1. The Evolution & Ecology of Trilobites
M. Cunniffe
Payne Lab

2. The trilobite: an extinct arthropod
Diverse group of extinct arthropods
Exoskeleton
Jointed appendages
Trilobites first appear in the fossil record ~ 521 mya and lived for 270 million years

3. Extent of the Trilobite Orders over Geological Time
Trilobite Diversity Treatise of Invertebrate Paleontology (1997) figure p. 269 modified, S. Gonn website www. trilobites.info
What we know: Early Cambrian: Trilobites appear in the fossil record, large amount of diversity/growth, Late Devonian mass extinction: Trilobites are reduced to one single order, two families. Permian-Triassic mass extinction: Trilobites become extinct during this event in which 96% of marine animals and up to 70% of all terrestrial vertebrate species died out.

4. Trilobite genera across geologic time
This is similar to Gonn’s information on slide 3, however, this graph was generated with our own data 7/13

5. The ecospace project
The ecospace coding project consists of three major ecological factors of interest:
1. tiering: where does the organism live?
2. motility: does the organism move and if so, how fast does it move?
3. feeding: how does the organism obtain its nutrition?
The big picture: The Payne Lab has been documenting and organizing body size and ecospace data from all known fossil data. This information will be able to be utilized in a variety of ways for a multitude of comparison purposes across a wide array of scientific disciplines

6. our scientific questions
1. How many ecospace categories did the trilobites occupy?
2. Does the ecospace diversification history parallel the taxonomic diversification history of trilobites?
3. Is there a relationship between ecospace occupation and body size evolution within the trilobites?
1. 8 codes so far, 2. yes, more ecospaces filled during the time frames where the number of genera was larger, less ecospaces when there were less genera 3. yes.

7. Ecospace diversity of trilobites
3249 genera from Treatise on Invertebrate Paleontology, 6th ed., Moore, Geological Society of America (University of Kansas), 1077 with full ecospace codes, 1450 with body size data, 640 with both ecospace and body size data
111     less than 1%        3 genera
115     6%                      62 genera
121     20%                  213 genera
311     less than 1%        1 genera
312     24%                 258 genera
315     48%                 518 genera
412     less than 1%        2 genera
415     1%                     14 genera

8. Trilobite Ecospace and Body Size diversity over geologic time
111= black, 115=blue, 121=red, 311=magenta, 312=yellow, 315=green, 412=brown, 415=orange

9. Comparison of trilobite Body size vs. ecospace
Body size data is a significant factor in an organism’s metabolism and other morphological aspects and is therefore an important biological question to explore. Here, trilobite diversity in body size mirrors the large ecospace categories, 312 and 315.

10. acknowledgements Special thanks to: Matt Knope Noel Heim
Meghan Faerber
Laura Zalles & Nicole Childs
the Payne lab group
Jon Payne

11. These next slides are for supplemental/ background information/potential audience questions

12. Patterns of Marine Animal Diversification Raup & Sepkoski, Science 1982
Late Devonian mass extinction: Trilobites are reduced to one single order.
Permassian-Triassic mass extinction: Triolobites become extinct during this event in which 96% of marine animals and up to 70% of all terrestrial vertebrate species died out.
Late Devonian

13. Geologic time periods
From Gonn website,

14. Bambach’s ecospace coding system: Tiering
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
Some general everyday examples: 1. fish, 2. crinoids, coral, 3. gastropods, 4. bivalves, 5. clams, 6. clams
Infaunal: refers to organisms that live in the substrate of a body of water, i.e. the soft bottom of the ocean

15. Tiering
Image:

16. Bambach’s ecospace coding system: Motility
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)
Some general everyday examples: 1. fish and arthropods, 2. gastropods, 3. clams, 4. mussels, 5. some brachiopods, 6. some brachiopods

17. Bambach’s ecospace coding system: Feeding Mechanism
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)
Some general everyday examples: 1. brachiopods, 2. some bivalves 3. some bivalves 4. gastropods 5. cephalopods

18. Body size data from the fossil record
From J. Payne’s 2008 paper, Two phase increase in the maximum size of life over 3.5 billion years reflects biological innovation and environmental opportunity. “In particular, the observed episodes of dramatic increase suggest the origins of key evolutionary innovations, the removal of environmental constraints, pulses of diversification, or more likely, some combination of these. The relative stability in maximum size between these episodes of increase suggests the encountering of new environmental or biological upper bounds.”

19. Trilobite Body size diversity of geologic time
The difference between this graph and the following one is the number of data points—we do not have body size data for all of the trilobite genera for which we have ecospace data. This is the companion scatterplot to the color coded ecospace scatterplot included in the fellowship powerpoint presentation.