Tyrannosaurus rex possessed a preposterously massive skull - 5 feet long (1.5 meters) and built to ‌enable bone-crunching bite force - ​but presented preposterously puny arms. And many other meat-eating dinosaurs shared this mismatched combination of traits. So how did this come to be?Researchers studying this phenomenon have now documented how skull robustness in meat-eating dinosaurs started to evolve first, as plant-eating dinosaurs that they hunted became bigger soon after dinosaurs became Earth's dominant land animals, leading to a subsequent reduction in the arms.They identified five lineages of theropods - the two-legged group that spans all the meat-eating dinosaurs - in which this phenomenon independently appeared, underscoring the evolutionary advantages that drove these traits.T. rex's tiny arms long have been the object of fascination, even spawning online memes ⁠mocking the fearsome predator's inability to do things like clap its hands, scratch its nose or perform a push-up.Dinosaurs first appeared roughly 230 million years ago during the Triassic Period, then dominated the landscape during the subsequent Jurassic and Cretaceous Periods before being doomed by an asteroid strike 66 million years ago. The earliest theropods had well-developed arms useful for subduing prey, but that changed following the appearance of ever-larger plant-eaters including the long-necked sauropods."Body size in dinosaurs increased ‌massively from the Triassic to the end-Cretaceous, so it's likely that the increase in body size drove some theropods to shift towards using their heads more than their limbs in hunting. Effectively, the forelimbs became redundant in hunting," said Charlie Scherer, a University College London doctoral student in paleontology and lead author of the study published in the journal ‌Proceedings of the Royal Society B."Natural selection will act on the traits which allow an animal to survive and ‌thrive in its ecosystem. If that means sacrificing the size of the arms for a stronger head, which is the primary weapon for the animal, ‌then that's likely what will happen," Scherer said.The researchers created ‌a new methodology for quantifying skull robustness based on traits including skull dimensions, bite force, tooth shape and cranial bone-fusion patterns.Tyrannosaurus, which lived in North America during the Cretaceous, scored the highest, followed by Tyrannotitan of Cretaceous South ​America.A CLOSE ASSOCIATIONThe researchers found that ‌skull robustness was closely associated with forelimb reduction.The theropod ​lineages in which this phenomenon occurred were: tyrannosaurs including Tyrannosaurus; carcharodontosaurs including Carcharodontosaurus ⁠of Cretaceous Africa; megalosaurs including Megalosaurus of Jurassic England; ceratosaurs including Ceratosaurus of Jurassic North America and Europe; and abelisaurs including Abelisaurus of Cretaceous South America.These lineages included apex predators that relied on large body size and strong jaws to tackle various types of large plant-eating dinosaurs including sauropods, horned dinosaurs, armored dinosaurs and duck-billed dinosaurs.One of ​the earliest theropods to exhibit this ⁠phenomenon was Eoabelisaurus, which lived in Jurassic South ⁠America about 170 million years ago.Some lineages of large theropods retained long and strong arms. These included such dinosaurs as Spinosaurus of Cretaceous Africa and Megaraptor of Cretaceous South America.These theropods "have incredibly large and mobile arms for their body size, which suggest a more prominent role for them in hunting compared to something like T. rex," ⁠Scherer said.Small theropods also kept useful arms, including the lineage that led to birds.For theropods like Tyrannosaurus, scientists are not sure what function small arms served. Not only were the length and strength of the arms of Tyrannosaurus diminished, but it retained only two fingers on its hands."Potentially, they did nothing with them - they were just useless. This raises the question: why did they have tiny arms, rather than no arms? If the tiny arms are still there, then it is possible that they still retain some kind of function that we are not aware of," University College London paleontologist and study ‌co-author Paul Upchurch said."For me, however, this is unlikely, and I think something else is going on," Upchurch said.When an anatomical structure is no longer helpful, genetic changes can result in its reduction ​so the animal does not waste energy and resources building something it does not need, Upchurch said."But we know that genetics is complicated, and very often genes have more than one role. For example, a gene might be involved in building something that the animal no longer needs, but the same gene might also be doing something in another part of the body that the animal does still need. This means that the gene is maintained because it is still doing ​something useful, so the useless structure persists in a reduced ‌form rather than disappearing completely," Upchurch said.

MANILA, Philippines: A Philippine anti-graft court ordered the arrest of a prominent senator on Friday over allegations he pocketed a kickback of millions of dollars in a flood-control project, in the latest crisis to entangle the Senate.Sen. Jinggoy Estrada surrendered and posted bail before the Sandiganbayan court, allowing him to remain free while the case proceeds.The court barred Estrada from leaving the country while facing the first of two corruption-related charges in relation to the flood control project anomalies.Another warrant for his arrest for the second charge, which is non-bailable, is expected to be issued by the court soon, top anti-graft prosecutor Jesus Crispin Remulla told The Associated Press.Estrada, 63, has strongly denied allegations mainly by a former government public works engineer that he received more than 570 million pesos ($9.3 million) in kickbacks."I intend to avail myself of every lawful means to defend myself and clear my name,” Estrada said.The senator was an actor like his father, former President Joseph Estrada. Both have been previously detained on other corruption-related charges.Several other senators and members of the House of Representatives have been implicated in the flood control anomalies in a poverty-stricken Asian archipelago that is among the most vulnerable to deadly floods and typhoons.Another senator, Ronald dela Rosa, has gone into hiding after the International Criminal Court issued a warrant for his arrest for an alleged crime against humanity.Dela Rosa was a former national police chief who enforced a brutal anti-drugs crackdown under then-President Rodrigo Duterte that left thousands of mostly petty suspects dead. The unprecedentedly large numbers of killings alarmed Western governments.Duterte, who stepped down in 2022 after his stormy six-year term, was arrested last year on orders of the ICC and flown to the Netherlands, where he was detained and will face trial for alleged crimes against humanity starting in November over some of the killings.Duterte and dela Rosa have denied any wrongdoing but Duterte had repeatedly threatened drug suspects with death.Dela Rosa has been absent in the Senate since November for fear of getting arrested. On May 11, he suddenly reappeared to help an ally, Sen. Alan Peter Cayetano, capture the Senate presidency with a slim majority of 13 votes in the 24-member chamber.Dela Rosa dashed to the Senate plenary hall after government agents tried to arrest him. He was taken into the Senate’s protective custody but fled two days later after the chamber’s security chief and two aides opened fire after seeing government agents in an adjacent building.The dozens of gunshots did not cause any injuries but sparked chaos in the Senate that police investigators said may have provided dela Rosa a cover to escape.Estrada, dela Rosa and Cayetano are allies of Duterte and his daughter, Vice President Sara Duterte, who was impeached by the House of Representatives in an overwhelming vote on May 11 over criminal allegations that include unexplained wealth and threatening to have President Ferdinand Marcos Jr., his wife and a former House speaker assassinated.The vice president, who has announced plans to seek the presidency in 2028, denies the allegations but has not answered them in detail.Despite the crises besetting the Senate, it has convened as an impeachment court for the vice president’s trial that may start in July.