J477 - Tyrannosaur Dinosaur Tooth - Nanotyrannus Premaxillary Tooth (cf Aublysodon) - Hell Creek Fm

Nanotyrannus lancensis is a small, fast, agile tyrannosaur from the Late Cretaceous Hell Creek Formation (originally part of the Lance Formation), known for being small and distinctly different from T. rex, with recent studies confirming it's a separate species, not a juvenile T. rex, based on unique features like more teeth, larger hands, and distinct bone structures. Meaning "dwarf tyrant," it was a capable predator of smaller prey, coexisting with T. rex.

Key Facts

Name Meaning: "Dwarf tyrant" from Greek nanos (dwarf) and tyrannos (tyrant).
Species Name: lancensis refers to the Lance Formation where its skull was found.
Size: Around 15-18 feet long, much smaller and lighter than an adult T. rex.
Habitat: Hell Creek Formation (Late Cretaceous), same time and place as T. rex.
Lifestyle: Fast, agile pursuit predator, likely hunting smaller dinosaurs like pachycephalosaurs.
Controversy: Long debated as either a distinct species or juvenile T. rex, but recent evidence strongly supports it as its own genus.
Distinguishing Features: Narrower skull, more teeth, larger hands, and different bone structures than T. rex. 

The Debate & Resolution
Juvenile T. rex Theory: Many scientists thought smaller tyrannosaur fossils from Hell Creek were young T. rex because no large Nanotyrannus fossils existed, and T. rex juveniles were rare.
Separate Species Theory: Researchers found that Nanotyrannus fossils showed adult-like traits (fused bones) and unique features that T. rex never developed, making it biologically impossible to grow into a T. rex.

Current Consensus: Nanotyrannus is a separate, distinct genus of small tyrannosaur, coexisting with T. rex as a unique, agile predator. 

Aublysodon teeth from the Hell Creek Formation (typically Montana/South Dakota, not Iowa) are generally considered to be non-serrated premaxillary teeth from juvenile or subadult Tyrannosaurus rex, rather than a distinct genus. These rare, D-shaped teeth are often sold by collectors as "Aublysodon" or "Nanotyrannus," showcasing a smooth,,,Sometimes striated appearance. 

Key Details on Hell Creek "Aublysodon" Teeth:
Classification: Aublysodon is considered a nomen dubium (doubtful name). The teeth are widely recognized as juvenile T. rex.
Characteristics: These teeth are characterized by lacking serrations (non-denticulate) on the premaxillary (front) teeth. They may show longitudinal striations, giving them a faceted appearance.
Occurrence: While Aublysodon was originally described from the older Judith River Formation, similar-looking teeth are found in the late Maastrichtian Hell Creek Formation.
Size: They are typically small compared to adult T. rex teeth, often measuring less than 1 inch in length.
Discovery: These fossils are found in the Hell Creek formation of Montana and Dakota, often in sandy or clay layers, frequently as isolated finds. 

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