1 / 26

Systematics of Some Enigmatic “Fossils”

This course explores the systematics of enigmatic fossils, Paperclipidae and Pastaformes, covering topics such as phylogenetic reconstruction, morphological species concept, and different interpretations of data. It encourages student participation and group work.

swelch
Download Presentation

Systematics of Some Enigmatic “Fossils”

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Systematics of Some Enigmatic “Fossils” (a.k.a. “Paperclipidae & Pastaformes”) Allison Tumarkin-Deratzian Dept. of Earth & Environmental Science Temple University Philadelphia, PA

  2. 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

  3. Paperclipidae Original Assumption (unstated): 1 individual = 1 species 7individuals Outgroup taxon not in set; described as headless straight pin or eyeless needle

  4. THE ISSUES: SYNAPOMORPHY, AUTAPOMORPHY • Characters (0=absent, 1=present): • Wire bent • Wire doubles back on itself • Wire crosses over itself How do we construct a simple cladogram? Outgroup

  5. Outgroup 3 2 1

  6. THE ISSUES: PARSIMONY, REVERSAL • Characters (0=absent, 1=present): • Wire bent • Wire doubles back on itself • Wire crosses over itself • Head What hypothesis yields the shortest tree? Outgroup

  7. Outgroup 4 3 2 1 Tree length = 4 steps Most parsimonious tree (MPT)

  8. Outgroup 3 2 1 -4 4 Tree length = 5 steps

  9. THE ISSUES: CONVERGENCE, CONSENSUS & POLYTOMIES • Characters (0=absent, 1=present): • Wire bent • Wire doubles back on itself • Wire crosses over itself • Head • Plastic Did plastic evolve more than once? Outgroup

  10. Outgroup 5 5 3 4 2 1 Hypothesis 1 – Plastic evolved convergently in two lineages Tree length = 6 steps

  11. Outgroup 4 4 -2 3 -1 5 2 Hypothesis 2a – Plastic evolved only once; head evolved convergently in two lineages 1 Tree length = 8 steps

  12. Outgroup 2 3 1 -4 5 2 4 1 Hypothesis 2b – Plastic evolved only once; wire bending/doubling evolved convergently in two lineages Tree length = 8 steps

  13. Outgroup 5 5 3 4 2 1 Plastic more likely evolved twice. This is not the only possible MPT. Tree length = 6 steps (MPT)

  14. Outgroup 3 5 5 4 2 1 Tree length = 6 steps (MPT)

  15. Outgroup 3 5 5 4 2 1 Tree length = 6 steps (MPT)

  16. Outgroup Strict consensus of three MPTs showing polytomy.

  17. Paperclipidae Original (unstated) Assumption: 1 individual = 1 species ARE YOU SURE? THE ISSUE: WHAT IS THIS INDIVIDUAL?

  18. Size as ontogenetically variable / sexually dimorphic Species A adult, Species B, Species A juvenile OR Species A male, Species B, Species A female

  19. Plastic as ontogenetically variable / sexually dimorphic Species A, Species B adult, Species B juvenile OR Species A, Species B male, Species B female OR Species A adult male, Species A juvenile, Species A adult female

  20. Paperclipidae IF PLASTIC IS NOT DIAGNOSTIC AT SPECIES LEVEL, ARE THESE ALSO THE SAME SPECIES?

  21. Pastaformes Given: the spaghetti is the outgroup and no other individual is from the same species as the spaghetti. Outgroup 13individuals

  22. STEP 1: HOW MANY SPECIES DO YOU HAVE?

  23. STEP 2: DEFINE USEFUL CHARACTERS Is penne flat? The answer may surprise you…. What is “flat,” exactly?

  24. STEP 2: DEFINE USEFUL CHARACTERS What is the difference between curved, twisted, and spiral?

  25. STEP 3: CONSTRUCT CHARACTER MATRIX

  26. STEP 4: RUN ANALYSIS

More Related