the presence of pennaceous feathers, egg pigmentation, and a progressive trend toward tooth loss across the clade, makes Oviraptorosauria one of the most important groups for understanding the evolutionary transition from non-avian dinosaurs to birds.

Prosauropoda is an informal taxonomic grouping of sauropodomorph dinosaurs that lived from the Late Triassic to the Early Jurassic period (approximately 230–180 million years ago) and achieved a global distribution across nearly all continents. The group was named by German paleontologist Friedrich von Huene in 1920 to unite the presumed ancestral stock of the giant Sauropoda. Representative genera include Plateosaurus, Massospondylus, Lufengosaurus, Riojasaurus, Thecodontosaurus, and Melanorosaurus, ranging in body length from roughly 1 to 12 meters. Morphologically, prosauropods were characterized by small skulls relative to body size, leaf-shaped (phyllodont) teeth with coarse serrations, elongated necks of approximately ten cervical vertebrae, and hindlimbs substantially longer than their forelimbs. Most were herbivorous or omnivorous, and the majority were obligate or facultative bipeds, though more derived forms transitioned toward quadrupedality. During the Late Triassic, prosauropods constituted the first globally dominant radiation of large herbivorous dinosaurs, comprising up to 95 percent of known biomass in some communities. However, modern cladistic analyses have consistently demonstrated that Prosauropoda as traditionally conceived is a paraphyletic assemblage—a grade of increasingly sauropod-like basal sauropodomorphs rather than a natural monophyletic clade. Consequently, the term 'basal Sauropodomorpha' is now preferred in formal systematic contexts, though 'prosauropod' remains widely used informally for convenience.

**Saurischia** is one of the two major lineages of dinosaurs, characterized by a pelvis in which the pubis points forward and downward, retaining the ancestral reptilian condition. The clade comprises two morphologically disparate subgroups: the predominantly carnivorous **Theropoda** and the herbivorous **Sauropodomorpha**. Key synapomorphies uniting these subgroups, as formalized through cladistic analysis, include elongated posterior cervical vertebrae, accessory articulations (hyposphene–hypantrum) on trunk vertebrae, a hand nearly half the length of the forearm or longer, the second digit being the longest finger, and a robust first digit (thumb) with a large claw borne on a short, laterally deflected metacarpal. Saurischians first appear in the fossil record during the Late Triassic, approximately 235 million years ago, with early representatives such as *Eoraptor* and *Herrerasaurus* known from the Ischigualasto Formation of Argentina. The most significant evolutionary legacy of Saurischia is the origin of **birds** from within the theropod lineage (specifically Maniraptora), meaning that all approximately 10,000 living bird species are saurischian dinosaurs, making this clade the only dinosaur lineage to have survived the end-Cretaceous mass extinction and persist to the present day.

Sauropoda is a clade of saurischian dinosaurs within Sauropodomorpha, encompassing the largest terrestrial animals in Earth's history. They first appeared in the Late Triassic (approximately 230 million years ago), reached peak diversity and abundance during the Late Jurassic through Early Cretaceous (approximately 150–120 million years ago), and persisted until the end-Cretaceous mass extinction approximately 66 million years ago — a duration of over 140 million years. Sauropods are characterized by extremely long necks and tails, proportionally small heads, columnar limbs, and an obligate quadrupedal stance. Typical sauropod species had body masses of 15–40 metric tonnes by conservative estimates, while the largest forms such as Argentinosaurus are estimated at 65–75 tonnes. This unprecedented gigantism was enabled by a specific combination of ancestral traits and evolutionary innovations, including an avian-style air-sac respiratory system that pneumatized the axial skeleton and reduced body density, a non-masticatory feeding strategy that permitted a lightweight skull, high basal metabolic rates supporting rapid growth, and an oviparous reproductive mode that allowed faster population recovery than in large mammalian herbivores. Sauropod fossils have been recovered from every continent including Antarctica, and as the dominant megaherbivores of Mesozoic terrestrial ecosystems, they played a central ecological role throughout their long evolutionary history.

**Theropoda** is a clade of saurischian ("lizard-hipped") dinosaurs that first appeared in the Late Triassic, approximately 235 million years ago, with non-avian members persisting until the end-Cretaceous extinction event 66 million years ago. The group is predominantly composed of bipedal, carnivorous dinosaurs characterized by hollow, thin-walled (pneumatic) bones, sharp recurved serrated teeth, three main weight-bearing toes on bird-like feet, and reduced forelimbs with clawed grasping hands. Theropods exhibit the widest body-size range of any dinosaur group, spanning from the crow-sized *Microraptor* to enormous predators such as *Spinosaurus* (estimated at 14–15 metres in length) and *Tyrannosaurus rex* (up to 12–13 metres). Phylogenetically, Theropoda includes all birds, meaning that approximately 11,000 living avian species are direct descendants of theropod dinosaurs. This makes Theropoda the only dinosaur lineage that survives to the present day, representing one of the most significant evolutionary success stories in vertebrate history — from apex terrestrial predators of the Mesozoic to the globally distributed avian diversity of the modern era.

Tyrannosauridae is a family of large-bodied coelurosaurian theropod dinosaurs that dominated apex predator niches in Late Cretaceous ecosystems of Laramidia (western North America) and Asia, from approximately 80 to 66 million years ago. The family is divided into two subfamilies: Albertosaurinae, which includes the more gracile genera Albertosaurus and Gorgosaurus from North America, and Tyrannosaurinae, which encompasses the more robustly built genera Daspletosaurus, Teratophoneus, Tarbosaurus, Zhuchengtyrannus, Nanuqsaurus, and Tyrannosaurus. Tyrannosaurids are characterized by massive, deep skulls with fused nasal bones, heterodont dentition featuring D-shaped premaxillary teeth and thick, peg-like lateral teeth suited for bone-crushing bites, proportionally tiny two-fingered forelimbs, long and powerful hindlimbs with an arctometatarsalian foot structure, and forward-facing eyes that afforded binocular vision. The largest member of the family, Tyrannosaurus rex, exceeded 13 metres in length and is estimated to have weighed up to approximately 8.4 metric tons, with a maximum bite force estimated at 35,000 to 57,000 newtons at the posterior teeth—the highest of any known terrestrial animal. Tyrannosaurids occupied the role of top predators until the end-Cretaceous mass extinction event approximately 66 million years ago, and their evolutionary success across diverse Laurasian environments makes them among the most studied groups of non-avian dinosaurs.