Question 1

How do you say Isotelus rex?

Accepted Answer

You say it like this: eye-SOT-eh-lus RECKS. Break it into four parts: EYE, then SOT, then eh, then lus, and finish with RECKS just like the word 'wrecks'. The stress falls on the SOT in the middle of the first word. A good memory trick is to say 'I SOT a RECKS' and picture finding the fossil yourself.

Question 2

What does Isotelus rex mean?

Accepted Answer

Isotelus comes from two Greek words: 'isos' meaning equal and 'telos' meaning end, describing how the front and back of the animal look almost mirror-image symmetrical. Rex is Latin for king, the same word used in Tyrannosaurus rex. Together the name means something like 'the equal-ended king', celebrating both the creature's distinctive body shape and its record-breaking size.

Question 3

How big was Isotelus rex?

Accepted Answer

The largest confirmed Isotelus rex specimen measures over 70 centimetres, which is about 28 inches long. That makes it roughly the diameter of a large car tyre or a medium pizza box, except much heavier and armoured. It is officially the largest trilobite fossil ever found anywhere in the world, a record that has held up through multiple new discoveries since the 1800s.

Question 4

Was Isotelus rex a real insect?

Accepted Answer

Isotelus rex was not an insect at all, even though it sometimes gets categorised that way. It was a trilobite, which is its own extinct class of arthropods, more distantly related to modern horseshoe crabs than to any insect. Isotelus actually lived tens of millions of years before the first true insects evolved on Earth, so calling it an insect is a bit like calling a shark a fish because they both live in water.

Question 5

Where was Isotelus rex found?

Accepted Answer

The record-breaking giant specimen of Isotelus rex was discovered in Manitoba, Canada. The broader genus Isotelus is commonly found across the northeastern United States and eastern Canada, particularly in states like Ohio, where it is so common and beloved that Isotelus was named the official state fossil of Ohio in 1985. The fossils turn up in Ordovician-age limestone and dolostone rocks throughout the Great Lakes region.

Question 6

When did Isotelus rex live?

Accepted Answer

Isotelus rex lived approximately 445.5 million years ago during the Late Ordovician Period. To put that in perspective, that is about 200 million years before the first dinosaurs walked the Earth, and nearly 440 million years before humans appeared. It lived in warm shallow tropical seas that covered much of what is now North America, long before any land animals existed at all.

Question 7

What did Isotelus rex eat?

Accepted Answer

Isotelus rex was a carnivore that hunted by burrowing through the soft sediment on the seafloor. It used its massive shovel-shaped head to plough through mud, feeding on polychaete worms, soft-bodied molluscs, and other small creatures hiding just below the surface. Think of it like a giant prehistoric vacuum cleaner, slowly cruising the seafloor and hoovering up anything soft and edible it could dig out.

Question 8

Why is Isotelus the state fossil of Ohio?

Accepted Answer

Isotelus trilobite fossils are extremely common in Ohio because the state sits on top of ancient Ordovician-age limestone that was once the floor of a warm shallow sea. Ohio officially recognised Isotelus as its state fossil in 1985, making it one of the most celebrated state fossils in the United States. The fossils are so plentiful and well-preserved in Ohio that amateur collectors regularly find complete or near-complete specimens, which is rare for creatures this ancient.

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