Redescription ofParexus recurvus, an Early Devonian acanthodian from the Midland Valley of Scotland

The diplacanthid fishes (Acanthodii, Diplacanthiformes, Diplacanthidae) from the Middle Devonian of Scotlan

“…Doliodus and Diplacanthus are coded (0), Mesacanthus and Rhadinacanthus are coded (1), based on Gross (1947) and this paper; Lupopsyrus is coded (0) based on Hanke and Davis (2012); Parexus is coded (0) based on Burrow et al (2013). 13.…”

“…Brachyacanthus, Climatius, and Doliodus are coded (1), Diplacanthus and Rhadinacanthus are coded (0) based on Gross (1947); Parexus is coded (1) based on Burrow et al (2013). 12.…”

Morphology and histology of acanthodian fin spines from the late Silurian Ramsåsa E locality, Skåne, Swede

“…This morphotype is here interpreted as a pectoral spine, because of its strong curvature and overall likeness to climatiid and diplacanthiid pectoral spines illustrated by Miles (1973, figure 33) and Burrow et al (2016, figures 5.4, 14) respectively. However, it also shares similarities with the dorsal fin spines of some climatiid acanthodians (compare Burrow, 2007, figure 5; Burrow et al, 2013, figure 7B). Unlike the other climatiid fin spines from Ramsåsa, morphotype C is composed entirely of dentine.…”

“…Indeed, Vergoossen (2004) suggested a dorsal, median position of similar spines that were figured by Gross (1971, plate 8, figure 19, 22b, 24). The posterior dorsal fin spines in climatiids are generally smaller, straight, and often lack denticles (e.g., Burrow et al, 2013, figure 7), which could suggest such an affinity for morphotype G. Vergoossen (2004) only reported two "gomphonchid" scales and no poracanthodids from the residues associated with the macro-remains at the NRM, but other samples from Ramsåsa site E contained poracanthodid scales. Regarding this, and the uncertainties surrounding the morphological and histological distinctiveness of these remains when found disarticulated, morphotypes D-F are here regarded as ischnacanthiform spines.…”

“…Abbreviations: cc, central cavity; k, keel; med.c, median canal; r, ribbing; rib.c, ribbing canals; s, sulcus. squamation in early gnathostomes (e.g., Trinajstic, 2001;Brazeau, 2012;Burrow, 2013;Burrow et al, 2013Burrow et al, , 2015Burrow et al, , 2016Chevrinais et al, 2017) will undoubtedly influence future designations of isolated material. On the other hand, the taxonomical framework based on isolated material that Vergoossen (2004) described from Ramsåsa site E may enable an assignment of the spines treated herein on a higher taxonomic level.…”