[Rockhounds] The 120-year search for the purpose of T. rex's arms

[Kreigh Tomaszewski]

he end of the season was approaching rapidly – the last shot at success in
what had been a very expensive expedition.

It was August 1902 and Barnum Brown had taken a team of palaeontologists
deep into the strange, undulating landscape of banded hills in the Badlands
of Montana. Amid soaring temperatures and caking dust, they searched for
fossils – hacking away at the golden-brown earth with chisels and pickaxes,
carving out mini quarries at scattered locations, sometimes uncovering
half-decent finds only to abandon them. They urgently needed something good
to send back to the American Museum of Natural History
<https://www.amnh.org/>.

>From his office in New York, Brown's boss was just as anxious as his
distant employees. Henry Fairfield Osborn had recently taken delivery of
their latest prize, a vast hunk of rock containing the skull of a kind of
early duck-billed dinosaur. It had been tenderly carted all 2,100 miles
(3,379km) from the dig site – a labourious, risky journey involving horses,
railway lines and lots of heavy lifting. Only then did Osborn discover that
hidden within its stony tomb, the fossil had been a crumpled, misshapen mess
<http://research.amnh.org/paleontology/letters/1902-montana-cretaceous/07-25-02.html>
all
along. The specimen was banished to the museum basement, but he felt that
it might as well have been thrown away.

But now things were looking up. Brown had uncovered a number of bones from
a promising large carnivorous dinosaur
<http://research.amnh.org/paleontology/letters/1902-montana-cretaceous/08-12-02.html>
that
was entirely new to science. Its hip bone was 5ft (1.5m) long, let alone
the rest. This was *Tyrannosaurus rex* – the first ever discovered. Brown
had never seen anything like it.

In a letter to Osborn, Brown wrote
<http://research.amnh.org/paleontology/letters/1902-montana-cretaceous/09-03-02.html>:
"There is no question but what this is the find of the season so far for
scientific importance [sic]." Little did he know, it was more like the find
of a century – a discovery that would transform our understanding of
dinosaurs and galvanise public interest in this previously obscure group of
ancient creatures well into the modern era.

But right from the beginning, one aspect of these kings of the "tyrant
lizards" was deeply mysterious: their puny arms. Brown's *T. rex* skeleton
was missing all its fingers and both its forearms, which were drawn on
early portraits using surprisingly accurate guesswork – prompting
speculation that they surely couldn't really be *that* stumpy
<https://digitallibrary.amnh.org/bitstream/handle/2246/1464/v2/dspace/ingest/pdfSource/bul/B021a14.pdf?sequence=1&isAllowed=y>.
What could have been their purpose? And how did they end up being so small?
https://www.bbc.com/future/article/20221025-why-did-t-rex-have-such-puny-arms