Predicated on all of our studies, R
The first about three profile claims reinforce the latest articulations amongst the face aspects with the mouth musculature (Schumacher, 1973 ). The location of abducens courage foramen are to start with hypothesized as a possible synapomorphy supporting a beneficial crocodylomorph + aetosaur clade personal from almost every other pseudosuchians (Gower, 2002 ), however, more recent phylogenetic analyses, in addition to ours, highly recommend which apomorphy advanced at least twice-just after in aetosauriforms and once inside crocodylomorphs. Although not quantified within this study, a dorsoventrally thickened head rooftop (i.e., nasals, frontals, and parietals) is even common by R. callenderi, erpetosuchids, and aetosaurs.
callenderi and you will aetosaurs express similarities regarding the dimensions of brand new hindlimb so you’re able to forelimb and you may form of this new humerus and you will proximal foot issues, regardless of if those people parallels were not unambiguous synapomorphies. Especially, R. callenderi and you will aetosaurs express a shortened radius in accordance with the humerus, and you can good concave posterior surface of your own calcaneal tuber, in the event this type of apomorphies features a more extensive shipment one of Archosauria. R. callenderi and you may aetosaurs show middle trunk area backbone having diapophyses and you can parapophyses that build sideways where both articulations originate toward a transverse procedure. Large aetosaurs (e.grams., D. spurensis, MNA V9300; T. coccinarum, NMMNH P-12964; Parker, 2008 ; Heckert mais aussi al., 2010 ) grow these procedures laterally and you will partly or completely coossify these to the fresh respective rib to create a broad dorsal body. The extension of one’s transverse process within the R. callenderi or any other aetosaurs appears to associate towards the presence away from broad osteoderms. While doing so, not quantified in the phylogenetic analysis, Roentgen. callenderi and you can aetosaurs show a great hypertrophied last trochanter of the femur, a characteristics state in past times thought novel so you’re able to aetosaurs (Small, 2002 ).
The latest parallels of your own osteoderms off R. callenderi, aetosaurs, and you will An excellent. geoffreyi render a lot more support with the the new clade, Aetosauriformes, shown right here. callenderi, An excellent. geoffreyi, and aetosaurs display the second carapacial synapomorphies (Contour twelve): (a) the current presence of horizontal osteoderms at the least from the trunk area (also contained in erpetosuchids); (b) a keen prior club found on the prior edge of the fresh osteoderm (and additionally distributed to Elizabeth. olseni and you will crocodylomorphs); (c) a ventral carapace throughout the trunk; and you will (d) presacral dorsal osteoderms which might be greater than just long. Covered with a complete group of paramedian, lateral, and you may ventral osteoderms, the latest osteoderm arrangements out-of Roentgen. callenderi and you will A. geoffreyi one another be like compared to aetosaurs ( ).
Obviously there clearly was however a big morphological pit between the skeletal morphology from Roentgen. callenderi and this out-of aetosaurian people in Aetosauriformes given the highest assistance on the monophyly of all the other aetosaurs in this investigation while others (age.g., ). Following divergence out-of Roentgen. callenderi + An excellent. geoffreyi and you can aetosaurs using their well-known ancestor, the fresh skull, carapace, and you can postcranial bones from aetosaurs underwent after that evolutionary transformations according to almost every other diapsids. New skulls regarding aetosaurs display changes of your anterior part of the fresh new head by the elongating brand new premaxillae to form an anteroposteriorly expanded external naris; the brand new supratemporal fenestra turned laterally oriented, and in new mandible new anterior dentition is actually quicker and you will became “slipper-shaped” (Desojo ainsi que apex al., 2013 ; Reyes mais aussi al., 2020 ). New carapace of aetosaurs became even more thorough, level perhaps the ventral portion of the tail (Heckert ainsi que al., 2010 ). The fresh postcranial bones was after that changed to compensate to the heavy carapace having hypertrophied limb facets (just like ankylosaur dinosaurs) such as the robust humeri and you may tibiae together with a beneficial noticable olecranon procedure of the fresh ulna. With a practically identical armor carapace is it no wonder these types of exact same facets during the R. callenderi are particularly equivalent inside their standard of robustness.