#palaeocene

Colombia - Selandian Stage, 60Ma before present

It has been 6 million years since the asteroid impact that brought the Mesozoic era to an end, and the world has recovered. Lush green forests cover the wet of the Earth once more, no longer strangled by clouds of ash, and the seasons pass by in their normal state. It has, however, been getting considerably hotter during this time, and this has shaped the emerging world of the Cenozoic. A new biome has come to dominate the inflated tropical regions of the equator; tropical broadleaf rainforest, an ecosystem type synonymous with this climate today.

It is not just the flora that has been shaped by this heating world, but the fauna. Cold-blooded reptiles have done exceptionally well post-extinction, with their slowed metabolisms, which had increased their chance of survival during the cold, harsh decades after the impact, now speeding up in the heat, allowing them to dominate the megafaunal roles of the Palaeocene world.

This where the timeline diverges.

The first five million years of the Paleocene occur as in our timeline. After a slow recovery multituberculates explode in diversity, dominating the mammal faunas of the north hemisphere. Meanwhile, in the southern continents, gondwanatheres and dryolestoids do the same. Therians radiate in the background, placentals in particularly producing a myriad of forms.

But while in our timeline multituberculates rapidly decline at the end of the Danian (circa 61 million years) and therians take hold, this doesn’t happen here. Instead, multituberculates continue their trajectory as dominant land mammals, while therians decline in their stead. Whatever caused the decline of multituberculates in our timeline doesn’t affect them here; it instead cuts the branches of the therian family tree, and by the end their brief period of exploration comes to an end.

The climate is temperate, warming as the era goes on. Flowering plants dominate the scene, but not as much as in our world, there being also a wealth of conifers, ferns, horsetails and ginkgos among others (this could explain why multituberculates have not declined, but fails to explain why therians did…) In these conditions various groups have prospered in the post-Cretaceous world, including the sole surviving dinosaurs, birds, as well as crocodylomorphs, turtles, amphibians and the mysterious choristodere reptiles. Squamates aside from snakes were strongly impacted by the KT event, and it took them over ten million years to recover in our timeline; this recovery does not happen here, making them join therians on the path to damnation.

In the north hemisphere, cimolodont multituberculates are the dominant mammals. Kogaionids make a brief tour throught Europe, but increasing competition from recently-arrived North American and Asian clades force them back to the isolation of Balkanatolia. Taeniolabidoids dominate herbivorous guilds, taeniolabidids as large sized herbivores across the northern continents and lambdopsalids as a myriad of digging, running and even hopping forms in Asia. Ptilodontoideans diversify across the canopies, and go on to produce the first largest multituberculate carnivores. Microcosmodontids remain largely small sized insectivores, but already vie for large sized predatory roles in some environments. Meniscoessids, inversely, occupy herbivorous roles and don’t diversify as much. Djadochtatheroideans, which evolved in Asia’s desert environments during the Cretaceous, have a hard time ajdusting to a greener world, but still succeed as the mostly predatory eucosmodontids and herbivorous boffiids.

In the trifecta of South America, Antarctica and Australia, gondwanatheres and dryolestoids continue the reign they enjoyed in the Cretaceous. The former are mostly herbivorous, while the latter fulfill all manner of roles from sengi-like runners to large carnivores to long-necked leaf-eaters that earn the title of largest land animal… for now at least. Curiously, some northern mammal groups penetrate into South America from North America much as in our world, but unlike our timeline marsupials are not the ones leaving a lasting legacy. And unlike our timeline, ferugliotheriid gondwanatheres invade the north successfully.

Africa stands as an isolated oddity. Here, a sole lineage of gondwanatheres, the galulatheriids, dominate herbivorous niches, while kogaionids diversify as carnivores and insectivores; whereas the latter have been here all along since the Cretaceous or are recent immigrants from Europe and/or Balkanatolia is unknown. Also weird are Madagascar and India, two isolated landmasses bearing a similar gondwanathere/kogaionid fauna, though the former are composed of sudamericids and adalatheriids instead. India is marching northwards at great speeds, and soon contact between the two faunas will begin…

Table of contents

Example Site: Santa Lucia Formation

Heavy Feetsies

Example Site: Khashat Formation

The PETM – Why It Feels Like Deja Vu

The Palaeocene Eocene Thermal Maximum was an event that took place 56 million years ago at the end of the Palaeocene and lasted for 150,000 – 200,000 years. The average global temperature rose by 5-9°C (9-16°F) leading to mass migrations and extinctions of flora and fauna.

The event was discovered when marine sediment cores from Antarctica showed a large and sudden excursion ( a sharp spike in the values) in carbon isotopes, indicating that a large amount of CO2 had been rapidly expelled into the atmosphere. Sounds familiar doesn’t it?

Further evidence of a large expulsion of CO2 is shown within marine sediment cores. As you can see, there is an abrupt change from white to red, indicating a rapid dissolution of calcium carbonate (white mud) that only recovers after the event (the red clay). (Increases in CO2 dissolved within seawater lead to calcium carbonate dissolving and eroded terrestrial clays (red) are deposited instead).

Today global temperatures are increasing at rate that far exceeds that of the PETM; a warming of 1°C per 100 years compared to 0.025°C in the Palaeocene.

While current global temperatures are far lower than those during the PETM it is the speed of the change that matters. All life forms take time to adapt and evolve, and it is the rapidity with which the world is warming that is threatening life as we know it. Humans are not immune to this change, and it is very likely that the current warming could lead to the next mass extinction if it is not curtailed.

Climate change is still a topic of hot debate but the most important fact to remember is this: No matter what happens the Earth will still exist and life will find a way to go on. The Earth has survived global glacials as well as global deserts and has feedback cycles that always return it to a habitable state. However, these climate shifts always incur casualties, and if there is another mass extinction, there is no guarantee that the human race will survive to tell the tale. There is no doubt that humans are expelling large volumes of CO2 into the atmosphere and therefore control over the future really does lie in our hands.

Watson

Reference: https://www.e-education.psu.edu/earth103/node/639

Morocco - Thanetian stage, 57Ma before present

As the Palaeocene epoch continues, temperatures remain high, and life continues to evolve in the hothouse. The jungles of Jbel Guersif are too thick for giant reptilian predators, and the lush foliage provides food and shelter to the many warm blooded decendents of the survivors of the asteroid impact. Small birds flit through the canopy, and mammalian predators stalk through the branches.

Titanoides – Late Paleocene (59-56 Ma)

Our record of the Cenozoic era is very rich. Super rich. With a few exceptions, we understand the ancestry of not only most living mammals, but most living vertebrates. A lot of this knowledge goes unnoticed, though. Maybe because so many of these animals are so similar to the stuff we have now. I will admit that the Cenozoic is the era I know the least about. Part of the idea behind this blog is to educate myself, so we’re going to talk about mammals I had no idea existed until about a week ago.

Titanoides is an old mammal from North Dakota. It lived just in the wake of the K-Pg extinction event, which, if you don’t know, was the one that hit the earth so hard that non-avian dinosaurs died out and the Mesozoic era was cancelled. Life is super tenacious, though. Barely 5 million years after the extinction event, mammals and birds had already filled the niches left by larger animals.

Let’s take a quick look at its anatomy. It’s a squat and stocky animal, about 10 ft (3.5 m) long. It probably weighed over 300 lbs (136 kg).* Titanoides was the largest mammal in its habitat, and one of the largest animals of its day. Mammals are set apart from their kin by their diverse teeth, and this one is no exception. It had two enlarged canine tusks. It was a quadruped with big, clawed paws. You might think this animal was a predator, but it was actually an herbivore. Titanoides’ home state of North Dakota was, believe it or not, a dense tropical swamp during the Paleocene, and our friend Titanoides used its tusks to uproot plants and tubers, or to strip bark from trees. It was definitely no pushover, though. The tusks, combined with its claws and beefy body, meant it was absolutely capable of squaring up with anything trying to eat it. It seems a bit like the Paleocene equivalent of a hippo, although we don’t have anything to suggest it was aquatic. It’s similar in that it falls into the “big plant munchers that will fuck you up” category.

Here, follow me to the Taxonomy Zone real quick. Titanoides is what’s called a pantodont.

“Hey, Dylan, what the hell is a Pantodont?”

Thank you for asking! I didn’t really know either. Pantodonts are an extinct suborder (or order, who knows?) of mammals that had a short burst of existence during the beginning of the Paleogene period. They were some of the first large mammals, and to find how they relate to animals alive today, we have to dig a little. They have no living descendants. They fall under the order Cimolesta, which is also extinct. Buuuut, certain members of Cimolesta may have been ancestors to the currently-living order Carnivora (pretty much every carnivorous mammal except whales). So, to put it in terms that make sense, pantodonts are distant great-great-great-great cousins of our modern meat-eating mammals. Here’s a (really simplified) chart:

So, yeah, Titanoides has deep roots. It is deep roots, really. But it’s important, because it’s one of the first big grazing animals in the asteroid’s wake. It’s a sign of things to come for mammals, really, if you’re looking back on the history of life on earth like most of us are. But in the Paleocene, it was just an animal. It’s like looking back at today from 30 million years in the future. Elephants and giraffes, and maybe even humans, would seem like halfway points in a timeline of our descendants’ evolution.

@archensmogon Far from being a “monster”,Titanoboa was the cuddliest snake of all time -- always willing to give everything a friendly hug.