The Semi-Compleat Trilobite

by Andrew MacRae
Copyright © 1996-2003


(about the title)

A far more complete presentation of trilobite images, links, and related information can be found at Kevin Brett's Trilobite home page.

The quality of some images presented here is not great because I often use a video-capture setup with limited resolution. It is more convenient than film, and, most importantly, it saves film and processing costs for a project which is just for fun.

The trilobite images are arranged in approximate stratigraphic order, with the oldest at the bottom and youngest at the top, and subdivided into geologic periods. Additional information is available on the subdivision of the geologic time scale.

Carboniferous and Permian

No specimens available, yet. Trilobites are comparatively rare after the Devonian.

Devonian

Cheirurus

A specimen of Cheirurus (Crotalocephalina) gibbus (Beirich) from Devonian-age rocks in Morocco. This phacopid trilobite has a bizzare inflated glabella and hypostome.

Lateral View -- colour

Cheirus gibbus

Oblique Lateral View -- greyscale

In this image, like most scientific illustration, the specimen is coated with ammonium chloride sublimate in order to reduce the effects of colouration and enhance surface morphological features and contrast.

Cheirurus gibbus

Detail of cephalic region -- greyscale

This image shows an eye and some of the detailed ornamentation on the cephalon.

Cheirurus gibbus

Phacops rana

Moscow Formation, Devonian, Erie County, New York, U.S.A.

Phacops rana slab with several specimens

Phacops rana complete specimen

Phacops rana two cephalons

Phacops rana detail of cephalon, showing eye

Phacops rana detail of schizochroal eye

Phacops rana detail of schizochroal eye, dorsal view

Leonaspis williamsi

Haragan Formation, Devonian, Coal Co., Oklahoma, U.S.A.

Leonaspis williamsi Leonaspis williamsi

Silurian

?Acaste sp.

Stonehouse Formation, Late Silurian (Pridoli), near Arisaig, Nova Scotia.

Note the large schizochroal eye and furrowed glabella. McLearn, 1924 assigned this species to Dalmanitina, but I suspect it is Acaste downingiae (Murchison), or a close relative. Unfortunately, I know of no subsequent published work on the trilobites of Arisaig, so I can not confirm the identification.

Acaste sp.cephalon

Homalonotus sp.

Green Member, Moydart Formation, Late Silurian (Ludlow), near Arisaig, Nova Scotia, Canada.

This specimen comprises only the cephalon, but is remarkably well preserved compared to most Homalonotus specimens in this formation. Even the hypostome is preserved (the two triangular projections just above the anterior margin). Unfortunately, without the pygidium, this specimen can not be identified to species level. The specimen is coated with KOH sublimate, and is about 5 centimetres wide.

Homalonatus sp.cephalon

Ordovician

Diacalymene

A specimen of Diacalymene ouzregui from Ordovician-age rocks near Erfoud, Morroco.

Diacalymene ouzregui dorsal view Diacalymene ouzregui lateral view Diacalymene ouzregui posterior view Diacalymene ouzregui anterior view

Flexicalymene

A specimen of Flexicalymene from Ordovician-age rocks near Arnheim, Ohio. The family resemblance to Diacalymene is pretty obvious. This photo was taken by Rick Larush (rick@geo.ucalgary.ca).

Flexicalymene

Pseudogygites latimarginatus

This trilobite specimen is an ammonium chloride coated latex cast of an external mold. Middle Ordovician, near Collingwood, Ontario.

Pseudogygites latimarginatus Pseudoogygites latimarginatus

Triarthrus sp.

Ordovician, south shore of the Ottawa River, Ottawa, Ontario, Canada. A partial cephalon with only one genal spine preserved. The specimen is partly replaced by pyrite.

Triarthrus sp. Triarthrus spinosus

Homotelus bromidensis

Bromide Formation, Ordovician, Criner Hills, Carter County, Oklahoma, U.S.A.

Homotelus bromidensis

Ogygiocaris carella

Ordovican, Llandvirn, Rorrington Green, Shropshire, England.

Note the structural deformation.

Ogygiocaris carella Ogygiocaris carella -- complete

Amphilichas halli

Waynesville Formation, Ordovician, Clinton Co., Ohio, U.S.A.

Amphilichas halli Amphilichas halli

Cambrian

Asaphiscus wheeleri Meek

Wheeler Formation, Middle Cambrian, Antelope Springs, Utah, U.S.A.

Asaphiscus wheeleri complete specimen

Elrathia kingii (Meek)

Wheeler Formation, Middle Cambrian, Antelope Springs, Utah, U.S.A.

Elrathia kingii complete specimen

Olenellus sp.

Forteau Fm., Late Cambrian, Mt. St. Margaret, Car Bay, Northern Peninsula, Newfoundland, Canada.

Olenellus sp.Olenellus sp

Olenoides serratus

From the middle Cambrian Burgess Shale, Walcott Quarry, Stephen Formation, near Field, British Columbia, Canada.

Olenoides seeratus Olenoides serratus

Peronopsis interstricta (White)

Wheeler Shale, Middle Cambrian, House Range, Utah. An agnostid (Order Agnostida) trilobite, with only two thoracic segments.

Peronopsis interstricta Peronopsis interstricta

Trilobites from Murchison's Siluria, 1867

Siluria

Unless otherwise noted, images are copyright (c) Andrew MacRae, email: macrae@geo.ucalgary.ca, and are freely distributable for non-commercial use provided the original source is indicated.


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