Saurornitholestes

Chapter • Meet the dinosaur

Overview

Saurornitholestes langstoni was a small, lightly built predatory dinosaur, roughly 1.8–2 metres long and weighing an estimated 6–12 kilograms – about the mass of a large fox, but with a far longer tail. It carried its body horizontally over two long, slender hind legs, with a stiffened tail acting as a counterbalance. The second toe of each foot bore the enlarged sickle-shaped claw typical of dromaeosaurids, held clear of the ground while walking. The skull was light and comparatively long, with large eye sockets. Close relatives preserved with skin and feather impressions show that this whole group was feathered, and the closely related Velociraptor preserves quill knobs on the forearm. Saurornitholestes is therefore reconstructed today with a full coat of feathers, wing-like arm feathers and a feather fan at the tail tip – even though feathers have never been found directly with this species. Its teeth reveal a lot about its lifestyle. They were curved, blade-like and serrated, but the denticles on the back edge were markedly larger than those on the front – a pattern distinctive enough that isolated Saurornitholestes teeth can be identified without any other bones. In their 2019 description of a nearly complete skull, Philip Currie and David Evans showed that the first premaxillary tooth was unusually long and fang-like, with a D-shaped cross-section. They suggested it may have been used to strip feathers and flesh from prey, or possibly for preening the animal's own plumage. Saurornitholestes was a predator that most likely targeted animals smaller than itself: lizards, early mammals, juvenile pterosaurs, hatchling and young plant-eating dinosaurs, and eggs. A wing bone from a large azhdarchid pterosaur from the Dinosaur Park Formation carries bite marks and a broken-off dromaeosaurid tooth, showing that these animals at least fed on pterosaur carcasses. The sheer abundance of the fossils – Saurornitholestes is the most common small predatory dinosaur in the formation – suggests it was a numerous and successful part of the ecosystem. The holotype was found in 1974 by amateur collector Irene Vanderloh in Dinosaur Provincial Park, Alberta, Canada, and described in 1978 by Hans-Dieter Sues. The species name honours the American palaeontologist Wann Langston Jr., while the genus name means roughly "lizard-bird thief", a nod to how bird-like the skeleton is. Additional material has turned up in the Judith River Formation of Montana and the Fruitland and Kirtland formations of New Mexico, though much of it consists of isolated teeth and scattered bones. Only with the skull described in 2019 did researchers gain a clear picture of what the head actually looked like.

Chapter • Where it lived

Habitat

Saurornitholestes lived roughly 76.5–74.8 million years ago, in the later part of the Cretaceous (the Campanian stage). Its fossils come almost entirely from western North America, above all from the Dinosaur Park Formation of Alberta, Canada, but also from the Judith River Formation of Montana and the Fruitland and Kirtland formations of New Mexico. The landscape was a warm, humid coastal floodplain along the Western Interior Seaway, crossed by meandering rivers and dotted with swamps, lagoons and stands of conifers, cycads and early flowering plants. Here Saurornitholestes shared its world with horned dinosaurs such as Centrosaurus, duck-billed Corythosaurus, armoured ankylosaurs, the large tyrannosaurid Gorgosaurus, as well as turtles, crocodilians, lizards and huge azhdarchid pterosaurs.

Chapter • Wild behavior

Behavior & Ecology

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Chapter • Scientific place

Taxonomy