Predator/prey relationships in 40 million year old fossils from South Carolina: Latitudinal...
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Transcript of Predator/prey relationships in 40 million year old fossils from South Carolina: Latitudinal...
Predator/prey relationships in 40 million year old fossils from South
Carolina: Latitudinal variation in drilling predation and selectivity of prey drill-hole
site and prey species
UNCW Undergraduate Research Fellowship Proposal
Patti Mason, April 22, 2005
Acknowledgments: Thanks to Dr. Richard A. Laws and Dr. Patricia H. Kelley for their assistance and support
• Escalation (Vermeij, 1987) : states that biohazards, such as predation and/or competition increase through geologic time
• Vermeij looked at the fossil record of predatory snails for evidence of escalation.
• Predatory naticids (snails) move within the sediment to find prey and then drill through the shell and ingest the prey tissue.
Background
Predatory Naticid (w/ drill hole) Bivalve Prey
• Kelley and Hansen surveyed 143,000 fossil molluscs from 28 geologic formations. They found:
0.000.050.100.150.200.250.300.350.400.450.50
RP PR C K BR ML BL BS CM G MB RB MS BY
Stratigraphic Level
Dri
lling
Fre
quen
cy
Bivalves
Gastropods
Total
+ correlations with:
• Species diversity
• % Naticids
• % Preferred Prey
• The data showed a rising and falling of drilling frequency instead of a consistent rise, perhaps related to mass extinctions.
Courtesy Kelley & Hansen, 2003
Justification• We have data from Virginia and North Carolina to the Gulf Coast states.
• Data from South Carolina will help fill in the gaps!
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RP C BR BL CM MB MS BE CH E CR FN
Stratigraphic Level
Dri
lling
Fre
quen
cy
All GastropodsTurritellids
Drilling Frequencies:
Turritellid snails vs all snail species
Fig. 1. Orangeburg Group (Nystrom et al, 1989)
Methods
1. Return bulk sample of fossils to lab for study.
2. Tabulate location and frequency of drill holes (Drill hole frequency = % individuals with complete naticid drill-holes).
3. Measure common prey species for size, shell thickness, and internal volume for cost-benefit calculations, and any drill holes documented.
4. Test my hypotheses.
Research Hypotheses Drilling frequencies between those for Virginia and the
Gulf Coast
Drill site and prey selection will be more pronounced than older assemblages
Naticid predation in South Carolina predicted by cost-benefit analysis
Drilling frequencies similar to those of equivalent fossil assemblages
% of naticids present proportional to drilling frequency
% of preferred prey proportional to drilling frequency
Thank You