Tyrannosauridae Lecture Notes

Overview of Tyrannosauridae

• Family of large theropod dinosaurs.
• Includes famous species Tyrannosaurus rex and relatives.
• Classified into two subfamilies:
  • Albertosaurinae
  • Tyrannosaurinae
• Albertosaurinae: more slender builds, lower skulls, longer leg bones than Tyrannosaurinae.
• Well-studied with multiple complete remains available.
• Distinction between Tyrannosauridae (family) and Tyrannosauroidae (superfamily).

Genera of Tyrannosauridae

1. Raptorex

   • Identity unclear, juvenile estimated at 3 years old.
   • Known from a single specimen, likely from Mongolia.
   • Similar proportions to juvenile tyrannosaurids like Tarbosaurus.
   • Validity disputed; suggested to be related to Tarbosaurus and Tyrannosaurus.

2. Nanotyrannus

   • Controversial genus; holotype discovered in Hell Creek formation, Montana.
   • Initially described as a new species of Gorgosaurus (1946), later as a new genus (1988).
   • Re-examined in 1999 revealed it was a juvenile, possibly of Tyrannosaurus rex.
   • Recent studies suggest valid but distant relationship to Tyrannosaurus, ongoing debates.

3. Aublysodon

   • Described from tooth fossils in 1868; many names attributed to it.
   • Most specimens now assigned to juvenile tyrannosaurids, validity is disputed.

4. Deinodon

   • No longer considered valid; described from teeth that likely belonged to Gorgosaurus.
   • Most specimens reassigned or classified as nomina dubia.

5. Alioramus

   • Slender, relatively small-sized; two species from Nemegt formation, Mongolia.
   • Anatomy resembles juvenile tyrannosaurines; likely hunted smaller prey.
   • Coexisted with other theropods and dinosaurs.

6. Nanuqsaurus

   • Discovered in Prince Creek formation, Alaska; size estimates vary.
   • Adapted to polar conditions; speculated to have insulating feathers.

7. Lythronax

   • Means "gore king"; small tyrannosaurid with short snout and broad skull.
   • Known from partial skeleton in Wahweap formation, Utah.
   • Oldest tyrannosaurid discovered (~81.5 million years ago).

8. Qianzhousaurus

   • Medium-sized, slender; closely related to Alioramus.
   • Agile, fast-moving predator; discovered in Nanxiong formation, China.

9. Teratophoneus

   • Described from partial specimens in Utah; evidence of possible gregarious behavior.

10. Thanatotheristes

    • Means "reaper of death"; described in 2020 from incomplete specimen.

11. Albertosaurus

    • Named after Alberta, Canada; over 30 specimens known, indicating possible pack behavior.
    • More slender build; fossil evidence shows it lived with diverse species.

12. Gorgosaurus

    • First described in 1914; known from many complete skeletons in Dinosaur Park formation.
    • Similar to Albertosaurus; changes from agile juveniles to robust adults.
    • Lived in diverse subtropical climate with other dinosaurs.

13. Dynamoterror

    • Described in 2018; validity questioned due to limited remains.

14. Bistahieversor

    • Described in 2010; classification unclear, initially categorized under Aublysodon.

15. Daspletosaurus

    • Contains three species; heavily-constructed skull and muscular body.
    • Evidence of social behavior; possible apex predator in its ecosystem.

16. Zhuchengtyrannus

    • Large tyrannosaurid found in China; closely related to Tarbosaurus and Tyrannosaurus.

17. Tarbosaurus

    • Large Asian tyrannosaurid known from over 30 specimens.
    • Similar anatomy to Tyrannosaurus; evidence of predation and scavenging.

18. Tyrannosaurus

    • Largest tyrannosaurid and most massive predator; iconic dinosaur.
    • Two valid species: Tyrannosaurus rex and Tyrannosaurus mcraeensis.
    • Known for powerful bite force and opportunistic feeding behavior.
    • Coexisted with many other dinosaurs until the K-Pg extinction event.

Conclusion

• Numerous obscure invalid tyrannosaurid genera exist, mostly misnomers.
• Tyrannosaurids are notable for large size, robust skulls, and apex predator status in ecosystems.
• Evolution and diversification in late Cretaceous allowed them to fill niches left by older carnosaurs.