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Description
Thanks to lack of overlap of its material with the holotypes of other proposed Morrison species, the taxonomy of the New Mexico allosauroid NMMNH P-26083 is currently a mystery, as it has no distinguishing features from either Allosaurus fragilis or Saurophaganax/Epanterias. The massive size of the individual (far larger than any A.fragilis, its femur is as long as Saurophaganax's and has a larger circumference, and its caudal vertebrae are among the largest ever found on theropods) would suggest affinity with the later genus, but its stratigraphic position is very close to the Cleveland-Lloyd Quarry, which preserves dozens of individuals of Allosaurus and no traces of S.maximus. It's possible this was part of a transitional population between the two, but we know way too little about the evolution of Morrison allosauroids to say.

References:
-Gilmore, Charles W. (1920). "Osteology of the carnivorous dinosauria in the United States National Museum, with special reference to the genera Antrodemus (Allosaurus) andCeratosaurus" (PDF). Bulletin of the United States National Museum. 110 (110): 1–159. doi :10.5479/si.03629236.110.i .
-Madsen, James H. Jr. (1976). Allosaurus fragilis: A Revised Osteology. Utah Geological Survey Bulletin 109 (2nd ed.).
-Williamson, T.E., Chure, D. A large allosauroid from the Upper Jurassic Morrison Formation (Brushy Basin Member), West-Central New Mexico. The Continental Jurassic, Michael Morales, ed., 1996. Museum of Northern Arizona Bulletin 60.
-Chure, D., 2000, A new species of Allosaurus from the Morrison Formation of Dinosaur National Monument (Utah-Colorado) and a revision of the theropod family Allosauridae. Ph.D. dissertation, Columbia University, pp. 1–964

Description
Thanks to lack of overlap of its material with the holotypes of other proposed Morrison species, the taxonomy of the New Mexico allosauroid NMMNH P-26083 is currently a mystery, as it has no distinguishing features from either Allosaurus fragilis or Saurophaganax/Epanterias. The massive size of the individual (far larger than any A.fragilis, its femur is as long as Saurophaganax's and has a larger circumference, and its caudal vertebrae are among the largest ever found on theropods) would suggest affinity with the later genus, but its stratigraphic position is very close to the Cleveland-Lloyd Quarry, which preserves dozens of individuals of Allosaurus and no traces of S.maximus. It's possible this was part of a transitional population between the two, but we know way too little about the evolution of Morrison allosauroids to say.

References:
-Gilmore, Charles W. (1920). "Osteology of the carnivorous dinosauria in the United States National Museum, with special reference to the genera Antrodemus (Allosaurus) andCeratosaurus" (PDF). Bulletin of the United States National Museum. 110 (110): 1–159. doi :10.5479/si.03629236.110.i .
-Madsen, James H. Jr. (1976). Allosaurus fragilis: A Revised Osteology. Utah Geological Survey Bulletin 109 (2nd ed.).
-Williamson, T.E., Chure, D. A large allosauroid from the Upper Jurassic Morrison Formation (Brushy Basin Member), West-Central New Mexico. The Continental Jurassic, Michael Morales, ed., 1996. Museum of Northern Arizona Bulletin 60.
-Chure, D., 2000, A new species of Allosaurus from the Morrison Formation of Dinosaur National Monument (Utah-Colorado) and a revision of the theropod family Allosauridae. Ph.D. dissertation, Columbia University, pp. 1–964