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What did the T. rex use its little arms for? – Aurora, age 11, Pemberton Township, New Jersey

One of the most famous dinosaurs to ever roam across Earth, Tyrannosaurus rex, has filled people’s minds with wonder since the first skeleton was discovered in the early 1900s.

Scientists believe T. rex, or King of the Tyrant Lizards, as its name translates, was a fearsome predator. An adult T. rex was massive in size – approximately 40 feet (12 meters) long and 20 feet (6 meters) tall, weighing as much as an African elephant. Each of its enormous sharp teeth could be near a foot (0.3 meters) in length from the root to the tip.

I’m a paleontologist, and I use fossils to study how animals lived and evolved over long periods of time. One of the coolest things about being a paleontologist is that there are always new questions to ask and new things to learn – even about a super-well-known dino like T.rex, which went extinct just over 65 million years ago.

One T. rex mystery has to do with this giant predator’s relatively tiny arms. Why would it have arms so short that it couldn’t even reach its own mouth? How did it use them?

How ‘short’ is short?

First, let’s define what we mean by “short.”

The biggest T. rex could measure 45 feet (14 meters) from the snout to the tip of the tail, but their arms were only about 3 feet (1 meter) long. On average, a T. rex’s arms were just about 30% of the length of its legs.

In comparison, humans have, on average, arms around 66% of the length of their legs. If people had the same arm proportions as a T.rex, a 6-foot (1.8 meters) tall person would have arms only 10 or 12 inches (25 to 30 centimeters) long!

T. rex isn’t the only dinosaur with such short arms. The evolutionary trend toward shorter arms in theropods – the larger group of meat-eating, two-legged dinosaurs that T. rex belongs to – happened multiple times. Similar to how wings separately evolved in different animals – like birds and bats – traits can emerge many times in evolutionary history.

You can see the shortening of T. rex arms as a pattern in its family tree, as earlier relatives had proportionally longer arms.

How did they use their mini-arms?

Short arms don’t seem to have been a problem for these mighty dinosaurs. T. rex was a successful carnivorous species that existed for over a million years. They only went extinct when an asteroid hit the Earth, causing a global mass extinction.

Scientists have suggested a few ideas to possibly explain how T. rex used their arms. Maybe they were used as some kind of social display that could impress other T. rex – kind of like the bright feathers of a peacock that can attract potential mates.

But male and female T. rex skeletons don’t show the major differences that paleontologists would take as clues that they relied on social displays to attract mates. And while animal behavior can sometimes be preserved, such as in bite marks or fossilized footprints, it’s rare to have enough fossil data to draw clear conclusions.

Maybe T. rex used their arms as weapons to attack or hold down prey. But these options seem unlikely since T. rex’s huge jaws would have made contact with an enemy or prey before the short arms would have been able to reach it.

Some scientists have recently hypothesized that T. rex‘s short arms were an adaptation to competition with other carnivores. If multiple predators were feeding on a carcass, one could get hurt by accidental bites or even intentional warning bites for getting too close. Shorter arms would be less likely to get chomped. Similar things occur today with territorial carnivores, like Komodo dragons.

Maybe the arms didn’t have a purpose

Another possibility is that the arms served little or no purpose at all, so over time, they became vestigial. That’s the scientific term for body parts that don’t have clear purposes anymore, but are still passed down through evolution.

One example is a whale’s hindlimbs. Whales evolved from mammals that lived on land that had large legs to move around. The bones are still present in today’s whales, but have gotten much smaller over millions of years and have no function.

Some scientists have suggested a different idea: T. rex’s arms may have evolved to be smaller as another body part grew larger. The fossil record reveals that arms got shorter as theropod skulls got larger across many different dinosaur groups, including T. rex. Larger skulls likely would have made it easier to hunt and eat larger prey.

Researchers can use mathematical equations to accurately predict theropod arm length if they know the animal’s skull size and length of its upper leg bone, the femur. It turns out that larger skulls are strongly linked to shorter arms in theropods.

The reason for the change in arms, however, isn’t as clear. Some scientists have argued that the smaller arms could have helped with balance as the head got larger, but others aren’t so sure. In evolution, there isn’t always a reason why a change occurs – sometimes, changes just happen. In this case, we don’t yet know if there was a benefit for the arms to get smaller as heads got larger.

So for now, we don’t really know how T. rex used its arms or why they evolved to be so small, proportionally. As scientists find new data, we will continue to test hypotheses to better understand why this tiny-arm trend occurred so many times in theropod evolution. That’s what makes science so exciting – a future fossil discovery could be the missing puzzle piece that helps us answer these questions.

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Sarah Sheffield does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

A rapid series of administrative, staffing and policy changes the Social Security Administration underwent early on in the second Trump administration are making it much harder to get disability benefits that millions of Americans rely on to make ends meet.

The agency cut more than 7,100 jobs – more than 13% of its workforce and its largest staffing cut ever. It closed six of its 10 regional offices, moved more services online and expanded the use of automated and artificial intelligence systems on its public phone lines.

Some rules changed and changed back again. For instance, Social Security officials announced in March 2025 that people would no longer be able to apply for benefits on the phone, only to reverse course a month later.

We’re social work professors at California State University, Sacramento, Binghamton University in New York and the University of Wisconsin-Madison who study these programs. And we have each independently found that even before 2025, it was hard to get disability benefits.

Now, we’ve found that the process has become even harder.

Missing metrics

In June 2025, the agency removed key customer service metrics, such as phone wait times and disability claim processing times, from its website. This data had provided the public with critical transparency about the agency’s performance.

Lacking insight into the impacts of the many changes underway, we launched a project to study how they were affecting access to disability benefits. We interviewed benefits representatives – lawyers, social workers and other kinds of advocates who help applicants and beneficiaries navigate Social Security systems.

We conducted in-depth interviews with 52 advocates at 32 nonprofits, such as legal aid agencies and disability organizations. These organizations collectively assist over 8,000 people every year.

We’re referring to these advocates by pseudonyms to maintain their privacy. Many insisted that neither they nor their employers be identified due to fear of retaliation by the Trump administration.

We published our findings in collaboration with two national disability advocacy organizations, the Disability Rights Education and Defense Fund and the American Association of People with Disabilities, in March 2026. We took the step of publishing with these organizations before submitting our work to academic journals because we wanted to share these findings with the public as soon as possible.

16 million people get these benefits

The Social Security Administration is a federal agency that runs some of the country’s biggest social safety net programs, including benefits for more than 60 million retired workers, as well as survivor benefits for the spouses of workers who have died and their children who are under 18.

In addition, the agency administers two kinds of disability benefits to a total of 16 million people.

Supplemental Security Income, or SSI, is a public assistance program for low-income older adults and people with disabilities under age 65. In 2026, it provides a maximum of US$994 per month for any one person getting benefits.

Social Security Disability Insurance, or SSDI, provides a limited pension for those who have worked long enough to qualify and now have disabilities that prevent them from working any longer. Payments vary based on one’s past wages, but the monthly average in 2026 is about $1,634.

To receive either kind of benefits, Americans must meet the Social Security Administration’s strict definition of disability, which considers health status, past education and employment and age to determine if a physical or mental disability makes someone unable to work.

There are no time limits on how long you can receive SSI benefits. But children and adults under age 65 are subject to periodic assessments of their eligibility and must adhere to the program’s rigid rules. For example, they can’t have more than $2,000 in assets at any time while receiving benefits, must submit their pay stubs for any earned income monthly, and must report any changes in their living situation, marital status or bank accounts.

Encountering long wait times and chatbots

The Trump administration made no formal changes to eligibility criteria for SSI or SSDI, despite considering proposals that could have narrowed eligibility rules and potentially excluded millions who qualify for these benefits today or reduced the size of benefits payments for many people with disabilities.

But when the Urban Institute, a nonpartisan research center, analyzed state-level data from the first half of 2025, it found that 7% fewer claims for disability benefits were submitted to the Social Security Administration than during the same period a year earlier.

We got more insight into these changes during our interviews.

We heard that with fewer employees, the agency had fewer people available to answer phone calls, contributing to long waits. Customer service protocols also changed so that phone calls to the Social Security Administration were routed to field offices the callers hadn’t dialed, where staff couldn’t help them.

Other benefits representatives encountered AI chatbots that did not answer their questions, or found that staffers with specialized knowledge had been reassigned to perform other tasks.

“I just have so many cases that are stuck in purgatory because they don’t have enough workers to work them,” said Jane, a paralegal we interviewed in Social Security’s Kansas City region. “They don’t have enough workers to answer the phone to tell me what’s happening to them.”

Field office frustrations

Another source of friction emerged around visits to Social Security Administration field offices.

The agency has more than 1,200 field offices across the nation where people can seek services. Shortly before Trump took office in 2025, the agency began moving from walk-in services to requiring appointments. But the Social Security Administration had promised in 2024 that it would “not turn people away” if they couldn’t or didn’t want to make an appointment.

And yet benefits representatives told us in 2025 that many field offices did require appointments, and turned people away if they arrived without them.

This was especially frustrating because it was hard to make those appointments over the phone anymore, said Freddie, a benefits representative in the Denver region. “Now, we can’t reach anybody at Social Security,” she told us. “We can’t get through to make an appointment.”

As of May 2026, 10 offices in nine states are either open on an appointment-only basis or closed to the public until further notice.

Obstacles online and in person

The Social Security Administration’s push to conduct business online assumed that everyone could easily use digital platforms. But that’s simply not true for many of the most vulnerable low-income people with disabilities who have or are applying for SSI and SSDI benefits.

As Michael, an attorney in the Atlanta region, explained, it’s not reasonable to assume that “someone who’s in their 20s, but unhoused” or “someone in their 70s and having issues with memory loss” can handle an online application process.

Another challenge is the Trump administration’s crackdown on immigration, which has now extended to people who are authorized to live in the United States. Many immigrants who get disability benefits, or who support their relatives with SSI and SSDI benefits, are no longer sure it’s safe for them to visit Social Security offices.

Those fears were reinforced in February 2026, as reports emerged that some Social Security workers had been told to share appointment data with Immigration and Customs Enforcement agents.

Several benefits specialists told us they no longer know how to advise such clients about the potential risks of interacting with the Social Security Administration, including whether it was safe to visit field offices or whether the agency might share their information with immigration authorities.

Dying while waiting

Staff cuts meant that the problem-solvers who advocates had once turned to had left, taking years of expertise with them. The agency’s remaining staff members were harder to reach than ever. Some were less familiar with the intricacies of the Social Security Administration’s policies and procedures than their senior colleagues who had left.

As disability benefits have become harder to obtain, many people are suffering. We heard multiple accounts of terminally ill clients dying before receiving benefits for which they were eligible.

For example, Anne, an attorney in the agency’s Philadelphia region, described the case of a homeless, seriously ill client who couldn’t move forward because Social Security Administration staff told her that they couldn’t locate paperwork she had submitted three years earlier.

“This woman is dying,” Anne said. “All you have to do is push a little button to get this moving, and you’re telling me you can’t.”

Miranda, an attorney in the Philadelphia region, explained that in the past, she advocated for clients over complex legal issues. During the second Trump administration, that’s changed.

Now, her clients may find that they need an attorney simply “to make sure something gets off someone’s desk and then faxed into the system.”

Faxing, rarely necessary for most everyday business transactions, is commonly used during the disability benefits application process.

“It is taking more of my time to do the same amount of work, which then means we’re not able to take as many cases” said Megan, a paralegal in the Boston region.

Suggesting possible improvements

Our report includes recommendations for improving how the Social Security Administration responds to applications for disability benefits.

In our view, the agency should employ enough people to handle all applications and appeals in a timely and accurate manner while protecting the data privacy and accessibility for all applicants – including those from immigrant families.

We also believe that the agency’s leaders would be wise to listen seriously to feedback from professional benefits representatives who help people with disabilities apply for SSI and SSDI benefits, such as those we interviewed, and their clients.

Katie Savin is the Ford Fellow in Disability Policy Research at the National Academy of Social Insurance and a Benefits Futures Innovator at the Benefits Futures Studio, a project from the Aspen Institute Financial Security Program and the National Academy of Social Insurance. They have received prior funding from the Retirement and Disability Research Consortium, funded by the Social Security Administration.

Callie Freitag receives funding from the Disability Economic Policy Consortium via The Roosevelt Institute and the National Academy of Social Insurance.

Matthew Borus previously received funding from the Social Security Administration through the Analyzing Relationships between Disability, Rehabilitation, and Work (ARDRAW) small grant program.