It was described in February 2009 from the late Campanian to early Maastrichtian Adamantina Formation of the Bauru Basin in Brazil, dating to approximately 70 Ma.
Preserved elements show the presence of a rigid shield of hexagonal osteoderms just behind the head, followed by a series of mobile bands similar to those of armadillos that give the animal its name.
Initially these rock layers were thought to be Turonian to Santonian in age, but more resent research suggests that they were much younger, dating to the Campanian to Maastrichtian.
Specimen UFRJ DG 303-R, chosen as the holotype of the taxon, is a well preserved partial skeleton retaining the entire skull, the neck and cervical ostedeorms, the front of the torso and a nearly complete left forelimb.
Further back on the upper jaw the teeth are distinctly asymmetrical, with the outer edge being relatively smooth while the side facing inward is marked by a ridge covered in a series of tubercles.
The central portion of this armor is formed by a series of overlapping osteoderms, which are rectangular in shape and ornamented with circular pits similar to those seen in other neosuchians.
Based on fragmentary remains described by Cunha and colleagues, the osteoderms of the tail ranged from being rectangular in shape to being subtriangular, but generally wider than they were long like those of the torso.
[2] While Armadillosuchus, alongside Simosuchus, is among the most heavily armored Notosuchian, a 2022 study suggests that the osteoderms may not have been visible in life in the same way they appear in modern crocodilians.
The paper specifically covers Sharpey's fibers, a collagen structure anchoring the osteoderms to the underlying layer of the skin, known as the stratum compactum.
A similar condition can be seen in today's leatherback and softshell turtles, leading the authors to suggest that the osteoderms of Armadillosuchus were deeply embedded into the skin of the animal and covered in a leathery dermis.
[6] Recent phylogenetic analysis consistently show that Armadillosuchus is a derived member of the Sphagesauridae, a family of Notosuchians endemic to South America known for their heterodont dentition.
Candidodon Libycosuchus Simosuchus Pakasuchus Malawisuchus Morrinhosuchus Llanosuchus Notosuchus Labidiosuchus Mariliasuchus Adamantinasuchus Yacarerani Caipirasuchus Sphagesaurus huenei Armadillosuchus sp.
It is possible that they would have basked in sunlight to raise their body temperature and stuck to sunlit areas while foraging, but retreated into burrows should they be under threat of overheating.
[2] A 2019 study more closely examined the teeth of Armadillosuchus using a method known as orientation patch count rotated (OPCR), originally designed to analyse the complexity of the tooth occlusion in rodents.
This method has previously shown a clear relation between the morphology of premolar and molar teeth and the diet of various animal groups, including reptiles.
[5] In addition to being favorable for digging, the stout and robust body of Armadillosuchus, combined with the underlying armor plating formed by the osteoderms, may have also been an effective deterrent against predators.