Answer to fossil record puzzle may lie with teenage T rexes, study finds
Teenage T rexes and other carnivorous dinosaurs the size of lions or bears may have crowded out smaller species, explaining why there are so few of them preserved in the fossil record, research suggests.
Despite dominating the land for more than 150 million years, dinosaurs were not particularly diverse, and most known species were giants weighing 1,000kg or more – including massive, meat-eating megatheropods such as Tyrannosaurus rex.
Particularly absent from the fossil record are smaller dinosaurs weighing less than 60kg. This is very different to other vertebrate communities, which typically contain a broad spectrum of body sizes.
Now, a study published in Science hasprovided an explanation: megatheropods may have adopted a “grow fast, die young” approach that meant Earth was crammed with teenage meat eaters occupying ecological niches that would otherwise have hosted smaller carnivores.
To test this theory, Katlin Schroeder at the University of New Mexico and her colleagues analysed a dataset of dinosaur records representing 43 geographically located communities across seven continents, spanning 136m years. This confirmed that those communities containing megatheropods were largely devoid of medium-sized carnivores in the 100-1,000kg range, whereas those without megatheropods did contain these species.
Using existing information about the growth rates of these dinosaurs and the age at which they died, they also calculated that juveniles must have accounted for a substantial proportion of the total population of megatheropods – enough to have outcompeted similarsized adults of different species.
“Not only were there many more juveniles than adults, they would have been right in this mass range that we’re missing from other species,” Schroeder said. These young megatheropods may well have occupied a different ecological niche to the adults – just as Komodo dragons do today, with their young hatching from eggs, scurrying up trees and eating insects and lizards, until they grow too big and then drop to the ground and start hunting larger creatures, from rodents to water buffalo.
“One thing that stands out about megatheropods is that as they grew they changed a lot,” said Schroeder. “An adult Tyrannosaurus rex was this huge, robust, bone-crunching animal, but as juveniles they were fairly light, fleet-footed, and they didn’t have deep, heavy skulls. They may have been the same genetic species, but they were entirely different in appearance and function.”
Steve Brusatte, a professor of palaeontology and evolution at the University of Edinburgh, said:“This study puts numbers on something we’ve long suspected but haven’t really proven: that the biggest meat-eating dinosaurs filled different niches in the food chain as they grew from miniature hatchlings into adults bigger than buses.
“This seems to be a consistent pattern in dinosaurs, especially those communities in the Cretaceous, towards the end of their reign. There were few meat-eating dinosaur species of moderate adult body size, and that’s because the juveniles and teenagers and subadults of the big bruising dinosaurs were controlling those niches. It’s an ecological structure that is very unlike what we are used to with mammals today.”
Friday 26 February 2021
A new driverless electric bus has begun operating in the southern Spanish city of Málaga, in the first such project in Europe.
The bus, which began running on Saturday, is equipped with sensors and cameras and links Málaga’s port to the city centre on an 8km (five-mile) loop it does six times a day.
“The bus knows at all times where it is and what is around it,” said Rafael Durban Carmona, who heads the southern division of Spanish transport company Avanza, which leads the publicprivate consortium behind the project. It could “interact with traffic lights” that were also equipped with sensors that alert the bus when they turn red, he told Agence France-Presse.
The bus uses artificial intelligence to improve its “decisions” based on data recorded along the route. The 12metre (39ft) vehicle, which looks like a normal bus, can carry 60 passengers and was developed by the Spanish company Irizar.
Other driverless pilot projects already exist in Europe, but none of them involves a regular-size urban bus that runs on a normal street with other vehicles. Despite the advanced technology, there is a driver at the wheel to take control if necessary since Spanish law does not currently allow vehicles to operate without drivers.
“We put it in automatic mode and it runs completely autonomously,” says Cristobal Maldonado, the driver.
The project received funding from the Spanish government and was coordinated with several universities.
Last month, Singapore launched a self-driving bus trial with passengers booking through an app and the bus taking them around Singapore’s Science Park, a hi-tech business hub, during off-peak hours. China has also tested driverless taxis in several cities.
An Uber self-driving car hit and killed a woman crossing the street in the US in 2018, in what is believed to be the first death involving an autonomous vehicle.
Lack of regulation and concerns over safety on the part of the general public are two factors often cited by experts that stand in the way of the proliferation of driverless vehicles.