Shape shifting dinosaurs: the cause of premature extinction - Jack Horner 2011

Milly Kay
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Milly Kay
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Shape shifting dinosaurs: the cause of premature extinction - Jack Horner 2011
1 Fascination with dinosaurs?
1.1 big
1.2 different
1.2.1 Morphologicaly Used to define different species Limitations Museums Bones precious Barrier to cutting open bones Ego Find the biggest and best dinosaur possible New species by size and morphology Want to name a new dinosaur Origonal name sticks, second name gets thrown out Torosaurus now triceratops Anatatitan becomes Edmontosaurus
1.3 Extinct
2 1970
2.1 Where are all the juveniles?
2.1.1 Assumed that juveniles would be easily identified Anything that looked a little different got named as a new dinosaur
3 1975
3.1 Dr. Peter Dodson - University of Pennsylvania
3.1.1 Growth in dinosaurs is more like chicken and less like reptiles Allometric (relative) Cranial (skull) Ontogeny (growth) Example: Cassowary Birds with crests grow to around 80% before the crest starts to grow Retention of juvenile characteristic well into ontogeny Looks like two different species REFERENCE : Relative skull growth Example: Hypacrosaurus If it grew in a linear fashion it would have a crest around half the size of the adlut
4 Hell creek formation
4.1 Produces last dinosaurs
5 Dinosaur species - Skulls that change shape during ontogeny
5.1 Pachycephalosaurs, Stygimoloch and Dracorex
5.1.1 Cant determine relationship fully by looking at morphology Spike on Dracorex are growing, spike on Stygimoloch are reabsorbing and dome is growing and Pachycehalsaur dome is solid and spikes are still reabsorbing Easy to hypothesize that this is a growth series but need evidence
5.2 Triceratops
5.2.1 Horner and Goowdin 2006 - Major cranial changes during triceratops ontogeny : Juveniles grow horns grow backwards and then start to grow forwards and the triangular spikes along the frill as juviniles flatten out when they are older Cut open the skulls and found degree of sponginess relative to age. Smallest skull is spongy, intermediate was spongy however largest one is spongy also. Torosaurus - 3m long skull looks like triceratops but has mature bone Has holes in its frill. John Scannella 2010 5 questions for John Scannella Torosaurus Marsh, 1891, is Triceratops Marsh, 1889 (Ceratopsidae: Chasmosaurinae): Synonymy Through Ontogeny Hole starting to form in triceratops and shows as open in Torosaurus. Also found transitional skulls ‘Nedoceratops’: An Example of a Transitional Morphology 2010 - No juvenile Torosaurus found to date
5.3 Anatatitan is a juvenile Edmontasaurus
5.3.1 Cranial Growth and Variation in Edmontosaurs (Dinosauria: Hadrosauridae): Implications for Latest Cretaceous Megaherbivore Diversity in North America
5.4 T-rex and nanotyranus
5.4.1 Nano had 17 teeth has juvenlie bone, tyrannosaurus had 12 and more mature bone Less teeth as they get older Dinosaur Census Reveals Abundant Tyrannosaurus and Rare Ontogenetic Stages in the Upper Cretaceous Hell Creek Formation (Maastrichtian), Montana, USA
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