In a lush, past landscape, a hungry triceratops eats low-lying ferns and cone-shaped cycad plants to power its 10-ton frame. The animal swallows huge bites of roughage, seeds and everything before sauntering off in search of new feeding grounds.
Days later and miles away, the Triceratops empties its intestines and sows the seeds of the plants it has eaten with fertilizer in more distant soil than could be reached without it.
The proliferation of plant seeds in the bodies of animals, known as zoochory, is so common in modern ecosystems that plants often adapt their fruits and flowers to appeal to specific carriers. Fossils of feces and intestinal contents suggest that plant seeds also ride in dinosaur bellies, although it is unclear whether these relationships were as widespread and refined as they are today.
George Perry, a forest ecologist at the University of Auckland who studies human pressure on seed distribution, looked into this issue during New Zealand’s coronavirus lockdowns.
“I know from modern ecosystems that large animals are important distributors of seeds,” said Dr. Perry. “I thought I had all the parts: what is the most massive animal ever and how far could it have moved seed?”
In a study published Wednesday in Biology Letters, Dr. Perry set a framework for calculating the extent to which dinosaurs – weighing about 20 pounds to 90 tons – could have transported the seeds of prehistoric plants. He found that dinosaurs like Triceratops or Stegosaurus had the right mix of size and speed to lay seeds between three and 20 miles from parent plants. This is similar to the African bush elephant, which transports seeds an average of a mile and a half, but can move them up to 40 miles.
Dr. Perry’s simulations depend on two main factors: the speed of a dinosaur and the time it takes for it to hold back seeds before they are eliminated. It is difficult to determine these values because the fossil record is limited. However, body mass is related to walking speed and semen retention time of modern animals, which can be used as a rough analogue for earlier ecosystems.
“What we really want is to get a GPS tracker, put it on a dinosaur and follow it, but we can’t,” said Dr. Perry. Because of this, the study’s assumptions are “reasonably conservative,” he added.
Large animals usually travel farther and hold seeds longer than smaller animals. But extremely massive dinosaurs like the 90-ton Argentinosaurus may have been slower than medium-sized herbivores. That means Grazer like Triceratops were probably the most effective dispersers of seeds because of their more modest height and still amazing appetite.
“The seed dispersal potential of extinct animals is of great concern, and Dr. Perry made a reasonable estimate of that of dinosaurs,” said Tetsuro Yoshikawa, a plant ecologist at the National Institute for Environmental Studies in Japan who has published research on the subject.
“Since existing land animals such as elephants and bears can in some cases transport several kilometers of semen, large dinosaurs can have similar potential.”
Dr. Perry’s study is “a great example of how a scientist with shrewd lateral thinking can find insights into a question that – at face value – can only be answered with a time machine,” said John Hall, a University of Queensland plant ecologist and expert on Cycad plants.
Of course, it would be wonderful if scientists could dip their elbows deep in real dinosaur dung à la Ellie Sattler in Jurassic Park. Unfortunately, the finer details of these complex ecosystems will most likely remain shrouded in mystery and speculation.
“When we look at the natural world today, the diversity and intimacy of the close symbiotic relationships between plants and animals that pollinate flowers and disperse seeds is simply breathtaking,” said Dr. Hall.
There is “no reason not to believe that the spectrum of such relationships must have been just as complex and varied in prehistoric times,” he added, although “these relationships must remain enticingly lost to us.”
Comments are closed.