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Triarthrus Triolobites
Trilobite Facts

Beautiful Triarthrus eatoni trilobite fossil from New York.

Fast Facts about Triarthrus Trilobites

Name: Triarthrus (pronunciation: "TRI arth rus") - Common Species in New York: Triarthrus eatoni

Taxonomy: Phylum: Arthropoda - Class: Trilobita - Order: Ptychopariida - Family: Olenidae - Genus: Triarthrus

There are many species of Triarthrus. More common species include: beckii, canadensis, and eatoni.

Age: Ordovician

Distribution: North America, Northern Europe, and China
In North America, they are most commonly found in Kentucky, New York, Quebec, and Ontario.

Body Size:
Triarthrus are somewhat small trilobites and grow to around 5 cm, or 2" in length.

Physical Appearance:
Narrow with a long thorax, have a small pygidium, and a plain looking cephalon. The cephalon has a series of glabellar furrows (parallel ridges running across the glabella). The eyes are slender, and often difficult to see in specimens.

Fun Fact
Triarthrus trilobites have been made world famous because of specimens being found with soft tissue preservation.
These specimens come from the Beachers Trilobite Bed in New York. The fossils show piratized gills, legs, antennae, mouth parts, and even Triarthrus trilobite eggs.

By Didier Descouens (Own work) CC-BY-SA-3.0-2.5-2.0-1.0], via Wikimedia Commons - Descouens

Triarthrus Trilobite Facts and Information - The Details

Triarthrus trilobites, of the Ptychopariida Order, are known from the Upper Ordovician rock in North America and Northern Europe.

These trilobites are narrow with a long thorax, have a small pygidium, and a plain looking cephalon. One notable feature on the cephalon is the presence of a series of glabellar furrows (It has a wide glabella with notable parallel ridges running across it). The eyes are slender, and often difficult to see in specimens, unless they are well preserved.

Based on the strata they are found in, they appear to have lived on the sea floor near the exareobic zone, a zone that is below the oxygen level required by most organisms. Elrathia of the Cambrian also lived in this type of environment.

Triarthrus trilobites would have been an often overlooked, indistinct trilobite if it wasn't for its preference toward exareobic environments. These environments of little oxygen tend to favor fossilization. In one of these places in the Frankfort Formation, called Beecher's Trilobite Bed, Pyrite has delicately preserved Triarthus to the point of soft tissue preservation. In the Beecher's Trilobite Bed, which is only a few centimeters thick, come some of the finest preserved fossil trilobites in the world.

Triarthrus eatoni Trilobite Fossil from New York

This Triarthrus trilobite is a little chipped up, but it has a nicely preserved cephalon. Triarthrus have eyes, however, due to poor preservation, they are often not seen.
Fossil Info: Triarthrus eatoni - Central New York - Ordivician - Utica Shale

Recommended Books

Trilobites: Common Trilobites of North America (A NatureGuide Book)
by Jasper Burns, 2000

Jasper Burns has some great illustrated fossil guide books. This one is on the Trilobites of North America. It has detailed illustrations of 41 species of North American trilobites and includes information about trilobite paleobiology, vision, growth, extinction, and much more! It's a nice little resource book for those interested in North American trilobites. It's also a very inexpensive book. Check it out!

The Trilobite Book: A Visual Journey
by Dr. Riccardo Levi-Setti, 2014

This is an updated (2014) hardcover (kindle available) of his famous 1994 book. It now has color images instead of black and white ones. The images are of prefectly prepared trilobites from all over the world. this book is geared toward the beginner and does not get overly technical. However, it's wonderful just to see the pictures and is a must for any trilobite enthusiast.

Trilobites for Sale:

Trilobites from Fossil Era
Trilobite fossils are some of the most beautiful and collectible fossils in the world! There are countless species of trilobites. They make beautiful display and conversation pieces. Common ones make very affordable for gifts to fossil and paleontology enthusiasts. Fossil Era has a huge selection of top quality trilobites from many states and many countries. It's fun just to browse through the inventory and look at all the different types!

Triarthrus Fossil Examples

The Ordovician rocks of New York are one of the easiest places to find Triarthrus trilobites.

Here is another Triarthrus eatoni trilobite fossil. It is not as well preserved, but has no chips in it.

Formation:Utica Shale
Age:Middle Ordovician
Location:Central New York

That little bluish feather looking fossil against the Triarthrus cephalon might be a graptolite.

Formation:Utica Shale
Age:Middle Ordovician
Location:Central New York

Cephalon hash plates (fossils full of trilobite parts) are occasionally found in the Utica shale. These are from molts. Since the Triarthrus cephalons all have the same shape, they probably all accumulated together in the currents, then fossilized.

Formation:Utica Shale
Age:Middle Ordovician
Location:Central New York

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