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Systematics of Some Enigmatic “Fossils”
Allison Tumarkin-DeratzianDept. of Earth & Environmental Science
Temple UniversityPhiladelphia, PA
(a.k.a. “Paperclipidae & Pastaformes”)
• Audience– intermediate-level Paleontology & Stratigraphy course
for Geology and Environmental Science majors
• Background– basic principles of phylogenetic systematics
• synapomorphy, outgroups & character polarity, parsimony• structure and reading of cladograms
– major sources of intraspecific morphological variation• ontogenetic change, sexual dimorphism
• Goals– Acquire hands-on experience with phylogenetic
reconstruction– Apply morphological species concept to identification
and classification of organisms– Compare outcomes derived from different
interpretations of identical data– Encourage student participation and group work
Paperclipidae
7 individuals
Original Assumption (unstated) : 1 individual = 1 species
Outgroup taxon not in set; described as headless straight pin or eyeless needle
1 2 30 0 0
1 0 0
1 1 0
1 1 1
Characters (0=absent, 1=present):(1)Wire bent(2)Wire doubles back on itself(3)Wire crosses over itself
THE ISSUES:SYNAPOMORPHY,AUTAPOMORPHY
How do we construct a simple cladogram?
Outgroup
1
2
3
Ou
tgro
up
1 2 3 40 0 0 0
1 0 0 0
1 1 0 0
1 1 1 0
0 0 0 1
Characters (0=absent, 1=present):(1)Wire bent(2)Wire doubles back on itself(3)Wire crosses over itself(4)Head
THE ISSUES:PARSIMONY,REVERSAL
What hypothesis yields the shortest tree?
Outgroup
1
2
34
Ou
tgro
up
Tree length = 4 stepsMost parsimonious tree (MPT)
1
2
3
4
-4
Ou
tgro
up
Tree length = 5 steps
1 2 3 4 50 0 0 0 0
1 0 0 0 0
1 1 0 0 0
1 1 1 0 0
0 0 0 1 0
1 1 0 0 1
0 0 0 1 1
Characters (0=absent, 1=present):(1)Wire bent(2)Wire doubles back on itself(3)Wire crosses over itself(4)Head(5)Plastic
THE ISSUES:CONVERGENCE,CONSENSUS & POLYTOMIES
Did plastic evolve more than once?
Outgroup
1
2
3
4
5 5
Ou
tgro
up
Tree length = 6 steps
Hypothesis 1 – Plastic evolved convergently in two lineages
Ou
tgro
up
1
2
-2 34 4
5-1
Tree length = 8 steps
Hypothesis 2a – Plastic evolved only once; head evolved convergently in two lineages
Ou
tgro
up
1
2
3
4
21-4
5
Tree length = 8 steps
Hypothesis 2b – Plastic evolved only once; wire bending/doubling evolved convergently in two lineages
1
2
3
4
5 5
Ou
tgro
up
Tree length = 6 steps (MPT)
Plastic more likely evolved twice.
This is not the only possible MPT.
1
2
3
4
5 5
Ou
tgro
up
Tree length = 6 steps (MPT)
1
2
3
4
5 5
Ou
tgro
up
Tree length = 6 steps (MPT)
Ou
tgro
up
Strict consensus of three MPTs showing polytomy.
Paperclipidae
Original (unstated) Assumption: 1 individual = 1 species
ARE YOU SURE?THE ISSUE:WHAT IS THIS INDIVIDUAL?
Species A adult, Species B, Species A juvenile
Species A male, Species B, Species A female
Size as ontogenetically variable / sexually dimorphic
OR
Species A, Species B adult, Species B juvenile
Species A, Species B male, Species B female
Species A adult male, Species A juvenile, Species A adult female
Plastic as ontogenetically variable / sexually dimorphic
OR
OR
Paperclipidae
IF PLASTIC IS NOT DIAGNOSTIC AT SPECIES LEVEL, ARE THESE ALSO THE SAME SPECIES?
Pastaformes
13 individuals
Given: the spaghetti is the outgroup and no other individual is from the same species as the spaghetti.
Outgroup
STEP 1:HOW MANY SPECIES DO YOU HAVE?
STEP 2:DEFINE USEFUL CHARACTERS
Is penne flat?
The answer may surprise you….
What is “flat,” exactly?
STEP 2:DEFINE USEFUL CHARACTERS
What is the difference between curved, twisted, and spiral?
STEP 3:CONSTRUCT CHARACTER MATRIX
STEP 4:RUN ANALYSIS