The Identity Crisis of Pliosaurus Andrewsi

0:00The Toyota Tundra and Tacoma are built to keep going, blending rugged muscle with precision engineering, all supported by Toyota's time-tested legacy of dependability. Step into a Tundra and feel the unyielding capability with the available iForce Max engine, Tundra puts out impressive power, torque, and towing performance and the roomy high-tech cabin, keeps you connected on the go. Or take a look at Tacoma made for drivers who push past the path agile, tough and relentless with available features like crawl control, portable JBL speaker, a power lift gate, so gear goes in fast, and the adventure keeps moving. The Tacoma and Tundra are engineered to endure season after season, mile after mile, so drive one home today, visit toyota.com or stop by your local Toyota dealer to find out more Toyota. Let's go places. Imagine you're swimming in a massive crowded underwater neighborhood. But this is definitely not a vibrant little coral refilled with colorful fish darting around in eminies. Right, no. You are swimming through a Jurassic Sea, and every single shadow passing over you belongs to an apex predator.

1:04It's a prehistoric ecosystem packed to the absolute brim, just overflowing with marine reptiles, heavily armored fish, and these deep-diving ichthyosaurs. It's terrifying to even picture. And today we are going to focus on one very particular creature from this ancient ocean, a creature that, well, scientists have been arguing about for over 150 years. Yeah, it genuinely stands as one of the most frustrating and honestly fascinating taxonomic puzzles in all of paleontology. Because the animal we're examining today has been renamed, categorized, and then aggressively evicted from its own family tree more times than almost any other marine reptile. It really is the perfect case study. It shows exactly how difficult it is to categorize ancient life when all you have are scattered fragments of bone and, you know, a constantly shifting understanding of evolution. Which brings us to today's source material. We're pulling from a comprehensive Wikipedia article detailing the extinct marine reptile currently known as pleasaurus and juicy.

2:05We're at least, uh, that's what we call it for now. Right. So our mission for this deep dive is threefold. First, we are going to explore the century and a half long soap opera of how this animal was actually classified. The drama is real with this one. It really is. Second, we're going to reconstruct this unique apex predator from snout to flipper, looking at a physical contradiction that completely baffled scientists. And third, we are going to figure out exactly how it managed to survive in a sea completely overloaded with rival sea monsters. Okay, let's unpack this. Starting with an identity crisis that spans generations of paleontologists. Calling it an identity crisis might actually be underselling it. The timeline of discovering and naming this animal is incredibly convoluted. Let's wind the clock all the way back to 1871. We have a scientist named John Phillips. Right. And he's examining some pleasaur fossils that were found by Charles Leeds over in England, specifically in the Oxford clay formation. Yeah. So Phillips is looking at a swimming paddle and a pretty well preserved jawbone.

3:08And he analyzes these pieces. And he decides to name the creature. Play a saurus. Question mark grandest. He literally includes a question mark in the official scientific name. He does. I mean, that feels like the 19th century equivalent of a paleontologist just throwing their hands up in the air and saying, I have no idea. It really is. But it's also a remarkable bit of honesty for that era. Because that question mark tells you immediately that Phillips wasn't entirely convinced by his own classification. He knew he had a large marine reptile, but the proportions just didn't fit, right? Exactly. The morphology of that jawbone didn't neatly align with the existing understanding of the pleasaurus genus at the time. And that initial hesitation, well, it basically opened the floodgates for decades of taxonomic chaos. Total chaos. Because jump to 1889 and another paleontologist, Richard Leidecker, steps up to the plate. Leidecker takes one look at the specimen and decides Phillips was completely wrong. Right. He moves the animal into a totally different genus. He renames it Plenestys Philarchus.

4:11But he doesn't even stick to his own theory. No, he doesn't. Just one year later in 1890, he changes his mind again. Just because he notices these bones are significantly larger than other typical Plenestys specimens. Right. So he reassigns it yet again to a proposed species called Plenestys Avanti. This sounds exhausting. The classic problem in early paleontology, honestly. Size was very often used as a primary metric for determining a new species. Instead of looking at the actual nuanced anatomical differences. Exactly. Leidecker saw a bigger bone and just assumed, well, it has to be a different species within the Plenestys umbrella. And so the animal just sat there, categorized under that name, gathering dust until 1913. Which is when Charles William Andrews enters the narrative. Right. Andrews examines a partial skeleton of a large pliosaur found by Leeds. And he starts to notice fundamental structural differences. He realizes that the jaw and the vertebrae are more philogically completely distinct from Plenestys. He essentially looks at it and says, this isn't Pellanestys and it isn't quite pliosaurus.

5:13It's doing its own thing. He recognizes it as an intermediate form, a bridge between species. But amazingly, it takes almost another 50 years for anyone to formally act on Andrews observation. Science can move very slowly sometimes. Yeah, fast forward to 1960. A scientist named Lambert Beverly Tarlo decides to finally clean up the mess. Tarlo selects a very specific partial skeleton when the features a complete spine, the jaw, and the limbs. And he designates that as the holotype, the gold standard for the species. Right. And he officially names the creature Pliosaurus Andrew Gose. He uses that specific epithet to directly honor Charles William Andrews for his insights way back in 1913. And at that point, you would think the debate was finally closed, right? You really would. Tarlo established a holotype, honored the scientist who recognized its unique traits, and firmly planted it in the pliosaurus genus. For decades, this classification was considered entirely settled. But taxonomy is never truly finished. No, it simply waits for better analytical tools.

6:16Which brings us to the 2010s when modern science drops a massive plot twist on this poor creatures identity. After fighting for a century to get this animal properly classified into the pliosaurus genus, a new wave of researchers ended up kicking it right back out. They did. What's fascinating here is how the advent of modern computational biology completely upended a century of visual assumptions. What's fascinating here is exactly that. In the early 2010s, researchers conducted rigorous, phylogenetic, and anatomical revisions. They took all the morphological data, every ridge on the teeth, every measurement of the vertebrae, the exact proportions of the skull, and fed it into modern, cladistic analyses. So they let the computers do the heavy lifting? Right, and the resulting family tree was undeniable. This animal possessed unique characteristics, particularly in its teeth, that separated it from every valid species of pliosaurus. It's incredible. The computer essentially looked at the data, and confirmed what John Phillips suspected in 1871 with his little question mark.

7:16Full circle. Yeah. And because it doesn't belong in pliosaurus, but hasn't officially been assigned a new genus name yet, the scientific community handles this in a wonderfully quirky way. Today, its name is written as pliosaurus in quotation marks, followed by andrously. It wears those quotation marks like a temporary badge, just signifying its pending taxonomic status. It's like calling it the artist formerly known as pliosaurus. So where does it actually belong? Well, the current consensus places pliosaurus and russai as a basal member of a clad called thalacifonia. Okay, let's break that down for the listener. Sure, thalacifonia is a specific group of short-necked pliosaurus. And being a basal member means it sits near the root of that family tree. It's somewhere right between polineas, tees, and similestes. So it's a transitional form? Exactly. Being a transitional form like this makes its anatomy incredibly revealing because it bridges the evolutionary gap between completely different types of specialized marine hunters. Let's actually build this beast for you, the listener,

8:18because the anatomy is where this story shifts from a historical puzzle into a true biological marvel. Paint the picture. If this animal swam past you in that Jurassic Sea, it would present a classic pliosaur morph body plan. It was a medium-sized marine reptile. But keep in mind, medium in this ecosystem means it had a skull that measured one full meter in length. It's over three feet of pure jaw and muscle, just the head. Right. Behind that massive skull, it had a heavily built barrel-shaped body, which was designed for powerful bursts of speed rather than sustained graceful cruising. And it had a remarkably short neck, like exactly 78.3 centimeters long, based on a 2023 study of the holotech specimen. They get incredibly precise with these measurements. And to navigate the water, it utilized four large flippers. But the back pair were larger, right? Yeah, the hind flippers were noticeably larger and more robust than the front ones, which provided the primary thrust for swimming. But the defining feature of this animal,

9:19the thing that caused so much confusion, is what was going on inside that one meter skull. The teeth. At the very front of the jaw, where the two halves meet the symphysis it had at 12 pairs of teeth, and the seventh pair were these massive, deeply rooted canine-like teeth. Operating with about 64 teeth in total. And the structure of those teeth is the absolute key to unlocking its ecological role. They are highly distinct. In cross-section, they're completely round, and they feature these subtle, longitudinal ridges running down the crown. But that's not the weirdest part. No, the critical detail, the anomaly that separates it from its close relatives is the wear and tear. The dendle crowns exhibit a level of extreme abrasion. It extends considerably further down the tooth than in any other known plesiosaur. This is the grand contradiction of plesiosaurous and juicy. If you look at the shape of its skull, it has an elongated narrow snout. Which, evolutionarily speaking, is almost universally adapted for catching small, agile, slippery fish.

10:20Right. A narrow snout lets a predator snap its jaws shut through the water quickly because there's minimal drag. But its teeth tell a totally different story. Exactly. Its teeth were perfectly suited for heavy-duty cutting, and they were heavily worn down. If we connect this to the bigger picture for a second, you do not get extreme dental abrasion and deep wear patterns on cutting teeth from eating soft-bodied fish. You just don't. That specific type of wear strongly indicates it was attacking much larger, highly-resistant prey. It's an incredible morphological paradox. It possess the quick snapping, low-drag jaw of a fish eater, combined with a heavy-duty, heavily-worn dentition of an apex-big-game hunter. It completely broke the standard ecological rules regarding what long-snouted predators are actually supposed to hunt. So to understand why it evolved the specific contradiction, we need to look at exactly where it lived. We are traveling back to the Colombian stage of the Middle Jurassic, spanning roughly 166 to 164 million years ago.

11:22Geographically, we are focusing on the Peterborough member of the Oxford Clay Formation in modern-day England. Though the geography of the Colombian stage was vastly different from today. Right, the landmass that would eventually become England was submerged beneath an epicotinental sea. A shallow inland sea situated at a latitude of roughly 35 degrees north. And when we say shallow, we really mean it. A depth of only about 30 to 50 meters. That's incredibly shallow for a sea packed with giant monsters. It is, but up in the surrounding landmasses, the environment was surprisingly pleasant. It featured a Mediterranean climate with dry summers and wet winters. Though the region was gradually shifting toward a more arid climate, but the water itself was temperate. Isotope analysis from fossilized bivalves shows that the water temperature averaged around 15 degrees Celsius. Or 59 degrees Fahrenheit. Right, and it fluctuated seasonally, dropping to about 11 degrees Celsius in the winter and warming up to 17 degrees in the summer. But the chemical composition of that 50 meter deep water column was highly unusual.

12:25The sediment reveals the presence of green sulfur bacteria. And what does that tell us? Well, in modern marine environments, green sulfur bacteria are a clear indicator of eucinic conditions. Meaning low oxygen. Severely depleted oxygen levels, yes. Paired with high concentrations of toxic hydrogen sulfide. Typically, those chemical markers suggest a stagnant dead zone where complex life just cannot survive. But the Peterborough member was the furthest thing from a dead zone. The fossil record is packed with abundant traces of benthic organisms, creatures thriving right down on the seafloor. Which tells us that while there were definitely eucinic elements to the water chemistry, the bottom waters were not completely or permanently anoxic. The oxygen levels were dynamic. Here's where it gets really interesting. Because the sheer volume and diversity of life sharing the specific body of water is just staggering. Oh, it was packed. If you were diving in this 50 meter deep epicontinental sea, you would be surrounded by vast swarms of invertebrates,

13:26shelled ammonites, belemnites. You'd see a massive variety of fish, too, ranging from small agile swimmers all the way up to lead sick this. Right, that colossal filter feeding fish that cruise through the water like a Jurassic Balene whale. You would also encounter smaller, long neck pleasius ores like cryptoclytus, specializing in darting its head around to snatch up small prey. And don't forget ophthalmosaurus, that highly specialized ichthyosaur with a porcus-like body and gigantic eyes, perfectly adapted for diving into the darker depths to hunt squid. Add to that multiple-genera of marine crocodilians, some sleek and adapted for fish catching, others heavily armored. But the invertebrates, the giant fish, the marine crocs, they weren't the real issue in this ecosystem. The primary overcrowding problem came from the pliosaurids. The apex predators. Right, the fossil assemblage at the Peterborough member contains more species of pliosaur is than any other known site on Earth. This raises an important question. How do you fit that many distinct apex predators

14:27into a single shallow inland sea without them completely devastating the food web or just fiercely outcompeting each other into extinction? Let's look at the absolute gauntlet of neighbors that our animal pliosauris and juicy had to deal with. You have leoplaradon, similusties, poloniesties, marmenectis, russaurus, and patchy custosaurus. That is at least seven different, massive, heavily armed, carnivorous marine reptiles, occupying the exact same 50 meters of water. It sounds like a recipe for starvation. How did they do it? The mechanism that allowed them to coexist is a biological concept known as niche partitioning. Meaning they divided up the resources. Exactly. In highly crowded ecosystems, evolutionary pressure forces predators to specialize incredibly thoroughly. They divide the available resources so precisely that direct competition is minimized. They essentially split up the buffet menu. That's a great way to put it. And the Peterborough member stands as a master class in how nature engineers this delicate balance.

15:29Let's walk through that divided buffet. First, you have leoplaradon and urdisorse. Right, these were the absolute heavy hitters of the ecosystem. They possessed massive structurally robust skulls and powerful cutting teeth. So they claimed the top of the food chain. They did. They specialized in hunting the largest prey available, which likely meant praying on other large marine reptiles and the biggest fish. Then you have some elestis, which took a completely different morphological approach. It featured a very wide, exceptionally deep skull that housed a tremendously powerful bite force. Its specific niche was likely crushing large tush-shelled cephalopods. It didn't need a streamlined snout to chase fastfish. It simply needed the raw mechanical jaw strain to shatter heavy armor. On the opposite end of the spectrum, you have the fastfish hunters. That niche was dominated by pollen and astes. Right, it evolved the highly elongated snout and sharp piercing teeth, making it perfectly adapted for snapping up small, highly agile prey with minimal water resistance.

16:31We also have to mention patchy custisaurus, which found an entirely different way to avoid competition. It was a smaller, exceptionally heavily built pliosaur. Its skeletal structure was incredibly dense and its skull was structurally weaker than the midwater hunters. So it stayed low? Exactly. That immense bone density made it highly stable, strongly suggesting it was a dedicated bottom feeder. It cruised along the seafloor, picking up benthic prey, keeping completely out of the way of the massive predators hunting above it. Which brings us back to Plyosaurus and Jersey, navigating this incredibly specific ecosystem with its quotation marks and its contradictory anatomy. Right, because it was physically larger than the fish eating pollen astes and it shared that same low-drag elongated snout. But it also possessed those uniquely worn down, heavily abraded, cutting teeth. Through niche partitioning, Plyosaurus and Jersey carved out its own highly specific menu item. It utilised its quick snap of jaws to capture prey that was larger and tougher than the other long-snouted predators could handle,

17:31relying on its specialized cutting teeth to slice through them. Every single one of these massive marine reptiles survived by becoming a hyperspecialist. They subtly treat the length of their snouts, the exact cross-section of their teeth and the density of their skeletal structure, just enough to claim a unique, undisputed slice of the ecosystem. It is a stunning demonstration of evolutionary adaptation thriving within a confined environment. It really is. So what does this all mean? We started this deep dive looking at a confusing collection of bones that had paleontologists second-guessing themselves from 1871 well into the 2010s. And we uncover two brilliant takeaways. First, we see that science is a living, continuously self-correcting process. The quotation marks around Plyosaurus aren't a failure of taxonomy. They're a testament to the rigorous, ongoing revision of our understanding as new data and cladistic tools emerge. Absolutely. And second, we witnessed the sheer brilliance of niche partitioning. Life in the Oxford Clay Formation

18:32didn't just fiercely compete for a single resource. It adapted, partitioned, and specialized, allowing an incredibly diverse community of apex predators to thrive together in a shallow, fluctuating sea. There is, however, an inevitable consequence to that level of brilliant specialization. What do you mean? Well, the fossil record reveals that these long, snouted, paciferous forms like Plyosaurus and Drusy completely died out at the boundary between the middle and upper Jurassic. Yeah, this specific extinction event kicked off a gradual widespread decline in all Plesiosaur diversity. And it wasn't caused by a sudden catastrophic asteroid impact. It was driven by shifting ocean chemistry and steadily falling sea levels. So the environment just slowly changed around them? Exactly. When an ecosystem becomes as perfectly partitioned and tightly specialized as the Oxford Clay Sea, where every animal has evolved a highly specific jaw to consume a highly specific prey item, that very perfection makes them incredibly fragile.

19:32Because they have no backup plan. Right. When the ocean chemistry shifts and the water levels drop, the available buffet menu changes. And if your teeth, your jaw, and your entire body plan are irreversibly designed to eat only one thing, you are left entirely without options when that one thing disappears. That is a fascinating and sobering thought to leave on. Thank you for joining us on this deep dive into the chaotic taxonomic history, the bizarre anatomy, and the densely packed world of pliosaurus and drusaurusy. Keep digging into the mysteries of the ancient world and we will catch you on the next one. The Toyota Tundra and Tacoma are built to keep going, blending rugged muscle with precision engineering, all supported by Toyota's time-tested legacy of dependability. Step into a Tundra and feel the unyielding capability with the available iForce Max engine. Tundra puts out impressive power, torque, and towing performance and the roomy high-tech cabin. Keeps you connected on the go. Or take a look at Tacoma made for drivers who push past the path. Agile, tough and relentless with available features like crawl control,

20:33portable JBL speaker, a power lift gate, so gear goes in fast and the adventure keeps moving. The Tacoma and Tundra are engineered to endure season after season, mile after mile. So drive one home today, visit toyota.com or stop by your local Toyota dealer to find out more Toyota. Let's go places. You're listening to a podcast right now, driving, working out, walking the dog. If you're in a podcast, chances are you have something to say too. With RSS.com, starting your own podcast is free and easy. Upload an episode and we distribute it to Apple podcasts, Spotify, Amazon Music, and more. Track your listeners, see where they're from and start earning from ads just like this. If you've been thinking about starting a podcast, this is your sign. Start your new podcast for free today at RSS.com.