Eating medium-sized meat Dinosaurs Fossils are missing from the record, and paleontologists wonder why they discovered this.
Paleontologists have found gregantuan dinosaurs and tiny dinosaurs, but a new study has found a clear lack of medium-sized carnivorous dinosaur species, especially Criticism period (145.5 million to 65.5 million years ago).
Donating their detective hats, the researchers soon found a suspect; Megadropods – the largest of the carnivorous dinosaurs, e.g. Tyrannosaurus rex And Gorgosaurus, Weighing 2,200 pounds (1,000 kilograms) as an adult. It is possible that juvenile megadharopods messed up, the researchers said.
“Juvenile megadropods have eliminated other medium-sized dinosaurs, which could lead to a decline in global dinosaur diversity,” said study lead researcher Klin Tallin Schroeder, a doctoral student in the Department of Biology at the University of New Mexico.
However, not everyone is convinced that there are cases of missing medium-sized dinosaurs; For example, it is possible that there are fossils of medium-sized animals that have not yet been found, said Michael D’Amek, an associate professor in the Department of Biology at Adelphi University in New York, who was not involved. Study.
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Small, medium, large
Like egg-laying animals, all dinosaurs started small, weighing no more than 33 pounds (15 kg). As dinosaurs grew, some people occupied different structures and ate different foods than adults of the same species – for example, a young one T Rex Couldn’t take on a potential one Triceratops, And probably went after a small hunt.
To investigate a medium-sized mystery, Schroeder and his companions Palebiology Database, A profitable resource for paleontological data, and they classify more than 550 dinosaur species as small (22 to 220 pounds, or 10 to 100 kg), medium (220 to 2,200 pounds, or 100 to 1000 kg) or large (over 2,200 pounds). Does, or 1000 kg). During these dinosaurs lived within 43 communities (groups living at the same time and place) on seven continents. Jurassic period (201 million to 145.5 million years ago) and the Cretaceous period.
Researchers have found that there are always herbivorous dinosaurs in every size class in communities, while medium-sized carnivorous dinosaurs are rare in communities with megadropods.
“It’s possible that the ‘gap’ was caused by teenagers in those large megadropods, who were probably eating different things than their parents, and so they would compete with medium-sized carnivores.”
The team found that the distance of medium-sized dinosaurs in the Cretaceous was more pronounced than in the Jurassic period. During the Cretaceous period, apart from the megadharopods of Julsik, Julsi and Abelis were kings, and they “looked very different from different people, even from adults,” he said.
In other words, during the Jurassic period, megathoropods, e.g. Allosaurus, Not as much as they grew up, “and indeed they will be able to share food resources like giant sur ropods. [long-neck herbivorous dinosaurs] “With his parents,” Schroeder said. “Because of this more people are likely to coexist in the same communities, resulting in smaller [medium-size] Gap in non-vegetarian. “
But by the end of the Jurassic, many soropods became extinct, and so the dinosaurs liked it Allosaurus. “Like them, dinosaurs would have changed Tyrannosaurus As they evolved they used a wide variety of different resources, ”Schroeder said.
Next, Schroeder’s team wondered if juvenile megadropods had a greater impact on the formation of their communities than their peers. To find out, the researchers calculated how many children and adults of each race were in the community. After that, the team found biomass – the number of individuals in a species multiplied by their mass at a certain age.
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Researchers have found that in some megadharopod species, such as Allosaurus And Tyrannosaurus, Adolescents represented a much larger proportion than adults, probably because it was a dinosaur-eating-dinosaur world at the time, and megadropods did not always come of age. This suggests that “teens had as much (if not more) impact on their community than adults,” Schroeder said in an email. In fact, there were many medium-sized megadharopods, in the way they spoke, to be seen as their own species.
“When we added teenagers into communities as their own [species], The distance largely disappeared, ”Schroeder said.
However, it is possible that something else could explain this medium-sized mystery, D’Emek said. Of the Paleo-communities examined in the study, 12 out of 43 did not appear to follow the predictive method – medium-sized carnivorous dinosaurs were rarely seen in communities with megadharopods. In these 12 communities, “they have both large and medium-sized theropods,” de Imic said. Studies illustrate these exceptions in a variety of ways, but perhaps because medium-sized carnivorous dinosaurs were out, paleontologists have not found their remains in every community. “Even in relatively well-researched places around the world, new dinosaur species are discovered every year, so it’s not depleted,” D’Amekel told LiveScience in an email.
It is also possible that some of the dinosaur species in the study were misidentified. Recently paleontologists have begun to shape bone microstructure, which may reveal the age of dinosaurs at the time of death. “This may show that some of the smaller dinosaur individuals of one species were just juveniles of another species, or vice versa. In fact, the smaller dinosaurs were supposed to be juveniles of one species, rather than adults of the new dwarf species.”
The study was published online February 25 in the journal Science.
Published on Original Living Science.
