Ptomacanthus


Ptomacanthus is an extinct genus of spiny shark, an early relative of living cartilaginous fishes.

Location found

Ptomacanthus is known mainly from the Old Red Sandstone of the UK. The most completely known genus, P. anglicus is known from several articulated fossils from Wayne Herbert Quarry, Herefordshire, UK. Two indeterminate species are known from shoulder-girdles recovered from Castle Mattock Quarry, Herefordshire, UK, and Zaleszychi, Ukraine.

Description

The only species known in any detail, P. anglicus was a fish about 25 cm long. Like other acanthodians it had small, shark like scales, and a suite of fin-spines in front of its dorsal, pectoral, and pelvic fins.

Paleobiology

P. anglicus is important to our understanding of early vertebrate evolution as it preserves part of the braincase, a scientifically informative part of the skeleton. Because of the cartilaginous makeup of the acanthodian internal skeleton, it is very rarely preserved, and the braincase of Ptomacanthus is only the second acanthodian braincase known to science. The description of this braincase reignited debate over the relationships of acanthodians as well as those of early vertebrates more generally.