A re-assessment of the oldest therapsid Raranimus confirms its status as a basal member of the clade and fills Olson’s gap

The origin and evolution of Cynodontia (Synapsida, Therapsida): Reassessment of the phylogeny and systematics of the earliest members of this clade using 3D‐imaging technologies

“…By contrast, in the gomphodont Boreogomphodon , the maxillary canal has a unique morphology in which it arises laterally from the maxillary sinus (Figure 9p). A comparable morphology has not yet been described for any other non‐mammalian therapsid with a described maxillary canal system (Benoit et al, 2018, 2019, 2021; Benoit, Manger, Fernandez, & Rubidge, 2016; Benoit, Manger, Norton, et al, 2017; Benoit, Manger, & Rubidge, 2016; Benoit, Norton, Manger, & Rubidge, 2017; Duhamel et al, 2021; Pusch et al, 2019, 2020). In the basal therocephalian Lycosuchus , the caudal part of the maxillary canal gives off two branches for the alveolar canals of the CNV 2 , which radiate from the same point within the maxillary canal (Figure 9a,p), and probably represent the caudal and medial alveolar canals (Pusch et al, 2020).…”

“…This technology has been instrumental in understanding such topics as tooth replacement, internal snout and braincase morphology, brain and bony labyrinth evolution, facial innervation, and the origins of endothermy in synapsids. Although endocranial characters have been described for various therapsids in CT-assisted studies in recent years (e.g., Araújo et al, 2017Araújo et al, , 2018Bendel et al, 2018;Benoit et al, 2018Benoit et al, , 2019Benoit et al, , 2021Benoit et al, , 2022Benoit, Jasinoski, Fernandez, & Abdala, 2017;Benoit, Manger, Fernandez, & Rubidge, 2016, 2017Castanhinha et al, 2013;Duhamel et al, 2021;Gigliotti et al, 2023;Laaß, 2015aLaaß, , 2015bLaaß, , 2016Pusch et al, 2020), with special focus on cynodonts due to their importance for mammal origins (e.g., Abdala et al, 2013;Benoit, 2023;Crompton, 2013;Crompton et al, 2015;Crompton, Owerkowicz, et al, 2017;Huttenlocker & Sidor, 2020;Jasinoski et al, 2015;Kemp, 2009;Kerber et al, 2021Kerber et al, , 2024Norton et al, 2020Norton et al, , 2021Pavanatto et al, 2019;Pusch et al, 2019Pusch et al, , 2021Pusch et al, , 2023Rodrigues et al, 2013Rodrigues et al, , 2014Rodrigues et al, , 2018Rowe et al, 1995…”

Enigmatic humerus from the mid-Permian of South Africa bridges the anatomical gap between “pelycosaurs” and therapsids

“…Alternatively, BP/1/7395 may be a highly derived, late-surviving member of a monophyletic Sphenacodontidae which is partially convergent with therapsids. Irrespective of the length of the therapsid ghost lineage, high-precision geochronology constrains the Karelskraal Member to 260.8–260.23 Ma (Day et al, 2022), indicating that the form of primitive synapsid represented by BP/1/7395 persisted ∼10 Ma after Raranimus dashankouensis , the oldest-known probable therapsid (Duhamel et al, 2021; Liu et al, 2009). Raranimus is thus far represented by a single partial snout, rendering it difficult to evaluate whether cranial characters evolved at similar or different rates to postcranial characters during the transition to therapsids.…”

“…Notably, the earliest-known therapsids are already highly distinct from their sister group, the sphenacodontid "pelycosaurs," diagnosed by dozens of cranial and postcranial synapomorphies (Kemp, 2006;Sidor & Hopson, 1998). Given the exceptionally long ghost lineage separating the oldest known, well-supported members of Sphenacodontidae and Therapsida (>30 Ma; Duhamel et al, 2021;Sidor & Hopson, 1998), this level of morphological disparity is not unexpected. However, the dearth of more intermediate forms obfuscates attempts to understand the pattern of anatomical transformation from "pelycosaurs" to therapsids.…”

On taxonomic issues, ontogenetic series and tooth replacement. Comments on Diphyodont tooth replacement of Brasilodon—A late Triassic eucynodont that challenges the time of origin of mammals by Cabreira et al.

“…Computed tomography techniques have become more frequently used in palaeontology because they are non-destructive (e.g. Chang et al, 2021;D'Emic et al, 2013;Duhamel et al, 2021;He et al, 2018;Olroyd et al, 2021;Pusch et al, 2019Pusch et al, , 2020Snyder et al, 2020), and we considered that the data necessary to analyse dental replacement in our material by using this technique was sufficient. It is important to mention here that we have highresolution sub-micron synchrotron X-ray μCT data of the dentition of Thrinaxodon where the dentine-enamel junction, among other features, is clearly visible.…”