Nerepisacanthus, Strongylosteus, 'Proacanthodes' and Ischnacanthus

Nerepisacanthus denisoni (Burrow 2011; Middle Silurian, 13cm long) is the oldest near-complete acanthodian. Long tabulars readily identify this genus.

Strongylosteus hindernburgi (Henning 1925; originally Chondrosteus hindenburgi Pompeckj 1914; Early Toarcian, Early Jurassic; 3-4.5m) is traditionally considered "related to modern sturgeons, but with a different kind of mouth." Here it nests as a giant descendant of tiny spink sharks in the lobefin clade, led by Watonulus, not close to Chondrosteus.

Cheirolepis (holotype, Agassiz 1835; Pearson and Westoll 1979; Early to Middle Devonian, up to 55cm) nests as a basal spiny shark in the LRT. Fewer teeth line the deeper jaws. The tail is strongly heterocercal. Spines support the lateral fins and theskull is completely different than the classic drawing from a century ago (lowest image). No doubt the same specimen was used for both reconstructions, One traced, the older one done freehand.

Agassiz JLR 1835. Recherches sur les Poissons fossiles, 5 volumes. Imprimerie de Petitpierre et Prince, Neuchaatel, 1420 pp.

Burrow CJ 2011. A partial articulated acanthodian from the Silurian of New Brunswick, Canada. Canadian Journal of Earth Sciences. 48 (9): 1329–1341.

Burrow CJ and Rudkin D 2014. Oldest Near-Complete Acanthodian: The First Vertebrate from the Silurian Bertie Formation Konservat-Lagerstätte, Ontario. PLoS ONE 9(8): e104171. https://doi.org/10.1371/journal.pone.0104171

Deecke W 1889. Über Fische aus verschiedenen Florozonten der Trns. Palaeontographicd, 35: 97-L38, pls. 6-8, Stuttgart.

Deecke W 1911. Neueus Jahrbuch fur Minerologie 1911 (2):70.

Hennig E 1925. Chondrosteus Hindenburgi Pomp.---Ein «Stör» des württembergischen Ölschiefers (Lias\epsilon). Palaeontographica (1846-1933), 115-134.

Long JA 1995. The Rise of Fishes. Johns Hopkins University Press. Baltimore and London.

Pearson DM and Westoll TS 1979. The Devonian actinopterygian Cheirolepis Agassiz. Earth and Environmwiki/Cheirolepisental Science Transactions of The Royal Society of Edinburgh. 70(13-14):337–399.

Pompeckj JF 1914. Die Bedeutung des Schwäbischen Jura für die Erdgeschichte. Stuttgart, 1914

wiki/Strongylosteus
wiki/Nerepisacanthus
wiki/Cheirolepis