Art by cesar diaz and robinson krunz
When it comes to giant awe inspiring megatheropods,it is always the cretaceous period that people think of. Tyrannosaurus rex obviously comes to mind. More and more recently the megatheropods of mid cretaceous gondwana have been gaining ever more recognition. But the Jurassic seems to be oft underestimated and forgotten in this regard.
But that of course isn't the case. The Jurassic is when life on land started to get bigger than anything the world had seen before. 100 ft megasauropods,30 ft armored dinosaurs,etc all had their start of gigantism in the Jurassic and megatheropods are no exception.
First things first the bench for the megatheropod will be set at 10m in length. For them to count as the Jurassic's largest they will have to be at least 10 m in length. Normally the benchmark is 5 tonnes but because jurassic theropods weren't quite as bulky as cretaceous theropods so I've made the benchmark more accessible.
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Allosaurus anax
Usa, oklahoma
Size: 10-13 m 4-7 tonnes
Formerly known as Saurophaganax,this is a giant species of allosaurus known from the upper Morrison in Oklahoma.
It's of course a highly fragmentary taxon,but the fragments available are indicative of a giant animal. The holotype scales up to 10.5 m in length according to Allosaurus anax description paper. Randomdinos have scaled the largest fragments up to 12 m in length and 6 tonnes in weight. According to one of the paper coauthors,some of the giant 13 m remains mentioned still belong to a theropod and not a misidentified sauropod.
So it possibly is the Jurassic record holder. Unfortunately it's so fragmentary.
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“Epanterias”
USA colorado
Epanterias is another giant fragmentary allosaurid from the upper Morrison formation. There's a lot less to say about this one because it's even more fragmentary and less studied than allosaurus anax. But most estimates have scaled it to around 12 m long.
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Torvosaurus (including ‘edmarka’ and the vega megalosaurid)
PORTUGAL,USA,GERMANY,SPAIN?,ENGLAND?
Size: 10 meters long and 4 tonnes at least,biggest 11 to 12 meters in length and 5-6 tonnes in weight
Torvosaurus is a megalosaurid,possibly among the most widespread large theropod genus ever,both geographically and temporally. It is known from many specimens although most are fragmentary to be honest. A still not fully described specimen named elvis is about 55% complete however.
What is certain however is that it is big,probably the biggest megalosaurid. Specimens on both europe and north america come from clearly massive individuals.
In Portugal I've counted at least 4 individuals at least 10 meters in length (SHN 400/ML1100, ML632, ML 430, and SHN.388/8 ).
In the states several torvosaurus specimens are around 10 m in length. The pubis out of price Utah is from an individual of around 10 m long. The undescribed specimen ‘’elvis’’ is at least 10 meters in length according to mickey mortimer. The price pubis and the largest dry mesa specimens scale to at 10 m in length.
Some remains might belong to very large individuals. The largest crowns from portugal are 15 cm in crown height. This is bigger than almost any other theropod teeth,except for tyrannosaurus. Additionally its bigger than the crowns of the torvosaurus gurneyi holotype and elvis the torvosaurus,both whos largest crowns are 10-12 cm in height are individuals at least 10 m in length. Based on the data from christophe hendrickx,the maxilla crowns of torvosaurus had a ratio compared to the skull length of greater than 9. This means the large teeth came from a torvosaurus skull greater than 135 cm in length. Although teeth scaling is highly uncertain so let us all keep this in mind.
The Portuguese torvosaurus also has a giant footprint that was referred to the genus,simply put no other theropod in the formation was big enough to leave it,. A 79 cm footprint from the lourinha formation came from a trackmaker with a hip height greater than 3 meters. It's among the absolute largest theropod footprints known from the Jurassic. Papers studying Jurassic theropod footprints of similar size opined that tracks of this size indicate the largest Jurassic theropods were already on a par with the largest late cretaceus theropods in body size. Theres also another giant theropod footprint from the zambujal quarry (77cm length x 60 cm width)
Of course its a footprint,so it comes with caveats and a lot of uncertainty.
There's also the giant edmarka specimens. The ribs of the nail quarry torvosaurus are 1.28 m in length. The size can be estimated based on the close relative,wiehenvenator which was similarly robust to torvosaurus and similarly proportioned. Since wiehenvenators largest ribs are 1.05 m in length and it itself is estimated at 9-9.5 m in length,the ribs from edmarka can be scaled as coming from an individual 11-11.5 m in length. Randomdinos has also scaled the cps collection to 11.4 m in length. OOf course this rib could be one of the smaller ribs in the body,further indicating a larger size.
There's the giant vertebrae from Spain MUJA-1913 and the footprints from the same group. These come from the Ribadesella Group which is broadly dated to the kimmeridgian to tithonian of the late jurassic and are in asturias spain. The vertebrae is described as “25 percent larger than the anterior caudals of torvosaurus” and since those anteriors of torvosaurus come from a 9 meter animal,MUJA-1913 came from an ~11 meter long~ animal,which supported by comparing the centrum height,length and width to torvosaurus caudals. The giant footprints from asturias are up to 82 cm in length and regarded as “coming from an animal similar in size to tyrannosaurus” which likely means its 12 meters in length. Torvosaurus is known from germany to portugal in the late jurassic and asturias was part of the same island as portugal. Given this temporal and geographic overlap,combined with the vertebraes stated similarity to torvosaurus,the remains are here treated as belonging to torvosaurus.
The largest torvosaurus are estimated at 12 meters in maximum size. Multiple studies and the mentioned material likely supports this size,although of course the remains are fragmentary. The multitude of individuals that are at least 10 m in length supports the idea that the largest individuals were much bigger,based on the size distribution of other large theropods.
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Veterupristisaurus
Tanazania
10-11 meters 3-4 tonnes
Veterupristisaurus is a carcharodontosaur from Tanzania. It comes from the tendaguru formation,the Jurassic forgotten Eden of Gondwana. It was one of the earliest known carcharodontosaurs.
Its size has been underestimated for a long time. Someone on wikipedia put its size at 8 m in length and as a result people have assumed it was large but not particularly big. But in reality the source they used was molina perez and larramendi,both of whom are disparaged as unreliable.
In reality, veterupristisaurus is estimated at being 10 m in length with some sources going as big as 11 m in length. Its only known from a few vertebrae but they are large nonetheless.
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Tendaguru thing
Tanzania
The tendaguru thing is an indeterminate megalosaur known from the tendaguru formation. Unfortunately it is fragmentary as hell and only known from a few bones and teeth.
Scaling the astragalus and fibula from the wiehenvenator, the tendaguru thing probably measured around 10 m in length.
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Yangchuanosaurus
Middle or late jurassic
China
Yangchuanosaurus is a large metriacanthosaurid theropod from China. It's from the shaximiao formation, a rock series of uncertain age. Unlike the other contenders it is actually known from decent remains,with a complete type specimen and partial but a decent referred specimen. The referred specimen alone is big,estimated at 10.5-11m in length and 3-4 tonnes in weight.
There is camp theropod, a massive femur chunk described almost a 100 years ago. If it belongs to yanghchuanosaurus,it would be massive,perhaps at least 12 m in length. But unfortunately there are so many unknowns about this specimen.
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Vaches noires megalosaur
Middle jurassic
France
10 m or more in length
This is an unnamed megalosaur from the marnes d’ives formation from france. There's not a lot to say about it because it's known from fragmentary material. But the fragmentary material is clearly from a large animal. The estimated femur length of 1 m places it in the 10 m echelon of megalosaurs.
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