page_title: List of dinosaurs of the Morrison Formation
section_title: Coelurosaurs
hierarchical_section_title: List of dinosaurs of the Morrison Formation / Theropods / Coelurosaurs
caption_attribution_description: English: A side view portrait of Hesperornithoides
context_page_description: The Morrison Formation is a distinctive sequence of Upper Jurassic sedimentary rock that is found in the western United States, which has been the most fertile source of dinosaur fossils in North America. It is composed of mudstone, sandstone, siltstone and limestone and is light grey, greenish gray, or red. Most of the fossils occur in the green siltstone beds and lower sandstones, relics of the rivers and floodplains of the Jurassic period.
context_section_description: Coelurosaurs, more derived types more closely related to birds, included Coelurus fragilis, Ornitholestes hermanni, Tanycolagreus topwilsoni, the possible troodontid Koparion douglassi, the definite troodontid Hesperornithoides, and the early tyrannosauroid Stokesosaurus clevelandi.
caption: Hesperornithoides
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