Phoebeannaia mossae, Caron & Venkataraman & Tietjen & Fls, 2023

Phoebeannaia mossae

The ethmoid region preserves details of the olfactory system, optic musculature and anterior palatal articulation. Given that most known Carboniferous actinopterygian fossils lack a preserved ethmoid region, it is notable that the morphology displayed by Phoebeannaia mossae does not closely resemble the complete ethmoid known from Kentuckia deani . Instead, it is more similar to incompletely recovered specimens of Lawrenciella schaefferi Poplin, 1984 ( Hamel & Poplin, 2008) and Kansasiella eatoni ( Poplin, 1974) . The olfactory tracts descend slightly as they progress anteriorly before passing separately though foramina in the postnasal wall (I; Fig. 11A, B). Above and lateral to the canal for the olfactory nerves, depressions mark the anterior dorsal myodome (a.d.myo; Fig. 11A, B); these depressions extend forward through a notch in the postnasal wall and might have allowed the musculature for the superior obliques to meet across the midline as suggested in Kansasiella ( Poplin, 1974) . The ventral anterior myodome (a. v.myo ; Figs 7A, B, 11A, B), located just below the olfactory tracts, appears as an indentation in the postnasal wall with two distinct depressions—likely origins for the inferior oblique muscles—and a dorsal midline passage that has been hypothesized to transmit the profundus nerve (V.pr; Fig. 11A, B) in the contemporaneous Lawrenciella schaefferi ( Hamel & Poplin, 2008) . Ventral to the ventral anterior myodome is a thin midline ridge (l.r; Fig. 7A, B) rising from the basisphenoid. The postnasal wall broadens ventrally and forms rectangular, posterolateral-facing processes for articulation with the palatoquadrate (eth.p.a; Figs 9A, 11B). The anterior surface of the postnasal wall supports two lateral depressions that form the posterior wall of the nasal capsules (p.n.w; Fig. 11A).