The spiny dogfish (Squalus) enters the LRT

Slow, low and slinky,
the spiny dogfish shark (Squalus acanthias, Linneaus 1758; up to 1m in length; Figs. 1, 2) enters the large reptile tree (LRT, 1634+ taxa) basal to the angel shark (Squatina, Fig. 4) and the eagle ray (Aetobatus, Fig. 5) on one branch, and basal to the classic sharks, the mako (Isurus) and hammerhead (Sphyraena) on the other branch. On the ancestral side, Squalus is derived from two other small slinky sharks each with a terminal mouth, Cladoselache (Fig. 3) and Chlamydoselachus.

Spiny dogfish are bottom-dwellers.
A tiny spine precedes each dorsal fin. They exude a mild venom, a precursor trait to descendant sting rays. The rostrum is elongate, making the jaw underslung. The lateral gill slits are set low, anterior to the pectoral fins. The anal fin is absent. Note the straightening of the heterocercal tail.

Squalus retains a gill bar
lateral to the jaws (red). The orbit is enormous and so is the naris, so this hunter relies on sight and smell.

PS: Quick Reminder
The LRT nests guitarfish, like Rhinobatos, and skates with Isurus, not with this clade. And nests Manta with Rhincodon, the whale shark, not with this clade, despite the massive convergence.

References
Linnaeus C 1758. Systema naturæ per regna tria naturæ, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata.

wiki/Squalus