Fasolasuchus

Fasolasuchus is an extinct genus of loricatan. Fossils have been found in the Los Colorados Formation of the Ischigualasto-Villa Unión Basin in northwestern Argentina that date back to the Norian stage of the Late Triassic, making it one of the last "rauisuchians" to have existed before the order became extinct at the end of the Triassic.^[1][2]

Fasolasuchus Temporal range: Norian ~220–213 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Fasolasuchus in front of the sauropod Lessemsaurus, in Singapore
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Clade:	Archosauria
Clade:	Pseudosuchia
Genus:	†Fasolasuchus Bonaparte, 1981[1]
Species:	†F. tenax
Binomial name
†Fasolasuchus tenax Bonaparte, 1981[1]

Description

Diagram showing preserved portions of the skull compared to a human

Fasolasuchus is likely the largest known "rauisuchian", with an estimated length of 8 m (26 ft)^[3] to 10 m (33 ft).^[4][5] 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 metres (23 ft), and many medium sized theropods as large as Ceratosaurus.^[6][7][8] Like Saurosuchus, it had only a single row of caudal osteoderms, unusual among "rauisuchians".^[9] 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.^[10][11]

Phylogeny

Cladogram after the analysis of Nesbitt (2011):^[12]

Paracrocodylomorpha	Poposauroidea Loricata Prestosuchus Saurosuchus Batrachotomus Fasolasuchus Rauisuchidae Crocodylomorpha

Paleobiology

A model of Fasolasuchus at Talampaya National Park

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.^[7]