The Semi-Compleat Trilobite

(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 nformation 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

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.

Detail of cephalic region -- greyscale

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

Phacops rana

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

slab with several specimens

complete specimen

two cephalons

detail of cephalon, showing eye

detail of schizochroal eye

detail of schizochroal eye, dorsal view

Leonaspis williamsi

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

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.

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.

cephalon

Ordovician

Diacalymene

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

dorsal view lateral view posterior view 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).

Pseudogygites latimarginatus

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

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 spinosus

Homotelus bromidensis

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

Ogygiocaris carella

Ordovican, Llandvirn, Rorrington Green, Shropshire, England.

Note the structural deformation.

Ogygiocaris carella -- complete

Amphilichas halli

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

Amphilichas halli

Cambrian

Asaphiscus wheeleri Meek

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

complete specimen

Elrathia kingii (Meek)

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

complete specimen

Olenellus sp.

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

Olenellus sp

Olenoides serratus

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

Olenoides serratus

Peronopsis interstricta (White)

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

Peronopsis interstricta

Trilobites from Murchison's Siluria, 1867

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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