Imaginary titans

For some time I had an idea to make a series of draw comparison related to the idea of doing a “before and after” of certain prehistoric animal reconstructions, something similar to what users here on deviantart has done with draws or silhouettes, however, instead of being just one animal comparison, these would be properly chart showing the changes of such animals over the years, based on a specific topic or a specific documentary.

Here, I chose a particular topic to begin with, the case of the oversized animals, creatures that once were considered to be beings of massive length or mass by the paleontological community or in most of the cases, in the popular media, and have been changed over the years with new discoveries or re-interpretations, some of the estimations are quite light in changes which some can still be considered as giant creatures even with the slight reduction, others are really marked such measures changes to the point it seems like a joke that once was considered to be giants at the first place, and some are in the brink to change with a new discovery in any moment.

I must say that I have tried to collect only estimations made in the scientific field both popular (e.g., documentary) and professional, so there will not be estimations made in common entertainment media such as movies (Jurassic Park), fictional books (Kronos Rising) or video games (Ark)

If anyone has any complain or critic about the information, size, species or anything else, and even some suggestions for others oversized prehistoric animals, you’re welcome to tell, especially if I’m wrong, all for the sake of accuracy.

1) Pachycephalosaurus
It seems from many years since its discovery, this large Pachycephalosaur was considered to be 8 meters long, at least the original upright kangaroo posture interpretations which was common in many book illustrations, toys and old media that I guess was based on original ornithopod proportions looking that the head was smaller in comparison with the body. (If anybody knows a better reason you’re welcome to correct me)

Current estimates
In recent years there was a reinterpretation of the proportions of Pachycephalosaurus this based on several more complete specimens of others species, giving it a change of look and also of size, now being a 5 meters long herbivore, still being the largest of its group.

2) Ornithocheirus (Tropeognathus)
This very fragmentary genus of pterosaur first discovered in UK, was featured in the documentary walking with dinosaurs as a flying giant of around 12 meters in wingspan and weighting 100 kg, being one of the largest pterosaurs ever. 

Current estimates
To explain a little why I added two pterosaurs, the actual Ornithocheirus (a) which had a very problematic taxonomic history with many fragmentary remains classified to this genus, with around 28 species in total named, but at the end many of these were considered to belong to separate genus, some from the same family and some others from different affinity, with only now one type species, O. simus, being this one around 5 meters of wingspan, and never being 12 meters.

The actual pterosaur which the WWD refer as “Ornithocheirus mesembrinus” was actually Tropeognathus mesembrinus (b) from Santana formation, but this wasn’t estimated to be 12 meters in any point either, the largest specimens so far know in that time were about 6 meters, and the specimens which the documentary were suppose to be base on (MN 6594-1 specimen), is calculated to be about 8 meters of wingspan, being not a giant, but still a pretty large pterosaur, one of the biggest non-azhdarchid pterosaurs known.

3) Amphicoelias fragillimus
This species was described in 1878 by Edward Drinker Cope, Being the holotype specimen a vertebra of 1.5 meters in length (AMNH 5777) and a femur, this get lost in some point to never to appear again for unknown reasons (probably due to poor care that destroyed the holotype) and only leaving as a record the existence of these notes and sketches.  Throughout the years, based on what has been left, attempts were made to make possible estimates of the size of this specimen, the majority being inferred that this species has the same proportions of more complete specimens of Diplodocids, giving a size estimation of 58 meters in length, with a weight of 120 tons, making it one of the largest dinosaurs that ever existed.

Current estimates
There have been debates about the possible length of the specimen AMNH 5777 over the years, this mostly because the only thing left of the original are only notes which It has been suggested that could contain typographical errors in the measurements or even be completely wrong, and taking proportions of smaller species not always turn out to be accurate or even plausible, so make an length estimation of this species based on the original vertebra turns out to be a complicate challenge. Of course as the chart is about originally oversized animals and then were downsized, I had to see if someone had tried to make an Amphicoelias smaller version with a plausible interpretation to be part of this chart, good thing there is one.

In this case I used the Amphicoelias reconstruction by , being 48 meters long.

4) Leedsichthys problematicus
The great Jurassic filter feeder ray-finned fish pachycormid discovered in the Oxford Clay Formation, was subject to many size changes, over the years it was difficult to give an accurate or plausible size estimation because of the poor remains found, at first estimated to have a measure of about 9 meters in proportion to the Hypsocormus genus , but around the 80 the discovery of a new pachycormid, this called Asthenocormus, led to new interpretations of the possible length from 13 meters to 27 meters, based on an extrapolation of the gill basket size, in some cases in popular scientific media mentioned to even be around the 30 to 35 meters long.

Current estimates
Some years after the discovery of many new specimens, like “Ariston” (PETMG F174), Dr. Jeff Liston in his studies estimated that Leedsichthys was smaller than what was thought, being about 9 to 10 meters in first estimations, and in later specimen comparison it give lengths between 7 and 12 meters, also pointing out that linear extrapolation of the gill basket would be flawed because gills grow disproportionally in size for the oxygen demand of a huge body. The most plausible estimations now are around the 16 meters.

5) Kaprosuchus
The unusual “boar croc” was discovered and described in 2009 by Paul Sereno and Hans Larsson in the monograph "Cretaceous Crocodyliforms from the Sahara" together with other specimens of Saharan Crocodyliformes. Being the holotype a well preserved skull (MNN IGU12) of about 50 cm, Sereno give an estimated length of around 6 meters.

Current estimates
As far I can found, there aren’t any background affirmation for the original Sereno estimations, even more there are been some counterarguments for such size estimations based on comparisons of actual crocodilians with a same head size, as well with more complete relatives like Mahajangasuchus, the most plausible estimations for the actual holotype put the length of Kaprosuchus in 3.3 meters.

6) Quetzalcoatlus
After the first fossils were discovery in the Javelina formation at Big Bend National park, Texas, it was estimated 3 probable wingspan size extrapolated from the proportions of others pterosaurs, being 11, 15 and 21 meters, being the middle one choose, but very light in weight being estimated to be less than 100 kg.

Current estimates
After subsequent discoveries of small specimens of Azhdarchid and a better known of the morphology of these ones, there were quite a few changes in their proportions, resulting in a more compact animal than previously believed; now it is estimated to have an 11 meters wingspan.

7) Allosaurus maximus (or Saurophaganax maximus depending on how valid still it is)
This Allosaurid named by Daniel Chure in the middle 90s, has gone through an interesting history of genus validation based on several specimens since the early 30s for what belongs to it, and even now the legitimacy of this genus is in dispute and with consideration of most of the specimens belong to Allosaurus (As well Epanterias).

Something remarkable about this theropod has been the estimates of its length, which would make this Jurassic theropod the largest of all from that period, being at the same level as the Cretaceous theropods in size, with a length of 14 meters in length.

Current estimates
It seems that there is no evidence supporting such lengths as the original estimates is considered to being incorrect, the specimen which belongs is probably an 11 meters long animal. Based on Allosaurus reconstruction by 

8) Spinosaurus
The enigmatic African spiny theropod, for many years this Spinosaurid had been one of several contenders to the title of the largest theropods in history thanks to several estimates made over the years, being first at least 15 meters long and with a weight of 6 tons, but by the end of the 20th century and in the beginning of the 21st century this creature get its highest estimations, being the largest based on Suchomimus body proportions in relation on their skull lengths, making it a great theropod of about 18 meters long and a weight of 7 to 9 tons, although some posterior mass estimations give it a body mass of about 11.7 to 16.7 tons. Spinosaurus in this form became a very iconic image for many years in popular culture.

Current estimates
Over the years there were quite a few counterarguments about the methodology used to make a reasonable approximation of the length of Spinosaurus, even some making new size estimations giving to this theropod a body length between 12 to 14 meters and a body mass of 12 to 20 tons, although these were criticized too for the theropod choices.

In 2014 things took an unexpected turn with the announcement of a new specimen, the FSAC_KK 11888, a partial subadult skeleton from Kem Kem beds, North Africa, which presented quite different proportions from what was estimated or speculated, showing Spinosaurus as short legged theropod of semi-aquatic habits, However, in the following years the veracity and validation of the specimen as Spinosaurus has been doubted, althouth being asserted in several cases, but not described properly and in full format, even to complicate more the subject, with the confirmation a second spinosaur genus in the region, Sigilmassasaurus, is difficult to assign the neotype specimen to a specific genus.

From these actual proportions if are trully confirmed to belong to Spinosaurus, it is believed that some of the largest specimens could have reached 15 meters in length as was estimated early, and not being the tall creature as the Suchomimus original proportions suggested.

9) Rhamphosuchus
This great Miocene Tomistominae (False Gharial) from India, only know by fragmentary tip jaw remains, was once considered to be one of the largest crocodiles ever, with a size estimation of about 15 to 18 meters for many decades.

Current estimates
After a re-study in 2001, it was downsized to a length of about 8 to 11 meters.

10) Bruhathkayosaurus
This supposed sauropod titanosaur was discovered in the region of Tamil Nadu, in the district of Tiruchirappalli, around 1989, being the remains a part of the pelvis and the tibia, these were referred to as belonging to a theropod by the shape of the Ilium, however, a later opinions determined it as a sauropod, probably a titanosaur around 1999. The measurements given at that time put it as a gigantic animal of around 35 to 40 meters in length, with an estimated weight of 175 to 220 tons, turning it into the heaviest terrestrial animal ever to have existed, aside of Amphicoelias.

Current estimates
Did you ever hear the tragedy of Bruhathkayosaurus the giant?
Seriously speaking, the history of the discovery of this "sauropod" could be said to be a tragedy since the only known remains discovered by Yadagiri and Ayyasami (those who were behind the discovery and identification of the supposed "stegosaurus" Dravidosaurus which is recognized now as a plesiosaur) were not properly recorded or conserved, these were described poorly, they took terrible pictures of such specimens, they made quite terrible sketches and to make it worse after the discovery they did not bother to collect those remains and the most terrible thing, they left them at the mercy of the Indian monsoons and erosion for the next 15 years after the discovery.

So there are 2 ways to see this in a speculative way given the situation: Option a, in the case that this genus has been what was suggested, a sauropod, the size of this would not have been the one that had been suggested years after its discovery, if an estimate can be made based on the measurements given of the remains, the length that could be obtained would be much less than the proposed 39 meters, being something approximately an animal of 28 meters in length or less, and probably with a much lower weight than previously estimated, probably being with a mass close or less than for example, Giraffatitan.

Or Option b, is just a 2 meter long tree trunk remain and a bunch of rocks with the shape of an eroded Ilium.

So pick one.

11) Kelmayisaurus
This theropod carcharodontosaurid from the early cretaceous was discovered in the early 70s in the city of Karamay, Xinjiang, western china, is known from a very fragmentary holotype formed by a complete left dentary and a partial maxilla. The main peculiarity of this theropod came from another specimen mentioned in the book “The Dinosaur Project: The Story of the Greatest Dinosaur Expedition Ever Mounted”, being the species called “K. giganteus”, being referred from a fragmentary giant vertebra column, it was estimated to had a length of about 22 meters, making it one of the largest theropods known.

Current estimates
The mentioned “K. giganteus” is considered to be a nomen nudum and the actual vertebrae column remains probably belongs to a sauropod. The original holotype specimen was estimated to be 9 to 11 meters of length making it a medium size carcharodontosaurid.

12) Mosasaurus hoffmanii
At first I wanted to introduce estimations made to the Tylososaurus made by "WWD: Sea Monsters" because was emphasized that these reached a length of 18 meters in length, being quite exaggerated with the current estimates that said that they reached 14 meters at maximum, however, I saw that it was more appropriate to introduce a much more recent size estimation mentioned in a scientific article, in this case of the specimen  CCMGE 10/2469 discovered in Penza, Russia, being estimated to have a size of about 17 meters long based in a head-body radio of 1:10 by Russell (1967), making it the largest Mosasaur ever.

Current estimates
Giving the point that for such proportions make people draw Mosasaurus with Tylosaur bodies, one person (mention below) took the time to do their research, and as a result, his detailed research revealed that Mosasaurus was quite robust and bulkier in comparison to its relative, giving it a different body ratio and making the 1:10 body-head radio inaccurate. The current estimates make the Penza specimen around 12 to 13 meters in length.

Based on M. hoffmanii reconstruction by  

13) Megalosaurus
It would seem strange to put a very outdated reconstruction in this place, however, at the time it had been considered as real by early paleontology. So, Megalosaurus could earn the title of not only being one of the first dinosaurs identified, but also for being the first oversized dinosaur ever, in their first reconstructions created by William Buckland considering him as a massive quadruped lizard with an upright posture of amphibious habits, based in estimations given by Cuvier, this was calculated to be a 12 meters long creature with a weight of an 7 ft tall elephant.

Current estimates
After the lizard model was abandoned, the original size estimations were considered to be quite exaggerated with new reconstructions, so most of the later estimations calculated Megalosaurus to be about 9 meters in the beginning and being in recently decades calculated to be 6, 7 or 8 meters long, with a weight less than a ton.  
Based on Megalosaurus skeletal reconstruction 

14) Iguanodon
Like with Megalosaurus, at first Iguanodon was estimated to be a massive lizard like animal being extrapolated the proportions at first from an iguana because the resembles of the Iguanodon teeth with these ones, giving a size estimations of about 18 meters long. 

Current estimates
Again, like Megalosaurus, the lizard model disappeared and over the time this animals has gone through several alterations in their body shape interpretations, varying in designs over the years until they reach their final form (?) being a semi-quadruped herbivore with disproportionately huge hands, with a length around 10 meters and a weight of 3.4 tons, with inferred specimens that can reach 13 meters long.
Based on Iguanodon skeletal reconstruction by

15) Megalodon
Formally Carcharocles megalodon, It has been a shark with problematic size estimations thanks to its many fragmentary fossils being thousands of teeth and some vertebrae, which has given several measures, from the original 30 meters long Bashford Dean estimation in 1909 based on a jaw reconstruction, being downsized to 13 meters to a time later being estimated with a size of 24 to 25 meters long as maximum length.

Current estimates
Actual estimations give a length of about 16 meters to a maximum of 18 meters.

16) Liopleurodon
The biggest size estimation given to a pliosaur ever, the genus Liopleurodon had been described as a giant 25 meters long and weighing around 150 tons in the WWD series being based to fragmentary fossil teeth remain, it becomes one of the documentary's most iconic animal as well one of the most iconic pliosaurs next to with Pliosaurus or Kronosaurus.

Current estimates
The history of the Liopleurodon oversize case is already one the most known around the paleontological community both amateur and professional, that has caused wars of discussions and lots of defenders as well as opposites, and at the end letting a legacy and the perpetual idea of super pliosaurs, but as far is know, there hasn’t been any super pliosaurs and less super Liopleurodon discovered so far, although there has been wild estimations of 15 meters long specimens of others species, which at the end these became very dubious for how fragmentary the evidence has been.

The estimations made by the documentary were not in some points supported by some scientific article or any authority in the matter like with "Ornithocheirus", just made to get the attention of the public, as well, such measure was doubted even for being a maximum size, and most of the estimations made after based on the original remains in comparisons with others Pliosaur suggested that the actual Liopleurodon was 10 meters long, at least at first, and from here Liopleurodon gets smaller and smaller. Studies of other specimens such as Kronosaurus and the discovery of a complete specimen of L. ferox which shown that the skull was 1/5 of the body size gave an approximate length of 6.9 meters, based on the largest specimen found.

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Liopleurodon fin proportions changed.