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?