The next hurdle in the fish subset of the LRT: the humpback transition

Several extinct fish
have a buffalo-like hump in their back (Fig 1). We’ll look at two today and more later.

Figure 1. Middle Devonian Cheiracanthus compared to Late Jurassic Thaiichthys. These two humpbacked fish share several other traits despite their chronological separation.

Cheiracanthus (Middle Devonian)
(Fig 1) is a humpback spiny shark. The mandible is about as long as the skull.

Thaiichthys (Late Jurassic)
(Fig 1) shortens the jaw line and increases the hump size as the fins turn from spines to rays with a robust leading edge ray.

The overall proportions
and skull details indicate homology rather than convergence. The LRT now nests these two together. This could change as studies continue.