Nqwebasaurus

Type Species: Nqwebasaurus thwazi

Classification: Dinosauria – Saurischia – Theropoda – Tetanurae – Coelurosauria – Tyrannoraptora – Maniraptoromorpha – Ornithomimosauria

Time Period: Early Cretaceous

Location: South Africa  

Diet: Herbivore or Omnivore

The African dinosaur Nqwebasaurus – whose full name means ‘fast runner of the Kirkwood district’ – lived during the earliest stage of the Early Cretaceous. This is the only named coelurosaur discovered in Africa, and it shows that coelurosaurian dinosaurs lived in Gondwana 50 million years earlier than previously thought. 

This ornithomimosaur was small, only about a foot high and three feet in length. Its long, three-fingered hands had a partially opposable thumb and a recurved claw. Unlike most theropods – but in keeping with some other ornithomimosaurs – its first and second digits were recurved while the third claw was not. Ornithomimosaurs ran the gauntlet of dietary styles, and Nqwebasaurus was likely an herbivore, as it lacked serrations on its maxillary teeth and used gastroliths to assist in pulverizing its food. Skeptics point out that some predators use gastroliths – particularly those that eat fish and invertebrates; thus Nqwebasaurus may have been an omnivore.  Nqwebasaurus also had fewer teeth than most other theropods; ornithomimosaurs ran the gauntlet of teeth types, with some having few teeth, others having lots of teeth, and even some, like Gallimimus, who had no teeth but a keratinous bill! Some scientists speculate that Nqwebasaurus was partially feathered or had a feather coat for insulation; this reasoning is based on its relationship to other feathered dinosaurs.

Juravenator

Type Species: Juravenator starki 

Classification: Dinosauria – Saurischia – Theropoda – Tetanurae – Coelurosauria – Tyrannoraptora – Compsognathidae   

Time Period: Late Jurassic 

Location: Europe 

Diet: Carnivore

The small bipedal theropod Juravenator lived among the large islands and archipelagos of prehistoric France and Germany. During the Late Jurassic, much of modern western Europe was submerged by the Oxford Sea and shallow sea armlets of the Tethys Sea that were ringed with coral reefs. Emerging from this vast spider-web network of waterways were dry, forested islands cut by streams and lagoons. These islands catered to smaller terrestrial organisms: lizards, mammals, and a number of small-fry dinosaurs, Juravenator among them. This theropod lived alongside its larger cousin Compsognathus, the squirrel-like theropod Sciurumimus, and a number of paravians, such as Ostromia, Wellnhoferia, Alcmonavis, and of course the infamous Archaeopteryx. Juravenator is known from a single juvenile specimen that was twenty-nine inches head-to-tail. This fleet-footed hunter likely preyed on lizards, mammals, and insects. The scleral rings of Juravenator resemble those of nocturnal birds, suggesting that it was a night-time hunter (but some believe these scleral rings are due to the fact that it was a juvenile and that adults would’ve been daytime hunters). A patch of Juravenator’s skin shows dinosaur scales as well as traces of proto-feathers. 

Compsognathus

Type Species: Compsognathus longipes

Classification: Dinosauria – Saurischia – Theropoda – Tetanurae – Coelurosauria – Tyrannoraptora – Compsognathidae   

Time Period: Late Jurassic 

Location: Europe 

Diet: Carnivore

The small bipedal theropod Compsognathus lived among the large islands and archipelagos of prehistoric France and Germany. During the Late Jurassic, much of modern western Europe was submerged by the Oxford Sea and shallow sea armlets of the Tethys Sea that were ringed with coral reefs. Emerging from this vast spider-web network of waterways were dry, forested islands cut by streams and lagoons. These islands catered to smaller terrestrial organisms: lizards, mammals, and a number of small-fry dinosaurs, Compsognathus among them. This theropod lived alongside its smaller cousin Juravenator, the squirrel-like theropod Sciurumimus, and a number of paravians, such as Ostromia, Wellnhoferia, Alcmonavis, and of course the infamous Archaeopteryx. Compsognathus itself may have island-hopped all the way down to Portugal, for teeth that may belong to this dinosaur have been found in the Lourinha Formation. 

Compsognathus is known from two nearly complete specimens, one from France and one from Germany. The French specimen was forty-nine inches long, and the German specimen was 35 inches long. This lithe theropod likely weighed as little as seven pounds full grown. Compsognathus had long hind legs and a long tail, which it used for balance while running; some scientists have postulated that it could reach speeds up to forty miles per hour. Its forelimbs were smaller than its hindlimbs, and each hand bore two large clawed digits and a third, smaller digit that may have been non-functional. Their delicate skulls were long and narrow with tapered snouts. Its eyes were large in proportion to the skull, indicating that it was a visually-oriented predator that relied more on sight than smell for hunting. Its long neck enabled it to move its head side-to-side without moving its body, helping it spy out prey; and the long neck would’ve come in handy when plunging its head into the undergrowth to root out hiding prey. This dinosaur was designed for catching small and fast-moving prey like lizards that would’ve scurried into the undergrowth as soon as they were seen. Compsognathus’ speed is attested by a proportionately small humerus when compared to the lower legs, a trademark of a fast runner. It balanced itself on its toes rather than the flat of its foot, another design appropriate for speed; this digitigrade stance meant that the main foot bones extended the length of the leg and thus increased its stride. Its tail, held erect off the ground, would’ve served as a balancing aid as it chased prey through the wooded islands of prehistoric western Europe. Its small, sharp teeth were suited for a diet of small vertebrates and perhaps even insects. Its frontmost teeth were unserrated, but those farther back in the jaw were flattened and recurved. The specimens we have preserve part of its diet: in the French specimen, the remains of unidentified lizards and sphenodonts (lizard-like reptiles) are found in its thoracic cavity; in the German specimen, the articulated remains of a full lizard are in plain view. These lizard remains were originally thought to belong to an embryonic Compsognathus, which would’ve rewritten the book on dinosaur reproduction, but further research showed that it belonged to a Bavarisaurus lizard. This lizard was fast and agile, which meant that Compsognathus would’ve also needed to be fast and agile in order to hunt it. Compsognathus may also have preyed on small mammals, as its close Early Cretaceous relative Sinosauropteryx has been discovered with the remains of small mammals in its stomach. 

Some artistic renditions depict Compsognathus with feathers while others do not; this is because the presence of feathers or feather-like features on this theropod is hotly debated. While some of Compsognathus’ relatives have been preserved with the remains of simple feathers covering the body like fur, this isn’t the case with Compsognathus. Archaeopteryx, found in the same sediments as Compsognathus, is preserved with plenty of feathers, which means that the environment was suitable for feather preservation. A patch of fossilized skin from the tail and hind-limb of its close relative Juravenator show mainly scales, though there is some indication that simple feathers were present in some areas. There are thus three possibilities when it comes to Compsognathus: it may have been featherless, it may have had partial feathers such as may be the case with Juravenator, or it may have been fully feathered like its more distant cousins. The jury is out until more evidence comes in. 

a Compsognathus perches atop a dead juvenile dwarf sauropod

Ornitholestes

an artistic depiction of Ornitholestes with a nasal horn

Type Species: Ornitholestes hermanni

Classification: Dinosauria – Saurischia – Theropoda – Tetanurae – Coelurosauria – Tyrannoraptora – Maniraptoromorpha  

Time Period: Late Jurassic 

Location: United States 

Diet: Carnivore

The ‘bird robber’ Ornitholestes is known from a single partial skeleton with a badly crushed skull found in Wyoming at the turn of the 20th century (making it the first theropod discovering of the 1900s). Ornitholestes was a short-bodied theropod that grew to about eight feet in length and stood three feet tall at the hips. It had a relatively short neck with a slight sigmoidal (or S-shaped) curve. Its tail was long and whip-like and accounted for half its length. Its skull was proportionally smaller than that of most theropods, but it remained heavily built with a short snout and robust lower jaw. Its front teeth were conical-shaped with few serrations whereas the back teeth were recurved and sharply serrated like those of most theropods; the teeth didn’t extend as far back as its eyes, and neither tooth row spanned more than a third of the skull length. It’s likely that Ornitholestes used its front conical-shaped teeth for tearing flesh from its prey while the recurved back teeth were used to slice through the meat before swallowing. Ornitholestes’ forelimbs were relatively long, slightly under two-thirds the length of its hind legs. The first and second fingers of its three-clawed hands were the same size, but the claw bone was likely stunted. Ornitholestes was able to bend its forearm at an angle more acute than ninety degrees, which is characteristic of maniraptors but absent in more primitive theropods such as Coelophysis and Allosaurus. When Ornitholestes bent its elbow, its arms moved inwards towards its body; this would’ve increased in grasping ability. Though Ornitholestes is often portrayed as a fast, agile runner, its lower limb bones were relatively short. Some scientists believe that its innermost toe was larger than its other toes and suggest that it may have had a sickle claw similar to those of the dromaeosaurs. Many modern reconstructions depict Ornitholestes with a covering of feathers; this isn’t because feathers for this dinosaurs have been discovered but because they are present in so many of its kin that it’s thought by many that all coelurosaurs (to which Ornitholestes belongs) had some sort of rudimentary feathery covering. These feathers would’ve have been used for flight but for display, insulation, or for brooding eggs. Early depictions of Ornitholestes show it with a nasal horn akin to a chicken’s comb. When the specimen was discovered, it had an area of broken bone near the nostril that appeared to bulge upwards. Paleontologist Gregory S. Paul interpreted this as a nasal horn, but this interpretation has been rejected; the upward flare of crushed bone was likely due to post-mortem crushing of the skull. Below is a modern depiction of Ornitholestes - covered in fur, eating an early mammal, and lacking a nasal horn:

Debate swirls around Ornitholestes’ diet. When it was first discovered, it was argued that it utilized its grasping ability and the balancing power of its tail to catch birds. Though this theory had its detractors – a simultaneous theory was that its strange tooth design indicated a ‘transitional’ stage between a carnivorous and herbivorous diet – the original theory gained steam and became the dominant theory (hence the meaning of Ornitholestes’ name, ‘Bird Robber’). Over the decades, both the ‘bird robber’ and transitional diet theories have faded out of vogue. Most modern paleontologists believe that Ornitholestes preyed upon small terrestrial vertebrates such as mammals, lizards, frogs, and even dinosaur hatchlings. Another theory is that Ornitholestes used its front conical teeth to catch fish in the many streams, rivers, and lakes of the Morrison Formation, and some scientists  believe that Ornitholestes engaged in pack hunting behavior to bring down medium-sized prey such as the ornithopod Camptosaurus. Some argue that Ornitholestes and its slightly larger contemporary Coelurus lived side-by-side by utilizing niche partitioning in which Coelurus hunted at night and Ornitholestes hunted during the day. 

Coelurus

Type Species: Coelurus fragilis 

Classification: Dinosauria – Saurischia – Theropoda – Tetanurae – Coelurosauria – Tyrannoraptora – Maniraptoromorpha  

Time Period: Late Jurassic 

Location: United States 

Diet: Carnivore

Coelurus was the first small theropod from the Morrison Formation to be named, and it was named after the numerous hollow spaces – called pleurocels – oddly distributed among its vertebrae. These pneumatic vertebrae lightened the skeleton, making Coelurus more swift of foot and lightweight. It grew up to eight feet in length, stood two feet tall at the hips, and weighed around forty pounds. Its elongated neck vertebrae gave it a longer neck than is seen in most theropods, and its long, slender hind legs indicate that it was a lightly-built swift runner, certainly faster than its similar but shorter-footed contemporary Ornitholestes. It shared its environment with much larger dinosaurs, and it may have needed to use its speed to avoid being preyed upon by larger theropods (or from being trampled by hapless sauropod herds). It likely hunted lizards and early mammals, though it may have preyed upon smaller ornithopods such as Dryosaurus and Othnielosaurus, particularly if they were weak or juvenile. While there’s no indication that Coelurus hunted in packs, it’s possible that it utilized pack-hunting behavior in taking down smaller-sized ornithopods. 

Coelurus lends its name to the clade Coelurosauria, which in the early days of dinosaur taxonomy included all small theropod dinosaurs. Our knowledge of dinosaur relationships has greatly increased, so now Coelurosauria includes all theropod dinosaurs more closely related to birds than to carnosaurs. Coelurosauria branches off into well-known dinosaur groups such as the dromaeosaurs, the ornithomimosaurs, and the tyrannosaurs. Coelurus belongs to the Tyrannoraptorans,  members are all descendants of the last common ancestor of Tyrannosaurus rex and the common house sparrow; within that clade, Coelurus is a member of the smaller clade Maniraptoromorpha, which is a ‘transition’ clade between the tyrannoraptorans and the ‘New Coelurosaurs’ (Neoceolurosauria), which includes all compsognathids and the maniraptoriformes. Coelurus’ placement indicates that it’s somewhat of an oddball in theropod taxonomy, and its only concrete neighbor was its Morrison Formation contemporary Ornitholestes.