Presence of the functional head joint mapped onto the latest molecular analysis [15] of the family Stomiidae.

2017-02-01T17:30:02Z (GMT) by Nalani K. Schnell G. David Johnson
<p>(A, B) Functional head joint absent in basal stomiids (blue box). The notochord does not overlap the basioccipital ventrally (small black box), e.g., in the cleared and double stained (c&s) specimen of (A) <i>Flagellostomias boureei</i>, BMNH 2002.8.5.786–788 and the histological sagittal section (hss) of (B) <i>Idiacanthus antrostomus</i>, SIO 97–85. (C–F) Intermediate stage of the functional head joint (red box), where the chordal sheath slightly overlaps the basioccipital ventrally (best seen in the histological sections (D, F). (C) <i>Grammatostomias dentatus</i>, USNM 234036 (c&s). (D) <i>Grammatostomias circularis</i>, NSMT-P 99317 (hss) and (E) <i>Bathophilus vaillanti</i>, USNM 234150 (c&s). (F) <i>Bathophilus filifer</i>, SIO 03–189 (hss). (G–P) Presence of the functional head joint (green box). The notochord overlaps the basioccipital ventrally in a resting position (G, I, K, M, O). Unfolding of the ventral sheath of the notochord during manipulative elevation of the head in c&s specimens (H, J, L, N, P). Green arrow heads indicate the two genera (<i>Aristostomias</i> and <i>Photostomias</i>) that have the occipital condyle composed of the exoccipitals and the basioccipital. (G) <i>Pachystomias microdon</i>, USNM 297922. (H) <i>Malacosteus australis</i>, USNM 296675. (I) <i>Aristostomias xenostoma</i>, USNM 296715. (J) <i>Photostomias</i> sp., USNM 296650. (K) <i>Eustomias obscurus</i>, USNM 206711. boc, basioccipital; c1, first centrum; exo, exoccipital; na1, first neural arch; nc, notochord. Scale bars, 1 mm.</p>