Functional Morphology

What is it?

• Analyzing function of structures in living organisms

• Inferring function from structure in extinct organisms

• Getting past “Just-So” stories

Methodologies

• Analogy to living organisms– Assumes the analogy is valid

• Biomechanical analysis• Building physical models• Building mathematical models

Case Study: Archeocyathids

• Hypothesis: archeocyathids used Bernoulli’s principle to move water through the pores

• Method: Build models of archeocyathids with different combinations of pores and septa

• Results: the model most like an actual archeocyathid most effectively created smooth flow of water

Case: Horseshoe crab spines

• Question: Are the spines important in settling through the water?

• Method: Build models with varying spines and drop them in water.

• Results: No spines and very long spines create turbulent movement; moderate spines allow smooth downward motion (presumably less attractive to predators)

Case: Pterosaur flight

• Question: flapping or gliding?• Method #1: calculate wing loading• Method #2: compare wing structure to

albatrosses• Method #3: plot wing loading v. wing shape

and plot for many modern flyers• Method #4: build a model• Result: ???

Case: Robot clams

• Question: how does the structure and ornamentation of shell affect burrowing ability?

• Method: build robot clams, vary the shell shape and ribs, vary the sediment

• Result: the little dent behind the beak turns out to be important. So do ribs parallel to the shell edge.

Case: Saber-tooth cats

• Question: function? Slash? Pierce?

• Method #1: compare to the gape of modern cats, calculate bite force

• Method #2: look at tooth edge (relatively dull), compare to modern Komodo dragon

• Results:???

Sauropod necks

• Possible functions of very long necks:– Underwater grazing/breathing– Tree-top browsing

Underwater sauropods

• Problems:– Water pressure preventing breathing– Biomechanics of legs• Capable of supporting dinosaur on land

– Shape of thorax• Hippopotamus has rounded thorax• Rhinos and elephants are slab-sided• Sauropods are slab-sided

Tree-top browsing• Evidence:– Range of motion of vertebrae in

apatosaurs• Computer modeling put together all the

vertebrae on Apatosaurus, found 2-3m of reach

• Evidence of strong ligamental system – head held itself up and required effort to pull it down.

– Blood pressure issue• Brachiosaur computed to require 600+ mmHg

(giraffe is 320)– Tripod position for brachiosaurs –

biomechanically possible

Your task

• Read/Skim your paper• Be prepared to present the case, answering

these questions:– What’s the question/hypothesis?– What’s the methodology?– Results?– Do you think it’s a valid method and/or

conclusion?