Saurophaganax in
Planet Dinosaur (2011):
I already talked about one abstract from SVP (2024), but there's another one that I need to discuss regarding another theropod I've talked about before.
We finally got some more research on the enigmatic theropod, Saurophaganax, brought to us by Danison et al., (2024). However, the authors of this abstract have made some pretty surprising claims that could change our view on the theropod completely... For example, the scientists claim that Saurophaganax wasn't even a theropod!
Danison et al., (2024) examined the Saurophaganax material. They started off with a fourth metatarsal, which showed signs of fast growth and what appears to be an External fundamental System (EFS). This doesn't seem to match the growth trajectory of Allosaurus, thus the authors separate Saurophaganax from Allosaurus. That is, if "the appositional rate of the metatarsal is representative of the whole animal." However, it's the last conclusion that floored me. The authors stated that the Saurophaganax vertebral elements (atlas and dorsal vertebrae, and the caudal chevrons) belonged to sauropods and not theropods! In fact, they might belong to an already established sauropod taxon. The holotype of Saurophaganax is the mid-dorsal neural arch (dorsal vertebra) (Chure, 1995, pp. 104 and 106). Based on Danison et al., (2024), this would make Saurophaganax a sauropod or a synonym of another sauropod! The name "Saurophaganax" might not even exist anymore... The skull and limb/long bone elements, said to have belonged to Saurophaganax, do resemble theropoda though. In particular, they are "largely consistent with Allosaurus." (SVP, 2024, pp. 164-165).
Danison et al., (2024 [SVP, 2024]):
P. 164:
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P. 165:
Honestly, I don't know what to think. I was certain that the
Saurophaganax material belonged to a carcharodontosaurid. However, some of the bones did resemble
Allosaurus, like the giant humerus OMNH 01935. Chure (1995) said that the bone was "robust," yet "closely resembles that of
Allosaurus," (p. 103). Smith (1998) said that the humerus matched the
Allosaurus growth chart and "non-size-related variation," despite being large (pp. 131, 134, 138-139). In fact, Smith said that the
Saurophaganax material "
lies on the same growth trajectory for Allosaurus in almost every case," (p. 140). I've also noted before that OMNH 01935 is morphologically indistinct from other humeri of
Allosaurus.
Saurophaganax was more of a chimera than people thought. Heck, I originally asserted that
Saurophaganax was a chimera (half carcharodontosaurid and half
Allosaurus) until I discovered that other carcharodontosaurid taxa had similar bones to it, excluding OMNH 01935. The giant humerus still confused me, but I still thought that it belonged to
Allosaurus. I still think that. In fact, aside from (possibly) the fourth metatarsal and the vertebrae, other postcrania bones resemble
Allosaurus', according to Danison et al., (2024).
I decided to see if it was possible for the
"Saurophaganax" atlas to resemble a sauropod's atlas, or not. I saw
Apatosaurus louisae's atlas, and... Yeah, they look really similar:
Apatosaurus louisae's atlas and axis ("at" is atlas) (
Gilmore, 1936, p. 192):"
Saurophaganax's" atlas (OMNH 01135) (Chure, 1995, p. 104):
"
Saurophaganax" was a chimera after all... I truly believe that some
Allosaurus bones got jumbled up in the skeletal material. Now, it seems that some
Allosaurus AND probably some sauropod bones got mixed in there as well. I wonder if there's any actual "
Saurophaganax" material left to keep the taxonomic name alive?
I'm not going to make any final conclusions until the authors finish their paper. I want to give them a chance, and go about this with an open mind. If this is the end of "Saurophaganax,' then so be it. It was a lot of fun to research the animal.
Links:
Danison et al., (2024) (SVP, 2024, pp. 164-165):
https://vertpaleo.org/wp-content/uploads/2024/10/2024_SVP_Program_Final3.pdf
Gilmore (1936) (P. 192):
https://www.biodiversitylibrary.org/page/53145444#page/254/mode/1up
Chure (1995):
https://www.researchgate.net/publication/230892243_A_reassessment_of_the_gigantic_theropod_Saurophagus_maximus_from_the_Morrison_Formation_Upper_Jurassic_of_Oklahoma_USA
Smith (1998):
https://www.researchgate.net/publication/272151969_A_morphometric_analysis_of_Allosaurus
Update (6/20/26):
I knew some Allosaurus bones got mixed in with the "Saurophaganax" material! I've been saying this for years. Now, a new paper written by Danison et al. states exactly what I've been saying!
Note: Download the paper. Some things in the abstract are different from what's stated in the paper.
"Saurophaganax" is officially a nomen dubium, and a chimera (pp. 81, 106, and 108). The atlas and dorsal vertebrae, and chevrons, are neosauropoda (like Camarasaurus), a diplodocid, or nomen dubium (pp. 81, 89-90, 93-95, and 108-109). Amazingly, the authors recognized that carcharodontosaurids had similar morphologies in their dorsal vertebrae compared to "Saurophaganax's" (the "Saurophaganax" holotype OMNH 1123), in particular Tyrannotitan/Giganotosaurus chubutensis and Lusovenator! I said that! However, the authors disagreed that OMNH 1123 could be definitively referred to a theropod. They didn't even know if it could accurately be assigned to a sauropod, but they decided that it probably was a sauropod that resembled Apatosaurus sp. (pp. 93 and 95). Either way, they put OMNH 1123 as a nomen dubium (pp. 95 and 108). I was right about "Saurophaganax" being a chimera! I'm also surprised that the authors also noticed a possible carcharodontosaurid connection to "Saurophaganax!"
Atlas vertebrae of
Allosaurus jimmadseni (A), "
Saurophaganax" (B), and
Camarasaurus sp. (C) (p. 89 Figure 4):
"
Saurophaganax" holotype OMNH 1123 (A) compared to
Apatosaurus sp. OMNH 1366 (B). The sprl in
Apatosaurus sp. seem to match the al in "
Saurophaganax" (p. 94 Figure 8):
See p. 93 for the comparison between the laminae of the two bones. I wonder... Are the laminae in OMNH 1123 so wide because the specimen was a hatchling, or juvenile? If the animal grew, would the laminae become elongated like Apatosaurus' are? That's just a guess though.
The Allosaurus material was either named Allosaurus anax, or Allosaurus sp. (pp. 82-83, 106-109). The giant humerus, OMNH 1935, which I thought had to be Allosaurus, was "indistinguishable from that of Allosaurus fragilis and Allosaurus jimmadseni." The authors said it was an allosaurid, despite it's great size (pp. 100-101, and 106), but for some reason they didn't put it as Allosaurus anax or Allosaurus sp. Since the authors agreed with me that OMNH 1935 was basically Allosaurus, I'll place the giant humerus under Allosaurus sp. myself.
Originally, I put the femora in Allosaurus but switched to putting it in "Saurophaganax." I also put the tibiae in "Saurophaganax." It turns out that the femora were Allosaurus after all, but not A. fragilis or A. jimmadseni. The authors called it Allosaurus sp. (pp. 102 and 109). The tibiae were also assigned to Allosaurus sp. (pp. 104 and 109). The postorbital, a cervical vertebra, two dorsal centrum, and fibulae, were assigned to Allosaurus anax and not "Saurophaganax" (pp. 82-83, and 108-109). The metatarsals, which I thought were either Allosaurus or a carcharodontosaurid, were put under Allosaurus sp. (pp. 106 and 109). I was VERY conservative in estimating how much of the "Saurophaganax" material belonged to Allosaurus! That is shocking!
Speaking of Allosaurus maximus, it's a synonym of "Saurophaganax maximus" because it used the specimen OMNH 1123 as the holotype. That's probably the reason why Allosaurus anax was erected as the new genus name, along with the fact that the authors see the Allosaurus material as distinct from A. fragilis and A. jimmadseni (p. 107).
"Saurophaganax" was a chimera (like I've stated before), and a nomen dubium. "Saurophaganax" wasn't even a carcharodontosaurid, like I originally hypothesized. It probably didn't even exist! However, I'm just glad that I was right about the Allosaurus bones being lumped into the "Saurophaganax" material. Heck, almost all of the bones were Allosaurus sp. or Allosaurus anax! I wasn't going far enough! However, it's good to double-check and be cautious at times.
Vindication, once again! I was made fun of, and criticized, for my abstract that I wrote on Saurophaganax. I said that it was a chimera that contained carcharodontosaurid and Allosaurus bones. Now, this paper comes out and confirmed 2/3 of what I proposed. I've said this before, and I'll say it again: don't give up!
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