Lythronax

Name

Lythronax (Greek for "gore king"); pronounced LITH-roe-nax

Habitat

Woodlands of North America

Historical Period

Late Cretaceous (80 million years ago)

Size and Weight

About 24 feet long and 2-3 tons

Diet

Meat

Distinguishing Characteristics

Moderate size; long skull; foreshortened arms

About Lythronax

Despite what you may have read in the press, the newly announced Lythronax ("gore king") isn't the oldest tyrannosaur in the fossil record; that honor goes to pint-sized Asian genera like Guanlong that lived tens of millions of years earlier. Lythronax does, however, represent a crucial "missing link" in tyrannosaur evolution, since its bones were unearthed from a region of Utah that corresponds to the southern portion of the island of Laramidia, which straddled North America's shallow Western Interior Sea during the late Cretaceous period. (The northern part of Laramidia, by contrast, corresponds to the modern-day states of Montana, Wyoming, and North and South Dakota, as well as parts of Canada.)

What the discovery of Lythronax implies is that the evolutionary split leading to "tyrannosaurid" tyrannosaurs like T. Rex (to which this dinosaur was closely related, and which appeared on the scene over 10 million years later) occurred a few million years earlier than was once believed. Long story short: Lythronax was closely related to other "tyrannosaurid" tyrannosaurs of southern Laramidia (most notably Teratophoneus and Bistahieversor, in addition to T. Rex), which now appear to have evolved separately from their neighbors in the north--meaning there may be many more tyrannosaurs lurking in the fossil record than previously believed.