WEBVTT 00:00:00.000 --> 00:00:02.640 Welcome, everyone. We're really thrilled to have 00:00:02.640 --> 00:00:05.139 you joining us today for another custom -tailored 00:00:05.139 --> 00:00:07.620 deep dive into your source material. Yeah, thanks 00:00:07.620 --> 00:00:10.339 for tuning in. We have a really fascinating puzzle 00:00:10.339 --> 00:00:12.339 to put together today. We really do. So the mission 00:00:12.339 --> 00:00:14.759 for this session takes us... Plunging headfirst 00:00:14.759 --> 00:00:18.179 into the murky, highly competitive depths of 00:00:18.179 --> 00:00:20.280 paleontological history. Right into the deep 00:00:20.280 --> 00:00:22.600 end. Exactly. We are setting out to solve an 00:00:22.600 --> 00:00:26.100 identity crisis that is literally millions of 00:00:26.100 --> 00:00:28.320 years in the making. Yeah. And along the way, 00:00:28.320 --> 00:00:30.800 we're looking at how a notoriously crowded ecosystem. 00:00:31.719 --> 00:00:35.100 I mean, an ocean packed wall to wall with massive 00:00:35.100 --> 00:00:39.060 apex predators somehow managed to avoid collapsing 00:00:39.060 --> 00:00:41.340 under the weight of its own biodiversity. It's 00:00:41.340 --> 00:00:43.200 a great setup. And the material we are drawing 00:00:43.200 --> 00:00:45.420 from to explore this is a comprehensive Wikipedia 00:00:45.420 --> 00:00:49.179 article detailing a very specific extinct marine 00:00:49.179 --> 00:00:52.079 reptile, a creature known to the scientific community 00:00:52.079 --> 00:00:55.359 as Pliosaurus and Druduci. And you obviously 00:00:55.359 --> 00:00:57.079 can't see us in the studio right now, but we 00:00:57.079 --> 00:00:58.840 are absolutely putting air quotes around that 00:00:58.840 --> 00:01:01.140 genus name. Oh, heavily utilizing the air quotes. 00:01:01.159 --> 00:01:03.659 quotes today. Okay, let's unpack this. Because 00:01:03.659 --> 00:01:06.000 the most glaring detail at the very top of our 00:01:06.000 --> 00:01:08.060 source material is that typographical mystery. 00:01:08.640 --> 00:01:11.359 The animal's official current scientific name 00:01:11.359 --> 00:01:14.780 features quotation marks around the genus. Pleiosaurus 00:01:14.780 --> 00:01:18.510 and Drususii. And seeing punctuation like that 00:01:18.510 --> 00:01:21.269 in peer -reviewed taxonomy usually signals a 00:01:21.269 --> 00:01:23.849 really fascinating historical mess. It's essentially 00:01:23.849 --> 00:01:26.590 a taxonomic white flag. In the strict, highly 00:01:26.590 --> 00:01:29.829 regulated world of zoological nomenclature, those 00:01:29.829 --> 00:01:31.650 quotation marks indicate that the scientific 00:01:31.650 --> 00:01:34.109 community knows the current classification is 00:01:34.109 --> 00:01:37.629 phylogenetically incorrect. But a formal reassignment 00:01:37.629 --> 00:01:40.209 just hasn't been published yet. Exactly. The 00:01:40.209 --> 00:01:42.290 story of this particular animal represents a 00:01:42.290 --> 00:01:45.609 150 -year -long string of revisions. It all starts 00:01:45.609 --> 00:01:48.810 back in the late 1800s, when Charles Leeds first 00:01:48.810 --> 00:01:51.890 excavated its fossils from the Oxford Clay Formation 00:01:51.890 --> 00:01:54.170 over in England. And the initial naming attempt 00:01:54.170 --> 00:01:57.829 was made in 1871 by John Phillips. He examined 00:01:57.829 --> 00:02:00.450 a jawbone and a swimming paddle from Leeds' collection, 00:02:00.650 --> 00:02:03.829 and he cataloged it as Pleiosaurus grandus. But 00:02:03.829 --> 00:02:05.549 he actually included a question mark right there 00:02:05.549 --> 00:02:07.109 in the publication. Which tells you a lot about 00:02:07.109 --> 00:02:09.289 the confidence level at the time. Right. I mean, 00:02:09.310 --> 00:02:11.469 Victorian paleontologists were often working 00:02:11.469 --> 00:02:14.340 with... really fragmentary remains, and they 00:02:14.340 --> 00:02:15.919 knew they were making highly educated guesses. 00:02:16.180 --> 00:02:19.319 The field back then relied heavily on overall 00:02:19.319 --> 00:02:22.039 morphological similarities. You know, the general 00:02:22.039 --> 00:02:25.280 gestalt of the animal. They didn't have the rigorous 00:02:25.280 --> 00:02:28.120 statistical character matrices we use today. 00:02:28.219 --> 00:02:30.639 So consequently, the specimen was bounced around 00:02:30.639 --> 00:02:33.060 constantly. Just constantly relabeled. Yeah. 00:02:33.580 --> 00:02:36.479 In 1889, Richard Lidecker examined the remains 00:02:36.479 --> 00:02:39.020 and assigned them to a newly established genus 00:02:39.020 --> 00:02:41.680 calling it Pellinistes phylarchus. But his own 00:02:41.680 --> 00:02:43.900 assessment didn't even last a full calendar year. 00:02:44.120 --> 00:02:47.039 No, it didn't. By 1890, Lidecker noticed the 00:02:47.039 --> 00:02:49.900 immense size discrepancy between this specimen 00:02:49.900 --> 00:02:52.879 and typical Pellinistes material, which prompted 00:02:52.879 --> 00:02:56.000 him to propose a new species entirely. Polonistes 00:02:56.000 --> 00:02:58.560 avanci. The nomenclature of this animal was shifting 00:02:58.560 --> 00:03:01.039 almost seasonally at that point. And then Charles 00:03:01.039 --> 00:03:03.280 William Andrews stepped in a few decades later, 00:03:03.400 --> 00:03:06.960 right? In 1913. Yes. Andrews analyzed a secondary, 00:03:07.199 --> 00:03:09.719 more complete partial skeleton that Leeds had 00:03:09.719 --> 00:03:12.060 recovered. And he noted that the osteological 00:03:12.060 --> 00:03:15.020 features of the mandible and the vertebrae deviated 00:03:15.020 --> 00:03:17.919 far too significantly from the established Polonistes 00:03:17.919 --> 00:03:20.939 baseline. So he theorized it represented a distinct 00:03:20.939 --> 00:03:23.740 transitional form. Right. A bridge between Polonistes 00:03:23.740 --> 00:03:28.000 and the... Which brings us to the supposed end 00:03:28.000 --> 00:03:32.039 of the taxonomic ping pong in 1960. Lambert Beverly 00:03:32.039 --> 00:03:35.159 Tarlow published a definitive reassessment declaring 00:03:35.159 --> 00:03:38.039 the animal a distinct species within the Pleiosaurus 00:03:38.039 --> 00:03:40.520 genus. And he named it Pleiosaurus angiosephi 00:03:40.520 --> 00:03:44.159 to honor Andrew's earlier diagnostic work. Tarlow 00:03:44.159 --> 00:03:46.699 even designated a specific, highly complete partial 00:03:46.699 --> 00:03:49.280 skeleton as the holotype. It had the mandible, 00:03:49.379 --> 00:03:52.199 teeth, a full vertebral column, and portions 00:03:52.199 --> 00:03:54.500 of the appendicular skeleton. But what's fascinating 00:03:54.500 --> 00:03:57.099 here is the methodology of paleontology experienced 00:03:57.099 --> 00:04:00.439 a massive paradigm shift between 1960 and the 00:04:00.439 --> 00:04:03.099 2010s. The digital revolution, basically. Essentially, 00:04:03.280 --> 00:04:06.340 yes. The advent of modern phylogenetic analysis 00:04:06.340 --> 00:04:09.180 allowed researchers to input hundreds of specific 00:04:09.180 --> 00:04:11.879 osteological characters into computational models. 00:04:12.219 --> 00:04:15.120 This generates cliograms based on shared derived 00:04:15.120 --> 00:04:17.800 traits, rather than just relying on a scientist 00:04:17.800 --> 00:04:19.879 looking at it and making a qualitative visual 00:04:19.879 --> 00:04:22.319 assessment. And when paleontologists ran the 00:04:22.319 --> 00:04:25.279 matrix for Pliosaurus and Drusii, Tarlow's classification 00:04:25.279 --> 00:04:27.980 completely fell apart. It really did. And the 00:04:27.980 --> 00:04:29.980 defining features of the teeth were the smoking 00:04:29.980 --> 00:04:33.600 gun. Right, because all valid, recognized species 00:04:33.600 --> 00:04:36.920 within the true Pliosaurus genus exhibit a highly 00:04:36.920 --> 00:04:40.379 distinct dental morphology. Their teeth are trihedral. 00:04:40.500 --> 00:04:43.040 Which means the cross -section of a true Pliosaurus 00:04:43.040 --> 00:04:46.060 tooth shows a definitive triangular shape. It 00:04:46.060 --> 00:04:48.439 has three distinct faces. But the dental array 00:04:48.439 --> 00:04:50.420 of our creature is completely conical. Yeah, 00:04:50.459 --> 00:04:52.000 the cross -sections are round. It fundamentally 00:04:52.000 --> 00:04:54.939 lacks the primary synapomorphy, the shared trait 00:04:54.939 --> 00:04:58.000 of the genus it was assigned to. So the phylogenetic 00:04:58.000 --> 00:05:00.500 models ultimately placed it outside the pliosaurus 00:05:00.500 --> 00:05:03.319 genus entirely. The data shows it is a basal 00:05:03.319 --> 00:05:05.459 member of the Thalassophonia clade. These are 00:05:05.459 --> 00:05:07.819 the classic short -necked pliosaurs. It sits 00:05:07.819 --> 00:05:11.000 much further down the evolutionary tree, wedged 00:05:11.000 --> 00:05:13.769 somewhere phylogenetically. Between Polonistes 00:05:13.769 --> 00:05:17.550 and Simulastes. Which leaves it in taxonomic 00:05:17.550 --> 00:05:20.550 purgatory. It requires an entirely new genus 00:05:20.550 --> 00:05:23.949 designation. But until a dedicated paper is published 00:05:23.949 --> 00:05:26.550 officially minting that new name, it retains 00:05:26.550 --> 00:05:29.149 the old one, quarantined in those quotation marks. 00:05:29.370 --> 00:05:30.930 And for you, the listener, I think it serves 00:05:30.930 --> 00:05:33.449 as a stellar reminder that scientific knowledge 00:05:33.449 --> 00:05:36.149 is inherently iterative. I mean, fossilized bone 00:05:36.149 --> 00:05:38.350 doesn't change, but the analytical frameworks 00:05:38.350 --> 00:05:40.720 we use to interpret those bones. are constantly 00:05:40.720 --> 00:05:43.519 evolving. It demands that we revise old assumptions. 00:05:43.759 --> 00:05:46.000 Exactly. So you've established what it isn't. 00:05:46.000 --> 00:05:48.639 Let's construct what it actually was. Because 00:05:48.639 --> 00:05:51.100 the cranial measurements alone are staggering. 00:05:51.360 --> 00:05:54.120 The holotype features a skull measuring a full 00:05:54.120 --> 00:05:56.199 meter in length. That's over three feet of jaw. 00:05:56.459 --> 00:05:59.199 It utilized a classic pliosoromorph body plan. 00:05:59.379 --> 00:06:01.120 If you are familiar with the plesiosoromorph 00:06:01.120 --> 00:06:03.360 build, you know, the elongated, highly flexible 00:06:03.360 --> 00:06:05.920 necks and diminutive little skulls, you will 00:06:05.920 --> 00:06:08.379 recognize this as the complete biomechanical 00:06:08.379 --> 00:06:10.800 inversion of that. The pliosoromorphs invested 00:06:10.800 --> 00:06:14.560 heavily in cranial capacity. The source material 00:06:14.560 --> 00:06:17.180 indicates the cervical vertebral column on this 00:06:17.180 --> 00:06:20.579 holotype was exceptionally abbreviated. It measured 00:06:20.579 --> 00:06:24.199 only 78 .3 centimeters. So that massive meter 00:06:24.199 --> 00:06:27.959 -long skull sat on a remarkably short neck, which 00:06:27.959 --> 00:06:30.720 was attached to a robust barrel -shaped torso. 00:06:31.100 --> 00:06:33.600 And locomotion was achieved through four massive 00:06:33.600 --> 00:06:36.279 hydrofoils, right? Yeah, four huge flippers. 00:06:36.959 --> 00:06:40.100 Plesiosaurian underwater flight is a really unique 00:06:40.100 --> 00:06:42.980 biomechanical adaptation. They didn't rely on 00:06:42.980 --> 00:06:45.439 tail -driven propulsion like ichthyosaurs or 00:06:45.439 --> 00:06:48.259 mosasaurs did. And interestingly, in this specific 00:06:48.259 --> 00:06:51.139 species, the posterior flippers, the back ones, 00:06:51.300 --> 00:06:53.879 were significantly larger than the anterior ones. 00:06:54.000 --> 00:06:56.160 They needed to generate immense thrust from the 00:06:56.160 --> 00:06:58.399 rear just to propel that massive head through 00:06:58.399 --> 00:07:00.339 the water column. Here's where it gets really 00:07:00.339 --> 00:07:02.699 interesting. The structural engineering of that 00:07:02.699 --> 00:07:05.939 one meter skull presents a massive biomechanical 00:07:05.939 --> 00:07:07.660 contradiction. It's one of the weirdest things 00:07:07.660 --> 00:07:09.939 about this animal. The mandibular symphysis, 00:07:10.139 --> 00:07:12.579 which is the fused front portion of the lower 00:07:12.579 --> 00:07:16.490 jaw, held up to 12 pairs of teeth. The mandible 00:07:16.490 --> 00:07:19.769 as a whole contained roughly 64 teeth, and the 00:07:19.769 --> 00:07:22.310 seventh pair were heavily pronounced. They were 00:07:22.310 --> 00:07:25.470 broad caniform fangs, essentially. And the contradiction 00:07:25.470 --> 00:07:28.209 lies entirely between the morphology of the snout 00:07:28.209 --> 00:07:30.410 and the morphology of those teeth. Walk us through 00:07:30.410 --> 00:07:33.550 that. Well, the animal possessed a highly elongated, 00:07:33.550 --> 00:07:37.110 attenuated rostrum, a very long, narrow snout. 00:07:37.319 --> 00:07:40.040 In aquatic environments, a narrow snout is a 00:07:40.040 --> 00:07:43.879 highly specialized adaptation to reduce hydrodynamic 00:07:43.879 --> 00:07:46.300 drag. It allows the predator to rapidly snap 00:07:46.300 --> 00:07:48.759 its jaws laterally through the water. Exactly. 00:07:48.879 --> 00:07:51.319 It is an evolutionary design highly optimized 00:07:51.319 --> 00:07:54.360 for capturing small, evasive, agile prey. Like 00:07:54.360 --> 00:07:56.980 a modern gharial or a river dolphin. They utilize 00:07:56.980 --> 00:07:59.779 that exact same hydrodynamic principle to catch 00:07:59.779 --> 00:08:02.360 quick fish. You do not evolve an attenuated rostrum 00:08:02.360 --> 00:08:04.879 to grapple with massive, heavily armored macro 00:08:04.879 --> 00:08:07.600 predators. No, you'd snap your jaw. But the dental 00:08:07.600 --> 00:08:09.540 morphology tells a completely different story. 00:08:09.720 --> 00:08:12.680 The teeth are conical, with smooth enamel interrupted 00:08:12.680 --> 00:08:16.379 by distinct longitudinal ridges. But most importantly, 00:08:16.639 --> 00:08:19.220 their structural geometry is specifically adapted 00:08:19.220 --> 00:08:21.879 for cutting. And cutting teeth are required for 00:08:21.879 --> 00:08:25.860 processing large prey. You need them for shearing 00:08:25.860 --> 00:08:28.399 chunks of flesh from animals that are just too 00:08:28.399 --> 00:08:30.860 massive to be swallowed whole. So the snout is 00:08:30.860 --> 00:08:33.919 engineered for evasive micro -prey, but the teeth 00:08:33.919 --> 00:08:36.360 are engineered for large game processors. That's 00:08:36.360 --> 00:08:38.639 completely contradictory. And it's compounded 00:08:38.639 --> 00:08:41.639 by the taphonomic evidence. The source material 00:08:41.639 --> 00:08:44.259 highlights an extreme degree of dental wear on 00:08:44.259 --> 00:08:46.700 the crowns of these teeth. The abrasion extends 00:08:46.700 --> 00:08:49.240 considerably further down the tooth shaft than 00:08:49.240 --> 00:08:51.519 in any other known representative of the entire 00:08:51.519 --> 00:08:54.179 plesiosaurian order. So the mechanical stress 00:08:54.179 --> 00:08:56.460 it was subjected to was entirely unique within 00:08:56.460 --> 00:08:59.460 its clade. To contextualize why an animal would 00:08:59.460 --> 00:09:01.639 evolve such a hyper -specific, contradictory 00:09:01.639 --> 00:09:04.360 set of tools, we really have to look at the environment 00:09:04.360 --> 00:09:06.379 that was shaping it. We are looking at the middle 00:09:06.379 --> 00:09:08.840 Jurassic period, specifically the Calovian stage. 00:09:09.080 --> 00:09:13.159 That spans roughly 166 to 164 million years ago. 00:09:13.340 --> 00:09:15.710 If we connect this to the bigger picture. The 00:09:15.710 --> 00:09:17.750 ecosystem preserved in the Peterborough member 00:09:17.750 --> 00:09:20.830 of the Oxford Clay Formation wasn't a pelagic 00:09:20.830 --> 00:09:23.710 open ocean environment. It was an epicontinental 00:09:23.710 --> 00:09:26.629 sea. Effectively, a flooded continental shelf. 00:09:26.870 --> 00:09:29.450 Right. The bathymetry data suggests it was remarkably 00:09:29.450 --> 00:09:32.250 shallow, averaging only 30 to 50 meters in depth. 00:09:32.429 --> 00:09:35.450 And situated at a paleolatitude of roughly 35 00:09:35.450 --> 00:09:38.590 degrees north. The surrounding landmasses experienced 00:09:38.590 --> 00:09:41.429 a Mediterranean climate. They had distinct wet 00:09:41.429 --> 00:09:44.070 and dry seasons. We even have highly granular 00:09:44.070 --> 00:09:47.669 data regarding the marine climate itself. Paleoclimatologists 00:09:47.669 --> 00:09:50.549 have analyzed oxygen isotopes preserved within 00:09:50.549 --> 00:09:53.529 the fossilized shells of bivalves from this specific 00:09:53.529 --> 00:09:55.730 stratigraphic layer. And what did they find? 00:09:55.909 --> 00:09:58.110 They determined the water maintained a mild average 00:09:58.110 --> 00:10:00.970 temperature of about 15 degrees Celsius. So nearly 00:10:00.970 --> 00:10:03.570 60 degrees Fahrenheit. The biomass sustained 00:10:03.570 --> 00:10:06.389 within that warm, shallow... 50 -meter -deep 00:10:06.389 --> 00:10:08.490 water column is almost difficult to comprehend. 00:10:08.710 --> 00:10:10.350 I mean, the benthic zone on the seafloor was 00:10:10.350 --> 00:10:14.169 just blanketed with diverse invertebrates, ammonites, 00:10:14.250 --> 00:10:16.809 nautiloids, bivalves. And moving up the water 00:10:16.809 --> 00:10:19.149 column, you encounter Pachycormid filter feeders 00:10:19.149 --> 00:10:21.570 like Leedsichthys. Those were massive. They were 00:10:21.570 --> 00:10:24.129 essentially operating as the baleen whales of 00:10:24.129 --> 00:10:26.639 the Jurassic ecosystem. And the reptilian diversity 00:10:26.639 --> 00:10:29.419 alongside them is staggering. You have Opsalmosaurus 00:10:29.419 --> 00:10:31.539 inhabiting these waters. That's an ichthyosaur 00:10:31.539 --> 00:10:34.080 featuring these massive sclerotic rings adapted 00:10:34.080 --> 00:10:37.500 for extreme deep diving. Which suggests they 00:10:37.500 --> 00:10:40.720 likely hunted squid nocturnally or maybe ventured 00:10:40.720 --> 00:10:43.370 into deeper adjacent basins off the shelf. The 00:10:43.370 --> 00:10:45.669 ecosystem also supported multiple clades of marine 00:10:45.669 --> 00:10:48.750 crocodiles. Teleosauroids hunted with their gharial 00:10:48.750 --> 00:10:51.509 -like rostra, while metrier hinkids exhibited 00:10:51.509 --> 00:10:54.830 extreme marine adaptations. They shed their armor, 00:10:54.950 --> 00:10:57.690 their osteoderms, and developed hypocircle tail 00:10:57.690 --> 00:11:00.509 flukes like fish. You also have the smaller long 00:11:00.509 --> 00:11:03.190 -necked plesiosaurs like Cryptoclytus darting 00:11:03.190 --> 00:11:05.450 through the shallows. But the most pressing ecological 00:11:05.450 --> 00:11:08.129 issue in the source material, the real anomaly 00:11:08.129 --> 00:11:10.629 that demands an explanation, is the presence 00:11:10.629 --> 00:11:14.190 of the pliosaurids. The massive apex macro predators. 00:11:14.409 --> 00:11:16.370 Yes. The Peterborough member yields a higher 00:11:16.370 --> 00:11:18.850 diversity of pliosaurid species than any other 00:11:18.850 --> 00:11:21.309 fossil assemblage on the entire planet. Which 00:11:21.309 --> 00:11:24.269 introduces a massive problem regarding the competitive 00:11:24.269 --> 00:11:28.129 exclusion principle. You have a shallow, geographically 00:11:28.129 --> 00:11:30.929 constrained sea that is packed with multiple 00:11:30.929 --> 00:11:35.309 species of giant apex predators. And basic ecology 00:11:35.309 --> 00:11:38.070 tells us two species competing for the exact 00:11:38.070 --> 00:11:40.330 same resources in the exact same environment. 00:11:41.019 --> 00:11:44.580 cannot stably coexist. One always outcompetes 00:11:44.580 --> 00:11:46.629 the other. This raises an important question 00:11:46.629 --> 00:11:49.490 regarding how this immense predator density avoided 00:11:49.490 --> 00:11:52.549 immediate ecological collapse. And the stabilization 00:11:52.549 --> 00:11:55.309 mechanism here is extreme niche partitioning. 00:11:55.350 --> 00:11:57.429 The pliosaurids didn't engage in direct competition 00:11:57.429 --> 00:12:00.350 because each species evolved morphological extremes. 00:12:00.509 --> 00:12:02.769 Right. They effectively siloed themselves into 00:12:02.769 --> 00:12:06.009 highly specific trophic distinctives. Let's actually 00:12:06.009 --> 00:12:07.909 break down that resource allocation among these 00:12:07.909 --> 00:12:09.769 predators. Let's look at the roommates in this 00:12:09.769 --> 00:12:12.090 flat share, starting with the top tier, the predators 00:12:12.090 --> 00:12:15.139 hunting other massive marine reptiles. Myopleurodon 00:12:15.139 --> 00:12:17.659 phyrox and Erdosaurus occupied that macro predator 00:12:17.659 --> 00:12:20.399 niche. Their cranial robusticity and their immense 00:12:20.399 --> 00:12:23.320 bite force allowed them to target large plesiosaurs 00:12:23.320 --> 00:12:25.919 and massive ichthyosaurs. They claimed the absolute 00:12:25.919 --> 00:12:28.720 top of the trophic web. The bruisers. Exactly. 00:12:29.279 --> 00:12:31.779 then moving to the hard -shelled prey, the massive 00:12:31.779 --> 00:12:34.299 cephalopods and ammonites, populating the water 00:12:34.299 --> 00:12:37.559 column. Semelestes vorax exploited that specific 00:12:37.559 --> 00:12:41.139 resource. It evolved a remarkably wide, deep 00:12:41.139 --> 00:12:44.159 skull, capable of generating the immense crushing 00:12:44.159 --> 00:12:47.500 force necessary to shatter dense cephalopod shells. 00:12:47.940 --> 00:12:50.820 It was operating essentially as a marine nutcracker. 00:12:51.000 --> 00:12:53.179 Which leaves the small, rapid -evation fish. 00:12:53.600 --> 00:12:56.370 Peloninistes claimed the agile prey. Its highly 00:12:56.370 --> 00:12:58.830 attenuated rostrum and piercing, rather than 00:12:58.830 --> 00:13:01.509 crushing or cutting teeth, made it the optimal 00:13:01.509 --> 00:13:04.269 pursuit predator for small, evasive targets. 00:13:04.549 --> 00:13:06.850 And finally, down to the benthic zone, hunting 00:13:06.850 --> 00:13:09.590 directly along the mud. Pachycystosaurus doni 00:13:09.590 --> 00:13:12.409 utilized pachyostosis. That's a densification 00:13:12.409 --> 00:13:14.809 of the bone structure to provide natural ballast. 00:13:14.929 --> 00:13:17.470 Like a diver's weight belt. Exactly. It possessed 00:13:17.470 --> 00:13:20.029 a relatively fragile skull, which indicates it 00:13:20.029 --> 00:13:22.830 avoided struggling prey. Instead, it used its 00:13:22.830 --> 00:13:25.610 dense skeleton to stabilize itself while foraging 00:13:25.610 --> 00:13:28.009 along the sea floor. It completely avoided the 00:13:28.009 --> 00:13:30.389 pelagic hunting grounds of the larger pliosaurids 00:13:30.389 --> 00:13:33.360 above it. So what does this all mean? Well, when 00:13:33.360 --> 00:13:35.779 we look at our friend Pleiosaurus and Drusii, 00:13:35.899 --> 00:13:38.899 in air quotes, its contradictory anatomy suddenly 00:13:38.899 --> 00:13:41.799 makes perfect sense. It was substantially larger 00:13:41.799 --> 00:13:44.960 than the fish -snatching Pelonistes, and it retained 00:13:44.960 --> 00:13:48.299 a similarly elongated snout for hydrodynamic 00:13:48.299 --> 00:13:51.340 speed. Yet it possessed cutting teeth and exhibited 00:13:51.340 --> 00:13:54.700 extreme dental wear. It was exploiting a very 00:13:54.700 --> 00:13:57.559 narrow trophic margin. It was capable of processing 00:13:57.559 --> 00:14:00.039 prey that was too large or heavily armored for 00:14:00.039 --> 00:14:02.799 Pelonistes to handle. But its hydrodynamic snout 00:14:02.799 --> 00:14:05.679 allowed it to capture agile prey that the massive, 00:14:05.820 --> 00:14:08.799 bulky Liopleurodon could never catch. It essentially 00:14:08.799 --> 00:14:11.080 threaded the needle between two separate apex 00:14:11.080 --> 00:14:13.480 niches. And the lesson here for you, the listener, 00:14:13.539 --> 00:14:15.960 isn't some forced business metaphor about finding 00:14:15.960 --> 00:14:18.340 your market niche. It is a profound realization 00:14:18.340 --> 00:14:21.120 about evolutionary biology. Life's capacity for 00:14:21.120 --> 00:14:23.480 morphological plasticity means biodiversity isn't 00:14:23.480 --> 00:14:25.259 strictly limited by the physical volume of an 00:14:25.259 --> 00:14:28.139 environment. It's limited by biomechanical ingenuity. 00:14:28.360 --> 00:14:40.649 Nature can pack a half dozen apes. The deep dive 00:14:40.649 --> 00:14:43.149 into this one creature ultimately serves as a 00:14:43.149 --> 00:14:46.029 masterclass in synthesis. It demonstrates how 00:14:46.029 --> 00:14:48.149 phylogenetic modeling corrects the assumptions 00:14:48.149 --> 00:14:51.590 of 19th century taxonomy. And how analyzing the 00:14:51.590 --> 00:14:54.289 biomechanics of a single mandible can map the 00:14:54.289 --> 00:14:56.710 trophic structure of an entire vanished ecosystem. 00:14:57.480 --> 00:15:00.279 It underscores that the fossil record isn't just 00:15:00.279 --> 00:15:03.539 a catalog of dead animals. It is a complex, interactive 00:15:03.539 --> 00:15:07.080 puzzle of biomechanics and paleoclimatology. 00:15:07.200 --> 00:15:09.379 It really is. But before we wrap up this session, 00:15:09.460 --> 00:15:11.480 there is one final detail from the source material 00:15:11.480 --> 00:15:14.000 regarding the fate of this perfectly tuned ecosystem. 00:15:14.769 --> 00:15:17.690 Despite their incredible morphological plasticity 00:15:17.690 --> 00:15:20.330 and their flawless niche partitioning, these 00:15:20.330 --> 00:15:23.590 long -snouted, fish -eating pliosaurs experienced 00:15:23.590 --> 00:15:26.110 an abrupt extinction at the boundary between 00:15:26.110 --> 00:15:28.370 the Middle and Upper Jurassic periods. It marked 00:15:28.370 --> 00:15:30.730 the beginning of a gradual, sustained decline 00:15:30.730 --> 00:15:33.509 in overall plesiosaurian diversity globally. 00:15:33.830 --> 00:15:35.870 And the paleontological consensus suggests their 00:15:35.870 --> 00:15:38.090 demise wasn't driven by biological competition. 00:15:38.450 --> 00:15:40.809 They weren't out -hunted or out -maneuvered by 00:15:40.809 --> 00:15:43.309 some new apex predator. No, their extinction 00:15:43.309 --> 00:15:45.779 was driven... by shifting ocean chemistry and 00:15:45.779 --> 00:15:48.840 rapidly fluctuating sea levels. The very environment 00:15:48.840 --> 00:15:51.919 they had perfectly adapted to simply ceased to 00:15:51.919 --> 00:15:54.440 exist. It leaves you with a fascinating dynamic 00:15:54.440 --> 00:15:58.159 to consider moving forward. How does a highly 00:15:58.159 --> 00:16:01.019 specialized apex predator, a creature perfectly 00:16:01.019 --> 00:16:03.240 engineered to exploit a hyperspecific margin 00:16:03.240 --> 00:16:06.419 of its ecosystem, survive when the fundamental 00:16:06.419 --> 00:16:08.879 chemistry of its world turns against it? It is 00:16:08.879 --> 00:16:11.299 a sobering perspective on the limits of specialization. 00:16:11.500 --> 00:16:13.740 It really is. Thank you so much for joining us 00:16:13.740 --> 00:16:15.080 for this deep dive into the source material. 00:16:15.399 --> 00:16:17.740 Keep analyzing the data, keep questioning the 00:16:17.740 --> 00:16:19.799 consensus, and we will catch you on the next 00:16:19.799 --> 00:16:19.960 one.