The late Viséan anthracosauroid Eldeceeon rolfei from the East Kirkton Limestone of Scotland is re-described. Information from two originally described and two newly identified specimens broadens our knowledge of this tetrapod. A detailed account of individual skull bones and a revision of key axial and appendicular features are provided, alongside the first complete reconstructions of the skull and lower jaw and a revised reconstruction of the postcranial skeleton. In comparison to Silvanerpeton, the only other anthracosauroid from East Kirkton, Eldeceeon is characterised by a proportionally wider semi-elliptical skull, comparatively smaller nostrils set farther apart, smaller and more rounded orbits, a shorter skull table with gently convex lateral margins, and a deeper suspensorium with a straight posterior margin and a small dorsal embayment. The remarkably large hind feet and elongate toes of Eldeceeon presumably represent an adaptation for attaining high locomotory speed through increased stride length and reduced stride frequency. This would necessitate great muscle force but few muscle contractions. At the beginning of a new stride cycle, repositioning the pes anteriorly and lifting the toes off the ground would require a strong and large muscle to pull the femur upward and rotate it inward and forward. It is hypothesised that such muscle might correspond to the puboischiofemoralis internus 2, which would extend along the posterior half of the vertebral column, consistent with the occurrence of long, curved ribs in the anterior half of the trunk. Using maximum parsimony and Bayesian inference, cladistic analyses of all major groups of stem amniotes retrieve a sister group relationship between Eldeceeon and Silvanerpeton, either as the most plesiomorphic stem amniote clade or as a clade immediately crownward of anthracosauroids.

Two distinct species have been recently recognized for the genus Sotalia: S. fluviatilis, occurring in the Amazon River basin, and S. guianensis, from Honduras (15°58′N and 85°42′W) to Santa Catarina State (Florianópolis, southern Brazil—27°35′S and 48°34′W). For the first time the sternum and the appendicular skeleton of the two species of the genus Sotalia are compared. A comparative osteological work was performed with marine samples (from the States of Ceará, north-eastern and Santa Catarina, southern regions of Brazil) and riverine samples (Amazonas State) in relation to metric characters (scapula, flipper and sternum). There was a clear distinction of two species in relation to postcranial skeleton in the morphometric analysis (canonical variate analysis) presented. The flipper and the glenoid cavity of the scapula were proportionally wider in the fluvial species. The sternum, however, was smaller in this species in relation to the maximum width of the manubrium. Nevertheless, this structure still needs to be further studied.

The postcranial skeleton of Ariekanerpeton sigalovi (Seymouriamorpha: Discosauriscidae; Lower Permian, Tadzhikistan) differs from that of like-sized Discosauriscus specimens in showing: wider interclavicle anterior plate with smaller, rhomboidal sculptured field on its ventral surface not reaching plate posteromedial margins; broader interclavicle plate-stem junction; slightly narrower interclavicle posterior stem; anteroposteriorly narrower clavicle ventral plate with convex posterior margin; shorter, more robust humerus; four phalanges on fourth manus digit (five phalanges in Discosauriscus); ilium more elongate dorsoventrally with anteroposteriorly narrower neck; posterior process of iliac blade oriented distinctly posterodorsally rather than horizontally; more gracile atlantal rib; broadened distal end of second presacral rib. A revised cladistic analysis of the best known seymouriamorph species retrieves Ariekanerpeton either as sister group to both species of Discosauriscus, or to D. austriacus only.