--Click here to find out!

Just Starting:
-Site Map
-Glossary of terms
-Geological Time
-Dorsal Morphology
-Ventral Morphology
-Internal Anatomy
-Trilobite Eyes
-Major Features
-Special Terms
-Facial Sutures
-Pygidium Size
-Hypostome Types
-Trace Fossils
-Feeding Habits
-Trilobite Localities

.Trilobite Origins
-Trilobite Orders
-Key to the Orders
-Evolutionary trends
-Pictorial Guides
-Trilobite Families
-Trilobite Genera
-ICZN Business
Miscellaneous Topics:
-Trilobite FAQ
-Trilobite Quiz
-Trilobite Links
-Trilobite Photos
-Glossary of terms
-Selected References
-Trilobite books
-Trilobite folio
-Site Accolades

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A Guide to the Orders of Trilobites
A site devoted to understanding trilobites
created and maintained by Sam Gon III
Walk back with me to a time when the world was very, very young...
walking trilobite ©2000
This award-winning website now available in book form!
This page last revised 01 SEPTEMBER 2005 SMGIII

click on my frontal glabellar lobe!

The Trilobite of the Month for September 2005 is a wonderfully inflated specimen of an undescribed species of Moroccan Cyphaspis, a member of the family Aulacopleuridae, in the order Proetida, Superfamily Aulacopleuroidea. I really enjoy the tubercles that ornament both the glabella as well as the genal spines. The elbow-like feature of each thoracic segment, called the fulcrum, is also quite evident, forming a roof-like peak that runs in a curve on both sides of the axis, from cephalon to pygidium.

Images like this help explain why trilobites are one of the best-known and appreciated groups of prehistoric animals. Each month, a new example of trilobite diversity will be showcased here. With over 15,000 described species, we may never exhaust the possibilities!
If you have a stunning image of a trilobite that you could share as a future "Trilobite of the Month," please let me know!

Harpidella christyi is a good representative trilobite Trilobites are the most diverse group of extinct animals preserved in the fossil record.  Nine orders of trilobites are recognized, into which 15,000+ species are placed.  Learn more about trilobite morphology, ecology, behavior, reproduction, and development, and how they relate to trilobite evolution and classification.  View galleries of trilobite images from the web, examine fact sheets, pictorial guides, and an identification key for each order, refer to a family listing, a genus listing, or consult a trilobite glossary and bibliography, explore links to other web resources on trilobites, and review books on trilobites, including an exclusive hardcopy folio adaptation of this website. 
Order Agnostida: highly specialized design
The Redlichiida: Most primitive order of trilobites
Corynexochida: spiny Cambrian predator trilobites
some of the most ornate trilobites are Lichida
The eyes have it! Phacopid compound eyes are distinctive
One of the last survivors - Proetida persisted until the Permian
Over 20% of all trilobites belong to the large order Asaphida
Order Harpetida has arrived!
The fundamental trilobite design typifies this order
. Click on the images, menu choices, or the FAQ listings below on this page to start exploring aspects of trilobite biology, and the salient characters that define the orders, constituent suborders, and superfamilies.
This site has enjoyed feedback from a growing number of trilobite workers from all over the world who have
generously offered their suggestions and corrections. I gratefully acknowledge their help and encouragement.
This website Copyright ©1999 - 2005 by S. M. Gon III

The Trilobite FAQ
Use the links on the right to answer the Qs on the left
Unfamiliar with trilobites altogether? Introduction to Trilobites
What are trilobite body parts called? Trilobite Dorsal Morphology
Unfamiliar with trilobite undersides? Trilobite Ventral Morphology
What about the inside of a trilobite? Trilobite Internal Anatomy
What was special about trilobite eyes? Trilobite Eyes & Vision
Want definitions of trilobite terms? Glossary of Trilobite Terms
How are the eight trilobite orders related? Trilobite Systematic Relationships
Want a list of all trilobite families? Phylogenetic List of Trilobite Families
Want a list of all trilobite genera? List of 5000 Trilobite Generic Names
How long ago did trilobites exist? Geological Time relevant to Trilobites
What ecological roles did trilobites play? Trilobite Ecology and Environments
How do we know about trilobite behavior? Trilobite Trace Fossils
What and how did trilobites eat? Trilobite Feeding Habits
How did trilobites reproduce and grow? Trilobite Reproduction & Development
What roles did sutures play in molting? Trilobite Sutures & Molting
How did trilobites defend themselves? Trilobite Enrollment & Coaptation
How did trilobites evolve? Trilobite Evolutionary Trends
What is the origin of trilobites? Trilobites Origins

What were the last trilobites?

Trilobite Extinction

Where in the world are trilobites found?

World Trilobite Localities
Think you know about trilobites now? Take the Trilobite Identification Quiz!
How big did trilobites get? World's Largest Trilobites
How do you prepare a trilobite fossil? Trilobite Preparation
Is this site available in hardcopy form? Yes! Preview the folio pages here
Are there many books on trilobites? Review recommended trilobite books!
Found mistakes or refinements needed? Please tell me about them

Search A Guide to the Orders of Trilobites

In these pages, you may recognize species that are common, well-known, or sitting in a familiar museum collection!
This guide might help you arrange trilobite diversity systematically, aid in identification of specimens, and enhance your understanding of these fascinating elements of Paleozoic biodiversity.  Happy browsing!  -- Sam Gon III
Trilobite Order Fact Sheets
detailed, descriptive characters and representative line drawings
Agnostus Redlichia Olenoides Arctinurus Acastoides Cyphoproetus Homotelus Harpes (Harpetidae) Elrathia
 Click on any of the images above to be sent to a page featuring details on trilobites in that Order
Trilobite Order Galleries
trilobite images from various locations on the web, arranged by order
Ptychagnostus (Ptychagnostidae)
Redlichia (Redlichiidae)
Olenoides (Dorypygidae)
Arctinurus (Lichidae)
Reedops (Phacopidae)
Gerastos (Proetidae)
Homotelus (Asaphidae)
Bolaspidella (Menomoniidae)
Click on any of the images above to be sent to a gallery featuring photos of trilobites in that Order
Thanks Andrew!
Asaphus kowalewski
Order Asaphida
The information in these pages was developed via examination and synthesis of the data present in a variety of works, including the two "Trilobite Treatises:" Moore 1959 (Treatise on Invertebrate Paleontology, Part O, Arthropoda 1, including Trilobitomorpha) and Moore & Kaesler 1997 (Treatise on Invertebrate Paleontology, Part O, Arthropoda 1, Trilobita, Revised, Volume 1: Introduction). Both may be reviewed here. Other important sources are cited in specific pages of this site, and are also listed in a brief bibliography. Sources of photos and line drawings (where not original) are clearly cited. Other trilobite web sites and individuals were inspirational sources and are cited where relevant. The three trilobite thumbnail images in the left column, for example, are c/o Andrew Milner. If you find your information or images on these pages without proper attribution, this is unintentional. Please contact me to rectify the situation.
Elrathia is considered by many the typical trilobite
Elrathia kingi
Order Ptychopariida
Information about extinct animals is always subject to interpretation and differences of opinion. In particular, the higher classification of arthropods and trilobites is neither simple nor agreed upon by all trilobite workers. The summaries here are complicated by the fact that the 1997 revision of the Treatise only covers two orders in detail: Agnostida and Redlichiida. The others are in preparation, so my attempts to synthesize data on the other orders is likely to be incomplete, although the arrangement of the families and some characteristic descriptions were provided by Fortey (in Moore & Kaesler 1997), and discussed in a number of recent revisions (e.g., Asaphida, Proetida, Harpetida, and Lichida). Any errors in the information here should be attributed to the compiler, Sam Gon III. Please inform him of any problems in accuracy or interpretation.
An internal mold of limestone
Sthenarocalymene celebra
Order Phacopida
This site's pages (and the majority of its figures) were designed and created by Dr. Sam Gon III, a biologist (PhD, Animal Behavior; MA, Zoology (Ecology, Behavior and Evolution) who is greatly intrigued by the expression of ancient biodiversity that trilobites represent. Sam's professional work is in the conservation of global biodiversity today. He serves as the Senior Scientist for The Nature Conservancy's Hawai‘i Field Office in Honolulu. Sam has long been interested in paleobiology, and in teaching himself about trilobites, using hyperlinks to cross-reference terminology and concepts, found himself developing something of potential interest to a broader audience. The site was unveiled in August 1999 and has attracted feedback from around the world, generating ongoing updates. For all the accolades this site has gathered, Sam is not a professional trilobitologist, but a devoted trilobitophile!

Dr. Sam Gon III c/o The Nature Conservancy of Hawai‘i, 923 Nuuanu Avenue, Honolulu, HI 96817, USA
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(“There has never been such a splendid site for Trilobites!!! EVERYTHING is there!!!! Such a pity....it’s in English.”)
To review other awards and accolades for
A Guide to the Orders of Trilobites
for valor in the face of extinction...
please click here

For your reading pleasure!
This website has been
adapted into book form
Click on me to preview sample pages!
click on this image to
view sample pages

Find out why Anomalocaris is such a popular mascot of animators!
Could the above creature be real? Find out!
Please visit the Anomalocaris Homepage!
(another creation of S. M. Gon III)
If you'd like to trade a trilobite, click here
Elrathia kingi are one of the most abundant trilobites in the world
These ptychopariids are found in Cambrian deposits in Utah, USA

TriloNet - Offener Fossilienring
TriloNet - Offener Fossilienring
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