Virtual Museum: Basal Coelurosauran Theropods

The Compsognathidae are primitive members of the Coelurosauria, the clade of theropods that includes all of the remaining groups covered below. This group is characterized by the presence of either simple protofeathers or more complex feathers (feathers may also be present in other theropods, but there has been no direct evidence for any non-coelurosaurs).

Compsognathus sp., like other members of this family, are small, agile dinosaurs. The exact makeup of this family, and their relationships to other coelurosaurs, is still debated. Reconstructed skeleton.

Taxonomy: Theropoda, Coelurosauria, Compsognathidae

Europe

Late Jurassic Period, 150 Ma

Museum of Ancient Life, Utah

Compsognathus longipes fossil cast.

Taxonomy: Theropoda, Coelurosauria, Compsognathidae

Solnhofen, Germany

Late Jurassic Period, 150 Ma

New Mexico Museum of Natural History & Science

Cast of Scipionyx samniticus fossil of a juvenile (possibly only a few days old) that preserved some internal structures (by 3D mineralization rather than impressions, including trachea, liver, stomach, intestine, muscles, and claw sheaths.

Taxonomy: Theropoda, Coelurosauria, Compsognathidae

Italy

Early Cretaceous, Albian Stage

Black Hills Institute Museum, South Dakota

Life model of Compsognathus sp. It should probably be covered in simple filamentous feathers.

Taxonomy: Dinosauria; Therapoda; Compsognathidae

Late Jurassic Period, 150 Ma; Europe

Museum of Ancient Life, Utah

Life model of Sinosauropteryx prima, the first dinosaur to be discovered covered in filamentous proto-feathers. In life, it was likely a tawny or buffy coloration with darker brown bands on its tail and a dark mask on its face.

Taxonomy: Dinosauria; Therapoda; Compsognathidae

Early Cretaceous Period, 130-125 Ma; China

Fernbank Museum of Natural History, Georgia

The Tyrannosauroidea is famous for its most derived members, but the more ancestral members of this groups were small, three-fingered, fairly long-armed dinosaurs similar to the Compsognathids. Some of these ancestral forms had simple "protofeathers." They had blunt tips to their snouts and had a distinct type of nipping tooth on the premaxillary bones.

Suskityrannus hazelae was formally described in 2019.

Taxonomy: Theropoda, Tyrannosauroidea, Basal Tyrannosauroids

Zuni Basin, New Mexico

late Cretaceous Period, 92 Ma

Arizona Museum of Natural History

The exact evolutionary position of Tanycolagreus sp. is debated: it may be a basal Tyrannosauroid.

Taxonomy: Theropoda, Coelurosauria

Morisson Formation, western North America

Late Jurassic Period, 153-150 Ma

Museum of Ancient Life, Utah

Life model of Dilong paradoxus, a small primitive relative of Tyrannosaurus and known to be covered in filamentous feathers.

Taxonomy: Dinosauria; Therapoda; Tyrannosauroidea

Early Cretaceous Period, 130-125 Ma; China

Fernbank Museum of Natural History, Georgia

The derived Tyrannosauridae are all very large predators with big heads and greatly reduced arms with only 2 fingers.

Albertosaurus sarcophagus is a fairly typical tyrannosaurid. It was about 9-10 m long.

Taxonomy: Theropoda, Tyrannosauroidea, Tyrannosauridae

Western North America

Late Cretaceous Period, 73-70 Ma

San Diego Natural History Museum

Gorgosaurus libratus is closely related to Albertosaurus (above), and is sometimes placed in that genus.

Taxonomy: Theropoda, Tyrannosauroidea, Tyrannosauridae

Two Medicine Formation, Teton Co., Montana

Late Cretaceous, Campanian Stage

Black Hills Institute Museum, South Dakota

Tarbosaurus bataar is a close relative of Tyrannosaurus rex. This specimen is a subadult.

Taxonomy: Theropoda, Tyrannosauroidea, Tyrannosauridae

Asia

Late Cretaceous Period, 70 Ma

Arizona Museum of Natural History

Bistahieversor sealeyi skull.

Taxonomy: Theropoda, Tyrannosauroidea, Tyrannosauridae

Kirtland Formation, New Mexico

Late Cretaceous Period, 75 Ma

New Mexico Museum of Natural History & Science

Alioramus sp. was a long-snouted tyrannosaur (skull cast).

Taxonomy: Theropoda, Tyrannosauroidea, Tyrannosauridae

Nemegt Beds, Mongolia

Late Cretaceous Period, Maastrichtian Stage, 68 Ma

Wyoming Dinosaur Center

Appalachiosaurus montgomeriensis is a basal member of the Tyrannosauridae or lies just outside this family. It is one of the few late Cretaceous dinosaurs from the eastern United States.

Taxonomy: Theropoda, Tyrannosauroidea, Tyrannosauridae?

Demopolis Chalk Formation, southeastern United States

Late Cretaceous Period, 77 Ma

Rocky Mountain Dinosaur Resource Center, Colorado

The skulls of tyrannosaurids changed considerably as they grew. These two skulls are from Daspletosaurus horneri, with the adult (holotype) at left and a late juvenile or subadult on the right.

Taxonomy: Theropoda, Tyrannosauroidea, Tyrannosauridae

Glacier Co., Montana

Late Cretaceous Period

Museum of the Rockies, Montana

Nanotyrannus lancensis is one of the most controversial dinosaurs, as many researchers believe it to be a juvenile Tyrannosaurus rex (see below). Although its skull (this is a cast of the holotype, the specimen used to name this species) is quite different from adult T. rex, other Tyrannosaurids show considerable change in the shape of the skull and the shape and number of teeth as they grew. More complete specimens may be needed to settle the debate.

Taxonomy: Theropoda, Tyrannosauroidea, Tyrannosauridae

Hell Creek Formation, Carter Co., Montana

Late Cretaceous, Upper Maastrichtian Stage

Black Hills Institute Museum, South Dakota

Tyrannosaurus rex is one of the most familiar and popular dinosaurs. It is the largest member of the Tyrannosauridae, about 12.5 m long. It had an exceptionally strong bite and its thick teeth were adapted for crushing bone.

Taxonomy: Theropoda, Tyrannosauroidea, Tyrannosauridae

Western North America

Late Cretaceous Period, Maastrichtian Stage, 67-66 Ma

Museum of Ancient Life, Utah

Tyrannosaurus rex skeleton with 60% real bone; replicated material in lighter color.

Taxonomy: Theropoda, Tyrannosauroidea, Tyrannosauridae

Hell Creek Formation, McCone Co., MT

Late Cretaceous Period, Maastrichtian Stage, 67-66 Ma

Museum of the Rockies, Montana

Adult Tyrannosaurus rex with juvenile (brown) and baby (tan) reconstructed skeletons. The juvenile is probably based on Nanotyrannus (which could be a juvenile T. rex) while the baby is based on a skull fragment now thought to belong to Daspletosaurus. Post-cranial remains are not well known for young T. rex so these skeletons are mostly extrapolated from young Tarbosaurus skeletons.

Taxonomy: Theropoda, Tyrannosauroidea, Tyrannosauridae

Montana

Late Cretaceous Period, Maastrichtian Stage, 67-66 Ma

Los Angeles Museum of Natural History

Tyrannosaurus rex skull growth series. The far left baby ("Chomper") is extrapolated from just a few skull pieces using a more complete 2-3 year old skull of Tarbosaurus as a guide. The juvenile 2nd from left is "Jane" which some researchers consider a separate species, Nanotyrannus lancensis. The third skull if from a gravid (pregnant but with eggs) female (determined by the presence of "medullary bone" that develops during egg laying in birds and some dinosaurs).

Taxonomy: Theropoda, Tyrannosauroidea, Tyrannosauridae

Montana

Late Cretaceous Period, Maastrichtian Stage, 67-66 Ma

Museum of the Rockies, Montana

Life model of Albertosaurus sp.

Taxonomy: Dinosauria; Therapoda; Tyrannosauroidea; Tyrannosauridae

Late Cretaceous Period, 73-70 Ma; Western North America

San Diego Natural History Museum

Life model of Daspletosaurus sp.

Taxonomy: Dinosauria; Therapoda; Tyrannosauroidea; Tyrannosauridae

Late Cretaceous Period

Dinosaur Resource Center, Colorado

The ornithomimids are commonly referred to as the ostrich-mimics, and indeed, they resemble these large flightless birds. They have long legs with long tarsal bones to increase stride length (indicating they were probably fast runners), fairly long arms, long necks and small heads with (in most) toothless beaks. They are believed to have been herbivorous or omnivorous.

Struthiomimus sp. is a typical derived ornithomimid.

Taxonomy: Theropoda, Coelurosauria, Ornithomimidae

Western North America

Late Cretaceous Period, 75-66 Ma

Museum of Ancient Life, Utah

Struthiomimus sedens fossil (head & neck have been restored).

Taxonomy: Theropoda, Coelurosauria, Ornithomimidae

Lance Formation, Niobrara County, WY

Late Cretaceous Period

Black Hills Institute Museum, South Dakota