M. Cunniffe Stanford IISME Fellow, 2013

 The Trilobite: An extinct Arthopod CheliceratesCrustaceansMyriapodsHexapodsTrilobites

  Trilobites were marine organisms that lived on Earth for over 270 million years and are considered known to be one of the most successful early animal groups  Trilobites are a member of the Arthropods. Of the five types of Arthropods, only the trilobites are extinct. The four extant Arthropod groups include:  Chelicerates (spiders, scorpions)  Crustaceans (lobsters, crabs, barnacles, shrimp)  Myriapods (millipedes, centipedes)  Hexapods (insects)  Trilobites are a highly diverse and geographically dispersed species with new species of fossil specimens discovered every year What is a Trilobite?

 Trilobite Fossil Distribution

  Trilobites first appeared in the Early Cambrian.  The height of their diversity occurred in the early Paleozoic.  Adaptive radiations occurred in the Ordovician, Silurian, and Devonian periods.  After the Devonian mass extinction, only two families in one single order of trilobites remained.  At the Permassian-Triassic mass extinction event, no trilobites were left. Evolutionary History of Trilobites

 Patterns of Marine Animal Diversification Raup & Sepkoski, Science 1982

 Trilobite Diversity Treatise of Invertebrate Paleontology (1997) figure p. 269 modified, S. Gonn website www. trilobites.info Extent of the Trilobite Orders over Geological Time

  Ecospace coding for trilobites and other groups is based upon three ecological areas of interest:  Tiering: where in the ocean did they live?  Motility: did they move and if so, how freely were they able to move?  Feeding Mechanism: how did they get their nutrition? Ecospace Coding

  1. Pelagic (out in the water column)  2. Erect (benthic, extending into water mass)  3. surficial (benthic, not extending upward)  4. Semi-infaunal (partly infaunal, partly exposed)  5. Living in the top ~5 cm of sediment  6. Living more than ~5 cm deep in sediment Tiering

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  1. Freely, fast moving (regularly moving, unencumbered)  2. Freely, slow (as above but with strong bond to substrate)  3. Facultative, unattached (moving only when necessary, free-lying)  4. Facultative, attached (moving only when necessary, attached)  5. Non-motile, unattached (not capable of movement, free- lying)  6. Non-motile, attached (not capable of movement, attached) Motility

  1. Suspension (capturing food particles from the water)  2. Surface deposit (capturing loose particles from a substrate)  3. Mining (recovering buried food)  4. Grazing (scraping or nibbling food from a substrate)  5. Predatory (capturing prey capable of resistance)  6. Other (photo- or chemo- symbiosis, parasites) Feeding Mechanism

 Ecospace Coding  Sea Star (echinoderm)  Tiering: 4  Movement: 2  Nutrition: 5

 Ecospace CubeTemplate

 Ecospace Cubes

 Ecospace vs. Niche Niche  The range of conditions and resources within which individuals of a species can persist  Is specific to each individual species  Competition and predation restrict the distribution of a species across its fundamental niche resulting in a species’ realized niche Ecospace  A more general way of looking at species specialization and interaction within a community  Unlike niches, more than one type of organism can inhabit the same ecospace

  For higher diversity in a community, there must be less competition between species  How?  Greater resources available  Reduced resource demand (general predation)  Intensified predation of a species subset (camoflauge in moth population)  Greater inter- and/or intraspecial ecological specialization of organisms  Morphology (species diversity) can be used as an indicator of niche diversity (Structure  Function) More on Niches

 Trilobite Fossils  Trilobite easily fossilized due to their easily preserved exoskeletons  Soft parts such as eyes can also be found due to the nature of the materials that surround the fossils  Trace fossils can be either resting or sediment furrows:  Hard fossils indicate protection, hunting, resting  Furrows in sediment suggest movement  Trilobite fossils can be used as index (aka guide, zone, or indicator) fossils to determine the age of surrounding rocks  Geologists and oil companies in particular use this process known as biostratigraphy

  The Paleozoic Era consists of 6 time periods:  Cambrian ~ mya  Ordovician ~ mya  Silurian  Devonian  Carboniferous  Permian ~ mya The Paleozoic Era

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 The Geologic Clock

Geologic time periods

 Anatomy of a Trilobite  Trilobites are arthropods and have  segmented bodies,  An exoskeleton  Jointed appendages  In addition, trilobites have complex and diverse eyes and a variety of mouthparts known as hypostomes

 Trilobite Feeding  Trilobites used their hypostomes to prepare food for digestion.  Conterminant hypostomes are firmly attached to the body and allowed for the digestion of a different type of prey than natant hypostomes, which did not have extra reinforcement for crushing moving prey

 Extension: Body Size Data  Body size in organisms is a biologically important data set  The study of allometry relates body size to other biological significant factors such as:  Body shape  Anatomy  Physiology  Metabolism  Behavior  All trilobite body size data is included on the original spreadsheet (see Attachment #7).  By sharing the spreadsheet with students electronically, students can reorganize data to create graphs for a variety of data groupings:  body size vs. ecospace designation  ecospace designation throughout various geologic time periods