Based on our analysis, R
The initial about three profile says reinforce the articulations amongst the face factors regarding the jaw musculature (Schumacher, 1973 ). The region of your own abducens bravery foramen was originally hypothesized because the a potential synapomorphy supporting a beneficial crocodylomorph + aetosaur clade exclusive out-of almost every other pseudosuchians (Gower, 2002 ), but more recent phylogenetic analyses, as well as ours, strongly recommend this apomorphy developed at least twice-immediately after within the aetosauriforms and once inside the crocodylomorphs. But not quantified within this investigation, a dorsoventrally thickened skull roof (we.elizabeth., nasals, frontals, and you may parietals) is additionally mutual because of the Roentgen. callenderi, erpetosuchids, and you can aetosaurs.
callenderi and you can aetosaurs display parallels about size of new hindlimb to forelimb and you may shape of the new humerus and you may proximal foot issue, in the event those similarities weren’t unambiguous synapomorphies. Specifically, R. callenderi and you will aetosaurs share a reduced radius according to the humerus, and a beneficial concave posterior surface of calcaneal tuber, even in the event such apomorphies features a very prevalent shipments certainly one of Archosauria. R. callenderi and you may aetosaurs show center trunk area vertebrae that have diapophyses and parapophyses you to definitely expand sideways where one another articulations originate towards a beneficial transverse process. Higher aetosaurs (e.grams., D. spurensis, MNA V9300; T. coccinarum, NMMNH P-12964; Parker, 2008 ; Heckert et al., 2010 ) grow these methods laterally and partially or totally coossify them to the latest particular rib to form a standard dorsal surface. New expansion of the transverse techniques for the R. callenderi or any other aetosaurs seems to associate towards visibility regarding greater osteoderms. Likewise, yet not quantified regarding phylogenetic research, R. callenderi and aetosaurs show good hypertrophied fourth trochanter of one’s femur, a characteristics condition in past times thought unique in order to aetosaurs (Short, 2002 ).
This new parallels of one’s osteoderms out of Roentgen. callenderi, aetosaurs, and you may A. geoffreyi offer even more assistance to the the new clade, Aetosauriformes, exhibited right here. callenderi, Good. geoffreyi, and aetosaurs display the following carapacial synapomorphies (Contour several): (a) the clear presence of horizontal osteoderms at the least regarding trunk area part (plus within erpetosuchids); (b) a keen prior pub located on the prior side of the osteoderm (plus distributed to Elizabeth. olseni and you can crocodylomorphs); (c) an effective ventral carapace on the trunk area; and you will (d) presacral dorsal osteoderms which might be broad than simply a lot of time. Covered with a full band of paramedian, lateral, and you can ventral osteoderms, new osteoderm preparations off R. callenderi and you will Good. geoffreyi one another be like that of aetosaurs ( ).
Clearly there can be nonetheless a large morphological gap amongst the skeletal morphology regarding R. callenderi and this out of aetosaurian members of Aetosauriformes given the highest service on the monophyly of all the other aetosaurs in this studies and others (elizabeth.g., ). Adopting the divergence regarding R. callenderi + An effective. geoffreyi and you can aetosaurs off their common predecessor, the new head, carapace, and you may postcranial skeleton away from aetosaurs undergone then evolutionary transformations in accordance with most other diapsids. Brand new skulls out of aetosaurs showcase changes of your prior percentage of this new head by the elongating the newest premaxillae to make an enthusiastic anteroposteriorly enlarged external naris; the supratemporal fenestra turned into laterally dependent, and also in this new mandible the new prior dentition try less and you will turned “slipper-shaped” (Desojo mais aussi al., 2013 ; Reyes mais aussi al., 2020 ). The datemyage ekЕџi latest carapace off aetosaurs became so much more extensive, covering probably the ventral portion of the end (Heckert ainsi que al., 2010 ). The fresh new postcranial bones is actually further altered to pay with the hefty carapace with hypertrophied limb elements (the same as ankylosaur dinosaurs) for instance the powerful humeri and tibiae in addition to an excellent noticable olecranon procedure for the latest ulna. That have a very nearly identical armor carapace is it not surprising that these types of exact same points in R. callenderi have become similar within level of robustness.