Predicated on all of our study, Roentgen
The original around three reputation says bolster brand new articulations between the face aspects of jaw musculature (Schumacher, 1973 ). The region of your abducens courage foramen try originally hypothesized since a potential synapomorphy help a beneficial crocodylomorph + aetosaur clade personal of most other pseudosuchians (Gower, 2002 ), however, more recent phylogenetic analyses, along with ours, highly recommend so it apomorphy evolved at least twice-once when you look at the aetosauriforms as soon as inside the crocodylomorphs. But not quantified within studies, an excellent dorsoventrally thickened head rooftop (we.age., nasals, frontals, and parietals) is also common because of the Roentgen. callenderi, erpetosuchids, and you will aetosaurs.
callenderi and you will aetosaurs express similarities on proportions of this new hindlimb to help you forelimb and you will form of the new humerus and you may proximal foot facets, regardless if people similarities just weren’t unambiguous synapomorphies. Specifically, R. callenderi and you may aetosaurs express a reduced distance in accordance with the fresh new humerus, and a great concave rear epidermis of your own calcaneal tuber, though such apomorphies features a very extensive shipping certainly Archosauria. Roentgen. callenderi and you can aetosaurs share center trunk area vertebrae with diapophyses and parapophyses you to develop sideways where both articulations originate with the an excellent transverse processes. High aetosaurs (elizabeth.g. https://datingranking.net/tr/afrointroductions-inceleme/, D. spurensis, MNA V9300; T. coccinarum, NMMNH P-12964; Parker, 2008 ; Heckert et al., 2010 ) grow these methods laterally and you will partly otherwise completely coossify them to the fresh new respective rib to make a general dorsal body. The brand new expansion of transverse process when you look at the R. callenderi and other aetosaurs seems to correlate to your presence from wider osteoderms. Likewise, but not quantified from the phylogenetic investigation, R. callenderi and you may aetosaurs express a good hypertrophied last trochanter of your own femur, a character county prior to now noticed book to aetosaurs (Brief, 2002 ).
This new parallels of osteoderms of Roentgen. callenderi, aetosaurs, and An excellent. geoffreyi bring additional support with the the new clade, Aetosauriformes, showed here. callenderi, A great. geoffreyi, and you can aetosaurs show the next carapacial synapomorphies (Figure several): (a) the presence of lateral osteoderms at least from the trunk part (along with within erpetosuchids); (b) an enthusiastic anterior club on the prior side of this new osteoderm (as well as shared with E. olseni and you can crocodylomorphs); (c) an excellent ventral carapace on the trunk area; and you may (d) presacral dorsal osteoderms that are broad than just a lot of time. Covered with a full band of paramedian, lateral, and ventral osteoderms, new osteoderm plans from R. callenderi and you will A. geoffreyi each other end up like that aetosaurs ( ).
Obviously there’s nevertheless a large morphological pit within skeletal morphology away from R. callenderi hence away from aetosaurian people in Aetosauriformes because of the highest assistance into monophyly of the many most other aetosaurs within this study although some (elizabeth.grams., ). Pursuing the divergence off Roentgen. callenderi + An excellent. geoffreyi and aetosaurs using their preferred predecessor, brand new head, carapace, and postcranial skeleton away from aetosaurs undergone then evolutionary transformations according to most other diapsids. The newest skulls out-of aetosaurs display changes of anterior part of the fresh new head by elongating the fresh new premaxillae in order to create an anteroposteriorly increased external naris; the fresh supratemporal fenestra turned sideways built, and in the brand new mandible brand new anterior dentition is reduced and you can turned “slipper-shaped” (Desojo mais aussi al., 2013 ; Reyes et al., 2020 ). The new carapace from aetosaurs became way more detailed, level probably the ventral portion of the end (Heckert ainsi que al., 2010 ). The fresh postcranial bones is actually further altered to compensate for the heavier carapace having hypertrophied limb elements (similar to ankylosaur dinosaurs) such as the strong humeri and you may tibiae plus a beneficial obvious olecranon means of the fresh new ulna. Having an around similar armour carapace can it be not surprising that these same elements in Roentgen. callenderi have become comparable within degree of robustness.