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Dinosaurs Were Faster Than Triassic
Monotreme Mammals And Their Respiratory Systems Were More Efficient
Dinosaurs
were able to walk and run faster than early Triassic monotreme mammals. The extant and fossil monotreme
body plans, with their splayed
reptilian pectoral girdles and mammalian pelvic girdles, and the extant monotreme low walking locomotion style, suggests that all early mammals walked like modern
monotremes. As a result, monotremes
could not move as fast as dinosaurs. Strong
competition from the faster dinosaurs likely forced mammals to be active at night, sleep in the day, and live in
secluded areas such as underground
burrows, wetlands, forest woody debris and forest canopies.
The nocturnal, burrowing and seclusive lifestyles, of the extant
Platypus and Echidna monotremes, provide supporting evidence for this
scenario.
Dinosaurs evolved a highly efficient respiratory system in the low
oxygen Triassic atmosphere. The modern dinosaurs, the birds, have the
same respiratory system and are able to breath more efficiently than
mammals in the low
atmospheric oxygen at
high altitudes. The
mammals, and the synapsid ancestors of the mammals, the pelycosaurs,
therapsids and thecodonts, evolved and used a respiratory system that
was more suitable for the high oxygen Carboniferous and early Permian
atmospheres. Triassic mammals were not able to breath as well
as dinosaurs. The dinosaurs' efficient respiratory system along
with their superior mobility, probably helped them out compete the
mammals and chase them into the night.
Although
dinosaurs did not cause the extinction of mammals, they may have
caused the end Triassic
extinctions of Cynodont
and Therapsid mammal like
reptiles, and Protodinosaur-Thecodonts.
Alternatively, the end Triassic extinctions
may have been caused by the extreme volcanic activity that
occurred then.
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