The fossil of a new dinosaur with short forearms, such as the Tyrannosaurus Rex, suggests that their disproportionate size had a purpose.
Scientists believe that carnivores may have used their tiny appendages to cling to each other during mating or to help themselves get up after a fall.
new dinosaur, Meraxes gigaslived for millions of years apart from the infamous Tyrannosaurus rex and, apparently, is not its close relative.
Its fossil was studied by researchers at the Ernesto Bachman Paleontological Museum in Neuquen, Argentina after it was discovered in Patagonia.
They also found that the species had a large, bumpy skull that it probably used for hunting.
Project leader Dr Juan Canale said: “Predation activities were most likely done with the head.
“I am inclined to think that their weapons were used for other purposes.
“They may have used their hands for reproductive behavior, such as holding a female during mating or supporting themselves to get up after a break or a fall.”
Fossils suggest Meraxes gigas (pictured) was 36 feet (11 meters) long and weighed 4 tons.
Reconstruction Meraxes gigas skeleton showing restored bones in white. A: left side of skull, B: right scapular-coracoid process, C: right complete pelvis, D and E: caudal vertebrae, F: left articulated tibia and fibula, G: left femur, H: left talus and calcaneus, I: Left foot, J: Articulated right arm. Individual scale rulers, 10 cm; common scale, 1 m
Bones of Meraxes gigas. A: Right side of skull, B: Articulated right arm, C: Sacrum, D: Left foot
Tyrannosaurus rex (pictured) were bird-like, carnivorous dinosaurs. It lived between 68–66 million years ago in what is now western North America.
The petrified bones of Meraxes gigas – named after the dragon from Game of Thrones – the show reached 36 feet (11 meters) in length and weighed 4 tons.
The specimen lived 90 million years ago in what is now northern Patagonia in Argentina and died at about 45 years of age.
His forearms were about 47 percent of the length of his thigh.
Dr. Canale added: “We found the perfect spot on the first day of our search, and Meraxes was found.
“It was probably one of the most exciting moments of my career.
“The fossil contains a lot of new information and is in excellent shape.”
‘Fossil Meraxes shows previously unseen entire regions of the skeleton, such as arms and legs, which helped us understand some of the evolutionary trends and anatomy of carcharodontosaurids, the group to which they belong.”
Carcharodontosaurids are a group of mostly large bipedal dinosaurs from the theropod dinosaur clade.
The larger their heads were, the smaller their arms became, which was also observed in tyrannosaurs, whose forearms were only about three feet long.
Fossil records also suggest Meraxes gigas descended from a large family before becoming extinct in the Late Cretaceous.
“The group prospered and reached its peak of diversity shortly before it died out,” Dr. Canale said.
Bones of Meraxes gigas were found at the Huinkul Formation paleontological site in the Neuquen Basin in northern Patagonia, Argentina.
Dr. Canale said: “We found the perfect spot on the first day of searching and Meraxes was found. It was probably one of the most exciting moments of my career.”
A study published today in Current biologyconcludes that T. rex and Meraxes gigas have evolved to have their tiny hands all by themselves.
The latter died out nearly 20 million years before the former, and they are also very far apart on the evolutionary tree.
However, the fact that they share the feature of shortened forelimbs suggests that they have some sort of survival advantage.
It is believed that they did not become short over the course of evolution because they lacked the benefit of predators, as fossil evidence shows that they were attached to powerful muscles.
“I am convinced that these proportionately tiny hands had some function,” Dr. Canale said.
“The skeleton shows large muscle inserts and fully developed pectoral girdles, so the arm had strong muscles.
“This means that the arms didn’t shrink because they were useless to creatures.
“The more difficult question is what exactly the functions were. Sex and balance are most likely.”
Meraxes gigas The skull was decorated with ridges, furrows, bumps and small horns, and was probably intended to attract potential mates.
Dr. Canale said: “These decorations appear late in development as individuals become adults.
“Sexual selection is a powerful evolutionary force. But given that we can’t directly observe their behavior, we can’t be sure.”
T Rex (left) and Meraxes gigas (right) evolved so that their tiny arms were completely separate. The skull of Meraxes gigas was decorated with ridges, furrows, knobs, and small horns, which were probably intended to attract potential mates.
The dinosaur with the oldest “navel” to which egg yolk sacs were attached has been discovered in 125-million-year-old fossils from China.
The oldest navel was discovered by paleontologists on a 125-million-year-old bipedal fossil. China.
A barely noticeable mark on the navel belongs to the genus of reptiles psittacosaurus who lived in the Cretaceous period.
The researchers note that dinosaurs did not have an umbilical cord, unlike humans, because they laid eggs.
Instead, the yolk sac of dinosaurs was directly attached to the body through a slit-like opening, which is also found in other land animals that lay eggs.
It was this hole that closed around the time the animal hatched, leaving a distinctive long umbilical scar.
3D reconstruction of a recumbent Psittacosaurus showing a long umbilical scar surrounded by characteristic scales, which was identified by the research team.
