Forces Driving Angiosperm Divergence II

Animal interactions

Herbivorous dinosaurs were very large.

Sauropods couldn’t chew, no grinding back teeth. Had peg like teeth - raked and sliced leaves from trees. May have swallowed stones to help break up food in stomach.

Hadrosaurs chewed plants with grinding back teeth.

Ages

1. Age of the Anchisaurs: late triassic (210 mya) to early jurassic (180 mya). Herbivory- ancient conifers and cycadeoids.

2. Age of the High Browers (feeders): mid(180mya) to late(140mya) jurassic. Brontosaurs and stegosaurs. Herbivory-recent conifers and cycadeoids.

3. Age of the Low Feeders: Cretaceous (145-66 mya). More diverse in herbivory. c.100mya hadrosaurs dozen of new species across North America and Eurasia. Presumably taking advantage of a new food source (angiosperms). Hadrosaurs evolved in tandem with ancient angiosperms. Fossils had twigs, berries and tough plants found in the stomach region. c.66my old coprolite (fossil poo) of a sauropod (from india) contained traces of grass- the earliest evidence for this plant yet.

Extinction of tall feeders

Herbivorous dinosaurs feed initially primarily on tall conifers and other gymnospersm. Herbivorous dinosaurs increase in capacity. Reach carrying capacity= maximum population an area will support without undergoing deterioration. Angiosperms were not main food source of dinosaurs and basal angiosperm seemed to be designed to go under their radar. Gymnosperms over exploited food source so they start to decrease = large dinosaurs decrease. With decreasing gymnosperm dominance angiosperms spread and diversify and eventually replace and dominant gymnosperms. Angiosperms become food source for hadrosaurs

KT extinction

Acted as selection forces on Angiosperm Divergence.

Birds evolved from small-bodied predatory dinosaurs. Now pollinators, herbivores, frugivores, granivores, dispersal agents.