This timeline is gives all prehistory events referred to in the series. While technically 12,000 years before Godzilla vs. Mothra is still prehistory, these events stretch far, far further back, to the point where it's possible to presume they are common to all timelines, even the reboots. If, one day in the future, I decide to cover the Mothra trilogy on this site as well, and need to have those differences reflected, I might edit this page, depending on how I handle that. But as it stands now this will cover all events in history relevant to the films up until the earliest divergence point within the continuity family, which is 10,008bce.
BP dates (before present) assume that P = 1950, which makes 1950BP the equivalent year of 1bce, meaning if the year is given as a, abce = aBP - 1949. Since every historical year is given based on the bce/ce dichotomy, I take the liberty of converting the BP dates here. This isn't meant to imply these prehistoric events occur literally that exact year, but given these are all fictional events from monster movies anwyas, I don't see why we can't just say they are in this context.
For years that are given as "such and such years ago" that are so old that they run into bce, we just use simple subtraction, and take the result as the astronomical year numbering given in ISO 8601. This treats the bce/ce split purely mathematically, which gives us a year 0, meaning negative numbers represent the year bce minus 1.
Permian Period
251,939,051 to 251,878,051bce
The formation of the Siberian Traps lead to the deadliest animal mass extinction event in the entire history of Earth, the Great Dying.* Somehow, a single branch of deep sea trilobites survive the extinction.
1
Triassic Period
226,998,051 to 201,398,051bce
Evolution of the large bodied coelophysid dinosaur
Gojirasaurus quayi occurs.** The descendants of this animal, the Gojirasaurids, will evolve into at least semi-aquatic niches by the beginning of the Jurassic period.
11
Jurassic Period
201,398,051 to 144,998,051bce
Over the course of this period some Gojirasaurids evole into fully marine animals.
1
Cretaceous Period
144,998,051 to 65,998,051bce
Over the course of this period the marine Gojirasaurids begin to re-adapt to land, becoming amphibious. This clade, the Godzillasaurids, as well as the deep sea trilobites that have evaded extinction since the Great Dying, also survive the KPg extinction that takes with it most non-avian dinosaurs.
1
Quarternary Period
1,998,051bce
The surviving descendants of
Gojirasaurus and the deep sea trilobites have by this time evolved into
Godzillasaurus and the trilobite species discovered by Dr. Yamane, respectively.
11
Sources
All colors and otherwise unsourced years are taken from the ICS timescale as of June 2023.
1 - Godzilla. Dr. Yamane's hypothesis about Godzilla is bizarrely elaborate for a 1950's sci-fi monster movie.
11 - In the finished film, Dr. Yamane erroneously describes the Jurassic period as having been 2 million years ago. This is just wrong, this is a factual error, he 100% is not saying that in this universe the Jurassic period was only 2 million years ago, that's not what's happening. What's actually happening is a bit of confusion between the various writers. Kayama set the origin for Godzilla's ancestry in the Jurassic, but threw in a 2 million year date in order to tie Godzilla's origin with that of man. This second part got lost and the two became conflated in the film, resulting in the very silly error. Apparently also the original date given for the Jurassic was 200 million years ago, which is interesting because it's accurate today, but wasn't at the time so far as I can tell. I can't exactly remember where I heard this, though, so take it with a grain of salt. As for why this information about the Triassic ancestors of Godzilla is even included when Dr. Yamane doesn't bring it up? Well because that 200 million year thing matches up with the range of Gojirasaurus, which was not only named after Godzilla (obviously), but in an article in the licensed book The Official Godzilla Compendium, the namer of Gojirasaurus, Kenneth Carpenter, posits Godzilla belonging to the same clade, therefore suggesting the two are related. But you can read more about that down below. At any rate, the 2 Ma date is used in the film repeatedly, so I figured it would be a disservice to the film to not have that mean something, so instead I've interpreted it as being the origin of Godzilla's genus.
* - Burgess, Seth D et al. “High-precision timeline for Earth's most severe extinction.” Proceedings of the National Academy of Sciences of the United States of America vol. 111,9 (2014): 3316-21. doi:10.1073/pnas.1317692111
** - Carpenter, Kenneth. "A giant coelophysoid (Ceratosauria) theropod from the Upper Triassic of New Mexico, USA." Neues Jahrbuch für Geologie und Paläontologie-Abhandlungen (1997): 189-208.
I found it here but it's one of those fucking pay sites, so have fun spending €29 on that I guess. In real life, the genus is contested, and its diagnostic features have been variably described as being material from a Shuvosaurus or indistinguishable from Coelophysis outside of its large size. This later opinion comes from Mickey Mortimer, who is a personal hero of mine because she's so damn thorough when it comes to phylogenetic testing. You can read her assessment of the material here on her website the Therapod Database (which is really incredible and I used to get lost in it for hours back in the day, though I don't know how much she's kept up with it now). At any rate, for our purposes here, it doesn't really matter if this name represents a distinct animal or not, because Godzillasaurus definitely doesn't exist in real life, and I'm only singling out Carpenter's name because it serves as a good starting point for everything we know about Godzilla's extensive ghost lineage as hypothesized by Dr. Yamane.
To address the elephant in the room, Gojirasaurus isn't a ceratosaur, that's an outdated hypothesis from the 90's that ceolophysids were nested inside of ceratosauria in a kind of basal two way split between ceratosaurs and tetanurines. We know now that coelophysids are more basal and ceratosaurs+tetanurines form a clade called averostra which coelophysids fall outside of. Do we know for sure that Godzilla is a coelophysid? No, not really, in fact there's a very compelling fan theory going around that he might not even be a dinosaur at all, but potentially a therapsid. Now, I love this idea, but I'm sticking with Godzilla being a dinosaur for a number of reasons. Number one with a bullet being that that's exactly what he was intended to be from the beginning. Tanaka wanted a dinosaur, and he was designed based on reconstructions of dinosaurs in popular media at the time. We could retcon his appearance based on the innacuracies of those reconstructions, sure, but he already consistently defies all our expectations of biomechanics and is a radioactive mutant, so... when the choices are "ignore something intended from the beginning that has been reaffirmed as the definitive classification within the films and explain issues with this as being related to Godzilla's anomalous nature" or "completely undo all of that because Godzilla doesn't look like a real animal, imagine that," I... well... come on, dude. Just, come on.
But as to why I believe Godzilla is specifically a coelophysid, it comes down largely to a process of elimination. If he's a dinosaur, then he's either a theropod, herrerasaur, or something more basal. Right away we need to rule out a herrerasaur identification because herrerasaurs might not even be dinosaurs at all, but more basal dinosauriformes. Personally I think, given the rarity of these results, it's more likely that herrerasaurs are a specialized early branch of saurischia than them being non-dinosaurs, but given one of the reasons for placing Godzilla inside of dinosauria is authorial intent, I would prefer to future proof this placement just in case I'm wrong about that, because I very well could be. There's also the problem with the number of fingers; herrerasaurs just have too many. Godzilla's tail isn't rigid, either, so he's not a tetanurine. That leaves us with either a basal, theropod-like dinosaur, or a non-tetanurine theropod. From there, Carpenter's analysis from The Official Godzilla Compendium connects him to Carpenter's genus by both being coelophysids (although at the time Carpenter called him a ceratosaur, but I've been over that), which is the only time the question has been addressed in licensed media. There aren't very many things he could be other than that, so even if it's wrong, it's good enough for me. Keep in mind also Godzillasaurus has a whopping two hundred million year long ghost lineage separating it from all known animals in real life. Godzilla is likely the most derived animal on the planet, so making any connection to the real life fossil record is a Herculean task.
Gojirasaurus quayi was found Copper Canyon formation of the Dockum group, which is of Norian age. When I went to the wikipedia page for it they list the range on the infobox as "210-201.3Ma," but I couldn't find anywhere in the article where they were getting the 210Ma from. So I figured, since we're dealing with a dubious genus to begin with, and the fact that this is intended to be a timeline for a series of monster movies and not a dissertation on actual history, I'd cast a wider net and just use the Carnian/Norian boundary from ICS.
