Oct 22, 2020 05:50 PM
https://slate.com/technology/2020/10/din...loaca.html
EXCERPT: . . . Even dinosaur models and sculptures often demur on the point of the dino butt, leaving the terrible lizards with terrible constipation. Now I finally have a clearer view, thanks to a fossil of a horned dinosaur called Psittacosaurus, described in a paper online earlier this month.
[...] It’s rare to get a look at something soft and fleshy on a dinosaur. We know most of what we know about Psittacosaurus the same way that we know things about most dinosaurs: from their bones. Durable skeletal parts are much more likely than skin and organs to survive the fossilization process, which involves burial and at least partial replacement of the original tissues. Most of the time, after a dinosaur dies, all the soft stuff just decays. But every now and then paleontologists find dinosaur “mummies” that preserve remnants of the soft bits either as impressions or geologically modified pieces of the original flesh. There’s no one way to make an exquisitely preserved dinosaur: Sometimes it happens when a dinosaur is quickly buried in ash; others dry out in the open for a while. For whatever reason, experts have uncovered several Psittacosaurus with preserved soft tissues. The fossilization in some of these specimens is so refined that we even know what colors these dinosaurs were, brown on top and lighter along the belly. The new fossil is one of the more detailed ones. It includes patches of skin and scales as well as the ornamental bristles on the tail. The most remarkable part is a patch of tissue between the hips and the base of the tail—aka a butt.
The actual description of the butthole, which appears in a paper that hasn’t yet been peer-reviewed, makes me have sympathy for a dinosaur that probably didn’t expect to have its posterior formally presented in the technical literature over 100 million years after its death. On the fossil, just below the tail, the butthole appears as a “blackish mottled ovoid area,” the paleontologists write (the image is on Page 4 of the PDF, found at this link). To the naked eye, the spot looks like a series of dark, stacked bands running between the base of the tail and hip bones, clearly different from the skin around it.
What those bands mean, the paper tells us, is that Psittacosaurus had a downstairs setup known as a cloaca. This is pretty different from our own mammalian plumbing. While we all know the old joke about “a playground next to a sewage system” in reference to the locations of our own sex organs and waste exits, we’ve got nothing to complain about compared with animals that have a cloaca. This orifice—its very name meaning “sewer”—is the only opening for the reproductive, urinary, and excretory systems. Something to keep in mind if books like Taken by the T-Rex are your jam.
By itself, evidence that non-avian dinosaurs had cloacae isn’t a huge shocker. While it’s possible that future peer review might interpret the fossil differently, the placement, color, and wrinkly texture of the tissue all seem to line up with what experts have long expected a dino butt to look like. Living dinosaurs—birds!—have cloacae, after all. Bird cloacae are round or square and normally covered up by feathers, unless you’ve ever seen an ostrich evacuate and wondered what the hell you’re looking at. Crocodiles and alligators, which are the closest living cousins of dinosaurs, have cloacae that are horizontal slits. According to a form of logic called extant phylogenetic bracketing, the fact that both birds and crocs have cloacae hints that the trait goes back to the last common ancestor of both groups—a creature called an archosaur that likely would have resembled a crocodile crossed with a greyhound—and would be present in the extinct animals that fall within those goalposts. A dinosaur butt, we’ve long known, should look something like a bird butt or a croc butt.
An educated guess is great, but firm evidence is better. Having a fossilized dinosaur cloaca actually available for study is like finally getting the pony you were always begging for on your birthday... (MORE - details)
EXCERPT: . . . Even dinosaur models and sculptures often demur on the point of the dino butt, leaving the terrible lizards with terrible constipation. Now I finally have a clearer view, thanks to a fossil of a horned dinosaur called Psittacosaurus, described in a paper online earlier this month.
[...] It’s rare to get a look at something soft and fleshy on a dinosaur. We know most of what we know about Psittacosaurus the same way that we know things about most dinosaurs: from their bones. Durable skeletal parts are much more likely than skin and organs to survive the fossilization process, which involves burial and at least partial replacement of the original tissues. Most of the time, after a dinosaur dies, all the soft stuff just decays. But every now and then paleontologists find dinosaur “mummies” that preserve remnants of the soft bits either as impressions or geologically modified pieces of the original flesh. There’s no one way to make an exquisitely preserved dinosaur: Sometimes it happens when a dinosaur is quickly buried in ash; others dry out in the open for a while. For whatever reason, experts have uncovered several Psittacosaurus with preserved soft tissues. The fossilization in some of these specimens is so refined that we even know what colors these dinosaurs were, brown on top and lighter along the belly. The new fossil is one of the more detailed ones. It includes patches of skin and scales as well as the ornamental bristles on the tail. The most remarkable part is a patch of tissue between the hips and the base of the tail—aka a butt.
The actual description of the butthole, which appears in a paper that hasn’t yet been peer-reviewed, makes me have sympathy for a dinosaur that probably didn’t expect to have its posterior formally presented in the technical literature over 100 million years after its death. On the fossil, just below the tail, the butthole appears as a “blackish mottled ovoid area,” the paleontologists write (the image is on Page 4 of the PDF, found at this link). To the naked eye, the spot looks like a series of dark, stacked bands running between the base of the tail and hip bones, clearly different from the skin around it.
What those bands mean, the paper tells us, is that Psittacosaurus had a downstairs setup known as a cloaca. This is pretty different from our own mammalian plumbing. While we all know the old joke about “a playground next to a sewage system” in reference to the locations of our own sex organs and waste exits, we’ve got nothing to complain about compared with animals that have a cloaca. This orifice—its very name meaning “sewer”—is the only opening for the reproductive, urinary, and excretory systems. Something to keep in mind if books like Taken by the T-Rex are your jam.
By itself, evidence that non-avian dinosaurs had cloacae isn’t a huge shocker. While it’s possible that future peer review might interpret the fossil differently, the placement, color, and wrinkly texture of the tissue all seem to line up with what experts have long expected a dino butt to look like. Living dinosaurs—birds!—have cloacae, after all. Bird cloacae are round or square and normally covered up by feathers, unless you’ve ever seen an ostrich evacuate and wondered what the hell you’re looking at. Crocodiles and alligators, which are the closest living cousins of dinosaurs, have cloacae that are horizontal slits. According to a form of logic called extant phylogenetic bracketing, the fact that both birds and crocs have cloacae hints that the trait goes back to the last common ancestor of both groups—a creature called an archosaur that likely would have resembled a crocodile crossed with a greyhound—and would be present in the extinct animals that fall within those goalposts. A dinosaur butt, we’ve long known, should look something like a bird butt or a croc butt.
An educated guess is great, but firm evidence is better. Having a fossilized dinosaur cloaca actually available for study is like finally getting the pony you were always begging for on your birthday... (MORE - details)
