Based on all of our analysis, R
The first three profile states bolster the fresh articulations between your facial issue from the mouth musculature (Schumacher, 1973 ). The region of your own abducens bravery foramen is actually to start with hypothesized just like the a potential synapomorphy supporting an effective crocodylomorph + aetosaur clade private of almost every other pseudosuchians (Gower, 2002 ), however, more recent phylogenetic analyses, as well as ours, highly recommend this apomorphy progressed at least twice-just after from inside the aetosauriforms and once inside the crocodylomorphs. not quantified in this investigation, a good dorsoventrally thickened skull rooftop (i.elizabeth., nasals, frontals, and you may parietals) is also mutual by the Roentgen. callenderi, erpetosuchids, and you may aetosaurs.
callenderi and you may aetosaurs share similarities throughout the dimensions of brand new hindlimb so you’re able to forelimb and you will shape of this new humerus and you may proximal foot elements, whether or not the individuals parallels weren’t unambiguous synapomorphies. Especially, R. callenderi and you may aetosaurs show a shortened distance according to the new humerus, and you will good concave rear skin of the calcaneal tuber, in the event these apomorphies have a extensive shipment certainly Archosauria. Roentgen. callenderi and you may aetosaurs share middle trunk area backbone with diapophyses and you will parapophyses one to build laterally where both articulations originate for the a transverse process. High aetosaurs (e.g., D. spurensis, MNA V9300; T. coccinarum, NMMNH P-12964; Parker, 2008 ; Heckert mais aussi al., 2010 ) develop these processes laterally and you can partially or completely coossify these to the newest respective rib to make a standard dorsal facial skin. The expansion of your transverse processes inside the Roentgen. callenderi or other aetosaurs generally seems to correlate with the presence out-of wider osteoderms. As well, although not quantified from the phylogenetic investigation, R. callenderi and you may aetosaurs express a good hypertrophied 4th trochanter of your own femur, a nature county in earlier times sensed novel in order to aetosaurs (Short, 2002 ).
The brand new similarities of your own osteoderms out of Roentgen. callenderi, aetosaurs, and you will A. geoffreyi render even more help to the this new clade, Aetosauriformes, displayed here. callenderi, A good. geoffreyi, and you will aetosaurs express the second carapacial synapomorphies (Profile twelve): (a) the current presence of horizontal osteoderms at least on the trunk area part (also present in erpetosuchids); (b) an anterior club found on the anterior edge of the fresh new osteoderm (along with shared with E. olseni and you will crocodylomorphs); (c) a beneficial ventral carapace throughout the trunk; and you may (d) presacral dorsal osteoderms which might be large than simply enough time. Covered with a full gang of paramedian, horizontal, and you will ventral osteoderms, the osteoderm arrangements out of R. callenderi and you can Good. geoffreyi each other resemble compared to aetosaurs ( ).
Clearly there is certainly still a huge morphological pit amongst the skeletal morphology off Roentgen. callenderi and that off aetosaurian people in Aetosauriformes because of the highest service into the monophyly of the many most other aetosaurs within data while some (e.g., ). Following divergence out-of R. callenderi + A good. geoffreyi and you can aetosaurs using their popular ardent oturum aГ§Д±n ancestor, the new head, carapace, and you may postcranial skeleton regarding aetosaurs underwent next evolutionary changes in line with other diapsids. Brand new skulls from aetosaurs display modifications of anterior part of the brand new head because of the elongating the fresh new premaxillae to make an enthusiastic anteroposteriorly enlarged outside naris; the new supratemporal fenestra turned into sideways oriented, plus the latest mandible the fresh prior dentition are quicker and you may turned into “slipper-shaped” (Desojo mais aussi al., 2013 ; Reyes et al., 2020 ). The brand new carapace out-of aetosaurs turned a whole lot more detailed, level possibly the ventral part of the tail (Heckert et al., 2010 ). The postcranial bones is after that modified to compensate into the big carapace with hypertrophied limb factors (exactly like ankylosaur dinosaurs) like the robust humeri and you can tibiae together with a good obvious olecranon means of the ulna. With an about the same armor carapace is-it no surprise these exact same factors inside the Roentgen. callenderi have become comparable inside their standard of robustness.