A few questions about trilobites

[Hapchazzard]

This has been bugging me for some time now, and I can't find any papers that answer these questions. I'm honestly surprised at how little research seems to have been done about these topics.

 

1. How fast were they compared to some modern-day benthic animals? Were they slow and cumbersome, or were they fast and agile? How did this change through time/environment? I assume that the earlier, Cambro-Ordovician trilobites would have been a fair bit slower than their later counterparts due to a lack of nektic predators that could easily pierce their armor, but this is just my assumption.

 

2. Did fish actually actively predate on them in any significant capacity? I often see it said that the rise of fish throughout the middle Paleozoic is a reason for the Trilobite's demise, due to increased predation, but I've never actually seen any significant evidence for this. I find it hard to imagine how Palaeozoic fish could have effectively preyed on them - their morphology just doesn't seem to have been suited to "breaking their defenses", so to speak. Even modern day fish seem to rarely actively hunt animals like crabs, which are somewhat analogous to the trilobites in terms of morphology and ecology.

 

3. Was their post-Devonian terminal decline due to environmental elimination (mainly, the destruction of the Tabulate-Stromatoporoid reefs which they seem to have inhabited in significant numbers), or due to something else?

[JohnBrewer]

@piranha among others may help. 

[gigantoraptor]

I don't think their speed evolved much, there have always been sea-predators. In the Cambrian period, the biggest known predator is Anomalocaris I guess. A theory says that Anomalocaris fed on hard shelled animals, like trilobites, althought this has been questioned. In the ordovician they had eurypterus to deal with. I think they just evolved their abilities to hide for their enemy's.

 

 

[piranha]

9 hours ago, Hapchazzard said:

1. How fast were they compared to some modern-day benthic animals? Were they slow and cumbersome, or were they fast and agile? How did this change through time/environment? I assume that the earlier, Cambro-Ordovician trilobites would have been a fair bit slower than their later counterparts due to a lack of nektic predators that could easily pierce their armor, but this is just my assumption.

 

Here is a study that utilized flow tank testing of trilobite genal spines:

 

Walkowicz, J. (2012)

Keeping a Flow Profile: The fluid dynamics and biomechanics of trilobite genal spines.

Department of Geophysical Sciences, University of Chicago, 14 pp.   PDF LINK

 

 

Some trilobites were probably fast.  There are a number of papers on trilobites that were swimmers:

 

Fortey, R.A. (1974)

A new pelagic trilobite from the Ordovician of Spitsbergen, Ireland and Utah.

Palaeontology, 17(1):111-124   PDF LINK

 

Fortey, R.A. (1985)

Pelagic trilobites as an example of deducing the life habits of extinct arthropods.

Earth and Environmental Science Transactions of The Royal Society of Edinburgh, 76(2-3):219-230

 

McCormick, T., & Fortey, R.A. (1998)

Independent testing of a paleobiological hypothesis: the optical design of two Ordovician pelagic trilobites reveals their relative paleobathymetry.

Paleobiology, 24(2):235-253

 

Shiino, Y., Kuwazuru, O., Suzuki, Y., & Ono, S. (2012)

Swimming capability of the remopleuridid trilobite Hypodicranotus striatus: Hydrodynamic functions of the exoskeleton and the long, forked hypostome.

Journal of Theoretical Biology, 300:29-38

 

 

 

9 hours ago, Hapchazzard said:

2. Did fish actually actively predate on them in any significant capacity? I often see it said that the rise of fish throughout the middle Paleozoic is a reason for the Trilobite's demise, due to increased predation, but I've never actually seen any significant evidence for this. I find it hard to imagine how Palaeozoic fish could have effectively preyed on them - their morphology just doesn't seem to have been suited to "breaking their defenses", so to speak. Even modern day fish seem to rarely actively hunt animals like crabs, which are somewhat analogous to the trilobites in terms of morphology and ecology.

 

This topic is highly speculative.  This paper will get you started in the right direction:

 

Babcock, L.E. (2003)
Trilobites in Paleozoic predator-prey systems, and their role in reorganization of early Paleozoic ecosystems.
Topics in Geobiology, 20:55-92

 

 

 

9 hours ago, Hapchazzard said:

3. Was their post-Devonian terminal decline due to environmental elimination (mainly, the destruction of the Tabulate-Stromatoporoid reefs which they seem to have inhabited in significant numbers), or due to something else?

 

Here are some excellent papers that discuss the extinction of late Devonian and Permian trilobites:

 

Feist, R., & Clarkson, E.N.K. (1989)
Environmentally controlled phyletic evolution, blindness and extinction in Late Devonian tropidocoryphine trilobites. 

Lethaia, 22(4):359-373   PDF LINK

 

Owens, R.M. (1994)
Pseudoextinctions in Late Devonian Proetide trilobites.

Historical Biology, 9(3):207-221

 

Brezinski, D. K. (1999)

The rise and fall of late Paleozoic trilobites of the United States.

Journal of Paleontology, 73(2):164-175

 

Owens, R.M. (2003)
The stratigraphical distribution and extinctions of Permian trilobites.
Special Papers in Palaeontology, 70:377-397

 

Feist, R., & McNamara, K.J. (2007)

Biodiversity, distribution and patterns of extinction of the last odontopleuroid trilobites during the Devonian (Givetian, Frasnian).

Geological Magazine, 144(5):777-796   PDF LINK

 

Feist, R., Mcnamara, K.J., Crônier, C., & Lerosey-Aubril, R. (2009)

Patterns of extinction and recovery of phacopid trilobites during the Frasnian–Famennian (Late Devonian) mass extinction event, Canning Basin, Western Australia.

Geological Magazine, 146(1):12-33   PDF LINK

 

McNamara, K.J., Feist, R., & Ebach, M.C. (2009)
Patterns of evolution and extinction in the last harpetid trilobites during the Late Devonian (Frasnian).
Palaeontology, 52(1):11-33   PDF LINK

 

Lerosey-Aubril, R., & Feist, R. (2012)
Quantitative Approach to Diversity and Decline in Late Palaeozoic Trilobites. pp.535-556

In: Earth and Life: Global Biodiversity, Extinction Intervals and Biogeographic Perturbations Through Time.   PDF LINK

 

Feist, R., & Mcnamara, K.J. (2013)

Patterns of evolution and extinction in proetid trilobites during the Late Devonian mass extinction event, Canning Basin, Western Australia.

Palaeontology, 56(2):229-259    

 

McNamara, K.J., & Feist, R. (2016)

The effect of environmental changes on the evolution and extinction of Late Devonian trilobites from the northern Canning Basin, Western Australia.

Geological Society London, Special Publications, 423(1):251-271

 

Shi, Z., et al. (2017)

Remains of trilobites and other species discovered in a volcanic ash bed of the end-Permian, Yangtze craton, South China.

International Geology Review, 59(7):905-917

[Hapchazzard]

Wow, thanks a lot @piranha, I really appreciate the effort! The members of this forum never cease to impress me with their helpfulness. This is exactly the type of literature I was looking for.