Kansasiella eatoni

Kansasiella eatoni

Part of the parasphenoid (psp; Fig. 9C) is attached to the neurocranium of FMNH UF462 and imaged in place due to difficulty distinguishing the exact boundaries between dermal and endoskeletal components. The parasphenoid extends from the ventral fissure to the ethmoid palatal articulation and bears high ascending processes (a.p.psp; Figs 7C, 9C) that nearly reach the spiracular canal. The anterior process is more extensive and straight sided than estimated in Poplin’s (1974: fig. 8) reconstruction. No other dermal bones are evident.

preservation. Circumorbital bones are known only from an unusually broad left nasal and an approximately triangular jugal (posterior infraorbital). The jugal portion of the infraorbital canal produces four short posterior branches. Cheek bones recovered include maxillae, a preopercular and quadratojugal. The maxilla is broad and bears a short anterior process, around half the length of the posterior, expanded portion of the bone. An anteriorly restricted lamina descending from the rear margin of the maxilla overlaps the lower jaw. The preopercular has a deeply notched anterior edge. The posterior limb is around one-third of anterior limb length, and the angle between limbs is barely pronounced. The preopercular sensory canal (po.sc, Fig. 5B) runs along the dorsal margin and exits dorsally prior to the anterior extremity of the preopercular bone. Ventrally, the canal passes into

NEUROCRANIUM

The braincase of Ph. mossae is barely distorted: the neurocranial roof is present in NHMUK P10419a and the bulk of the neurocranium in NHMUK P10419b ( Fig. 6). External, perichondral, surfaces are well preserved, but the internal walls and details of the endocranial space are lacking, perhaps unmineralized or eroded. Limited exposure of the cancellate endochondral bone is present posterior to the basipterygoid processes. No structural evidence indicates separate ossification centres; the entire neurocranium is thus reconstructed as one coherent entity.

A primary neurocranial roof is present, although it is partially obscured by overlying dermal bones as seen in Figure 4B. The orbits are large, and the interorbital septum is unossified ventral to the olfactory tracts. The anterior of the neurocranium is well preserved, making Phoebeannaia the third Carboniferous actinopterygian with a detailed anterior ethmoid region, joining Kansasiella eatoni and Kentuckia deani ( Rayner, 1951) . Phoebeannaia resembles Kansasiella in many aspects including general proportions, extent of fissures and location of articular surfaces and foramina. The following regional descriptions will therefore first detail Phoebeannaia and subsequently list salient differences observed in Kansasiella . Notable general differences in our Kansasiella specimens with reference to Phoebeannaia include the lack of a preserved ethmoid region (here considered incomplete relative to Poplin’s 1974 material) and dissociation of the occiput in FMNH UF464. Note that separation of the occipital region from the anterior neurocranium has been previously documented in Kansasiella ( Poplin, 1974) .

OCCIPITAL