Fossil Friday: Ornitholestes

Guilty Macelognathus flees the crime scene at the sight of a witness! Ornitholestes just wants an easy snack, and this raided turtle nest looks perfect.

Species: Ornitholestes hermanni (Or-nih-thoe-less-teez Her-man-eye)

What it means: Bird robber

Other Species: None

Where I live: Wyoming, U.S.A.- The Morrison Formation

When to find me: The Late Jurassic period, about 154 million years ago.

My favorite food: Meat! I’m a carnivore.

Pete walking alongside Nanosaurus and Ornitholestes.

My neighborhood: The Morrison Formation covers a huge expanse of land with a variety of different habitats teaming with life. Most of it was very much like the Serengeti of modern day Africa, only with prairies of drought-tolerant ferns and cycad relatives instead of grass. Dense woodlands of tall conifers like the modern araucaria, ginkgoes, and tree ferns would only lie in places of plentiful water such as the few permanent rivers or low areas where the underground water table was shallow. Other areas had far more sparse and shrubbier vegetation like the open woodlands of acacia trees in the Serengetti.

Life in this environment would’ve adapted to long months of harsh drought, followed by a few months of monsoon that flooded the rivers. Many of the larger herbivores may have migrated like the herds in Africa do today, while most carnivores stayed behind to feast on the dead and dying, or else become opportunistic hunters of less traditional diets for lean times, such as fish or turtles in the rivers.

A few of my neighbors: First let me share the plant-eating giants and smaller friends who sometimes join me for lunch…

  • Long-necked sauropods like Apatosaurus, Brachiosaurus, Camarasaurus, Diplodocus, Barosaurus, Suuwassea, Supersaurus, Haplocanthosaurus, and Dystrophaeus.
  • Armored dinosaurs like Stegosaurus, Hesperosaurus, Mymoorapelta, and Gargoyleosaurus.
  • Two-legged ornithopods like Dryosaurus, Camptosaurus, and Nanosaurus

Fellow predators in the neighborhood include dinosaurs like Allosaurus, Torvosaurus, Ceratosaurus, Saurophaganax, Marshosaurus, Coelurus, Elaphrosaurus, Koparion, Stokesosaurus, and Tanycolagreus.

Plus there are all the small snacks scurrying around…countless lizards, crocodile relatives on land and water, mammals, frogs, turtles, fish. Pterosaurs fly in the sky after bugs.

Fun Facts:

  • Ornitholestes was discovered in July of the year 1900, the first theropod of the century.
  • The name Ornitholestes comes from the Greek words for bird (ornithos) + robber (llestes). The species name honors Adam Hermann, who was the head preparator at the American Museum of Natural History, and directed the preparation, restoration, and mounting of the fossils.
  • Mr. Osborn proposed that Ornitholestes was adapted to pursue Jurassic birds and small animals. The predator’s light build, long arms, and similar tooth shape to modern lizards that specialize in bird hunting led to this hypothesis.
  • For many years, artists have portrayed Ornitholestes leaping after something that looks like Archaeopteryx (or even labeled as such in books), even though Archaeopteryx lived across the Atlantic ocean and would never have met Ornitholestes in life!
  • Another common art trope is a little horn on the end of Ornitholestes’ snout. This was because of misinterpretation of the fossil skull. During fossilization the skull was badly crushed, and a small bone jutted up at the end of the snout that looked like a horn. It is now known that this horn was actually a broken piece of the snout that was pushed out of place.
  • Did Ornitholestes have feathers? The ever increasing number of fossils discovered with feathers, and its proposed relationship within Coelurosauria (dinos more closely related to birds than Allosaurus) seems to suggest that it could. At the moment it is only an educated guess, but if it did have feathers, it’s likely to have looked a lot like fur- like kiwi or emu feathers.

Fossil Finds:

Known from a single partial skeleton with a badly crushed skull. The fossils found include…

  • 45 vertebrae: three of them from the neck, eleven from the spine, a complete sacrum, and twenty-seven tail bones
  • A complete pelvic girdle
  • Pieces of the arms and hind legs

References:

Foster, John. Jurassic West: The Dinosaurs of the Morrison Formation and Their World. Indiana University Press, 2007

H. F. Osborn (1903). Ornitholestes hermanni, a new compsognathoid dinosaur from the Upper Jurassic. Retrieved October 14, 2021 from the American Museum of Natural History digital repository. https://digitallibrary.amnh.org/bitstream/handle/2246/1502//v2/dspace/ingest/pdfSource/bul/B019a12.pdf?sequence=1&isAllowed=y

“Ornitholestes.” Wikipedia, https://en.wikipedia.org/wiki/Ornitholestes

“Ornitholestes.” Prehistoric Wildlife, http://www.prehistoric-wildlife.com/species/o/ornitholestes.html

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