Kristen Barrett
Department of Petroleum
Engineering, Louisiana State
University—Baton Rouge, LA
Early Ordovician of Russia (500 mya); www. digsfossils.com
Outline
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Background information
Fossils and trace fossils
Biostratigraphy
Analyzing the Paleozoic:
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Cambrian
Ordovician
Silurian
Devonian
Carboniferous
Permian
 Important trilobites
 Summary
Fossil trilobite (marine arthropod), Cambrian; www.willgoto.com
Trilobite Background Information
• Trilobites lived from
about 540Ma to 250Ma
This clock representation shows some of the major units of geological time and definitive events of
Earth history. The informal Hadean eon represents the time before fossil record of life on Earth, its
upper boundary is now regarded as 4.0 Ga; Woudloper, September 2007
Trilobite Background Information
• Taxonomy:
Kingdom
Animalia
Phylum
Arthropoda
Class
Trilobita
Orders:
Trilobite Background Information
• Molting
Fossil photos (top) from Ludvigsen 1979a. Molting sequence figure (bottom) adapted
from Ludvigsen 1979b.
Trilobite Background Information
 Skeleton development theories
 Advanced growth
 Predation
 Oxygen levels
The giant predator of the Cambrian seas, Anomalocaris, up
to 60 cm long; higheredbcs.wiley.com
Biostratigraphy
Trilobites from the Cambrian;
www.saudiaramcoworld.com
Biostratigraphy
• The most important reference fossil groups:
•foraminifera
•graptolites
•conodonts
•archaeocyathana
•trilobites
Photos of the five most important reference fossil groups in geologic history; http://www.trilobites.info/biostratigraphy.htm
Trilobite Fossils
Imprint of dorsal shield of
Devnoian trilobit; digsfossils.com
Trilobite - 450 mya; www.rogerwendell.com
Photo by Roger J. Wendell
Devonian Trilobite
www.mineraltown.com
The Ceratarges trilobite; digsfossils.com
Well preserved trilobite fossil from Paleo School Set
www.hgms.org
Trilobite Trace Fossils
•The three main types of trilobite trace fossils:
•Rusophycus
•Cruziana
•Diplichnites
Adapted from the Treatise of Invertebrate Paleontology, Part W. Trace Fossils (Revised)
all images this page ©1999, 2000 by S. M. Gon III. Created using Macromedia Freehand 8.0
Trilobite Trace Fossils
A very detailed
Rusophycus specimen
from Australia;
www.trilobites.info
Cruziana trail showing the central
paired leg grooves and the parallel
furrows on the outside edges. The
curved shape suggests a searching
pattern. www.trilobites.info
These Diplichnites tracks are
attributed to Isotelus trilobites
walking on the surface, rather than
plowing (furrowing) through the
surface layers. www.trilobites.info
In this trilobite ichnofossil, the animal approached from the right side, leaving Cruziana
across the substrate, then settled into the silty bottom, leaving a Rusophycus.
Image courtesy of Stefano Novello, July 2008
Trilobites in the Paleozoic
Class Trilobita: Paleozoic Era: Image above ©2009 by S. M. Gon III, created using Macromedia Freehand and PaintShop Pro
Trilobites in the Cambrian
• Warm seas
The map shows a reconstruction of the Earth as it was 530 million years
ago. Although the land was barren, the shallow seas teamed with primitive life:
trilobites, brachiopods, worms, sponges, and many other forms which have since
become extinct. And among the continents, Gondwana, at the bottom right, stands
over the rest in the same way that the "world-island" of Europe and Asia does today
www.palaeos.com
Trilobites in the Cambrian
 Cambrian Explosion
540 million years ago the first land plants evolved
from the land algae. These plants were like modern
moss. www.historyforkids.org
Trilobites in the Cambrian
• The first trilobites
Fallotaspis Cambrian
Trilobite from Zagora,
Morocco;
www.trilobites.org
Trilobites in the Ordovician
• Diversity declining
• Glaciation
Cowen, Richard. History of Life; 1995
Trilobites in the Silurian
• Drop in sea temperature
•Extinction of the
Asaphida
Homotelus florencevillensis is an Asaphid trilobite (Order: Asaphida; Family: Asaphidae
Subfamily: Isotelinae) coming from the Ordovician Maquoketa Formation dolomitic shale
strata of Clayton County, Iowa. This is a prone example of the type; most are found either
incomplete or enrolled, making this a most uncommon example. It has affinities with both
Isotelus and Anataphrus.
www.fossilmuseum.net
Phytoplankton seen under a microscope
www. visindavefur.hi.is/svar
Trilobites in the Devonian
• Rising sea level
• Frasnian-Femennian
extinction event
Trilobites in the Carboniferous
and Permian
• Proetida: last
remaining order of
trilobites
By the Carboniferous, the lone surviving trilobite Order was Proetida, and in a general sense all
Carboniferous trilobites are relatively rare. Among these "last of the trilobites" is Breviphillipsia sampsoni
(Superfamily: Proetoidea; Family: Phillipsiidae) from the Mississippian Chouteau Formation in Saline County,
Missouri. A defining characteristic of sampsoni is the granulous exoskeleton extending from cephalon to
pygidium, as is evident in the close-up pictures.
www.fossilmall.com
Trilobites in the Carboniferous and
Permian
Important Trilobites
• Furongian GSSP
Glyptagnostus reticulatus—
Furongian GSSP;
Source: www.trilobite.org
Hunan Province, China—location of the Furongian GSSP.
http://travel.nationalgeographic.com
Summary
• Paleozoic creatures
• Cambrian Explosion
• Exoskeletons
• Important index fossils
Paleozoic periods and number of trilobite families. All figures this page ©2009 by S. M. Gon III
Thank you!
Questions?
Russian Ordovician Trilobite; http://www.paleoart.com