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