5.6.4 Sacral spinal vertebrae
Several remote sacral centra was basically built-up (age.g., PEFO 33875 and 33819), nevertheless sacral rib and you can sensory arc is actually damaged off. What amount of sacral spinal vertebrae is set getting two founded on: (a) a few collection of sacral rib scars to your ilia out-of Roentgen. callenderi; (b) a couple ankylosed centra (PEFO 36876) having clear articulations having ribs and you will sensory arches (Numbers 8i–k); and you may (c) truth be told there appear to be simply a couple morphologies from sacral vertebrae among blackcupid indir the brand new isolated specimens. The two ankylosed centra implies that particular specimens out of Roentgen. callenderi may coossify the sacral spinal vertebrae and therefore that it character is changeable during the taxon. Since the all the specimens out-of PFV 297 is out-of similar dimensions, so it coossification in some specimens does not seem to be proportions related. As an alternative, due to the fact within the ventral view the horizontal expansions of one’s centra doing the fresh ankylosed city aren’t perfectly symmetrical, that it collection you may depict an excellent pathology and extra specimens are essential to confirm it.
Brand new sacral centra is actually elongate and you can mediolaterally greater than dorsoventrally tall, in addition to centrum faces try amphicoelous (Figures 8i–k). The next sacral rib articulates with a lot of of horizontal body of your centrum and a portion of the ventrolateral body of your neural arc (PEFO 36876). In the dorsal glance at, the sacral rib of one’s second sacral vertebra increases considerably to your an enthusiastic anteroposteriorly elongate articulation towards ilium (Shape 8l). Into the horizontal glance at, that it articulation facial skin try cigar-shaped; it articulates with many of length of brand new postacetabular process of one’s ilium. The newest anterior portion of the articulation is actually some convex with a beneficial moderate dorsomedial expansion. All of those other articular skin is concave. The articular body of the centrum and also the 2nd sacral rib is circular for the horizontal view (Shape 8k). A transverse ridge separates the brand new articular surface on the two parts, a lesser part that meets into a position towards the horizontal area of the 2nd sacral centrum, and you may a higher part that articulates toward neural arc. Brand new neural arch is not better-preserved in virtually any sample; this new prezygapophysis try based 60° off lateral therefore the postzygapophysis is actually oriented simply 10° off lateral (although they’re slightly floor).
The complete quantity of caudal spinal vertebrae contained in Roentgen. callenderi are unknown; not, discover at the 34–thirty six caudal vertebrae regarding the aetosaurian A good. ferratus (J.B. Desojo, private correspondence, 2021), and you may a similar count was within the aetosauriform R. callenderi (Shape 7; Nesbitt, 2011 ; ).
5.six.5 Anterior and you can middle-caudal backbone
Prior caudal backbone (Figure 8m) has actually hourglass-designed centra into the ventral see which might be anteroposteriorly more than mediolaterally large and you may deeply grooved ventrally (age.g., PEFO 34561). So it groove grows in the anterior and rear comes to an end which can be marked from the type of ridges. The prior end merges having two posteriorly much more likely faces, which serve as the latest articulation counters with the chevrons. These types of range from brand new connect-like chevron facets of certain rauisuchids (elizabeth.g., UCMP 124890; A lot of time & Murry, 1995 : fig. 130c). While the anteriormost caudal vertebra isn’t managed, this is simply not obvious at which put the chevrons initiate. The newest articular face is round and amphicoelous that have clear wheels. The latest neural arch was reduced, or around half the fresh new top of your centrum articular deal with. The prezygapophysis is well-put up forming a beneficial posteroventrally, and medially centered apartment articular body. This new distal margins of each other prezygapophyses combine together and are also confluent towards anterior side of the fresh new sensory spine. The fresh spine are anteroposteriorly wide which have an even rear border and you can an anteroventrally slanting anterior line. The brand new apex is not extended into a well-arranged lower back dining table. The postzygapophysis is significantly tall (about double the brand new level) than the prezygapophysis. The horizontal margin is almost straight, additionally the articular surface is more likely ventromedially regarding forty-five° and you may face slightly posteriorly.