| [♪ INTRO] Discovering a fossil is always pretty exciting. Each little piece gives us a little more insight into the history of life on our little green planet. The fact that we have fossils /at all/ is pretty remarkable; the odds of a living thing dying in just the right place to fossilize are extremely slim. So when we find fossils that change our understanding of whole groups of organisms, it’s extra special. And we’re regularly uncovering a range of relics left behind from our planet’s past. The more fossil specimens we find, the more we can learn about different groups of organisms that came before us, over millions of years. So here are five of our favorite fossil discoveries announced in 2022 that not only teach us about the world that was, but can help us better understand life on Earth today, as well. Our first fossil is a two-for-one special that gives us a gnarly look into ancient food chains. We’re talking about crocodilians, some of Earth’s most formidable flesh-eaters for hundreds of millions of years. And while their toothy grin may seem like an obvious giveaway of their dietary preference, it’s hard to know for certain what exactly these prehistoric crocs were chowing down on. Previously, paleontologists had to piece together the details of their diet from fossilized bite marks on their prey that got away, and fossilized croc poop. And although the evidence suggested that early crocodilians were feeding on dinosaurs, at least some of the time, we were missing more direct evidence this was the case. Until now! A recently discovered croc fossil from Australia is very likely a new kind of mid-Cretaceous crocodilian group dating to around 93 million years ago. Not only that, but it was also found with preserved stomach contents! This croc kicked the bucket very soon after finishing a meal, so it didn’t have time for its digestive enzymes to do their thing. And it turns out its final meal was a juvenile ornithopod, the group of dinosaurs that includes duck-billed hadrosaurs. Studying the crocs’ fossilized gut contents also confirmed that they chewed, dismembered, and crushed the bones of their prey in the same way their modern relatives do. And looking at the vertebrae of the croc, its strong neck indicated that this ancient predator likely ambushed its prey, much like most modern crocodilians. It’s yet to be confirmed, but the researchers think this young ornithopod may be a completely new dinosaur discovery too, since this is the first full body of an ornithopod that they’ve found from this particular location of Australia. Talk about a BOGO deal! When it comes to dinosaurs, the obvious fan favorite dinosaur is the formidable Tyrannosaurus rex. Its massive size, huge teeth, and terrifying jaws made the T. rex the ultimate predator, despite their comically small arms. But even as one of the most famous dinosaurs of all time, we still don’t fully understand why its arms are so tiny. It’s not the only ferocious dinosaur with teeny arms either. Other large, predatory dinos have shorter front limbs as well, like Carnotaurus. which is a member of a family called abelisaurids. And, these guys didn’t inherit those tiny limbs from their common ancestor; they both shrank their arms independently. And it turns out, little limbs showed up independently in a third group of dinosaurs as well. And this recent discovery has shed some light on the possible evolutionary pressures that resulted in this puzzling adaptation to appear in distantly related dinos. A new and massive meat-eating dinosaur was discovered in Patagonia in 2012, Meraxes gigas. And after years spent carefully extracting, preparing, and studying the fossil, a team of researchers have finally released some exciting conclusions around their find. Not only was this specimen an impressive beast, at almost 11 meters snout-to-tail and estimated to weigh over 4000 kilograms. It’s also the most complete fossil of its family, which means it gives us a lot of insight into this group. Its skull, hips, and all four limbs were intact. Which is key, because before this discovery, fossils from this group of dinosaurs left a lot of holes in our understanding of them. And we weren’t really sure what their head and forelimbs even looked like! This dino’s huge skull and tiny front limbs revealed that it was really similar in body form to tyrannosaurs. Which is a little bit odd because they’re actually pretty distantly related! Not only that, but the tyrannosaurs’ closer relations aren’t as physically similar as Meraxes, meaning this isn’t something that they just inherited from their earlier ancestors. So it turns out that tiny arms evolved at least three times, in three different families of dinosaurs. Which raises the question: Why do they need such tiny arms? Well, these researchers think that they didn’t. They argue that tiny limbs themselves didn’t evolve to fill a specific purpose, but that their limbs shrinking allowed their skulls to become massive. Basically, their body was being optimized for catching large prey thanks to a massive jaw, so their forearms just weren’t as important. Why bother to grow big ones that will just get in the way? So while their little arms look a bit goofy to us, they’re all part of the apparatus that made these predatory dinos so powerful back in their day. Now while the dinosaurs were certainly the most famed reptiles of their time, the other major reptile groups were already around too – like the humble lizard. Lizards and their relatives make up a group known as squamates, which have been around since the Jurassic period, although new evidence suggests there may have been a few dating even further back into the Triassic. We’re already pretty confident that squamates split from their closest living relatives, the tuataras, about 240 million years ago. However, because these lizards are so small, their bones don’t fossilize nearly as often, so there’s not as much that we know about squamates’ early evolutionary history. The big question on researchers’ minds has been which of the main few squamate groups broke away from the pack first. Genetic data on modern animals conflicts with the pattern we see in their anatomy, so researchers have been stumped; though the iguana group is often thought to be the first group to have branched off.. But in 2022, a study was published on a near-perfect, itty bitty fossilized lizard ancestor found in Scotland called Bellairsia gracilis, that may help us answer this question. This miniature fossil was special in a few key ways. For one, it’s really rare that researchers get to study a fossil that’s this complete. The largest missing pieces were from the tail and snout, but otherwise the body was about 70% accounted for, which is pretty impressive for a 168 million year old fossil. On top of that, this little guy helps fill in a 100 million year long gap in the fossil record for this particular group. It lived about 168 million years ago, which puts it right in the middle of a major hole in the lizard lineage. And by comparing the traits of this lizard-like ancestor to living squamates, the researchers were able to reconstruct which of those modern groups split from the rest before all the others. It turns out the traits this fossil shared with modern lizards were closest to geckos. So this discovery supports the hypothesis that geckos were actually one of the early splits in the modern squamate timeline, and not the iguanas after all. So this fossil has shed light on some pretty big secrets of its family tree, despite its miniature size. But there’s a lot more than just reptile fossils out there to be discovered. It turns out, animals don’t need to have bones for them to show up in the fossil record. Modern vampire squid are mollusks that live in the deep dark sea, and look like an octopus dressed as a dracula dog for Halloween. Their eight arms are connected to each other with webbing, and they have little fins that look like floppy ears. Basically, they’re adorable. Their name is pretty misleading though. Not only do they not drink blood, they aren’t even true squids! Their closest living relatives are actually octopuses, which you might guess based on their eight-legged similarities. These two major orders are clumped together in a bigger clade called Vampyropods. The other soft-bodied relatives, like squids and cuttlefish, have eight arms and two tentacles, but researchers weren’t completely sure whether that difference is due to octopuses and vampire squids losing two limbs, or squids and cuttlefish gaining them.. And in 2022, researchers published their work on the oldest known relative of the Vampyropods that sheds a little light on this tentacle question. They published their brand-new fossil species, named Syllipsimopodi bideni after current US president Joe Biden. And it turns out the researchers didn’t have to go very far to find this species. The fossil in question had been donated to the Royal Ontario Museum in 1988, but hadn’t been closely studied until now! At 328 million years old, this vampire squid is not only the oldest fossil record for this group, but it pushes back previously estimated timelines of the group’s origin by nearly 82 million years! This ancestor vampire squid also sports fins much like the modern vampire squid, and it’s the only known vampyropod with 10 suckered arms. This fossil shows that the ancestors of vampire squids and octopuses did start with ten arms, much like their current living relatives, the squid and cuttlefish. But the vampyropods lost a couple limbs somewhere along the way . This discovery has revealed a significant amount of info about these amazing animals’ evolutionary past, providing a bit more insight into the distant split between modern ten-armed mollusks and the vampyropods. But the jury’s still out on which group gives better hugs. Studying the form and function of organs is an important part of evolutionary research, as it helps us compare changes over time and between species. Unfortunately, paleontologists don’t usually have the luxury of studying these key features, since they’re too soft and squishy to fossilize. Most of the time. But in rare cases, ancient organs do become fossilized, as in the case of the oldest heart ever found, described in 2022. This ancient heart is about 380 million years old and belonged to a jawed fish, the group of fishes most closely related to the land-dwelling vertebrates, like us. And the heart wasn’t the only organ that was preserved from these fish fossils. Researchers also found the fish’s stomach, intestines, and liver, all of which is especially surprising given how rare it is for soft tissue to preserve at all. And much like with the lizard discovery, modern scanning technology was able to give us 3D images of these organs, including what the interior of these organs would have looked like, without having to break into the fossil itself. As it turns out, these two-chambered hearts were pretty advanced, and their distinct S-shape helps tell the story of how and when the heads and necks of our fishy ancestors began evolving. Their organs were laid out similarly to those of modern sharks, with the heart situated near the mouth, just behind the gills, which may bring new meaning to having your heart in your throat. This is completely different from the hearts of jawless fishes, which are found way further back in the body. But when some fishes began to evolve jaws, they developed more complex body forms to accommodate their changing mouths, including shifting their hearts forward. And this heart fossil shows us that this repositioning happened very early on! These types of discoveries really help us unravel some of the remaining evolutionary mysteries along the incredible transition from jawless fish all the way to modern jawed vertebrates, including us! It’s clear that fossils have so much to teach us. And the more of these incredible preserved specimens we uncover, the more mysteries we can solve. From ten-armed vampire squids to Scottish lizards, 2022 was pretty stellar for the world of paleontology. 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[♪ OUTRO] | [♪ 简介] 发现化石总是令人兴奋。 每一个小片段都让 我们对这个绿色小星球上的生命史有了更多的了解。 我们/完全/拥有化石这一事实 非常了不起； 生物在恰好成为 化石的地方死亡的可能性非常小。 因此，当我们发现化石改变了我们 对整个生物群的理解时，它就格外特别。 我们定期发现 地球过去遗留下来的一系列遗迹。 我们发现的化石标本越多，我们就越能了解数百万年 来出现在我们面前的不同生物群 。 因此，这里有五个我们在 2022 年宣布的最喜欢的化石发现 ，它们 不仅让我们了解过去的世界， 而且还可以帮助我们更好地了解 当今地球上的生命。 我们的第一块化石是二合一的特辑 ，让 我们对古代食物链有了一个粗略的了解。 我们谈论的是鳄鱼， 它们是数亿年来地球上最可怕的食肉动物 之一。 虽然它们露齿的笑容 似乎明显暴露了 它们的饮食偏好，但很难确定 这些史前鳄鱼到底在吃什么 。 以前，古生物学家必须根据逃跑 的猎物咬痕 化石和鳄鱼粪便化石拼凑出它们的饮食细节。 尽管有证据表明早期 鳄鱼 以恐龙为食，但至少在某些 时候， 我们缺少更直接的证据证明 确实如此。 到目前为止！ 最近在澳大利亚发现的鳄鱼化石 很可能是距今约 9300 万年前的一种新 的白垩纪中期鳄鱼群 。 不仅如此，还发现了 保存完好的胃内容物！ 这只鳄鱼吃完饭后很快就把水桶踢了 ， 所以它没有时间让消化 酶发挥作用。 事实证明，它的最后一餐是一只幼年 鸟 脚类动物，即包括鸭嘴鸭嘴龙在内的恐龙群 。 研究鳄鱼的肠道内容物化石 也证实，它们咀嚼、 肢解和压碎猎物的骨头 的方式与现代近亲相同。 看看鳄鱼的脊椎骨， 它强壮的脖子表明 这种古老的捕食者很可能 像大多数现代鳄鱼一样伏击猎物。 这还有待证实，但研究人员 认为这只年轻的鸟 脚类动物也可能是一种全新的恐龙 发现，因为这 是他们在澳大利亚这个特定地点发现的第一个完整的鸟脚类动物尸体 。 谈论 BOGO 交易！ 说到恐龙 ，粉丝最喜欢的恐龙显然是令人生畏的 霸王龙。 尽管霸王龙的手臂小得可笑，但 它巨大的体型、巨大的牙齿和可怕的 下巴使它 成为终极捕食者 。 但即使作为有史以来最著名的恐龙 之一， 我们仍然不完全理解为什么它的 手臂如此细小。 它也不是唯一 一种拥有细小手臂的凶猛恐龙。 其他大型掠食性恐龙的前肢也较短 ，例如食肉牛龙。 它是阿贝力龙科的成员。 而且，这些家伙并没有 从他们共同的祖先那里继承那些细小的四肢； 两人各自独立的缩了缩手臂。 事实证明，小肢体也独立出现 在第三组恐龙身上。 这项最近的发现 揭示了可能的 进化压力，导致这种 令人费解的 适应出现在远缘恐龙中。 2012 年在巴塔哥尼亚发现了一种新的大型食肉恐龙，即 Meraxes gigas。 经过多年仔细提取、 准备和研究化石， 一组研究人员终于 围绕他们的发现发布了一些令人兴奋的结论。 这个标本不仅是令人印象深刻的野兽， 从鼻子到尾巴的长度接近 11 米， 估计重量超过 4000 公斤。 它也是其家族中最完整的化石 ， 这意味着它让我们对这个群体有了很多了解 。 它的头骨、臀部和四肢完好无损。 这很关键，因为在这一发现之前， 这群恐龙的化石 在我们对它们的理解上留下了很多漏洞。 我们甚至不确定它们的头部 和前肢长什么样！ 这只恐龙巨大的头骨和细小的前肢 表明 它的体型与霸王龙非常相似。 这有点奇怪，因为它们 实际上是远亲！ 不仅如此，霸王龙的亲缘关系 并不像 Meraxes 那样相似， 这意味着这不是它们只是 从更早的祖先那里继承下来的。 所以事实证明 ， 在三个不同的恐龙科中，微小的手臂至少进化了三次。 这就提出了一个问题：为什么他们需要 这么小的手臂？ 好吧，这些研究人员认为他们没有。 他们争辩说，细小的四肢本身并不是 为了满足特定目的而进化的， 而是四肢缩小使 头骨变得巨大。 基本上，由于下巴很大，他们的身体正在优化 以捕捉大型猎物 ，因此他们的 前臂并不那么重要。 为什么要费心去种植那些 只会碍事的大植物呢？ 因此，虽然它们的小手臂 在我们看来有点傻，但它们都是 使这些掠食性恐龙 在它们的时代变得如此强大的装置的一部分。 现在，虽然恐龙无疑 是他们那个时代最著名的爬行动物 ，但其他主要的爬行动物群体也已经 存在——比如不起眼的蜥蜴。 蜥蜴和它们的亲戚组成了一个 被称为有鳞动物的类群， 自侏罗纪时期就已经存在 ，尽管新的证据 表明可能有一些 甚至可以追溯到三叠纪。 我们已经非常有信心 ，大约 2.4 亿年前，有鳞动物从它们现存的最近亲属大蜥蜴中分离出来 。 然而，由于这些蜥蜴太小了， 它们的骨头几乎不会变成化石， 所以我们对有鳞动物的早期进化 史知之甚少。 研究人员心中的一个大问题 是 ，少数主要的有鳞类群中哪 一个最先脱离了群体。 现代动物的遗传数据与 我们在它们的解剖结构中看到的模式相冲突， 因此研究人员被难住了； 尽管鬣蜥群通常被认为 是第一个分支出来的群。 但在 2022 年，一项关于在苏格兰发现的近乎完美的 小蜥蜴化石祖先的研究发表 了 Bellairsia gracilis，这可能有助于 我们回答这个问题 题。 这种微型化石在几个 关键方面很特别。 首先，研究人员很少 能够研究如此完整的化石。 最大的缺失部分来自尾巴 和鼻子， 但身体的其他部分约占 70% ， 这对于一个 1.68 亿年前的化石来说是相当令人印象深刻的 。 最重要的是，这个小家伙帮助 填补了这个特定群体化石记录中长达 1 亿年的空白 。 它生活在大约 1.68 亿年前， 这使它恰好处于蜥蜴谱系中一个大洞的中间 。 通过将这种类似蜥蜴的祖先的特征与现存有鳞动物的特征进行比较 ，研究人员能够重建 这些现代群体中哪些先于其他群体与其他群体分离 。 事实证明，这块化石 与现代蜥蜴共有的特征最接近壁虎。 因此，这一发现支持了这样的假设 ，即壁虎实际上 是现代有鳞动物时间轴的早期分裂之一 ，毕竟不是鬣蜥。 因此，尽管这块化石体积 很小，但它还是揭示了其家谱中一些相当大的秘密 。 但是，除了爬行动物 化石之外，还有很多东西有待发现。 事实证明，动物不需要有 骨头就能出现在化石记录中。 现代吸血乌贼是生活 在黑暗深海中的软体动物 ，看起来像万圣节装扮成德古拉 狗的章鱼。 它们的八只手臂用织带相互连接 ，它们的小鳍看起来像松软的 耳朵。 基本上，他们很可爱。 他们的名字虽然很误导。 它们不仅不喝血， 甚至都不是真正的鱿鱼！ 他们现存最亲近的亲戚实际上是 章鱼 ，您可能会根据它们八足的 相似性来猜测。 这两个主要目聚集 在一个更大的分支中，称为吸血龙。 其他软体亲戚，如 乌贼和墨鱼， 有八只手臂和两条触手，但研究 人员并不完全 确定这种差异是由于章鱼 和吸血乌贼失去了两条肢，还是 乌贼和墨鱼获得了它们 。 2022 年，研究人员发表了他们 关于 吸血龙类已知最古老亲戚的研究成果，为 这个触手问题提供了一些线索。 他们公布了他们全新的化石物种， 以现任 美国总统乔·拜登的名字命名为 Syllipsimopodi bideni。 事实证明，研究人员 不必走很远就能找到这个物种。 这块化石 曾于 1988 年捐赠给安大略皇家博物馆， 但直到现在才被仔细研究！ 这只吸血乌贼拥有 3.28 亿年的历史， 它不仅是该群体最古老的化石记录 ，而且还将此前 估计 的该群体起源时间线推迟了近 8200 万年！ 这种祖先吸血乌贼也 像现代吸血乌贼一样有鳍 ，它是唯一已知的有 10 个吸盘臂的吸血足类动物。 这块化石表明，吸血鬼 乌贼和章鱼的祖先 确实是从十只手臂开始的，很像它们现存的 亲戚乌贼和墨鱼。 但是吸血鬼在途中某处失去了几条肢体 。 这一发现揭示了 大量关于这些 神奇动物进化历史的信息，让我们 更深入地了解 现代十臂软体动物和吸血鬼动物之间的遥远分歧 。 但是陪审团仍然不知道哪组 拥抱更好。 研究器官的形式和功能 是进化研究的重要组成部分 ，因为它有助于我们比较 随时间和物种之间的变化。 不幸的是，古生物学家通常 没有研究这些 关键特征的奢侈，因为它们太软太 粘，无法形成化石。 大多数时候。 但在极少数情况下，古代器官确实会变成 化石， 例如 2022 年描述的有史以来发现的最古老的心脏 。 这颗古老的心脏大约有 3.8 亿年的 历史，属于一种有颌 鱼，与 陆地脊椎动物，比如我们。 心脏并不是 从这些鱼类化石中保存下来的唯一器官。 研究人员还发现了这种鱼的胃、 肠和肝， 考虑 到保存下来的软组织非常罕见，所有这些都特别令人惊讶。 就像蜥蜴的发现一样，现代 扫描技术 能够为我们提供这些器官的 3D 图像， 包括这些 器官的内部结构，而 无需深入研究化石本身。 事实证明，这些两腔 心脏非常先进 ，它们独特的 S 形有助于说明 我们鱼类祖先的头部和颈部如何以及何时 开始进化的故事。 它们的器官布局 与现代鲨鱼相似 ，心脏位于嘴巴附近，就 在鳃的后面， 这可能会给“ 心脏在喉咙里”带来新的意义。 这与无颌鱼的心脏完全不同 ，无颌鱼 的心脏位于身体更深处。 但是当一些鱼开始进化出下颚时，它们会进化 出更复杂的 身体形态来适应它们不断变化的嘴巴， 包括将它们的心脏向前移动。 而这颗心脏化石向我们展示了这种重新定位 发生在很早的时候！ 这些类型的发现确实帮助我们 解开了 从无颚鱼一直到现代有颚 脊椎动物（包括我们）的令人难以置信的过渡过程中遗留下来的一些进化之谜！ 很明显，化石可以 教给我们很多东西。 我们发现的这些令人难以置信的保存完好的 标本 越多，我们就能解开的谜团就越多。 从十臂吸血乌贼到苏格兰 蜥蜴， 2022 年对于古生物学界来说是非常辉煌的一年。 那么让我们看看在 2023 年我们还能找到什么！ 明年， 我们将继续为您带来更多科学 发现 ，这在一定程度上要感谢您的支持。 像您这样的 SciShow 观众通过成为频道的赞助人帮助 我们分享最新、最伟大 和最奇怪的研究 。 作为 SciShow 赞助人，您获得的不仅仅是 支持您喜欢的节目的满足感。 您还可以获得各种福利！ 您可以加入 discord 社区， 在我们的“ 快速提问”收件箱中向我们提出您的科学问题，阅读我们的每月时事通讯，每个月 佩戴一个闪亮的 新别针，甚至 在 SciShow 视频中展示您的名字。 单击 下面说明中的链接，这些特权都可以属于您。 赞助人可以在 patreon.com/SciShow 上支持这个 SciShow 频道，在 patreon.com/SciShowSpace 上支持 SciShow Space 频道， 在 patreon.com/SciShowKids 上支持 SciShow Kids 频道。 您可以支持 与您对话的任何 SciShow 频道。 我们非常感谢您 对又一个精彩的一年的支持。 [♪结尾] |
