Gladiopycnodus karami, Taverne & Capasso, 2013

Taverne, Louis & Capasso, Luigi, 2013, Gladiopycnodontidae, a new family of pycnodontiform fishes from the Late Cretaceous of Lebanon, with the description of three genera, European Journal of Taxonomy 57, pp. 1-30 : 5-10

Gladiopycnodus karami gen. et sp. nov.

Figs 1-6

urn:lsid:zoobank.org:act:BE468D57-6344-4EA5-8F40-2A0646799E2C

Diagnosis

Gladiopycnodontid with an extremely elongated snout, forming a sword-like rostrum horizontally oriented and greatly outpacing the lower jaw level. Anterior tip of the prefrontal ending in an acuminate point. Frontal long and narrow. Dermosphenotic and dermopterotic partly fused. Oral border of premaxilla and maxilla toothless but bearing very small spines. Five infraorbitals, the first one larger than the others. Large lower jaw horizontally oriented. Large prearticular bearing molariform teeth. Preopercle greatly hypertrophied, with an elongated and denticulated lower margin forming the ventral border of the skull behind the lower jaw. Cleithrum vertically oriented. Strong pectoral spine. Reduced pelvic girdle present. Nuchal horn absent. Long and robust postcoelomic bone. Dorsal fin with short isolated rays forming a series of finlets. Anal fin beginning with an extremely long and strong spine that greatly outpaces the tail level. Only a few short soft anal rays. Caudal fin with a convex posterior border. Large paired dorsal scutes between the skull and the tail. Body completely covered with small flakelike scales irregularly imbricated. Large rounded scales on the caudal peduncle. Two pelvic scutes. One postcloacal scute. No scute on the ventral margin of the body in the caudal region.

Etymology

The species name of the new Lebanese fossil fish is dedicated to Youssef Bey Karam (1823 - 1889), the famous hero of Lebanon who lived during the time this country was ruled by the Ottoman Empire.

Holotype

Sample CLC S-393, a complete specimen seen by its right side ( Figs 1-2 ). Total length (the anal spine comprised): 117 mm. Total length (only skull and body): 98 mm.

Other material

Three other specimens of the new species exist in private collections and, unfortunately, are not accessible for scientific study. However, the authors received good photos of these three specimens and a few anatomical details, not well preserved on the holotype, were revealed by their observation.

Formation and locality

Marine Upper Cenomanian, Haqel, Lebanon.

Holotype morphometric data

The morphometric data are given in % of the holotype standard length (91 mm).

Length of the head (rostrum included) .........................................................70.0 %

Depth of the head (in the occipital region) ...................................................27.5 %

Length of the rostrum (part anterior to the lower jaw level) ........................32.0 %

Maximum depth of the body (at the pectoral girdle level) ...........................33.0 %

Depth of the body at the anal fin origin ........................................................20.5 %

Length of the pectoral spine ......................................................................... 21.5 %

Predorsal length ............................................................................................75.5 %

Basal length of the dorsal fin ........................................................................25.0 %

Preanal length ...............................................................................................84.5 %

Basal length of the anal fin (spine comprised) ............................................. 11.0 %

Length of the anal spine ............................................................................... 43.5 %

Depth of the caudal peduncle..........................................................................6.5 %

Osteology

1. The skull ( Fig. 3 )

The head, rostrum comprised, is twice as long as the body. The dermal bones of the skull are ornamented with small tubercles and a few thin ridges on the anterior portion of the prefrontal.

The snout is greatly elongated, forming a sword-like rostrum that is horizontally oriented in the same axis as the braincase and the axial skeleton. This rostrum consists of the prefrontals, the premaxillae, the mesethmoid, the parasphenoid and probably the vomer. All these bones are very long. The most anterior parts of the mesethmoid and of the parasphenoid are hidden by the prefrontal and the premaxilla that are connected together. The vomer is hidden by the premaxilla. The pointed anterior tip of the rostrum is only formed by the prefrontal. The olfactive foramen on the mesethmoid is located at the level of the suture between the frontal and the prefrontal.

The skull roof comprises the dermosupraoccipital and paired frontals, parietals, dermopterotics and dermosphenotics. The frontal is flat, very long but narrow. Posteriorly, the bone is a little broader and contacts the dermosupraoccipital and the parietal. It also overhangs the well developed triangular autosphenotic. The dermosupraoccipital exhibits a pointed posterior corner but no real horn. This posterior spiny process reaches the first dorsal scute. The parietal is a large bone. It is not possible to say if a brush-like posterior process is present or not on the parietal, the region being hidden by the pectoral girdle and the first dorsal scutes. The zone where a dermocranial fenestra is present in some pycnodontiform fishes is broken on the holotype. However, photos of other specimens clearly show that such a fenestra does not exist in this species. The dermopterotic and the dermosphenotic are smaller bones than the parietal. They are fused together dorsally but remain separated ventrally.

The parasphenoid is long and toothless.A very small orbitosphenoid is present just behind the mesethmoid. The other endocranial bones of the braincase are hidden by the preopercle and the hyomandibuladermohyomandibula.

The upper jaw is a part of the rostrum and, thus, is located before the lower jaw, which does not participate in the rostrum. The premaxilla is a very long and rather broad bone that is located below the prefrontal and is sutured with it along its upper margin. The maxilla lies under the posterior extremity of the premaxilla. It is a much shorter bone shaped as a lance head with the point anteriorly oriented. The oral border of both bones bear very small spines but there are no true teeth.

The lower jaw is large and triangular in shape. The dentary is a small but long bone, reduced to its ventral branch and bearing two incisiform prehensile teeth. The upper part of the anterior margin of the dentary is ornamented with a few very small spines. The prearticular is the largest component of the lower jaw. Its inner face is never visible, neither on the holotype nor on the other specimens. However, some large molariform teeth are visible under a broken part of the prearticular on the photo of one specimen. The angular is as deep as long. The articular is longer but narrow.

Both the quadrate and the symplectic articulate with the lower jaw. As usual in pycnodontiform fishes, the quadrate does not possess an ossified quadratic process. The symplectic is a very robust curved bone pressed against the quadrate. A small metapterygoid overhangs the quadrate. The entopterygoid is a large and broad bone as long as the lower jaw. No ectopterygoid is visible.

There are five infraorbitals and a sclerotic ring. The ventral part of the first infraorbital is missing on the holotype, but an enlarged triangular-shaped first infraorbital is visible on the photo of one of the other specimens. However, this bone covers only a very small part of the cheek. The four other infraorbitals are well developed but narrower than the first one and more or less reduced to their neurodermic component. The greatly hypertrophied preopercle is by far the largest bone of the skull, all together deep and broad, with a very elongated ventral border that forms the ventral margin of the skull. Dorsally, the preopercle reaches the dermosphenotic and the autosphenotic and exhibits a posterior hollow in which the hyomandibula-dermohyomandibula fits. The opercle is well developed but a lot smaller than the preopercle. It is an ovoid bone with its dorsal and ventral extremities acuminate. The branchiostegal rays are not visible.

The hyomandibula and dermohyomandibula are intimately fused in a pyriform-shaped bone of the same size as the opercle and thus much smaller than the preopercle.Within this double composed bone, the small hyomandibula is anteriorly located and has a smooth surface, whereas the larger dermohyomandibula is posteriorly located and has a granulated surface. It is possible that a ventral branch of the hyomandibula is hidden by the preopercle. The hyoid bar is not visible.

2. The girdles ( Figs 2 , 4-5 )

The pectoral girdle is pressed against the skull. The dermal bones of the pectoral girdle are ornamented with small tubercles as those on the skull. The cleithrum is by far the largest element of the girdle. It is a very deep, broad and vertically oriented bone. There is a shortening in its upper part that creates a sort of hollow in its anterior margin. The opercle fits in this hollow. The posttemporal is a very small and more or less rounded bone wedged between the parietal, the supraoccipital and the first dorsal scute. The hypercleithrum (= supracleithrum) is larger and amphora-like in shape. The pectoral fin is lost and replaced by a big pointed spine, articulated on the cleithrum.

The pelvic girdle is hidden on the holotype because the fossilisation has pressed the pectoral and anal spines against each other. However, on one specimen seen in photo, two small, obliquely oriented pelvic bones are clearly visible between these two spines and some fragments of short pelvic rays appear under the pelvic scutes.

3. The axial skeleton

The body is fusiform. It is difficult to describe the axial skeleton in a detailed way, as it is generally more or less covered by the scales and it is not possible to count the vertebral segments. The holotype shows a few fragments of neural and haemal spines. On one of the specimens seen on photo, many scales on the body are lost and we can observe that the notochord is nearly completely surrounded by the neural and haemal arches. The neural and haemal spines are well developed but rather short. Each of them bears a broad anterior wing. The spines are not interlocked together by interdigitating sutures.

The presence of ribs is uncertain, the situs viscerum being hidden by the gigantic preopercle, the opercle and the pectoral girdle.

The post-coelomic bone is long and very robust. It reaches the vertebral axis dorsally and the inferior border of the fish ventrally. Its broad ventral part is backwardly curved.

4. The dorsal and anal fins ( Figs 2 , 4 )

The dorsal fin is composed of about ten very short, branched rays. They rise between the paired dorsal scutes and remain isolated from each other, forming a series of dorsal finlets. In one of the photographed specimens, the last dorsal rays near the tail are not isolated but pressed together.

The anal fin begins with a very strong and extremely long spine that extends backward greatly beyond the tail. A few short, branched rays follow this spine. The surface of the spine is ornamented with granulations ranged in regular ranks. The upper border of the spine bears two big and a series of small denticles. The spine is articulated on the post-coelomic bone and on the first pterygiophore, which is longer and separated from the other anal pterygiophores.

5. The caudal skeleton ( Fig. 2 )

The caudal skeleton is covered by scales and thus remains unknown.

The small caudal fin is not forked. Its posterior border is convex. The holotype has 17 principal rays, of which the most external dorsal and ventral ones are segmented, pointed and a little shorter than the 15 others, that are segmented and branched. There are 5 dorsal and 5 ventral procurrent rays.

6. Squamation ( Figs 5-6 )

Gladiopycnodus karami gen. et sp. nov. possesses four different types of scutes and scales.

The dorsal margin of the fish is covered by large and deep paired scutes that are ornamented with tubercles and some small irregular ridges. The two last scutes are less deep than the more anterior pieces of the series. The holotype bears thirteen pairs of these dorsal scutes. One sample seen on photo has about twenty paired dorsal scutes. This difference in the number of dorsal scutes perhaps reflects an individual variation within the species, but could have also a sexual origin. The ventral margin of the caudal region of the fish is devoid of such scutes.

The body is entirely covered by small flake-like scales that are irregularly imbricated. Most scales have a smooth posterior border, but some of them bear a few very small spines on their posterior border.

A series of large rounded scales cover the caudal peduncle. They are ornamented with tubercles.

Two pelvic scutes and one postcloacal scute are visible on the photo of the specimen that shows the pelvic girdle. A part of their margins is spiny.

Figures

Fig. 1. Gladiopycnodus karami gen. et sp. nov. Holotype CLC S-393.

Fig. 2. Gladiopycnodus karami gen. et sp. nov. Reconstruction of holotype CLC S-393.

Fig. 3. Gladiopycnodus karami gen. et sp. nov. Reconstruction of the skull of holotype CLC S-393.

Fig. 4. Gladiopycnodus karami gen. et sp. nov. Reconstruction of the pectoral girdle and of the anal fin of holotype CLC S-393.

Fig. 5. Gladiopycnodus karami gen. et sp. nov. The pelvic girdle as seen on the photo of a specimen in a private collection.

Fig. 6. Gladiopycnodus karami gen. et sp. nov., holotype CLC S-393. A. First dorsal scute. B. Some scales of the body. C. One scale near the caudal fin.