Minimocursor

MEANING: Smallest runner

PERIOD: Late Jurassic

CONTINENT: Asia

Minimocursor is a basal neornithischian dinosaur that is thought to have been abundant. It is the oldest and most completely known neornithischian from Southeast Asia. Like other small-bodied basal neornithischians, it ran on two legs and had a pointed beak. It is thought that adults could grow up to 2 m in body length.

Abstract from paper: An exceptional articulated skeleton of a new basal neornithischian dinosaur, Minimocursor phunoiensis gen. et sp. nov., was discovered in the Late Jurassic Phu Kradung Formation at the Phu Noi locality, Kalasin Province, Thailand, a highly productive non-marine fossil vertebrate locality of the Khorat Plateau. It is one of the best-preserved dinosaurs ever found in Southeast Asia. Minimocursor phunoiensis gen. et sp. nov. shows a combination of both plesiomorphic and apomorphic characters resembling those of Late Jurassic to Early Cretaceous small-bodied ornithischians from China: a low subtriangular boss is projected laterally on the surface of the jugal, the brevis shelf of the ilium is visible in lateral view along its entire length, a distinct supraacetabular flange is present on the pubic peduncle of the ilium, the prepubis tip extends beyond the distal end of the preacetabular process of the ilium, and the manus digit formula is ?-3-4-3-2. The phylogenetic analysis shows that this dinosaur is among the most basal neornithischians. This study provides a better understanding of the early evolution and taxonomic diversity of ornithischians in Southeast Asia.

Minimocursor is from the Late Jurassic. The Late Jurassic was a dynamic period, spanning from about 162 to 143 million years ago. The continents were continuing to drift apart, and the supercontinent Pangaea had fully split into Laurasia in the north and Gondwana in the south. This continental rearrangement led to the formation of large inland seas and shallow coastlines that fostered diverse ecosystems. The climate during the Late Jurassic was warm and humid, with lush forests of conifers and ferns that stretched across much of the continents, creating a rich ecosystem where dinosaurs flourished the dominant land animals.

Dinosaurs continued to diversify through the Late Jurassic, with some of the most famous species evolving in this time. Many well-known sauropods, such as Brachiosaurus and Apatosaurus roamed the land, exhibiting niche partitioning with their selectively distinct neck positions. Alongside them, stegosaurs became widespread, their plates and spikes making them one of the era's most recognizable groups. Theropods like Allosaurus and Ceratosaurus were the apex predators, evolving large, powerful bodies and sharp teeth that allowed them to hunt the gigantic herbivores. The early evolution of birds was taking place, setting the stage for the numerous species that would fill the skies in the eras to come.

Unlike the dramatic mass extinctions that marked the beginning and end of the Mesozoic, the Jurassic Period ended without a sharp boundary. As the continents continued to drift, ecosystems gradually transformed into unique habitats that supported the more specialized dinosaur species of the Cretaceous.

Minimocursor is a basal ornithischian. Ornithischia is one of the two major clades of dinosaurs, sister to the saurischia, which includes theropods and sauropods. Basal ornithischians were small, lightly built herbivores or omnivores and were typically bipedal, with long hind limbs and relatively short forelimbs, well-suited for swift movement. Their body plans were often simple, lacking the extreme specializations seen in later ornithischians like ceratopsians or hadrosaurs. Many had simple, triangular skulls with leaf-shaped teeth, suitable for cropping low vegetation, and some evidence suggests they may have lived in groups. Though they form the base of the ornithischian family tree, they do not belong to any of the more derived subgroups and instead exhibit a mix of ancestral traits.

Basal ornithischians are mostly known from the Jurassic. The absence of definitively known ornithischians from the Triassic has puzzled paleontologists, though some propose that certain Triassic animals, like the silesaurs, may fill this gap. However, these relationships remain debated. As the Jurassic progressed, basal forms gave rise to a wide array of more specialized ornithischians, but these early dinosaurs remain a crucial and still somewhat mysterious chapter in the evolutionary history of the group.