Strange Animals Podcast

• Episode 440: Trilobites!

  Thanks to Micah for suggesting this week's topic, the trilobite! Further reading: The Largest Trilobites Stunning 3D images show anatomy of 500 million-year-old Cambrian trilobites entombed in volcanic ash Strange Symmetries #06: Trilobite Tridents Trilobite Ventral Structures A typical trilobite: Isotelus rex, the largest trilobite ever found [photo from the first link above]: Walliserops showing off its trident [picture by TheFossilTrade - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=133758014]: Another Walliserops individual with four prongs on its trident [photo by Daderot, CC0, via Wikimedia Commons]: Show transcript: Welcome to Strange Animals Podcast. I’m your host, Kate Shaw. This week we’re going to learn about an ancient animal that was incredibly successful for millions of years, until it wasn’t. It’s a topic suggested by Micah: the trilobite. Trilobites first appear in the fossil record in the Cambrian, about 520 million years ago. They evolved separately from other arthropods so early and left no living descendants, that they’re not actually very closely related to any animals alive today. They were arthropods, though, so they’re distantly related to all other arthropods, including insects, spiders, and crustaceans. The word trilobite means “three lobes,” which describes its basic appearance. It had a head shield, often with elaborate spikes depending on the species, and a little tail shield. In between, its body was segmented like a pillbug’s or an armadillo’s, so that it could flex without cracking its exoskeleton. Its body was also divided into three lobes running from head to tail. Its head and tail were usually rounded so that the entire animal was roughly shaped like an oval, with the head part of the oval larger than the tail part. It had legs underneath that it used to crawl around on the sea floor, burrow into sand and mud, and swim. Some species could even roll up into a ball to protect its legs and softer underside, just like a pillbug. Because trilobites existed for at least 270 million years, there were a lot of species. Scientists have identified about 22,000 different species so far, and there were undoubtedly thousands more that we don’t know about yet. Most are about the size of a big stag beetle although some were tinier. The largest trilobite found so far lived in what is now North America, and it grew over two feet long, or more than 70 centimeters, and was 15 inches wide, or 40 cm. It’s named Isotelus rex. I. rex had 26 pairs of legs, possibly more, and prominent eyes on the head shield. Scientists think it lived in warm, shallow ocean water like most other trilobites did, where it burrowed in the bottom and ate small animals like worms. There were probably other species of trilobite that were even bigger, we just haven’t found specimens yet that are more than fragments. Because trilobites molted their exoskeletons the way modern crustaceans and other animals still do, we have a whole lot of fossilized exoskeletons. Fossilized legs, antennae, and other body parts are much rarer, and preserved soft body parts are the rarest of all. We know that some trilobite species had gills on the legs, some had hairlike structures on the legs, and many had compound eyes. A specimen with preserved eggs inside was also found recently. Some incredibly detailed trilobite fossils have been found in Morocco, including details like the mouth and digestive tract. The detail comes from volcanic ash that fell into shallow coastal water around half a billion years ago. The water cooled the ash enough that when it fell onto the trilobites living in the water, it didn’t burn them. It did suffocate them, though, since so much ash fell that the ocean was more ash than water. The ash was soft and as fine as powder, and it covered the trilobites and protected their bodies from potential damage, while also preserving the body details as they fos...

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• Episode 439: The Missing Echidna

  Thanks to Cara for suggesting we talk about the long-beaked echidna this week! Further reading: Found at last: bizarre, egg-laying mammal finally rediscovered after 60 years A short-beaked echidna: The rediscovered Attenborough’s long-beaked echidna: Show transcript: Welcome to Strange Animals Podcast. I’m your host, Kate Shaw. This week we’re going to learn about an animal suggested by Cara, the echidna, also called the spiny anteater. It’s a type of mammal, but it’s very different from almost all the mammals alive today. We talked about the echidna briefly in episode 45, but this week we’re going to learn more about it, especially one that was thought to be extinct but was recently rediscovered. Cara specifically suggested we learn about the long-beaked echidna, which lives only in New Guinea. The short-beaked echidna lives in New Guinea and Australia. The names short and long beaked make it sound like the echidna is a bird, but the beak is actually just a snout. It just looks beak-like from a distance and is covered with tough skin, sort of like the platypus’s snout is sometimes called a duck-bill. In June and July of 2023, an expedition made up of scientists and local experts from various parts of Indonesia, as well as from the University of Oxford in England, discovered and rediscovered a lot of small animals in the Cyclops Mountains. They even discovered an entire cave system that no one but some local people had known about, and they discovered it when one of the expedition members stepped on a mossy spot in the forest and fell straight through down into the cave. But one animal they were really hoping to see hadn’t made an appearance and they worried it was actually extinct. That one was Attenborough’s long-beaked echidna, a type of mammal known as a monotreme. There are three big groups of mammals. The biggest is the placental mammal group, which includes humans, dogs, cats, mice, bats, horses, whales, giraffes, and so on. A female placental mammal grows her babies inside her body in the uterus, each baby wrapped in a fluid-filled sac called a placenta. Placental mammals are pretty well developed when they’re born. The second type is the marsupial mammal group, which includes possums, kangaroos, koalas, wombats, sugar gliders, and so on. A female marsupial has two uteruses, and while her babies initially grow inside her, they’re born very early. A baby marsupial, called a joey, is just a little pink squidge about the size of a bean that’s not anywhere near done growing, but it’s not completely helpless. It has relatively well developed front legs so it can crawl up its mother’s fur and find a teat. Some species of marsupial have a pouch around its teats, like possums and kangaroos, but other species don’t. Once the baby finds a teat, it clamps on and stays there for weeks or months while it continues to grow. The third and rarest type of mammal these days is the monotreme group, and monotremes lay eggs. But their eggs aren’t like bird eggs, they’re more like reptile eggs, with a soft, leathery shell. The female monotreme keeps her eggs inside her body until it’s almost time for them to hatch. The babies are small squidge beans like marsupial newborns, and I’m delighted to report that they’re called puggles. There are only two monotremes left alive in the world today, the platypus and the echidna. The echidna has a pouch and after a mother echidna lays her single egg, she tucks it in the pouch. Monotremes show a number of physical traits that are considered primitive. Some of the traits, like the bones that make up their shoulders and the placement of their legs, are shared with reptiles but not found in most modern mammals. Other traits are shared with birds. The word monotreme means “one opening,” and that opening, called a cloaca, is used for reproductive and excretory systems instead of those systems using separate openings.

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• Episode 438: The Dragon Man Skull

  This week we're going to learn about a new finding about the skull referred to as the Dragon Man! Further reading: We’ve had a Denisovan skull since the 1930s—only nobody knew The proteome of the late Middle Pleistocene Harbin individual Show transcript: Welcome to Strange Animals Podcast. I’m your host, Kate Shaw. It never fails that only a few days after our annual updates episode, a study is published that’s an important update to an older episode. This time it’s an update so important that it deserves its own episode, so let’s learn more about one of our own extinct close relations, the Denisovan people. We didn’t know about the Denisovans until 2010, when DNA was sequenced from a finger bone found in Denisova Cave in Siberia in 2008. Scientists were surprised when the DNA didn’t match up with Neanderthal DNA, which is what they expected, since they knew Neanderthals had lived in the cave at various times over thousands of years. Instead, the DNA was for a completely different hominin, a close relation of both humans and Neanderthals. Since then, researchers have found some Denisovan teeth, two partial mandibles, a rib fragment, and some other bone fragments, but nothing that could act as a type specimen. The type specimen is the preserved specimen of a new species, which is kept for scientists to study. It needs to be as complete as possible, so a handful of fragments just won’t work. Even without a type specimen, having Denisovan DNA answered some questions about our own history as a species. Ever since scientists have been able to sequence genetic material from ancient bones, they’ve noticed something weird going on with our DNA. Some populations of people show small traces of DNA not found in other human populations, so scientists suspected they were from long-ago cross-breeding with other hominin species. When the Neanderthal genome was sequenced, it matched some of the unknown DNA traces, but not all of them. Mystery DNA sequences in a closely related population are called ghost lineages. The Denisovan DNA matched the ghost lineage scientists had identified in some populations of people, especially ones in parts of east Asia, Australia, and New Guinea. This is your reminder that despite tiny genetic differences like these, all humans alive today are 100% human. We are all Homo sapiens. Naturally, we as humans are interested in our family tree. We even have an entire field of study dedicated to studying ancient humans and hominins, paleoanthropology. Lots of scientists have studied the Denisovan remains we’ve found, along with the genetic material, but they really need a skull to learn so much more about our long-extinct distant relations. Luckily, we’ve had a Denisovan skull since the 1930s. But wait, you may be saying, you just said we didn’t have anything but bone fragments and teeth! Why didn’t you mention the skull? It’s because the skull was hidden by its finder, a Chinese construction worker. The man was helping build a bridge and was ashamed that he was working for a Japanese company. That region of China was under Japanese occupation at the time, and the man didn’t want anyone to know that he was working for people who were treating his fellow citizens badly. He thought the skull was an important find similar to the Peking Man discovery in 1929, so he hid the skull at the bottom of an abandoned well to keep it safe. He didn’t dare share any information about it until he was on his death-bed, when he whispered his secret to his son. It wasn’t until 2018 that the man’s family took another look at the skull and realized it definitely wasn’t an ordinary human skull. It was obviously extremely old and had a pronounced brow and really big teeth. In 2021 the skull was classified as a new species of hominin, Homo longi, where the second word comes from the Mandarin word for dragon. That’s because the area where it was found is called Dragon River.

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• Episode 437: Updates 8 and the Nutria

  Thanks to Nicholas, Måns, Warblrwatchr, Llewelly, and Emerson this week, in our yearly updates episode! Further reading: An Early Cretaceous Tribosphenic Mammal and Metatherian Evolution Guam's invasive tree snakes loop themselves into lassos to reach their feathered prey Rhythmically trained sea lion returns for an encore -- and performs as well as humans Scientists Solve Mystery of Brown Giant Pandas Elephant turns a hose into a sophisticated showering tool New name for one of the world’s rarest rhinoceroses Antarctica’s only native insect’s unique survival mechanism Komodo dragons have iron-coated teeth to rip apart their prey The nutria has really orange teeth: Show transcript: Welcome to Strange Animals Podcast. I’m your host, Kate Shaw. This week is our annual updates episode, and we’ll also learn about an animal suggested by Emerson. But first, we have some corrections! Nicholas shared a paper with me that indicates that marsupials actually evolved in what is now Asia, with marsupial ancestors discovered in China. They spread into North America later. So I’ve been getting that wrong over many episodes, over several years. Måns shared a correction from an older episode where I mentioned that humans can’t get pregnant while breastfeeding a baby. I’ve heard this all my life but it turns out it’s not true. It is true that a woman’s fertility cycle is suppressed after giving birth, but it’s not related to breastfeeding. Some women can become pregnant again only a few months after giving birth, while others can’t get pregnant again for a few years. It depends on the individual. That’s important, since the myth is so widespread that many women get pregnant by accident thinking they can’t since they’re still feeding a baby. Warblrwatchr commented on the ultraviolet episode and mentioned that cats can see ultraviolet, which is useful to them because mouse urine glows in UV light. Finally, Llewelly pointed out that in episode 416, I didn’t mention that fire ant venom isn’t delivered when the ant bites someone. The ant bites with its mandibles to hold on, then uses the stinger on its back end to sting repeatedly. Now, let’s dive into some updates about animals we’ve talked about in past episodes. As usual, I don’t try to give an update on every single animal, because we’d be here all week if I did. I just chose interesting studies that caught my eye. In episode 402, we talked about snakes that travel in unusual ways, like sidewinders. Even though I had a note to myself to talk about the brown tree snake in that episode, I completely forgot. The brown tree snake is native to parts of coastal Australia and many islands around Indonesia and Papua New Guinea. It’s not native to Guam, which is an island in the western Pacific, way far away from the brown tree snake’s home. But in the late 1940s, some brown tree snakes made their way to Guam in cargo ships and have become invasive since then. The brown tree snake can grow up to six and a half feet long, or 2 meters, and is nocturnal, aggressive, and venomous. It’s not typically a danger to adults, but its venom can be dangerous to children and pets. The government employs trained dogs to find the snakes so they can be removed, and this has worked so well that brown tree snake population is declining rapidly on the island. But that hasn’t stopped the snake from driving many native animals to extinction in the last 75 years, especially birds. One of the things scientists did in Guam to try and protect the native birds was to place smooth poles around the island so birds could nest on top but snakes couldn’t climb up to eat the eggs and chicks. But before long, the snakes had figured out a way to climb the poles, a method never before documented in any snake. To climb a pole, the snake wraps its body around it, with the head overlapping the tail. Then it sort of scoots itself up the pole with tiny motions of its spine...

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• Episode 436: Red-Eyed Tree Frog

  Thanks to Trech for suggesting this week's topic, the red-eyed tree frog! Further reading: Tadpoles hatch in seconds to escape predator The colorful red-eyed tree frog [photo by Geoff Gallice]: Show transcript: Welcome to Strange Animals Podcast. I’m your host, Kate Shaw. This week we’re going to have a short little episode about a little frog, suggested by Trech. The frog in question is the red-eyed tree frog, which is native to Central America, including parts of Mexico, and northwestern South America. It lives in forests, always around water. You might be thinking, “of course, frogs live in water,” but remember that this is a tree frog. It lives in trees. But it still needs water for its babies, just not quite in the way most frogs do. Before we learn about that, let’s learn about the frog itself. A big female can grow about 3 inches long, or 7.5 cm, while males are smaller. It’s a cute frog, of course, because frogs are always cute, but it’s also brightly colored. It’s bright green with red eyes, blue and yellow stripes on its sides, and orange feet. Ordinarily, a frog with such bright colors would warn potential predators that it’s toxic, but the red-eyed tree frog isn’t toxic at all. Its bright colors have a different purpose. When it’s sitting on a leaf, the bright colors are hidden and only the frog’s smooth green back is showing, which makes it look like just another leaf. Only its eyes are bright, but it closes its eyes when it’s resting. But if a predator approaches, the frog opens its eyes suddenly and jumps up, revealing all those bright colors. The predator is startled, and maybe even hesitates because it thinks the frog might be toxic, and by the time the predator decides it should try eating the frog after all, the frog is long gone. Oh, and if you’re wondering, the red-eyed tree frog can see through its eyelids. They’re actually not eyelids like we have, but a membrane that it can move over its eyes. The frog is nocturnal and eats insects like mosquitoes, crickets, and moths. It has a good sense of smell, which helps it find insects in the dark. The tree frog also has suction cups on its toes that help it stay put on smooth leaves. During the day it sticks itself to the underside of a leaf to sleep where it’s more hidden. The female also lays her eggs on the underside of a leaf. This protects them from heavy rain, since the frogs breed during the rainy season, and it also helps hide them from predators. The female chooses a leaf that’s growing above water, and if the leaf isn’t very big she’ll lay eggs on both sides of it and fold the leaf to help hide all the eggs. The eggs stick to the leaf with a type of jelly that also helps keep them from drying out. The eggs hatch in about a week, but they can hatch a few days early if a predator approaches. The embryonic tadpoles in their eggs can sense vibrations, and if a predator like a snake shakes the leaf as it approaches the eggs, the tadpoles can hatch within seconds. They drop straight down into the water below the leaf. Hatching early when in danger is called phenotypic plasticity, and it’s really rare. It’s especially unusual because the embryonic tadpoles can actually tell the difference between a typical predator of frog eggs and vibrations caused by other animals or the wind. They can hatch so quickly because the stress reaction causes the pre-tadpoles to secrete an enzyme from their little noses, which weakens the egg wall and allows them to push and wiggle their way out. Tadpoles stay in the water for several weeks, or sometimes several months depending on conditions, during which time they eat algae and other tiny food in the water. As they grow bigger, the tadpoles can eat bigger food, including other tadpoles. They switch to tiny insects after they metamorphose into froglets. At some point during its development, a red-eyed tree frog needs to eat enough food containing carotenoids in order to develop...

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