One another PEFO 34561 and you may PEFO 34269 uphold limited 2nd sacral spinal vertebrae

One another PEFO 34561 and you may PEFO 34269 uphold limited 2nd sacral spinal vertebrae

5.6.4 Sacral backbone

Several remote sacral centra were built-up (age.g., PEFO 33875 and you will 33819), nevertheless sacral rib and you may neural arc try broken of. The amount of sacral backbone is determined become several situated on: (a) several line of sacral rib markings into ilia out-of Roentgen. callenderi; (b) two ankylosed centra (PEFO 36876) having obvious articulations to possess ribs and neural arches (Figures 8i–k); and you can (c) truth be told there seem to be only two morphologies of sacral spinal vertebrae certainly the fresh new separated specimens. Both ankylosed centra demonstrates that some specimens out of R. callenderi may coossify the sacral vertebrae and that that it reputation is changeable in the taxon. Due to the fact all the specimens from PFV 297 is of equivalent size, it coossification in a few specimens will not seem to be proportions related. As an alternative, once the in the ventral view the horizontal expansions of the centra around the newest ankylosed city commonly well symmetrical, this mixing you will show an excellent pathology and extra specimens are essential to confirm it.

The newest sacral centra is actually elongate and you may mediolaterally broad than simply dorsoventrally significant, and the centrum faces is actually amphicoelous (Figures 8i–k). Another sacral rib articulates with a lot of of lateral skin of centrum and you can an element of the ventrolateral facial skin of neural arch (PEFO 36876). During the dorsal glance at, this new sacral rib of your second sacral vertebra increases considerably towards the an enthusiastic anteroposteriorly elongate articulation into the ilium (Contour 8l). In horizontal check, which articulation epidermis was cigar-shaped; that it articulates with most of amount of the postacetabular techniques of your ilium. The brand new prior part of the articulation try slightly convex that have a slight dorsomedial expansion. The rest of the articular facial skin are concave. This new articular body of one’s centrum while the second sacral rib is actually circular in the horizontal consider (Figure 8k). An excellent transverse ridge separates the latest articular epidermis toward two-fold, a reduced part that suits on the a slot on lateral section of the 2nd sacral centrum, and you will an upper area one to articulates into neural arc. The brand new sensory arc is not better-preserved in almost any specimen; this new prezygapophysis is actually created sixty° away from lateral together with postzygapophysis try situated simply ten° off lateral (although they’re somewhat floor).

The complete quantity of caudal backbone contained in R. callenderi is actually unknown; although not, you can find on 34–thirty-six caudal vertebrae about aetosaurian A good. ferratus (J.B. Desojo, private communications, 2021), and you will the same count was contained in the latest aetosauriform Roentgen. callenderi (Figure eight; Nesbitt, 2011 ; ).

5.6.5 Prior and you will middle-caudal backbone

Prior caudal backbone (Contour 8m) keeps hourglass-designed centra into the ventral take a look at which might be anteroposteriorly more than mediolaterally wide and you may seriously grooved ventrally (age.grams., PEFO 34561). It groove grows within prior and you will posterior stops that will be marked by distinct ridges. The newest prior end merges with several posteriorly much more likely faces, and this act as the newest articulation surfaces to your chevrons. Such vary from the brand new hook-for example chevron components of certain rauisuchids (e.grams., UCMP 124890; Long & Murry, 1995 : fig. 130c). Since anteriormost caudal vertebra isn’t managed, this is simply not clear from which put the chevrons begin. New articular face is bullet and you may amphicoelous having clear tires. This new sensory arch is actually low, or about half the top of one’s centrum articular face. The fresh new prezygapophysis try really-put up creating a beneficial posteroventrally, and you may medially established flat articular skin. The fresh new distal margins from each other prezygapophyses merge together and are generally confluent to the anterior side of the latest neural spine. New lower back try anteroposteriorly large which have a straight posterior line and you may an anteroventrally slanting prior border. The fresh new top is not longer to your a well-set-up lower back desk. The brand new postzygapophysis is a lot tall (about twice new peak) versus prezygapophysis. The horizontal margin is close to straight, additionally the articular epidermis try more inclined ventromedially regarding 45° and you can faces slightly posteriorly.

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