NOTE: A recent peer reviewed publication was released by experts Larramendi Asier , Gregory S. Paul2 , Shu-yu Hsu. The study is called A Review and Reappraisal of the Specific Gravities of Present and Past Multicellular Organisms, with an Emphasis on Tetrapods. It turns out we are actually likely underestimating the weights for Dinosaurs. So every size estimate featured on this answer and others of mine are now outdated. With the new density being used from the study large theropod mass should increase between 4-8%

Tyrannosaurus rex the meat-eating tank (Art work Tyrannosaurus Redesign

2018 — Saurian)

Is Tyrannosaurus now considered the largest theropod again?

Things are constantly changing in the realm of palaeontology. We will most probably never truly know what the absolute largest theropod dinosaur is and we most probably will never know what the largest-ever dinosaur is due to the nature of the fossil record. Fossilization is very RARE. Most organisms decompose quickly after they die. For an animal to be fossilized the remains usually need to be covered by sediment straight after death and this does not always happen.

Many animals just do not become fossilised sadly and we do not have a time machine so we can not go back and view these animals in there own times. But right now with the most up to date and most reliable geological studies and data from experts and well respected researchers Tyrannosaurus rex is the most massive and most robustly built out of the giant carnivorous dinosaurs that we have on record so far.

Specimens of Tyrannosaurus such as Sue or the more recently described Scotty are both estimated to be in the weight range of over 9 tons making them the largest theropod specimens known to science. That makes them more massive than other large predatory Dinosaurs such as Giganotosaurus and Spinosaurus and the other giant theropods but this could change in time with newer fossil evidence it just needs to be found first.

As previously mentioned Tyrannosaurus seems to be the most robust out of the large theropods. Having a more stocky build and a larger barrel-shaped chest with a wider heavier skull when compared to other carnivores such as Giganotosaurus Spinosaurus Mapusaurus and Acrocanthosaurus. So while other theropods are estimated to equal or even surpass Tyrannosaurus in length they do not weigh as much because they are not as heavily built or as robust.

Quote from Franoys paleo artist researcher and fully certified palaeontologist

“Tyrannosaurus rex has the most robust hind limbs of any member of the theropoda, the mid-shaft femur circumference of the largest specimens is only matched by Deinocheirus mirificus specimen MPC-D 100/127, which with a femoral circumference of 560 mm, matches those of Tyrannosaurus specimens RTMP 81.12 1 and Samson (560 mm), but still outsized by those of Scotty RSM 2523.8 (590 mm) MOR 1128 (580 mm), and Sue FMNH PR 2080 (580 mm).

The tibia also have the biggest circumferences of any member of theropoda, and they are also the longest. Femoral and tibial circumferences have allometric physical correlations with body mass since they are weight bearing bones, meaning this could be further indication of Tyrannosaurus having the most massive theropod specimens within it (as indicated by Campione et al 2014).The femoral tibial and fibular condyles are very wide and robust, and so is the femoral head, therefore the joints were adapted to withstand a lot of stress. Tyrannosaurus also has the longest ilia registered in theropoda, meaning the ischiotibialis was very wide and massive, the forth trochanter is very well developed so the legs were powered by big muscles as well and they were the most massive between those of it's kind. ”

Franoys regarding the skull of Tyrannosaurus

“Tyrannosaurus rex has got really wide skulls in general. Not just the snout, but specially the posterior cranial portion , due to adaptations for a stronger bite and binocular vision. The lower jaw bones are also really deep, and they have a bigger amount of bone surface than most theropod skulls,”

Franoys on his results regarding the mass of Tyrannosaurus specimen Sue and other large theropod dinosaurs

“The estimation of FMNH PR 2081 (Sue) that I have produced is moderately to substantially higher than the masses that I have calculated using this same methodology for the other largest theropod dinosaur specimens.

The mass of 8828 kg of Tyrannosaurus (FMNH PR 2081 Sue) is offered in contrast to that of 7560 kg of Spinosaurus (MNSM v 4047) , 6840 kg in Giganotosaurus (Mucpv Ch1), 6400 kg in Tyrannotitan (MPEF pv 1157), 6325 kg in Carcharodontosaurus (SGM din 1) and 6110 kg in Acrocanthosaurus (NCSM 14345). Therefore according to these the largest theropod specimen would belong to Tyrannosaurus rex.

The results compare well with those obtained with other volumetric estimations, falling between the estimations of Scott Hartman (8400 kg static1.squarespace.com/static… ) and Hutchison et al 2011 (9500 kg journals.plos.org/plosone/arti…). Considering that Scott showed concerns regarding the mass probably being on the low end, and Hutchinson showed concerns about their mass estimation potentially being too high, I find the results satisfactory and probable”

Tyrannosaurus rex size. by Franoys on DeviantArt

If you are going to research this for yourself I strongly suggest you look for accurate and up to date information because there is so much inaccurate information regarding the size of the large meat-eating dinosaurs on the Internet. I highly recommend looking for information from experts and palaeontologists and look for peer reviewed studies.

Whatever you do DO NOT go looking on YouTube for your information when regarding these animals. There are so many badly made videos on these kinds of topics created by either people who do not have the right information do not have the most up to date information or people who are biased towards certain animals.

Anyway back to the question and yes this is going to be a long answer so grab some food and get comfy and enjoy.

First Let's start with some size comparison diagrams (there is going to be a ton of these in this answer)

Tyrannosaurus rex specimen Sue (12.3 meters long 9.2 to 9.7 tons) compared with the largest estimated size for Mapusaurus so far (12.2 meters long and 7.6 tons) diagrams by Franoys

Tyrannosaurus rex (Sue) with Saurophaganax

Tyrannosaurus rex with its relative Tarbosaurus

Tarbosaurus with Tyrannosaurus rex skeleton side and top views

Estimating the mass for an extinct animal is very difficult. Currently one of if not the best methods for estimating the mass for a giant theropod is known as GDI analysis. Its a time consuming but rigorous process We calculate the mass of an animal by taking their average density and then finding their volume via a detailed 3d model. Most experts state this is currently the best method for calculating mass for a dinosaur.

Biped allometry has been getting much better recently at estimating the mass for giant theropods and is also very often used to calculate the mass for these animals. (Giganotosaurus holotype and Tyrannosaurus rex mass estimates got close to pre-density change volumetric estimates), but still sometimes produces impossibly low results especially for animals with reduced hindlimbs like Spinosaurus.

Most estimations put the most complete specimen of Tyrannosaurus known as Sue at 12.3 meters long 3.66 to 3.73 meters tall at the hips and in the weight range of 9.2 to 9.7 tons at around 8400 kg to 8828 kg with some higher estimations putting it at 10 tons. Sue is a huge specimen and was the most massive theropod specimen that we had on record until 2019 when the specimen nicknamed Scotty was described in more detail.

There have been even higher weight estimates for Sue. Different models used in these tests will get different results. One of these studies is Hutchinson et al (2011) This study found that Sue could be around 9502 kg that is 10.4 tons. These results were achieved by giving Sue a 13% broader model.

There is also the study conducted by Snively et al 2018 that got results similar with Sue being 9130 kg that is 10 tons and there was also a higher result that placed Sue at 9713 kg so 10.7 tons. There are issues with these higher end estimates. Because the models being used have areas with questionable tissue added and this can effect how accurate the results are.

Tyrannosaurus rex Sue model used in the Snively et al 2018 study

As you can clearly see in the above picture the model used in Snively et al 2018 is questionable. The tail is bulked up and the flesh added is excessive and this will effect the results of the study. So far our current understanding of Tyrannosaurus does not support this look for the animal. There is nothing to really suggest it carried this amount of flesh on its tail well not yet anyway so this means it is probably a good idea to not use this model for Tyrannosaurus rex unless you want to get really high mass estimates.

Sue skeleton diagram 2020 by Franoys a more realistic skeletal diagram

Franoys recently updated his Sue diagram with an updated mass estimate of 9110 kg (10 tons or 9.1 tonnes) Franoys added a little more muscle around the hips and the tail and this increased the mass. This result is similar to the the GDI mass estimate obtained in the study Lower rotational inertia and larger leg muscles indicate more rapid turns in tyrannosaurids than in other large theropods. The mass used in this study for Sue was 9130.87 kg. A more Conservative model used for Sue yielded a mass of 8302 to 8692 kg depending on superellipse cross-section.

You can read this study here Lower rotational inertia and larger leg muscles indicate more rapid turns in tyrannosaurids than in other large theropods this study contains the work from by multiple experts such as Eric Snively​1, Haley O’Brien2, Donald M. Henderson3, Heinrich Mallison4, Lara A. Surring3, Michael E. Burns5, Thomas R. Holtz Jr6,7, Anthony P. Russell8, Lawrence M. Witmer9, Philip J. Currie10, Scott A. Hartman11, John R. Cotton12

Scott Hartmans latest Sue diagram (This skeletal is also in the weight range of 9.1 tonnes with GDI analysis heavier than Scotts older Sue diagram that was 8.4 tonnes or 9.2 tons)

Tyrannosaurus specimen Sue with the modern day Elephant

Sue skeleton mount

NOTE: Sue has an updated skeletal mount compared to most other Tyrannosaurus specimens. It is the most accurate mount to our most current understanding when it comes to Tyrannosaurus Rex and its body structure. Even then as with most dinosaur skeletal mounts there are still issues. The gastralia and shoulders have been placed too low on the animals body making the torso look lower than it really should be.

This is why the mount for Sue has a wider and deeper torso than most other Tyrannosaurus mounts this also includes the specimen Scotty that has an older mount and has not been given the lower wider torso yet.

Sue was a big animal indeed but now there is a larger specimen of Tyrannosaurus. On 16 August 1991, a massive specimen of Tyrannosaurus was found this individual was nicknamed Scotty. It was noted that Scotty was very big but no one really knew just how big it was we just knew it was a very robust specimen.

But finally now in 2019 Scotty has finally been studied and described in more detail in a peer reviewed study called An Older and Exceptionally Large Adult Specimen of Tyrannosaurus rex by experts such as Phillip J. Currie,Philip J. Currie - Wikipedia Gregory M Erickson, and W. Scott Persons and these experts have found that Scotty is the most massive Tyrannosaurus rex known to science even more massive than Sue. Scotty is the most robust Tyrannosaurus and the overall largest theropod specimen now on record.

Scotty the most massive theropod known to science so far. NOTE: like previously stated there are some issues regarding the skeletal mount for Scotty. You can see that the ribs are not articulated like they really should be. The ribs should be articulated outward and meet the transverse processes of the dorsal verts. Scotty should have a really wide and deep torso more similar to how Sues is. Hopefully this will be corrected some time in the future.

Quote from the study An Older and Exceptionally Large Adult Specimen of Tyrannosaurus rex

“Here we describe an extremely large and relatively complete (roughly 65%) skeleton of Tyrannosaurus rex (RSM P2523.8). Multiple measurements (including those of the skull, hip, and limbs) show that RSM P2523.8 was a robust individual with an estimated body mass exceeding all other known T. rex specimens and representatives of all other gigantic terrestrial theropods”

Scotty was a massive animal its femur measures around 133 cm in length with a circumference of 59 cm. Sue’s femur measures 132.1 cm in length and only has a circumference of 57.5 cm the femur is a very important weight bearing bone. Currently the largest femur measured for any theropod belongs to Tyrannosaurus specimen Scotty RSM 2523.8. While Scotty’s skull is mostly complete, the possible length estimate of 161 cm that’s 9 cm more than Sue’s estimated skull length. Based on the skull and femur size its likely Scotty measured between 12.67 and 13.08 meters and could have weighed anywhere from 8,870kg (9.7 tons) to possibly 10,490 kg (11.5 tons). This makes Scotty the new record holder for largest T. rex and the largest land predator just surpassing the previous record-holder that was originally Sue.

Scotty the most robust Tyrannosaurus known

Scotty exceeds Sue in 84.6% of the published measurements. All of Scottys weight bearing elements are larger than Sues are.

Measurements, where Scotty surpasses Sue. Spreadsheet, created by Franoys on Deviantart ScottySue

Scotty exceeds Sue in 11 out of 13 bone measurements and that is just the bones measured for the latest study. If you take a look at there skeleton mounts or skeletal diagrams you can see other bones where Scotty exceeds Sue. Scotty has a larger longer and thicker built pubis.

The pubis has a direct coalition with the torso of an animal and is important when determining of torso depth. So it is highly likely that Scotty had a even deeper wider torso than the Sue specimen.

Scotty also has a larger ischium bone along with multiple caudal vertebrae that are thicker than Sues are. Scotty's whole hip girdle is more robust than Sues is and this is important because the hip girdle is the centre mass bearing structure for a theropod dinosaur. So its highly possible that Scotty carried around more weight than Sue did.

Scotty the Tyrannosaurus by Dan Folkes (practicing palaeontologist who's skeletal work has been featured in certified peer reviewed work ) Dans results are 12.4 meters long 3.9 meters tall at the hip and 9.9 tonnes (10.9 US tons) with detailed GDI analysis and 10.2 tonnes (11.2 US tons) using volumetric analysis.

Volumetric analysis results for Scotty

Scotty the Tyrannosaurus also 12.4 meters long by Thedinorocker Scotty skeletal by thedinorocker on DeviantArt

Tyrannosaurus RSM P2523.8 Scotty by Vitamin imagination Facebook https://www.artstation.com/artwork/AqR6gm

The rest of Scotty's body collectively implies a much brawnier body shape than other big Tyrannosaurus specimens and other big theropods. Plus a comparison of cubic femoral dimensions gives a much greater overall weight.

The latest study regarding Scotty describes its shoulder bones, hips and it's leg bones and they are all larger with Scotty than the corresponding bones in the Sue specimen. Scotty's bones were also examined and show higher levels of stress from carrying around more weight when compared to the bones of Sue.

Using the study by Snively et al 2018 we can compare the cross sectional of the sacral anterior vertebra. This is the method used to show the relationship between the animals body mass and the cross section area of the animals spine by showing the mass of an animal but also the stress of the upper body.

The results are once again higher for Scotty than they are for Sue. Scotty's cross sectional area was found to be 650 cm ^2. This means that Scotty was 4 percent larger when compared to Sue who's results were 625 cm^2.

Quote from W. Scott Persons

“It wasn’t until now we’ve been able to take a step back and look at the specimen as a whole, “And doing so there’s an oh gosh moment because the specimen really is enormous.”

“We looked at this from a number of different angles. Obviously the best way to do it is the direct one-to-one comparisons through the various skeletal elements,” Persons said. “When you look at everything from the shoulder to the hip to the leg to portions of even the toe bones, yes, Scotty the Tyrannosaurus rex comes out consistently just a smidgen-bit larger than Sue.”

‘I think there will always be bigger discoveries to be made, but as of right now, this particular Tyrannosaurus is the largest terrestrial predator known to science.’

While Persons is very happy about presenting Scotty to the world, he believes Scotty won’t be the largest for long.

“I can guarantee you that, in generations to come, it won’t be the biggest,” he says. “T. rex was around for millions of years, [and] we probably haven’t found the full extent of the range. There’s no way that we’ve happened to stumble across the largest member of the species.”

Both Sue and Scotty had their weights estimated in the latest study both specimens were directly compared. The method used to calculate the mass in the latest study was the same for both of the specimens and the data shows that Scotty is more massive than Sue is.

The latest study put Scotty's weight at an estimated 8870 kg(9.7 tons) while Sue is estimated at 8462 kg(9.3 tons) so Scotty was estimated to be 400 kg heavier than Sue.

As previously stated Franoys has the specimen Sue at around 8828 kg (9.7 tons). If we apply the same method that Franoys used to obtain his weight estimate for Sue and applied it to Scotty with the latest measurements we would get around 9238 kg (10.1 tons)

This is also not the first time that Scotty has been estimated to out mass Sue, however. There was a study conducted back in 2014 that estimated the weight for some of the large theropod dinosaurs and both Sue and Scotty were also included. This study concluded that Sue had a weight range of 5531kg(6 tons) to 9224kg(10 tons) and the most reasonable weight was 7377kg (8.1 tons) while Scotty had higher results with a weight range of 6000kg(6.6 tons) to 10007kg(11 tons) with the most reasonable weight being 8004 kg (8.8 tons) so Scotty was estimated to out mass Sue by around 700 kgs.

You can view this study here Body mass estimation in non‐avian bipeds using a theoretical conversion to quadruped stylopodial proportions

Also if we applied the excess fleshing to the tail of Scotty like in the Snively et al 2018 study conducted on Sue then Scotty would most likely be in the high 10 to 11 ton range. But like I have stated previously it is not the best idea to do that because of the issues with achieving those results. With the most current geological data on both specimens Scotty is around 400 kg to possibly 700 kg heavier than Sue is.

The latest study regarding Scotty also placed it as one of the oldest Tyrannosaurus specimens placing its age at roughly 30 years old when it died. This makes Scotty possibly the oldest Tyrannosaurus specimen even older than Sue who has been estimated to have been around 28 at the time of its death.

However a more recent study regarding the the growth rate of Tyrannosaurus rex A high-resolution growth series of Tyrannosaurus rex obtained from multiple lines of evidence suggests that Scotty was younger than Sue is.

Quote from the study A high resolution growth series of Tyrannosaurus by Thomas D. Carr one of the worlds leading experts on Tyrannosaurus rex

“ An initial analysis that included all of the specimens recovered 50 multiple most parsimonious ontograms a series of analyses identified 13 wildcard specimens. An analysis run without the wildcard specimens recovered a single most parsimonious tree (i.e., ontogram) of 3,053 steps. The ontogram is composed of 21 growth stages, and all but the first and third are supported by unambiguously optimized synontomorphies. T. rex ontogeny can be divided into five discrete growth categories that are diagnosed by chronological age, morphology, and, in part, size (uninformative among adults). The topology shows that the transition from shallow to deep skull shape occurred between 13 and 15 years of age, and the size of the immediate relatives of T. rex was exceeded between its 15th and 18th years. Although size and maturity are congruent among juveniles and subadults, congruence is not seen among adults; for example, one of the least mature adults RSM 2523.8 (Scotty) is also the largest and most massive example of the species.

A single growth series for T. rex was obtained that can be divided into 21 growth stages; FMNH PR2081 (Sue) was recovered as the most mature specimen, whereas RSM 2523.8 (Scotty) is one of the least mature adults.

In this study Sues age was concluded to be 28 while Scotty was in the range of 23 to 27 years old. You can read this detailed study here A high-resolution growth series of Tyrannosaurus rex obtained from multiple lines of evidence

Sue and Scotty comparison (Sue skeletal created by Randomdinos and Scotty created by Dan Folkes)

Sue and Scotty comparison by Thedinorocker on Diviantart

Comparisons of Tyrannosaurus specimens Stan Sue and Scotty from the book Mega Rex: A Tyrannosaurus Named Scotty by expert Scott Persons.

Scotty the Tyrannosaurus weight estimate from the femur compared to other big theropods from the latest study describing Scotty.

Scottys weight compared to other Tyrannosaurus specimens (click to zoom)

Scottys massive femur

Bigger animals need bigger and more robust legs to be able to support the weight and Scotty has slightly larger and more robustly build legs when compared to any other Tyrannosaurus specimen including Sue.

There are other large specimens of Tyrannosaurus such as Trix Trix (dinosaur) - Wikipedia this well preserved skeleton of Tyrannosaurus has been said to be similar to Sue in size. Trix is described as being roughly the same length and rusticity as Sue and some of the bones from Sue were used to complete the mount of Trix due to both animals being around the same size.

While we sadly do not have a detailed peer reviewed description for Trix we do have some more up to date information regarding the specimen and its size. Trix has been stated to be the third largest Tyrannosaurus currently known behind Scotty and Sue. Recently there was a study "Exploring walking and running gaits of #Tyrannosaurus rex using multibody dynamic simulations" this study featured Trix. The skeletal diagram for Trix featured in this publication has been measured at 12 meters long.

The max torso width of specimen Trix is about 160 cm when looking at the digital mount you can find online and, Scott Hartmans older GDI estimate for the specimen Sue was 8400 kg and used a top view that was also 160 cm the same as Trix.

So with this information and comparing Trix with other Tyrannosaurus specimens we can roughly estimate its mass. At 12 meters long and with wide torso like Sues Trix could mass around 8636 kg so 8.6 tonnes or 9.5 tons when using the new densities. So a very large animal. But this is a rough estimate a more detailed look at the specimen is needed so we can Know for sure but with the pretty limited info we have it is safe to say Trix was a huge animal.

Trix the Tyrannosaurus rex older mount

The new mount for Trix pictures by Pasha van Bijert

There is also the very well preserved specimen MOR 980 or Pex Rex or sometimes called Rigbys Rex

MOR 980 is a large Tyrannosaurus and it was discovered in 1997 near Fort Peck in Montana. The skeleton is well preserved and includes a decently complete skull with its jaws and multiple vertebrae of the back and its tail, a well preserved gastralium, and hipbone with complete ischium and a large pubis (One of the largest pubis bones currently measured for any Tyrannosaurus specimen this highly suggests a deep torso).

Sadly like the specimen Trix there has not been a detailed description of the specimen yet but It has been said by the Chicago museum's lead curator of dinosaurs that this specimen is in the same kind of size range as other large specimens like Scotty and Sue. MOR 980 with the limited information available is around 12 meters long and possibly around 8000 kg to 8200 kg. But this is a rough estimate. A detailed description of the specimen and further study is really needed so we can know for sure.

Mor 980 by Bricksmash

There are also a few fragmentary specimens for Tyrannosaurus that also show this impressive size fragmentary specimens are not as reliable for study as more complete and better-preserved specimens, however. Back in 1983, a partial Tyrannosaurus left dentary was discovered in the Elephant Butte Reservoir in New Mexico. The specimen was catalogued as NMMNH P-1013-1 and was described in 1986 by the American Palaeontologist David D. Gillette. It was a partial dentary that measured 89.5 cm in length and probably would have around 102.2 cm in total length when compared to the complete dentary of FMNH PR 2081 the Sue specimen that’s a big dentary and to put that into perspective the dentary of the Sue specimen measures 98 cm. Scaling from Sue yields a total Pre maxilla to Paroccipital skull length of around 158.5 cm and a total body length of 12.87 meters, compared to Sue’s 154 cm skull length and 12.35 m body length.

It's impossible to scale it accurately but applying the same logic to other partial Tyrannosaurus estimates and we get a Tyrannosaurus that could have been around 9.8 to 9.9 tons but this is very uncertain because all this specimen consists of is a partial jaw.

There is also the fragmentary specimen NHMUK PV R7994 that also goes by the name of Dynamosaurus. This is a fragmentary specimen for Tyrannosaurus rex that is also estimated to be similarly sized to the specimen Sue.

Tyrannosaurus specimens Dynamosaurus" and Sue both have a very robust jaw bone with a more flattened ventral edge and a more prominent anterior dorsal expansion. The dentaries are very robust and nearly identical in shape with a similar foramen near the anterior ventral edge a very large and similarly shaped internal mandibular fenestra, and the various sutures and ridges are basically identical between the two.

So while we can not be sure its pretty safe to say that when this Tyrannosaurus was alive it could have possibly massed around 9 tons like Sue and Scotty so around 8400 kg to 8800 kg but once again this is a rough estimate.

Specimen NHMUK PV R7994 12.4 meters long by Bricksmashtv on Deviantart

There is also the large skull known as MOR 008 (Image from Google images)

MOR 008 is a large and very robust Tyrannosaurus rex skull that is also sometimes referred to as Custer. It was discovered in 1967 by Dr. William MacMannis in the Hell Creek Formation near Custer, Montana . The skull length of 143 cm was reported by Dr Thomas D. Carr one of the leading experts regarding Tyrannosaurus this was reported in 2020 measured from the anterior margin of the premaxilla to the posterior margin of the quadrate.

This length was taken by Carr from the restored skull when he visited the Museum of the Rockies in June 2018 For comparison, the “corrected” skull of FMNH PR 2081 (Sue) measured 141 cm from premaxillae to quadrate, as reported by Carr. This means that MOR 008 is the larger specimen currently when using skull size.

MOR 008 compared with FMNH PR 2081 (Sue) (Image from The largest T. rex specimens (re-examined) by Paleonerd01 on DeviantArt

Quote from The largest T. rex specimens (re-examined) by Paleonerd01 on DeviantArt

“some researchers such as Scott Hartman of skeletaldrawing.com have pointed out that the skull could have been restored incorrectly with its length having been artificially exaggerated. If this is the case this would suggest the actual length of the skull is slightly smaller than that of Sue. Dr Carr however, also commented on the accuracy of the restoration, claiming that although the skull was badly damaged, Michael Holland, the artist who completed the restoration did his utmost to correct any distortion (T. D. Carr, pers. comm.). Holland also created the composite skull reconstruction for the holotype specimen, CM 9380 (formerly AMNH 973), which is on display at the Carnegie Museum of Natural History in Pittsburgh. It is worth noting however, that Holland left out the occipital bone from his reconstruction of MOR 008 meaning the actual skull length would be even greater”

Thomas Carr one of the worlds leading experts regarding the study of Tyrannosaurus on the skull of MOR 008

Currently MOR 008 is estimated to have a total body length of around 12.46 meters and would be in the same weight range as other large specimens such as Scotty and Sue or possibly even heavier. However, this should be treated as just a rough estimate because all we have for this animal is the really large skull and skull size proportional to body size does vary greatly among different individual specimens of Tyrannosaurus rex and other theropods. There is the possibility this was just a large headed Tyrannosaurus individual but either way the skull is very impressive.

Now we come to the pretty well known and highly controversial specimen (within the paleo community anyway) UCMP 137538. All this specimen consists of is a single pedal phalanx yes one single big toe bone and nothing more.

Image from paleonerd01

Just like many other cases of people over scaling using fragmentary specimens there have been way to many over inflated size estimates from this annoying toe bone and it has caused a ton of headaches when discussing the size of Tyrannosaurus. It was found in Garfield Country, Montana.

UCMP 137538 from the book Dinosaur Facts and Figures: The Theropods and Other Dinosauriformes

Any size estimate for this specimen is unreliable because like already stated its just one single toe bone. It could have belonged to a Tyrannosaurus that was slightly larger than Sue but not by much it could also have belonged to a Tyrannosaurus that had big feet or big toes or maybe one single big toe but was a smaller animal overall. We will never know for sure. It was estimated to be 12.3 meters long and 8.5 tonnes (9.3 tons) 200 kgs heavier than the weight estimate for Sue in the book Dinosaur Facts and Figures: The Theropods and Other Dinosauriformes but we can not be sure on the size of this animal and some of the other size estimates made within this book can be pretty questionable at times.

So large sizes for Tyrannosaurus do not seem to be a very rare occurrence when we look at the fossil evidence we have. Scotty and Sue sized individuals were probably pretty common. In an interview conducted by Brian Switek for National Geographic back in 2013 Dr. Thomas Holtz expert on Tyrannosaurus would go on to state.

“It is very reasonable to suspect that there were individuals that were 10, 15 or even 20 percent larger than Sue in any population.”

Other shorter specimens of Tyrannosaurus are estimated to be very massive animals. Take the holotype, for example, this skeleton is around 11.88 meters long but is still estimated to weigh over 8 tons at 7500 kg

Tyrannosaurus rex holotype by Franoys

There is also the specimen known as Stan this is another rather famous Tyrannosaurus specimen. Stan is known to have one of the very best skulls when it comes to Tyrannosaurus and just like Sue there has been a lot of study on this particular specimen. Stan is measured to be 11.78 meters long has a hip height of 3.64 meters and is estimated to weigh over 8 tons at 7722 kg with GDI analysis.

Stan the Tyrannosaurus by Franoys

Stan lurking in the background compared to other large theropods.

Stan

These two specimens of Tyrannosaurus are at a similar length to the largest specimen for Acrocanthosaurus known as Fran that is measured to be 11.54 meters long.

Acrocanthosaurus by Franoys

Acrocanthosaurus was a huge predator and is one of the largest theropods currently known. But due to Acrocanthosaurus not being as robust and not having the huge barrel-like chest that Tyrannosaurus has it weighs quite a lot less it is estimated to weigh around 6.3 tons with GDI analysis

Acrocanthosaurus with muscle attachment a huge Animal and top predator of its time.

But Tyrannosaurus rex takes it to another level just look at its bulk it was a meat-eating tank on legs.

T.rex with Acrocanthosaurus

Giganotosaurus is another massive predator and is even larger than Acrocanthosaurus and at one time was estimated to be the largest theropod known even larger than Tyrannosaurus but things have changed this happens quite a lot in Palaeontology. With the most current information, Giganotosaurus is now estimated to be around 12.2 m (the best preserved specimen) to 13.2 meters long(a isolated jaw fragment) and is estimated to weigh around 7.5 possibly 8 and at the very most 9 tons (8200 kg) with the largest estimated size. Franoys orignally got 7.5 tons (6840 kg) for the Giganotosaurus holotype with GDI analysis.

This mass estimate is coherent with other mass estimations published for the Giganotosaurus holotype specimen (Mazzeta et al 2004; 6510 kg, Campione et al. 2014; 6349 kg, Seebacher 2001; 6,594.8 kg 6800 kg Scott Hartman). This is the best and most reliable specimen to use for study,

Franoys recently updated his skeletal diagram for the Giganotosaurus holotype specimen and their have been some adjustments made. Like I stated before things are always changing in palaeontology.

Giganotosaurus Carolinii specimen Mucpv Ch1 (holotype). Originally described by Coria and Salgado in 1995 updated skeletal by Franoys.

The mass and length for this specimen were increased. Going from Frans work Giganotosaurus specimen Mucpv Ch1 is now 12.29 meters long and estimated to weigh around 7360 kg (7.2 imperial tons or 8.1 US tons)

Here Fran goes into detail to what has been changed regarding Giganotosaurus and lists the studies that were used to create the skeletal.

The first of a series of updates regarding the Carcharodontosaurids. Hopefully not other than the mass might change in the future.

-Updated and improved the skull, using data from the latest Kem-Kem beds monograph that helped a lot articulating and studying Carcharodontosaurine crania. (More on that with future updates).
Redrew the cervical centra and ribs, corrected the dorsal vertebrae proportions (now the centra is shorter in hight, but they have higher neural arches, over double the centrum height as described by Cuesta (2018).

-Changed the vertebral formula from 9 cervicals /14 dorsals to 10 cervicals and 13 dorsals, like Concavenator's description and Harris 1998 suggest, contra Stoval 1950 and Canale et al 2014. The original mounted skeleton also shows 10 cericals with 10 cervical ribs.

-Redrew the femora and updated the pelvic girdle.

-Rearranged the tail (I updated the whole Carcharodontosaurid composite tail, changing slightly the assigned positions of the perserved Acrocanthosaurus's caudal centra, in a way coherent with Cuesta's thesis about Concavenator corcovatus and BHI reports) augmented the intervertebral cartilague between caudal centra, and redrew and re scaled the posteriormost end of the tail using Concavenator instead of Allosaurus. As a result the animal now is slightly longer (a bit over the 12.2 m length listed in Currie & Carpenter (2000) and Coria & Currie (2006).

-Removed the caudal pleurocoels since Giganotosaurus lacks them even if they were said to be observed in Acrocanthosaurus. All other Carcharodontosaurids seem to lack them (Coria 2003, Cuesta 2018).

-Updated the mass estimation with the higher densities proposed by Larramendi& Paul( Used the roughly median value of 0.97 SG). It also takes into account the slightly deeper torso, however a full new GDI will have to be performed to make sure it checks after the changes made.

The Giganotosaurus holotype is the very best preserved specimen for the genus currently known. But we also do have a jaw fragment that has been asigned to the genus this specimen is known as mucpv-95 a pretty controversial specimen when it comes to the paleo community.

Why is specimen MUCPV-95 controversial? well because it's just one single jaw fragment and nothing else it's not a partial skeleton we have no other bones when it comes to this animal. This is a pretty big problem because basing this idea on just one jaw fragment is just not reliable at all you simply cannot extrapolate an unusually large size estimate for a big multi-tonne animal, reliably from a fragment.

Giganotosaurus specimen MUCPV-95

Giganotosaurus specimen comparison

Did this jaw fragment come from a larger individual than the holotype specimen ? we really can not say for sure. Despite the fragmentary nature of this specimen it still has not stopped people from estimating the animal's size, however. This jaw fragment could have belonged to a larger individual. This specimen has been estimated been around 12.5 to over 13.2 meters long and has been estimated to mass over 8 tons (7290 kg based on the 2.2% increase compared to the holotype) to 9 tons (8200 kg from Scott Hartman) but this is very uncertain because all this specimen consists of is one jaw fragment and nothing else.

Jaws of the big theropods tend to vary in size and shape quite often so yes this could be a larger specimen of Giganotosaurus or it could just be another 12 meters long or even shorter Giganotosaurus individual that just has a slightly bigger jaw or skull. We can never really be sure until we find a decent amount of the skeleton this is a problem often faced in palaeontology.

When MUCPV-95 was first described It was supposed to be around 8% larger than the jaw bone for the Giganotosaurus holotype because of the dentary being 8% longer but further study found this to be incorrect. This is because the dentary of the holotype is actually incomplete. While MUCPV-95 is complete not because the MUCPv-95 jaw fragment is actually larger its highly possible the individual the MUCPV-95 came from was really not larger than the holotype at all. Both dentaries bones have been measured previously in other studies and the difference between them is a tiny three millimetres that is nothing in the grand scheme of things.

Fragmentary pieces of bones from these huge animals DO NOT scale isometrically in Dinosaurs or in any living animal or extinct so using fragments is never very accurate. Animals are never perfect clones of each other. It's pretty common that we see animals being at similar height or lengths and weight but some have longer fingers or larger feet or have larger skulls. Some animals are taller and more lanky while others carry more weight around. The same can be said for the theropod Dinosaurs. All of them would have been different in some ways.

Quote from Franoys regarding the isolated jaw fragment MUCPV-95

But even then it is estimated that even a 13-meter long Giganotosaurus would weigh slightly less than the bulkier 12.3-meter long Tyrannosaurus it would require a 14-meter long Giganotosaurus to for sure outweigh a 12.35-meter Tyrannosaurus and so far there is no fossil evidence that shows Giganotosaurus growing to that kind of length. No large-bodied fully terrestrial theropod has ever reliably reached that length outside of estimates that usually end up being inaccurate.

It makes sense that Tyrannosaurus overall weighs more than Giganotosaurus because tyrannosaurids as a whole are very robust compared to other theropods.

Albertosaurus another Tyrannosaurid compared to Allosaurus top view

Giganotosaurus specimen mucpv-95 estimated size with Gigantosaurus holotype and Tyrannosaurus rex Sue by Scott Hartman

Giganotosaurus specimen MUCPV-95(largest estimated size for Giganotosaurus) with Tyrannosaurus specimen Sue comparison

Tyrannosaurus rex specimen Sue with the Giganotosaurus holotype specimen side and top views by Scott Hartman

Quote from Scott Hartman regarding the size of Giganotosaurus and Tyrannosaurus rex

“As near as I can tell, despite Tyrannosaurus and Giganotosaurus appearing similar in size in side view, there is little question that T. rex is actually the larger theropod based on known specimens. To be fair, there's only one good specimen of Giganotosaurus, and it took most of a century to find Sue, so it's certainly possible that as additional specimens are collected we will find larger southern giants. As always, please remember we don't have a statistically valid population of specimens from any of these large dinosaurs, so we are only comparing individuals, not species.“

Tyrannosaurus rex specimen Sue (black) with the Giganotosaurus holotype specimen (grey) below

Tyrannosaurus specimen Sue with the Giganotosaurus holotype specimen(the best-preserved specimen)

Also when we look at the most current measurements it supports that Tyrannosaurus is the taller animal. Multiple specimens for Tyrannosaurus are taller when we factor in hip height when compared to the most complete Giganotosaurus specimen. The Giganotosaurus holotype has a hip height of around 3.53 meters tall.

Tyrannosaurus rex specimens and hip height

Scotty=3.69 to 3.76 meters tall (this is could change with further study) Randomdinos has estimated Scotty to be around 3.8 meters tall.

Sue= 3.66 to 3.73 meters tall Randomdinos also has estimated Sue to be 3.8 meters tall. Most other estimates have Sue lower than this however.

Stan=3.64 meters tall

AMNH-5027= 3.63 meters tall

CM-9380 (holotype specimen)=3.67 meters tall

Giganotosaurus specimen MUCPV-95 has been estimated to possibly be around 3.9 meters tall at the hip. But once again all this specimen consists of is one jaw fragment we do not actually have the leg bones or the hips so we can not actually measure how tall this individual was .So despite being a very large animal and it does rival Tyrannosaurus in size Giganotosaurus does not surpass Tyrannosaurus rex with modern estimates from experts. For more information regarding the huge Giganotosaurus please see this answer here Joel Dale's answer to What is a Giganotosaurus? And how large is it?

Currently using the most up to date information from experts and the work from researchers there is no reliable size estimate for Giganotosaurus that puts its mass at over 13 or 14 or 15 tons.

These weight estimates seems to come from the same method that has been used to obtain other inflated mass estimates for other giant theropods in the past. It is an older less accurate method known as Skull length regression. This method is not as reliable as GDI analysis or biped allometry. Using this method we get 15 ton estimates for Carcharodontosaurus and 20 ton estimates for Spinosaurus. These estimates are not accurate when we look at the most current data but are still listed on Wikipedia.

Moving on there is also the well known giant theropod that comes from the exact same family group as Giganotosaurus and this genus is the shark toothed lizard Carcharodontosaurus. Carcharodontosaurus is another one of the largest theropods currently known and has been estimated by some to be even larger than both Giganotosaurus and Tyrannosaurus rex. There have been plenty of high 8 to 9 ton 13 to 14 meter long estimates made for Carcharodontosaurus in the past but these are now seen as inaccurate.

The issue is we really do not have enough fossil material to really know just how large it really was we can only go from the very limited evidence we have. More current and up to date estimates for Carcharodontosaurus place it at the 6 to 7 ton range Franoys estimated the largest specimen at 12 meters long and around 6325 kg so 6.9 tons. This estimate sits well with other more current estimates made for Carcharodontosaurus and this would make it smaller than both Giganotosaurus and Tyrannosaurus.

The largest specimen consists of fragments of a skull, that has had various different estimates and measurements made on it in the past.

Carcharodontosaurus multi view skull diagram by Franoys

Quote from Franoys practicing palaeologist and paleo artist regarding Carcharodontosaurus

The neotype consists of fragments of a skull, that when put togheter, is very big ( Sereno 1996) . When using Tyrannotitan to reconstruct the rear of the skull and Acrocanthosaurus to reconstruct the rest it ends at about 1.53 m long in maximum metric measurements (Currie and Carpenter 2000, Canale 2014) (far from the 1.6+ m that was reported to the press)
The skull is not only not as long as reported; it is also very narrow, and as a result, it's length alone is missleading to judge it's total size, and in fact the head does mass little compared to the more robust heads of other giant predatory dinosaurs. According to my best fit of the skull elements of the holotype and the neotype, the Neotype is an animal that would have a 12.5% bigger skull (roughly). With a skull about 1.35 m in length, the holotype of Carcharodontosaurus was not small headed, and had a similar skull/body ratio than all other Carcharodontosaurines.

Carcharodontosaurus is barely any bigger than Tyrannotitan in linear dimensions according to how most of the bones compare, the Carcharodontosaurus holotype has a femur smaller than that of the Tyrannotitan holotype, it's extrapolation to SGM din 1 size is barely any bigger than the same element in Tyrannotitan paratype, and the jugal of the Tyrannotitan paratype fits almost perfectly in SGM din 1 skull. Here it is scaled to be a vague (and optimistic) 0.5% bigger in linear dimensions based on marginal differences, and is also given a slightly lengthier tail to fit the only known caudal of the Carcharodontosaurus' holotype better.

So, is Carcharodontosaurus the enormous, small headed 8t or 9t+ ultra-giant that some people wanted to see in it's fragmentary ( and not that impressive) remains? It seems like it isn't, but further discussion on that will be for another journal.

Mathematical analysis on Carcharodontosaurus mass by Franoys on DeviantArt

Carcharodontosaurus diagram by Franoys

Tyrannosaurus with Carcharodontosaurus diagrams by Franoys

Spinosaurus is another well-known mega theropod and one of the largest theropods known and is often stated to be largest but is it really? well, let's take a look. The largest specimen we have of Spinosaurus is now estimated to be around 15 meters long and around 6.9 to over 7.6 tons a more recent GDI on the weight of this specimen has put its weight at around 6876 kgs you can view the GDI bellow

Most recent GDI on the weight of Spinosaurus by Franoys

There are also estimates of other smaller individuals of Spinosaurus that are mature individuals and are estimated to be around 11 to 13.7 meters long and weighing around 3 to over 5.7 tons.

Spinosaurus size estimates by Randomdinos

Spinosaurus is a very large animal but it is a thin animal for its impressive length the torso is not especially wide and neither deep the head is lightly built and narrow compared to Tyrannosaurus the back legs are very small the skull of Tyrannosaurus alone is estimated to weigh more than both of the legs of Spinosaurus combined. Therefore, it is very likely that Spinosaurus was less massive than Tyrannosaurus rex at least slightly-moderately less massive than the larger Tyrannosaurus rex specimens. So while Spinosaurus is so far the longest theropod at around 15 meters long it is not the most massive so it is not quite the largest. It is estimated right now that a 12-meter-long Tyrannosaurus is around 5000 kg heavier than a 12 meter long Spinosaurus so quite a large weight difference there.

If we take a Spinosaurus that is around 13.7 meters long it would weigh around 5200 kg so that is 5.7 tons and still a 12-meter long Tyrannosaurus still out masses it and if we had a Tyrannosaurus rex that was around 13.7 meters long it would weigh closer to 10-11,000kg so around 11 tons.

Spinosaurus specimen FSAC KK 11888 the best-preserved specimen of Spinosaurus so far 11.3 meters long and around 3.1 to 3.6 tons in weight

And once again we will use the Holotype specimen of Tyrannosaurus by Franoys 11.8 meters long and weighs 8.2 tons

So despite both of these specimens being very similar in length Tyrannosaurus weighs a lot more because of its more muscular and heavier build. Even palaeontologist Simone Maganuco who worked on the latest reconstruction of Spinosaurus has stated Tyrannosaurus was larger than Spinosaurus.

Quote from expert Simone Maganuco

I will also warn you when it comes to Spinosaurus there is a lot of misinformation regarding it and its size many people out there like to over-exaggerate its size this mostly stems from old estimates for the animal's length and weight these estimates were created before we really had a decent idea on how big Spinosaurus is and what its proportions were. Many people to this very day like to say that Spinosaurus could reach over 60 ft long and mass 10 to 20 tons even though these estimates are now very outdated and are not taken seriously by experts anymore. There are many pictures on the internet like these examples below

Note : (these are very out of date inaccurate or flat out over exaggerated size comparisons so please do not continue to share them around the internet there is already way too much of this stuff around thank you)

Very exaggerated and inaccurate size comparisons when it comes to Spinosaurus

Outdated size comparison (diagrams from Scott Hartman)

while this comparison was impressive for its time it is now inaccurate due to the more recent discoveries when it comes to Spinosaurus and its body structure and overall proportions. Many misinformed people to this day like to state its an accurate representation, however.

These are just some examples but there are many more just take a look on Google images and I'm sure you will find them. Stuff like this is very exaggerated and should not be taken seriously there is no concrete reliable evidence that supports extreme sizes like this when it comes to Spinosaurus or any big theropod.

No theropod currently known to science could grow to be over 23 meters long that is absolutely ludicrous but it still does not stop people from believing it and sharing it around the internet. The theropods are large but are not built like the giant Sauropod Dinosaurs there body's simply could not support sizes that large.

The size comparisons below are more up to date and more accurate to the more recent geological studies when it comes to Spinosaurus.

The largest specimen for Spinosaurus estimated size by Franoys 15 meters long and around 6.9 to 7.6 tons ( this skeletal was created before the latest publication on the tail of Spinosaurus)

Spinosaurus (specimen MSNM V 4047 the largest specimen for Spinosaurus) 15 meters long and around 6.9 to 7.6 tons compared with Tyrannosaurus specimen Sue 12.3 meters long and 9.2 to possibly 9.7 tons) art work created by Vitamin imagination (note this was created before the latest study on the tail of Spinosaurus but it still shows the differences in build between these two animals)

Sky view comparison of Tyrannosaurus and Spinosaurus

Spinosaurus snout (White) with Tyrannosaurus snout (Black) you can clearly see why the skull of Tyrannosaurus weighs more

In 2020 Nizar Ibrahim with his team released yet another ground breaking peer reviewed study that further progressed our understanding of the mighty Spinosaurus that further shows how specialised for an aquatic life the animal was.

three of the authors involved with it including the expert, Nizar Ibrahim , Cristiano Dal Sasso and Simone Maganuco from the Natural History Museum of Milan (Italy), have collaborated to study new fossil evidence that includes brand new fossil material of the tail of Spinosaurus.

The new Spinosaurus tail that has been uncovered with a full skeletal diagram of Spinosaurus specimen FSAC-kk 11888 the best preserved specimen for Spinosaurus.

The fossil tail bones, show us that the tail was pretty wide, and flexible this would have been a very helpful tool to help aid this large animal through deep water. The tail of Spinosaurus has been described as resembling that of a really large crested newt.

The researchers then concluded in the study that this is unambiguous evidence for an aquatic propulsive structure. Spinosaurus was very much at home in the rivers and the dark swamps and lakes of the Cretaceous of northern Africa. This is an animal that that took to the water and likely dominated its niche. It is very likely that Spinosaurus very rarely even came on to land at all.

Spinosaurus 2020 by Vitmain Imagination

The overall size for Spinosaurus is often changing. Currently with the most current geological data the largest estimates for Spinosaurus are now around 14.4 meters long( the animals length was slightly shortend because of the new tail)

The torso on the 2020 version has been made deeper while the shoulders have been lowered and the neck has become much thicker and obviously the new tail was added along with changes made to the animals arms they are not as large or as robust as before. Strangely the neck is not that thick on the 3D model released with the latest study it's only featured on the skeletal itself.

I have had many conversations regarding these changes and how this could effect the overall mass for Spinosaurus and most have stated that not much has really changed since the last GDI, mass analysis made by Franoys. The animal looses some tail length but then gains a bit of mass increase. Despite its impressive and large appearance the new tail spines didn't anchor a lot of muscle it was mostly just a large fin like structure. The new tail is also thinner than the older tail used on the 2014 version of the animal so it will not add a huge mass increase.

With all of this been taken into account when using the same bone density that we use for most other theropods that implies 3.42 tons for the neotype specimen and this then puts specimen MSNM-v-4047 at a huge 7.8 tons when using a 14.4 meter length 7.3 tons has also been proposed along with 8.2 tons but we can not be completely sure yet we really need a definitive Spinosaurus skeletal and a good GDI to get a better idea hopefully we will get that soon.

Spinosaurus specimen fsac-kk 11888 the best preserved Spinosaurus and overall best preserved Spinosaurid now known to science.

With all of this being taken into account Tyrannosaurus rex is still a lot more robustly built than Spinosaurus. Tyrannosaurus specimen Sue has a skull that is 1.52 meters long and estimated to weigh around 524 kgs .While the largest Spinosaurus specimen has an estimated skull length of 1.47 meters and would weigh around 144 kg

Accurate comparison Tyrannosaurus rex (Sue)with Spinosaurus MSNM-4047 Diagrams by Franoys (This was created before the latest publication on the tail for Spinosaurus so just try and picture the new tail being added here)

When it comes to Spinosaurus we really do not have enough well preserved specimens to really have a concrete understanding on its full size range. Right now with the most current information Spinosaurus is in the 3 to 7.6 ton range. There are other specimens for Spinosaurus that can be used to obtain very large individuals but once again this all stems from fragmentary fossil materiel and as previously stated this makes any size estimates being made from this fossil evidence very questionable.

One specimen now being used to obtain a very large Spinosaurus individual is NMC 42852 a 75 cm humerus and nothing more. The humerus is controversial because it shares similarities with a Spinosaurid known as Baryonyx a distant relative to Spinosaurus but it also shares similarities to a sauropod dinosaur Rebbachisaurus . The specimen has been disputed by researcher Andrea Cau and others within the paleo community agree with his findings. But then Nizar Ibrahim in the 2014 reclassified NMC 42852 as a Spinosaurus.

This just further shows the issues with using such fragmentary fossil evidence. We simply do not know for sure what it is yet. Also while Nizar Ibrahim did reclassify NMC 42852 as Spinosaurus in the 2014 study it still did not increase the size range for Spinosaurus. The largest specimen was still MSNM-v-4047 that was estimated to be around 15 meters long(now closer to 14.4/14.5 meters long) and in the 6 to 7 ton range . So far there are no modern official size estimates made from any experts regarding the specimen NMC 42852 that estimates it as larger than MSN-V-4047.

Franoys Spinosaurus skeletal also actually included a 74 cm humerus that is 9 cm longer than the 65 cm complete length estimate from the Russel 1996 study that describes the large humerus. And Fran's Spinosaurus skeletal while now outdated (it doe snot include the new tail yet) it still comes out at 15 meters long despite having a slightly longer humerus than what Russel 1996 estimated it at.

All Franoys needs to do now is to add the new updated tail which is a little shorter than the standard theropod tail that was used for Spinosaurus before and it will be accurate.

So even if you want to make the humerus measurements slightly larger you still get a 14.5m long Spinosaurus not a 16 meter one.

And because of all of these issues regarding the specimen many researches simply do not use it for scaling or study because it is simply not reliable. Despite these issues that has not stopped people from using this specimen to justify getting very large estimates for Spinosaurus. Sizes of over 16 meters long and possibly in the high 9 to 10 ton range.

But these estimates should be used with caution like previously stated no expert has estimated how large the animal might have been and we lack any other humerus to scale, unless one is finally found, or this specimen is associated with other bones it is an unreliable scaling

Further study and better preserved fossil evidence is needed to get a better idea on the size of Spinosaurus. Recently however Nizar Ibrahim conducted a AMA (Ask me anything) on Reddit and answered the many questions asked by eager paleo fans and some interesting things were brought to light.

Nizar would go on to state that Spinosaurus could end up being in the weight range of 10 to 12 tonnes but would also state we very well might be under sizing other dinosaurs also.

Quote from the Ask me anything conducted by Nizar Ibrahim on Reddit 2020

There was also some information shared regarding the arms of Spinosaurus and how the animal might have moved around while on the land even though Nizar thinks the animal very rarely left the water at all.

Nizar also brought up some information regarding a large humerus bone and stated it might be from a Titanosaur dinosaur or it might be a completely new genus.

Now with the most current data we have regarding Spinosaurus from the latest studies 10 to 12 metric tons is very very high. This is quite an unusual estimate due to the fact we can not replicate this result with the data we have currently using the models we have for Spinosaurus those sizes are simply not achievable . Even the very highest maximum size we can achieve for the largest specimens for Spinosaurus can only possibly be 8 to possibly 9 tons at the most. So right now we really do not know how Nizar has come to this conclusion we just know we can not replicate this result.

Maybe he knows something we simply do not or maybe he has more fossil evidence for Spinosaurus that increases its current size range but it has not been described yet. Or maybe we simply are just under sizing these animals and he knows a more up to date and more accurate way of estimating mass.

But right now with all of the geological data we have on these animals and seeing how both animals are built if Spinosaurus is around 10 or 12 tons then Tyrannosaurus would be in the weight range of 15 tons.

Yes you should be sceptical because these are very high estimates and there is so far nothing concrete that substantiates any big theropod reaching these kinds of masses with realistic size estimates. So far these high estimates have no actual basis for it- and until Ibrahim or some other expert puts out some sort of explanation or some new information these extreme size estimates should be taken with a grain of salt. So all i can say regarding this is is stay tuned.

So right now with the most up to date and most reliable information Tyrannosaurus rex is indeed the largest meat-eating dinosaur known due to its larger mass and overall more muscular build. The sizes of these animals are constantly changing and being adjusted. Palaeontology is always in flux and all of this could change at any time with more fossil evidence being discovered and it is very likely this will all change very soon.

Every animal i have brought up in this answer were huge predators and all were some of the largest that have ever existed on land. There is no way we have managed to come across the absolute largest individuals for any of these animals. There would have definitely been larger specimens roaming around but its very unlikely we will ever come across them.

Recently there was a study conducted that estimated there could have been around 2.5 billion Tyrannosaurus rex individuals that existed.

So do you honestly believe we have managed to be lucky enough to stumble across the absolute largest individuals that ever existed ? I really do not think so and this also applies to the other giant theropods.

But only time will tell. Who knows what's just buried out there just waiting to be stumbled upon there just might be a huge theropod out there that is even more massive than Tyrannosaurus Rex in fact its highly likely that is the case we just need to wait and see.

Accurate and most up to date size comparison of giant Theropod Dinosaurs arranged by length by Franoys(click to enlarge picture) Scotty the Tyrannosaurus is not included in this chart.

Tyrannosaurus rex with one of its biggest rivals Triceratops

The king of the Savannah meets the king of the Dinosaurs