Are Saurophaganax and Epanterias just Allosaurus?

[Concavenator]

So I searched for Allosauridae and I have read that this family´s genus are Allosaurus, Saurophaganax and Epanterias.But weren´t Saurophaganax and Epanterias just some especially big Allosaurus specimens? ( I read that Saurophaganax was a lot bigger than Allosaurus, but I highly doubt so). Plus, Saurophaganx has slightly different vertebrae.

More doubtful is even Epanterias.

Does anyone know further about this?

[suspsy]

With Saurophaganax, it depends on which paleontologist you ask. Some consider it a large Allosaurus specimen; others argue that it is its own monster.

Epanterias is known from only three pieces of vertebrae, so no one can say one way or the other.

[laticauda]

The debate still rages.  Saurophaganax is synonymous with Allosaurus according to many authorities but there are many who dissagree.  A morphometric analysis of Allosaurus by David K. Smith proposed that the dinosaur fell within the expected growth trajectory of Allosaurus.  Many sites reference possible Saurophaganax material from New Mexico, but I have yet to see any conclusions made from that material. 

Epanterias is an interesting story.  Cope, received several vertebrae from an unknown dinosaur excavated in the vicinity of Cañon City, and he named it Epanterias.  In the race to name things he didn't spend too much time on it.  Rather than being a sauropod, Osborn and Mook found Epanterias to be a theropod "which at present cannot be separated from Allosaurus".  As Suspy noted, it only known from the vertabrae and not enough to diffenetivly answer what it is. 

[Vidusaurus]

With regards to Epanterias, it definitely isn't its own genus; whether it represents Allosaurus or Saurophaganax largely depends on whether you think Saurophaganax is valid.
The arguments for the two genera being distinct seem to stem largely from differences in size, minute differences in the skeleton, and the fact that Saurophaganax is only present in the uppermost strata of the Morrison Formation, but, as @laticauda mentioned, studies have indicated that Saurophaganax falls within the expected growth trajectory of Allosaurus; the fact that known Saurophaganax material is exclusive to the upper levels of the Morrison is problematic, but can be explained if Allosaurus/carnosaurs in general experienced indeterminate growth (i.e. they simply kept growing until they died, rather than reaching an "adult" size and ceasing growth). In this scenario it likely would have been exceptionally rare for individuals to reach such large sizes as the Saurophaganax specimens, given they were often hunting prey at least as large as them, and often several times longer and heavier.
The differences in skeletal morphology being used to justify separation don't really hold a lot of weight given that extreme variation is already known from Allosaurus specimens (indeed, many new species have been created for a variant specimen of Allosaurus only to be sunk back into A. fragilis at a later date).

[stargatedalek]

Even if Saurophaganax is a different animal, for which the jury is still out on, it isn't compared to other animals "worthy" of it's own genus. Look at nearly any genus of modern animal and you will find morphological variation that makes Saurophaganax and Allosaurus look like copy and paste in comparison, and yet we give serious consideration to giving this thing it's own genus. The whole situation is ridiculous and frankly it's a perfect example to highlight a few glaring problems "paleontology culture" is suffering from. Namely the tendency to rely solely on genus names for identification, and the tendency to give every animal its own genus instead of a species title, either in response to the former or so it stays in the tabloids a few hours longer.

[Newt]

The uppermost Morrison, whence hails Saurophaganax, also yields exceptionally large apatosaurs, diplodocines, and camarasaurs. This may be happenstance, but may also be evidence of an evolutionary arms race among Morrison herbivores and predators.  On the other hand, the giant torvosaur sometimes called Edmarka rex is from the middle Morrison.


Stargatedalek - in defense of monospecific and paucispecific genera - there is no consistent ruler for what a "genus-level" distinction might be; even within neontology, "genus-level" distinctions among, say, primates are vastly different from those among, say, percomorphs. Every group of taxon specialists develops their own ruler, and vertebrate paleontologists have, for the last century and change, tended towards oversplitting of genera, possibly as a response to the tendency of Victorian-era paleontologists to ram every scrap into an existing genus, leading to virtually every big theropod being considered Megalosaurus, every non-elephantid proboscidean being considered Mastodon, and similar unhelpful scenarios. This was compounded by other researchers using the genus as an operational taxonomic unit for studies of evolutionary change - even when those genera were wastebasket taxa, invalidating their results.


In the face of the incomplete remains and poorly sampled diversity of extinct species, oversplitting genera is the cautious approach. Besides, all taxon ranks above species are meaningless in the brave new world of cladistics.

[VD231991]

With regards to Epanterias, it definitely isn't its own genus; whether it represents Allosaurus or Saurophaganax largely depends on whether you think Saurophaganax is valid.
The arguments for the two genera being distinct seem to stem largely from differences in size, minute differences in the skeleton, and the fact that Saurophaganax is only present in the uppermost strata of the Morrison Formation, but, as @laticauda mentioned, studies have indicated that Saurophaganax falls within the expected growth trajectory of Allosaurus; the fact that known Saurophaganax material is exclusive to the upper levels of the Morrison is problematic, but can be explained if Allosaurus/carnosaurs in general experienced indeterminate growth (i.e. they simply kept growing until they died, rather than reaching an "adult" size and ceasing growth). In this scenario it likely would have been exceptionally rare for individuals to reach such large sizes as the Saurophaganax specimens, given they were often hunting prey at least as large as them, and often several times longer and heavier.
The differences in skeletal morphology being used to justify separation don't really hold a lot of weight given that extreme variation is already known from Allosaurus specimens (indeed, many new species have been created for a variant specimen of Allosaurus only to be sunk back into A. fragilis at a later date).

The diagnosis of Saurophaganax maximus provided by Chure (1995) is based on multiple specimens that constitute at least four individuals, with the vertically oriented infrapostzygapophyseal lamina and presence of pleurocoels through the fifth dorsal centrum only present in the holotype dorsal neural arch 5. In his description of the giant Allosaurus species A. lucasi, Dalman (2014) notes a few differences between S. maximus and A. lucasi in the morphology of the quadrate and tibia even though no dorsal vertebral material is known from the latter taxon. Comparison of NMMNH P-26083 with A. lucasi would be appropriate to see if that specimen is conspecific with A. lucasi or Saurophaganax maximus.

Chure, D., 1995. A reassessment of the gigantic theropod Saurophagus maximus from the Morrison Formation (Upper Jurassic) of Oklahoma, USA. pp. 103-106. In: A. Sun; Y. Wang (eds.). Sixth Symposium on Mesozoic Terrestrial Ecosystems and Biota, Short Papers. Beijing: China Ocean Press.

Dalman, S., 2014. Osteology of a large allosauroid theropod from the Upper Jurassic (Tithonian) Morrison Formation of Colorado, USA. Volumina Jurassica 12(2):159–180.

[Concavenator]

V @VD231991 A.lucasi is no longer valid, according to Chure & Loewen (2020) the only 3 valid Allosaurus species are A.fragilis, A.europaeus and A.jimmadseni.

[dyno77]

Recently i came across  some photos of a reconstructed skull of saurophagnax ,and i recall some older photos showing how big its skull and arms would be compared to a human...it was massive and the other photo with its reconstructed skull was massive..it was way bigger than the largest allosaurus skull ,in fact its skull is almost as big as t rex..
Also i was watching a video and the expert on saurophagnax was mentioning how massive its femurs were..
As far as i know the more recent finds arent published yet...but there is more than just a few vertebra and femurs...
Dinosaur george would know alot more about this since he was involved in casting the saurophagnax skull years ago..and he seems to know about this particular dinosaur as much as the other experts...

[VD231991]

Recently i came across  some photos of a reconstructed skull of saurophagnax ,and i recall some older photos showing how big its skull and arms would be compared to a human...it was massive and the other photo with its reconstructed skull was massive..it was way bigger than the largest allosaurus skull ,in fact its skull is almost as big as t rex..
Also i was watching a video and the expert on saurophagnax was mentioning how massive its femurs were..
As far as i know the more recent finds arent published yet...but there is more than just a few vertebra and femurs...
Dinosaur george would know alot more about this since he was involved in casting the saurophagnax skull years ago..and he seems to know about this particular dinosaur as much as the other experts...

Does "Dinosaur george" refer to George Olshevsky? I know he died last year at age 75, but my best guess is that the Saurophaganax skull cast was modeled after Allosaurus fragilis while incorporating the very minimal cranial remains known for Saurophaganax maximus.