Fasolasuchus

Description

Fasolasuchus is likely the largest known "rauisuchian", with an estimated length of 8 m to 10 m.{{cite book | access-date = 14 September 2022 |editor-first=Julia Brenda |editor-last=Desojo |editor-first2=Randall B.|editor-last2= Irmis |editor-last3=Nesbitt |editor-first3=Sterling J. |editor-link3=Sterling Nesbitt This would make Fasolasuchus the largest terrestrial predator to have ever existed save for large theropods, surpassing the Cenozoic Barinasuchus, the rauisuchian counterpart Saurosuchus at 7 m, and many medium-sized theropods as large as Ceratosaurus. It had two rows of osteoderms along its back, these were likely in a one-to-one ratio with the vertebrae, but like Saurosuchus, it had only a single row on the tail, unusual among rauisuchians. It also had a hyposphene-hypantrum articulation that gave the vertebral column extra rigidity. This feature is also seen in several other rauisuchians such as Postosuchus as well as saurischian dinosaurs.

In the smaller individual (the holotype) the femur is 70 cm in length, double that of the fibula (35 cm).

Paleobiology

A study on bone microstructure determined that Fasolasuchus had a relatively fast growth rate, similar to most other rauisuchians, with the exception of Prestosuchus. The same study also determined that the specimen was somatically and skeletally mature, but it wasn't possible to determine sexual maturity: this may be due to taphonomic causes, however the bone cortex was mostly preserved and didn't show the changes in bone matrix or in vascularization that would be expected if the specimen was sexually mature. Alternatively, Fasolasuchus attained sexual maturity contemporaneously to or slightly later than somatic and skeletal maturity (although this growth pattern is today only found in birds, not crocodilians), or there were differences in the timing of maturity of different bones in the same individual, as reported in the tuatara and in some dinosaurs.

Phylogeny

Cladogram after the analysis of Nesbitt (2011):

References

References

1. Bonaparte, José F.. (March 1984). "Locomotion in rauisuchid thecodonts". [[Journal of Vertebrate Paleontology]].
2. (24 January 2013). "Rauisuchia". Geological Society, London, Special Publications.
3. Nesbitt, Sterling J.. (2011). "The Early Evolution of Archosaurs: Relationships and the Origin of Major Clades". Bulletin of the American Museum of Natural History.
4. (2016-07-30). "Cenozoic dinosaurs in South America – revisited". Memoirs of Museum Victoria.
5. (2023-07-31). "Palaeobiological inferences of "rauisuchians" Fasolasuchus tenax (Los Colorados Fm., Argentina) and Prestosuchus chiniquensis (Santa Maria Super sequence, Brazil) from the Middle-Upper Triassic of South America based on microstructural analyses". Journal of Anatomy.
6. (2023-08-16). "Functional morphology of the Triassic apex predator Saurosuchus galilei (Pseudosuchia: Loricata) and convergence with a post-Triassic theropod dinosaur". The Anatomical Record.
7. Sulej, Tomasz. (11 March 2005). "A new rauisuchian reptile (diapsida: archosauria) from the Late Triassic of Poland". [[Journal of Vertebrate Paleontology]].
8. (June 2007). "A revision of ''Poposaurus gracilis'' (Archosauria: Suchia) based on two new specimens from the Late Triassic of the southwestern U.S.A.". [[PalZ.
9. Apesteguia, Sebastian. (2005). "Thunder-lizards: the Sauropodomorph dinosaurs". Indiana University Press.
10. Nesbitt, Sterling J.. (2011). "The early evolution of archosaurs: relationships and the origin of major clades". [[Bulletin of the American Museum of Natural History]].