The Paleocene: What Came Next After All The Dinosaurs Died

[This is part of a series of posts about animals. To find other posts in this series, see here.]

Outside has gone through a number of patches throughout its four-billion-year history, but none have stuck out in the memories of fans as much as the K-T balance patch, which ended the Cretaceous expansion and ushered in the Paleocene. I’ve brought up the effects of this patch on particular guilds in many of my previous posts, but what I want to do today is to go into depth as to its implications for the meta as a whole. This post will tell the story of the K-T balance patch, and how the meta recovered from it.

To understand the impact of the K-T balance patch, we first have to understand a little bit about the meta in the Cretaceous period immediately prior to it. The Mesozoic era, which covered the period of about 185 million years preceding the K-T event, is often described as the age of giant reptiles, and while that’s not inaccurate, it’s also not the whole story. Game guides that talk about the Cretaceous period will often focus exclusively on the giant reptiles that dominated the period, while treating mammals, birds, and other builds of the time as low-tier lightweights that did nothing but get bodied constantly by dinosaurs. In reality, while dinosaurs and pterosaurs did dominate megafaunal niches throughout the period, other groups like mammals and birds were still fairly successful in lightweight-to-midweight roles.

Rather than looking at the Cretaceous meta as divided into high-tier giant reptiles and low-tier everything else, it’s probably more accurate to view it as one dominated by a few groups that each filled very specific niches. On land, dinosaurs held uncontested dominance over megafauna niches, either as apex predators or as giant herbivorous tanks, while mammals dominated small generalist roles. A similar division existed in the aerial meta, with pterosaurs controlling the megafaunal roles while birds remained small. However, just because mammals, birds and other non-reptiles were stuck in these small niches doesn’t mean that they weren’t meta-relevant or that they weren’t growing in diversity. The Cretaceous meta already had a variety of highly successful small mammal builds with a wide range of playstyles, and it was also the time when birds spread across the globe to become more and more dominant in the lightweight aerial meta. There were even some interesting developments in the fish and insect metas, including the introduction of the first ants. Nevertheless, with the exception of some large fish, none of these builds were able to really challenge the stranglehold of giant reptiles over megafauna and apex predator playstyles. Eventually, fans started complaining to the devs that the seemingly eternal dominance of the dinosaurs was making the heavyweight meta too stale and started calling for some sort of dinosaur nerf to make it more competitive again. What they ended up getting was probably a little more than they hoped for.

About 65 million years ago, the devs responded to dinosaur nerf requests by implementing one of the harshest mass-bannings in gaming history. The in-universe explanation for the eliminations was that a massive asteroid, about 10-15 km wide, had hit the Yucatàn Peninsula. The asteroid caused an outburst of thermal radiation that covered the entire planet for hours, cooking to death any organisms that got exposed to the heat. This alone was enough to wipe out just about every large land animal, leaving behind only those that were able to take shelter underground, underwater or in trees for the duration of the blast. Even after the heat subsided, the soot thrown up by the impact blotted out the Sun for over a year, causing a mass die-off of plants and phytoplankton and collapsing global food chains. By the time the patch was fully implemented, over 75% of the player base had been eliminated.

The harshness of this patch came as quite a shock to the playerbase, but competition went on among the survivors. There were a few noticeable patterns as to which builds survived and which ones died. Burrowing or diving animals were less likely to get eliminated, since they had an easier time sheltering from the extreme temperatures in both the early and later phases of the extinction. The survivors tended to be either omnivores, scavengers or insectivores, since pure herbivores struggled to deal with the mass die-off of plants while animals that hunted large prey suddenly faced a severe shortage of targets. The shallow oceans were hit hard, but both freshwater and deep-sea biomes were comparatively unaffected.

After the impact winter was over, the Paleocene expansion started. During this time, the climate reverted to a globally tropical-to-temperate state, pretty similar to the one that preceded the patch. The annihilation of large herbivores led to the growth of dense forests around the globe, even extending to the poles, but since lots of plants had also gotten banned, the diversity of the trees in these forests remained low. Flowers, which had first been introduced in the Cretaceous, continued to spread and diversify, becoming one of the game’s dominant plant groups.

With these general trends in mind, let’s now take a closer look at how particular groups were affected by the extinction, and how they dealt with the aftermath and recovery in the Paleocene.

IMPACTS OF THE K-T PATCH ON THE META

• Invertebrates

I’m going to start off by looking at the groups that tend to get ignored by most other discussions about this patch. Typical game guides pay so little attention to invertebrate builds when talking about the K-T event that you might think they were barely affected at all, but this is far from the case.

The one invertebrate group that does often get some attention is the cephalopod guild. During the Mesozoic, there had been a rift in the cephalopod playerbase between those players who optimized for a shelled tank role – nautiloids and ammonoids – and those who optimized for a mobile predator playstyle – the coleoids, the group that includes all modern cephalopod builds except the nautilus. By the end-Cretaceous, ammonites – the highest-ranked shelled tank cephalopods – had already been losing relevance in the meta for some time, but the patch forced them out of the game completely. There has been some confusion as to why the devs banned ammonites but left nautiluses alone, given that they seemed to be very similar builds. One reason might be that ammonites were highly specialized for a filter-feeding playstyle, hunting zooplankton and other small organisms. Nautiluses, by contrast, have much more robust mouth parts, which allow them to consume larger and harder-bodied prey than ammonites were capable of. This extra versatility might have given them the edge to let them survive in the new Paleocene meta.

The belemnites, another cephalopod group that thrived in the Mesozoic seas, followed a similar trajectory to the ammonites. In the late Cretaceous, their standing was already starting to decline, while octopuses and squid were gaining in popularity. However, the patch dealt the final killing blow to the belemnite faction, banning them all. The death of the ammonites and belemnites helped make room for octopuses and squid to replace them and explosively radiate into new niches, letting them become the powerhouses of the ocean meta that they are today.

A number of other marine invertebrates were also harshly affected by the patch. Microscopic plankton underwent a devastating loss of diversity, although the survivors recovered pretty rapidly in the Paleocene. The impact winter caused the death of many photosynthetic algae, and consequently killed off many coral builds that symbiotically relied on the algae. Echinoderms – the group that includes starfish, sea urchins and sea cucumbers – were severely nerfed by the patch; about a third of sea urchin builds got banned, mostly ones that lived in shallow water. Perhaps the most significantly under-appreciated change that resulted from the K-T patch was the nerfing of the bivalve faction. During the Cretaceous expansion, marine reef biomes were primarily composed, not of coral, but of box-shaped clams called rudists. Rudists were banned by the patch, to be replaced by the coral reefs that have continued to be the dominant reef type to the present day.

The group that probably came closest to emerging almost totally unscathed from the patch was the insect faction. A number of insects did go extinct during this time, but the rate of extinction was no higher than just the average background level of extinctions happening constantly. The insect meta has actually remained more-or-less static since this period; all of the major insect guilds from the Cretaceous still exist in more-or-less the same form today. Personally, I think the devs should consider a new patch to shake up the insect meta, but that’s a topic for another time.

• Amphibians and fish

Among vertebrates, amphibians and fish are also often ignored when discussing the impact of the patch. This is somewhat understandable, as these groups were nowhere near as harshly affected by the K-T patch as their air-breathing relatives, but there were still a few interesting changes in the amphibian and fish metas which are worth exploring.

Freshwater environments in general were far safer places to be in during this period than land or ocean environments, which is probably why so few amphibians got hit by the banhammer. The devs also probably didn’t feel the need to nerf amphibians much, since even by this point, the amphibian faction was already widely seen as a low-tier guild long past its peak. They had been rendered mostly irrelevant for millions of years by other vertebrate factions improving on them in just about every way. The patch did little to change this, but that didn’t stop the surviving amphibian mains from diversifying and attempting to take over empty niches. The global abundance of forests during the Paleocene granted a boost to the viability of amphibians for a time, as a number of frog mains started speccing into arboreal traits for protection against land-based predators. Another important innovation in the amphibian meta during this time was that some frog builds got the option to skip the tadpole stage and go straight from egg to juvenile, mitigating the worst aspects of their early-game vulnerability. Today, about half of all frogs make use of this option, and the overwhelming majority of all current frog builds can trace their origins back to this Paleocene radiation.

Fish were one of the groups that actually shot up in viability following the patch. During the Mesozoic, ocean biomes had been largely dominated by cephalopods and aquatic reptiles, with fish playing only a marginal role. After the patch banned most marine reptile builds as well as the then-dominant cephalopod classes, fish saw an explosion of popularity due to the relative lack of competition. While some fish groups did get banned, almost all of these were large predators that fed primarily on other fish, so their banning just made the surviving fish builds even more attractive to new players.

Nearly all fish alive today belong to the teleost guild, a group distinguished from other fish by the ability to protrude their jaws outwards from their mouth in order to grab prey more easily. In the wake of the K-T patch, teleost fish were one of the first groups to start diversifying. Many teleost players tried to replace the recently-banned predators; among these were the ancestors of modern-day tuna, plus the first barracudas. One of the fish groups that saw the biggest explosion in popularity were the spiny-finned fish known as acanthomorphs. This group today contains about a third of the vertebrate playerbase, and most of that can be traced back to their diversification in the Paleocene. Others evolved still stranger body plans; one group of fish even specced into having both their eyes on one side of their head, becoming the first flatfish. By the end of the Paleocene, fish had become the dominant guild of most ocean biomes.

Cartilaginous fish – the group that includes sharks, skates and rays – didn’t change as much in response to the patch as their bony counterparts. Sharks and rays took heavy losses, but ultimately recovered most of their pre-patch abundance while continuing to use basically the same strategies as before. The only noteworthy change in the shark meta during this time was that ground sharks overtook mackerel sharks as the dominant shark group. This happened because mackerel sharks have teeth that are adapted to hunting large or armoured prey animals, most of which had been banned by the patch, while ground sharks were better suited to hunting the smaller fish that remained. Today, ground sharks still make up most of the highest-ranked shark builds, although the #1 shark build, the great white, is a mackerel shark.

• Reptiles

As interesting as the effects of the patch on amphibians, fish, and invertebrates may be, there’s no question that the main reason it’s stuck out in the minds of fans is because of its impacts on the amniote meta. So I’ll finish off by looking at the impacts on each of the three major groups of amniote, starting with the group that lost the most from the patch, the reptiles.

The K-T balance patch is today mostly remembered as “the patch that wiped out the (non-avian) dinosaurs”. While that definition leaves out a lot, it is true that one of the most significant effects of the patch was to end the longstanding reptile dominance of the meta. All dinosaurs were wiped out, except for birds, which I’ll give their own section below. The pterosaurs, the dominant aerial predators of the Mesozoic, also bit the dust, as did most groups of marine reptiles, including the mosasaurs and plesiosaurs. While the current major reptile groups – crocodiles, lizards, snakes, turtles, and tuataras – all managed to survive the patch (or at least have remained very similar to their ancestors who survived), none of them managed to escape unscathed. Among the proto-crocodilians of the Cretaceous, about 50% were banned by the patch, including all of the large ones and all of the fully marine ones. Squamates, the group that includes lizards and snakes, also lost a number of their main guilds, and would take about 10 million years to recover from the setback. Rhynchocephalians had already been in decline for a while due to competition from lizards, but they were driven almost completely out of the game following the patch; today, they have only one build remaining, the tuatara. Turtles probably got off the lightest. About 10% of the existing turtle builds were banned, but none of the major guilds were wiped out.

Despite their losses, reptiles continued to be the top group in the meta for a while following the patch. Crocodilians remained near the top of the meta, as I discussed in my post on them, and while some squamate guilds were harshly affected by the patch, others took the opportunity to rise up in their wake. The squamate meta in the Paleocene became dominated by groups like iguanas and boas, both of which had been largely irrelevant to the meta before but have continued to rank highly into the present day. The highest-ranking snake in the history of the game, the Titanoboa, was a product of this period. However, the surviving reptiles were held back by their complacency. Reptile players who survived the extinction mostly focused their recovery efforts on attempting to go back to how things were before instead of exploring new strategies for the changing world. While groups like the squamates developed lots of new builds in the aftermath of the patch, the new builds still filled more-or-less the same roles in the environment as the old ones. None of the surviving reptile mains branched out and explored new strategies in the way that would have been required to really secure their dominance.

• Birds

It’s fairly well-known by now that dinosaurs didn’t actually get entirely banned by the K-T patch; the winged dinosaurs, or birds, were left alive and survived to the present day. What’s less well-known is how hard-fought the survival of the bird faction actually was. The vast majority of bird builds were hit by the same banhammer as the rest of the dinosaurs, including the enantiornithines, which up until then ranked at the top of the bird meta. The only bird group that actually managed to escape the banhammer were the neornithines. Most neornithines of the time were swimming or diving builds, which might have helped protect them from the patch as the water would have provided a shield from some of the environmental effects of the impact.

In the wake of the patch, neornithine mains took advantage of having all their main competitors for aerial dominance eliminated. Without pterosaurs to compete with them, birds quickly started evolving to become much larger than they ever had before. Of particular note were the pelagornithids, a group of birds that specced into tooth-like points on their beak’s edges for catching fish, and became the first large soaring birds to have an impact on the marine meta. The pelagornithids continued to be the top seabird guild for most of the Cenozoic, until being wiped out during the Pleistocene ice age. A lot of other new bird guilds were also created in the Paleocene. This diversification was probably fuelled in part by the aforementioned spread of global forests, and the consequent abundance of food that was most easily accessed by flying builds. With a few exceptions, nearly every modern bird build can trace its origins to the explosion of bird diversity during this period. 

Birds didn’t only radiate into new aerial niches. One of the most interesting developments in the bird meta during this time was that some birds gave up on flight altogether to become fully land-based or even marine creatures. The lack of large predators on land following the extinction of non-avian dinosaurs made this one of the safest times for bird players seeking to pursue this strategy. Penguins already existed before the patch, but it was only in the Paleocene that they fully gave up on flight and fully optimized for hunting underwater, exploiting the niches left vacant by the banning of the large marine reptiles. This was also the time of the first ratites, a group of flightless birds that includes the present-day ostrich, cassowary, emu and kiwi. Most of the largest land birds throughout the game’s history have been ratites. The first ratites were actually not flightless, but shortly after the guild was introduced, multiple groups of ratite players independently started speccing for large flightless builds, and these flightless birds were the only members of the group to survive to the present.

This period also saw the evolution of other kinds of flightless bird that did not survive to the present. The most iconic of these was the Gastornis, a giant European flightless bird known for its massive head and huge beak. While often assumed to have been an apex predator, the Gastornis was actually a herbivore that used its huge beak to crack open nuts and seeds. Gastornis players were able to survive the spike in global temperatures that ended the Paleocene expansion, and continued for a while into the Eocene, but then were eliminated from the game for reasons that are still unclear.

While the Gastornis was a herbivore, another iconic group of flightless birds from this time did take over large predator niches: the terror birds. Terror birds were a guild created by former theropod mains who were mad about their old builds getting banned and decided to try to turn birds into a kind of recreation of the old predator builds. They became the top predators of South America, and remained in that position for tens of millions of years until they got wiped out during the last Ice Age.

• Mammals

Mammals are generally seen as having been the biggest winners from the K-T patch, as the extinction of dinosaurs allowed them to diversify and expand into megafaunal niches. Just like with birds, this notion has some truth, but is overly simplistic.

The vast majority of the mammal builds that existed during the Late Cretaceous were wiped out by the K-T patch; less than 10% managed to make it through. Unlike with birds, where all of the remaining builds were clustered in the neornithine subclass, the surviving mammals were divided among all of the major mammal factions of the time. They didn’t exactly become dominant in the Paleocene; they largely continued to occupy small generalist niches, with birds and reptiles continuing to fill most of the apex predator roles. However, it is true that Paleocene mammals tried out a wide variety of new strategies which would set the stage for their dominance in all subsequent expansions.

At the start of the Paleocene, the highest-ranked mammal guild was the multituberculates. These were a group of small mammals that looked and acted a lot like present-day mice and rats, but had large, blade-like premolars for slicing nuts, and gave birth to underdeveloped young like marsupials. They had been the dominant small generalists on land and in trees during the Jurassic and Cretaceous, and while most of them got eliminated during the K-T patch, they were one of the first groups to recover and quickly reached new levels of diversity. However, they went into decline shortly after that as other mammal guilds developed competing builds that essentially did everything the multituberculates did better. These new builds were called rodents, and their descendants remain among the most successful mammals in the game to this day. The multituberculates would continue to decline until towards the end of the Eocene, the next expansion following the Paleocene, when they disappeared completely.

Next to multituberculates, the second most dominant group of mammals in the Cretaceous were the metatherians, the group which today includes only marsupials. This was the mammal group hit hardest by the mass extinction, and they never fully recovered. One silver lining for metatherian players was the introduction of sparassodonts towards the end of the Paleocene, a now-extinct group of predatory mammals closely related to and often confused with marsupials. Sparassodonts were the dominant predators in South America for much of the Cenozoic, serving as the South American equivalent to the placental carnivorous mammals of other servers, but then died out mysteriously during the Pliocene. However, with the exception of the sparassodonts, and a few other high-tier builds like the kangaroo, metatherians have remained fairly marginal in the meta ever since the K-T patch. I discuss the reasons for this in more depth in my marsupial tier list.

The group of mammals that won the most from the K-T extinction were the placentals. Today, placental mammals are by far the most successful mammal group, and probably the most successful animal group in the entire game. The Paleocene placental mammals weren’t quite there yet, but already diversifying into many of the major divisions that still exist today. Many of the Paleocene placental mammals are so different from their modern descendants (if they have any) that it’s hard to say which guild they were part of, but there are a few major guilds that have known members from this period, including the aforementioned rodents.

The Paleocene was the time of the first proboscideans, the guild that would later become elephants. Also alive in this period were the first hooved mammals, or ungulates, which would give rise to nearly all of today’s large herbivorous mammals aside from elephants. Deer, hippos, pigs, cows, horses, camels, rhinos, giraffes, tapirs, sheep, goats, antelope, and all other hooved mammals of today are all descended from these early ungulates. So are whales and dolphins, even though they’ve since dropped their hooves to better adapt to the water.

While proboscideans wouldn’t start developing their huge size until later to start growing huge, ungulates were already experimenting with megafauna builds during the Paleocene. One of the earliest guilds of ungulate formed were the uintatheres, which were by far the largest animals of the Paleocene. Uintatheres resembled modern-day rhinos or hippos, but with large tusks like elephants and blunt horns similar to those of giraffes. They were the dominant large herbivores from the late Paleocene until the mid-Eocene, when they mysteriously went extinct and were replaced in their niche by the even more massive brontotheres. 

The Paleocene was the time of the miacids, a group of marten-like predatory mammals with small bodies and long tails. Miacids would later evolve into the carnivorans, the group which includes most of the top predatory mammals in today’s meta; cats, dogs, bears, hyenas, raccoons, weasels, badgers, skunks, seals, mongooses, and wolverines are all numbered among their descendants. However, during the Paleocene, miacids remained fairly small and did not become apex predators anywhere, despite having already developed the flesh-shearing carnassial teeth that are the trademark of their descendants today. Instead, the dominant predatory mammals of this expansion were part of another early guild of ungulates called the mesonychids, one of the few hoofed predator guilds in the game’s history. While often imagined as akin to wolves with hooves, mesonychids had a noticeably different hunting style from present-day wolves, as their thick legs and ungulate spines lacked the flexibility that dogs and other modern carnivorans rely on when chasing down prey. Their teeth also weren’t as specialized for cutting meat as those of today’s carnivorans. Nevertheless, their powerful jaws, robust bodies and strong running abilities enabled them to become some of the top predators of the Paleocene Northern hemisphere. Sadly, they started to decline shortly after the Paleocene ended and were gone by the early Oligocene. Their dolphin-like molars have led some players to mistakenly believe that they actually took to the sea and became whales instead of getting banned, but source code analysis has debunked this.

While the mesonychids were taking over Eurasia, another now-extinct group of mammals was developing large predators of their own: the hyaenodonts. The hyaenodonts were in some ways similar to mesonychids, as both groups had large heads and limbs that sacrificed flexibility in exchange for efficient running; however, the hyaenodonts also had scissor-like carnassial teeth, a useful flesh-tearing adaptation which the miacids (and their later carnivoran descendants) copied. Hyaenodonts lasted much longer and spread much farther than the mesonychids ever did, but they still didn’t make it to the present day, getting banned during the late Miocene around 11 million years ago.

Of all the innovations that mammal players made during this period, the one that would prove the most significant in the long run was also one of the first. Relatively shortly after the K-T extinction, some mammals called plesiadapiforms decided to get rid of their claws and replace them with fingers, granting them a then-unparalleled ability to grasp and manipulate objects. These were the first of the primates, and the potential that this ability unlocked cannot be overstated. By refining the design of the fingers and combining them with high intelligence, primates have remained one of the highest-ranked guilds in the meta in every expansion from the Paleocene to the present. Eventually, one group of primates managed to create the most overpowered build ever seen in the game, a build so powerful that its mere existence actually caused another extinction event on par with that caused by the K-T patch – but that’s a topic for another post.