798
Journal of Paleontology 89(5):791–801
hyomandibula is wide. There is a large anterior process that is contacted by the autopalatine. The entopterygoid is bar-like and contacts anteriorly with the autopalatine which is long and stout. The autopalatine has two anterior well-separated processes, both ending in concave surfaces for articulation with the maxilla. A strong process articulates with the lateral ethmoid in the anterior third of the bone. The posterior half is as broad and flat as the anterior portion (Figs. 5.3, 6.3D). The quadrate is thick and trapezoidal, similar to that of Diplomystes. The suture with the hyomandibula is straight and occupies the two posterior thirds of dorsal margin.
Figure 10. Kooiichthys jono, n. gen. n. sp. (MPEF-PV 1613). (1) Ventral view of left pectoral spine, (2) detail of the articular portion, (3) detail of the posterior face. Scale bars = 1 cm.
Hyoid and branchial elements.—The shape of parurohyal is vaguely hexagonal in basal view with a short posterior process (Fig. 8). There is a deep, rectangular dorsal lamina occupying the entire length of the posterior process. The robust anterior medial process carries the exit for vessels. The dorsal and ventral hypohyals are robust and triangular. The dorsal one is larger and carries the process for articulation with paurohyal. The suture is straight and smooth. The exit of the hypohyal artery is bounded by both hypohyal bones. Anterior and posterior ceratohyals sutures are smooth. Both are huge and thick along the mid external surface. The posterior ceratohyal has a small exit for the artery. The interhyal is triangular with a slender dorsal process (Fig.7.5,7.6). Theceratobranchials1–4 are long and hollow. The ceratobranchial 5 is fragmentary. We did not observe either tooth patches or gill rakers. A putative basibranchial 3 is anteriorly expanded. Only two rectangular hypobranchials were preserved (Fig. 7.4). The pharygobranchial tooth plate is broken but appears to have been oval in shape (Fig. 4). We counted seven branchiostegals. Six are very slender but the first is laminar.
Figure 11. Phylogenetic relationships of Kooiichthys jono, n. gen. n. sp. (MPEF-PV 1613), obtained both under equal and implied weighting. Values over branches are absolute frequencies obtained after Symmetric Resampling and values under branches are Relative Bremer Supports, both calculated under implied weighting with K = 10.
with the articular is still visible. The retroarticular process is long. The coronomeckelian bone is laminar and trapezoidal and occupies a great portion of the lingual part of the angular+ articular +retroarticular complex.
Opercular apparatus and suspensorium.—The opercle is pre- served but it is so smashed that it can not be described. The interopercle is almost triangular, is thicker in the anterior part, and shows well developed anteroposterior radiating and ana- stomosing ridges (Figs. 1, 2, 5, 6). A part of preopercle is missing but it can be seen that the exposed surface of the bone is narrow (Fig. 7.3). The hyomandibula is very poorly preserved (Figs. 5, 6). The metapterygoid is subrectangular in outline with a dorsolateral process (Figs. 5, 6). The suture with the
Vertebral column and Weberian apparatus.—All the vertebrae of Weberian apparatus were preserved. No ossicles were found. The first vertebra is very short, wide, and completely free. The complex centrum is remarkably short. Putatively it is formed by second, third, and fourth vertebrae. The transverse process of the fourth vertebrae is broken. The body of the fifth vertebrae is short, completely free, without even a ventral lamina such as that of Diplomystes (Fig. 9). Only the base of both halves of the vertebra 4 neural arch is preserved.
Pectoral fin and girdle.—An almost complete left fin spine and a portion of the proximal right fin spine were preserved. The pectoral fin spine is long and stout. The head for articulation is radially striated distally. The shaft is covered dorsally and ventrally by longitudinal ridges. Proximally they are subparallel and distally they anastomose. There is a posterior sulcus with 19 irregular serrae. Some of them are bifid or trifid. Proximal and distal serrae are small but proximal are more robust than distal ones. Proximal serrae are oriented distally and distal ones are oriented posteriorly (Fig. 10). Neither soft rays nor radials are preserved. Only the horizontal lamina of both coracoids is present (Fig. 4). The suture between coracoids is smooth. The right cleithrum is much better preserved than the left one. It can be seen that the posterior cleithral process is short. The ornamentation on the postcleithral process is strong, with anteroposteriorly directed ridges, some of them anastomosed, and tubercles (Fig. 7.1).
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