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In today's issue
Good morning. In this issue: a tiger back in old forests, a tar pit full of hunters, a giant bird predicted from one bone, and one of the oldest arguments about T. rex.
The Caspian tiger is gone, but this summer a tiger was set free in its old forests
By reader request: why the La Brea Tar Pits trapped so many saber-toothed cats
The giant moa was identified from a single scrap of bone
The Deep Cut: why T. rex had such tiny arms (Premium)
THE BIG STORY
The Caspian tiger was wiped out by hunting and farming, and this summer a tiger was set free in its old forests
On July 31, 2026, a tigress named Umit was released into the riverside forests of Kazakhstan's Ile-Balkhash State Nature Reserve. She is the first tiger in Kazakhstan's wild in more than 70 years.
The tigers that once lived in this part of Central Asia were Caspian tigers. They lived in tugai forests, the dense woods and reed beds that grow along the region's rivers.
In the first half of the 20th century, soldiers hunted them across Central Asia. At the same time, Soviet farming projects cleared and drained the tugai forests to grow cotton and other crops. As their habitat turned into farmland, the tigers' prey declined too.
Kazakhstan's last confirmed Caspian tiger sighting was in 1948. The last widely reported Caspian tiger (Panthera tigris virgata) was shot in February 1970 in Hakkari province, Turkey, though some experts think a few lived on there for years after.
So who is Umit? She is not a Caspian tiger. She is an Amur tiger, brought from the Khabarovsk region in the Russian Far East.
With no Caspian tigers left to sample, researchers in 2009 turned to old museum specimens, some collected as early as 1877. They found that the Caspian tiger's main type of mitochondrial DNA differed from the Amur tiger's by a single letter. Because the two are almost identical genetically, Kazakhstan chose Amur tigers to bring tigers back.
That makes Umit a stand-in. The Caspian tiger itself is gone for good, and no release can bring it back.
Umit wears a GPS satellite collar, so specialists can track her remotely. In August, she was reported exploring the reserve's riverside tugai forests.
The photo above shows a captive Caspian tiger at Berlin Zoo around 1899, with color added later.
Hunting and farming drove tigers from these forests, and now a tiger roams them again.
QUICK STORY · BY READER REQUEST
Smilodon may have been lured into the La Brea Tar Pits by trapped prey, and thousands never got out
A Smilodon skull on display at the La Brea Tar Pits museum. Photo by James St. John (CC BY 2.0)
For every plant-eating mammal dug out of the La Brea Tar Pits in Los Angeles, scientists find about nine meat-eaters.
The pits have given up thousands of saber-toothed cats. In one study of 3,324 meat-eaters from the pits, about half were dire wolves and a third were Smilodon (Smilodon fatalis).
In living ecosystems, it is the other way around: plant-eaters far outnumber the hunters.
Scientists think the pits worked as a carnivore trap. A large plant-eater stuck in the sticky asphalt would draw in predators and scavengers, and many of them would get stuck too. It would not have to happen often. One major trapping event every ten years, over 30,000 years, would be enough to explain all the fossils.
Some scientists see the sheer number of Smilodon as a sign that they lived and hunted in groups.
The tar pits caught the hunters far more often than the hunted.
QUICK STORY
The giant moa was predicted from a single scrap of bone, and a few years later a shipment of bones proved Richard Owen right
In 1839, a London anatomist was shown a scrap of bone from New Zealand that looked like it came from an ox.
It was about 15 centimeters (6 inches) long, part of a thigh bone. Richard Owen, of the Royal College of Surgeons, studied it and decided it came from a large flightless bird, nearly the size of an ostrich. That November he told the Zoological Society of London that such a bird had lived in New Zealand, if it didn't still.
In January 1843, a shipment of moa bones reached him. They proved him right, and the bird turned out to be even bigger than an ostrich. Owen gave the giant moa its scientific name (Dinornis).
Female giant moa could reach leaves 3.6 meters (12 feet) off the ground. But by the time Owen saw that bone, the moa had been gone for centuries. Early Māori hunted them to extinction in less than 150 years after people settled New Zealand.
The photo above shows Owen beside a giant moa skeleton in the late 1870s.
One scrap of bone was enough for Owen to see a bird nobody alive had ever seen.
THIS WEEK IN FOSSILS
Paleontologists in Argentina have named Rinconraptor pipoae, a predatory dinosaur about 7 meters (23 feet) long that lived in northern Patagonia during the Late Cretaceous, more than 80 million years ago. [Palaeontologia Electronica]
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Did You Know? Arthropleura, a giant relative of millipedes, grew up to about 2.6 meters (8.5 feet) long around 300 million years ago. Scientists had studied it since 1854, but its head stayed a mystery until 2024, when CT scans of two young fossils from France revealed it. It had eyes on stalks, like a crab's.
READER REQUESTS
Some of you asked about this one, and we've already told its story.
Spinosaurus: how its first bones were destroyed in 1944, and how a box of fossils in Morocco led to new bones and a 2014 study [Read it]
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The Deep Cut: Why T. rex had such tiny arms
The mounted skeleton of Sue the T. rex at the Field Museum in Chicago. Photo by Zissoudisctrucker (CC BY-SA 4.0)
T. rex grew to about 12 meters (40 feet) long, and its arms were only about 1 meter (3 feet). When Barnum Brown found the first T. rex fossils in 1900, he thought the arms were too small to even be part of the skeleton. For more than a century, nearly every guess asked the same thing: what were they for? Then, in 2022, a paleontologist at UC Berkeley asked a different question. Not what the arms were for, but why they had shrunk in the first place...
The rest of this Deep Cut is for Premium members.
