Taxonomy and Phylogeny Flashcards
How was the first taxonomy of fossils made by ancestor descendant relationships ?
- Looked at characteristics
- Looked at stratisgraphic markers
- Both presence and absence of characters were considered
- Thought one species gave rise to another
- Relied on hunches
- However, speciation does not occur at the species level it occurs at the population level
How to do cladistic / phylogenetic analysis?
- Create a character matrix based only on the presence of characters
- Analyse character distribution using parsimony or bayesian methods (computer)
- Identify homologous characters - synapomorphies
- Establish sister group rather than ancestor - descendent relationship
- Accept only monophyletic groups
- Illustrate using a cladogram.
What are the different types of phylectic groupings on a cladogram?
- Monophyletic (correct)
- Paraphyletic (some species have been forgotten)
- Polyphyletic (wrong)
What are crown groups and stem groups?
- Crown group: Last common ancestor of all the living forms and all of its descendants
- Stem group: The extinct organisms more closely related to a particular crown group than to any other living group
What was Seeley’s scenario?
- Thought thecodontia gave rise rise to pterosaria, saurischia, ornithiscia and crocodile
- Saw them as a non-monophyletic group
However, Dinosaurs were probably a monophyletic group (when including birds)
Who was H. G. Seeley?
First person to really think about dinosaur phylogeny
What is the nearest sistergroup to the dinosaurs?
Pterosaurs
What type of dinosaur were Ornithicia?
- Armoured, horned and duck billed dinosaurs
- Bird-hip dinosaurs
What kind of phylogenetic group are the dinosaurs?
Monophyletic (if you include birds)
What were the features of the Stegosaurus?
- 3 - 9 m long
- Slow moving
- Not efficient runners
- Herbivores, have a huge gut and beak-like mouth
- Protected by large size, big plates on back and spikes on tails (huge force)
- Either have spines or sails in their back
- Very small brain
- Sister group to Ornithicians
How many species of stagosaurus have been described (and accepted)?
- 12 wiedely accepted described species
- Inflated number of dinosaur species
What are the features of Ankylosauria?
- Plated dinosaurs
- Less than 5m in size - can be 9m
- Big heavy with massive gut
- Herbivore
- Head and back covered in sheet of bone with spines
- Flexible tail with lumps of bones - swing for defence
- Very small brain 0.001 of body mass
What were the features of pachycephalosauria?
- Headbutters
- 16 species
- 2-8m in length
- 450 kg
- Very agile
- Up on two legs - bipedal
- Lived in herds / packs
- Average size brain - moderate intelligence because they live in herds
- Large lump on skull allows them to headbutt in a way of showing off to females etc.
What were the features of Ceratopsia?
- Frilled, 3 horned dinosaur
- Frill is too thin so be used in defence
- 40 species
- Vary in size - 1m - 9m
- Charging up to 30-35kph
- Average brain size
- Horn developed for defence but changed to display
- Lived in herds
What were the features of Euorithopa?
True Onithopoda
- Hypsilophodontidae (e.g. Hypsilophodon)
- Iguanodontia (e.g. Iguanodon)
- Range in size
- Smaller ones very fast
- Live in herds
- Intelligent
- Intercommunication
