Jaws

Both palatoquadrates are visible (Figs. 2, 3), but incompletely preserved. The right palatoquadrate is preserved in situ, while the left one is still attached to the dislocated dermal upper jaw bones. On the medial side of the left maxilla (A/I 4402b; Fig. 3), a single, slender dermopalatine and a fragmentary entopterygoid are seen. The elongate entopterygoid exhibits an oblique anterodorsal margin, dorsal to which the palatoquadrate is exposed. The lingual surfaces of the entopterygoid and dermopalatine show numerous minute teeth. The premaxilla is absent, but both maxillae are visible. Whereas the right maxilla is preserved in situ, the left one is found isolated anteroventral to the rest of the fossil. The latter is still attached to the palatoquadrate, entopterygoid, dermopalatine, and preopercle. The maxilla is cleaver-shaped, consisting of an expanded postorbital plate, and a short, slender anterior process, which rostrally bends medially. The elongate, relatively low postorbital blade is bounded by four margins. Its dorsal and anterodorsal borders are both concave. They meet in an obtuse angle. The posterior margin of the postorbital plate is straight and runs obliquely from anterodorsal to posteroventral in its upper part. In its lower portion, the posterior margin is more vertically oriented and marked by a posterior notch. The ventral margin of the maxilla is S-shaped, being concave in its posterior segment and convex in its anterior portion. The ornamentation of the postorbital plate of the maxilla consists of coarse tubercles, which gain in size in the posteroventral part of the bone (Fig. 4.1). A narrow, unornamented area along the anterior margin of the postorbital plate was in vivo laterally covered by the suborbitals. The anterior process of the maxilla does not show dermal ornament. The bases of small teeth are visible along the ventral margin of the postorbital blade of the left maxilla, and a strong internal (horizontal) lamina is preserved on the medial side of both maxillae (A/I 4402b; Fig. 3). Within the rostral process, the internal lamina closely follows the ventral margin of the maxilla, whereas in the postorbital plate, the lamina is distinctly offset to the ventral border. The internal lamina does not carry teeth in its posterior section, but small teeth are developed in its suborbital portion.

Both rami of the lower jaw are preserved. The right one is still in situ and the left one is found isolated. The mandible is curved medially throughout its length, but most distinctly in its rostral portion. The lateral side of the lower jaw, which is best seen on the left mandible on part b (Fig. 3), consists of three bones: dentary, angular, and surangular. The dentary is the largest of these elements. Laterally, it extends from the rostral tip of the lower jaw to almost the posterior margin. Several fairly small teeth are preserved along the dorsal margin of the dentary, arranged in more or less two rows (Fig. 4.2). The angular forms the posterior and posteroventral edge of the mandible. It has a triangular outline in medial view (Fig. 4.2); however, it is mostly covered by the dentary laterally, with only its marginal posterior and posteroventral portions exposed (Fig. 3). The surangular is located anterodorsal to the angular and posterodorsal to the dentary. It lacks a coronoid process. The mandibular sensory canal can be traced in the dentary and angular. This canal runs obliquely though the rostral portion of the dentary and successively approaches the ventral margin of this bone posteriorly. The canal pierces the angular through its anterior end and traverses this element close to its ventral and posterior margins. The ornamentation of the lower jaw consists of tubercles, which are particularly coarse in the rostral part, precisely in the region ventral to the mandibular sensory canal (Fig. 4.1). The surangular and adjacent, marginal areas of the dentary and angular lack ornamentation. The medial side of the lower jaw is visible on part a of the fossil (Figs. 2, 4.2). Lingually, the dentary does not reach as far posteriorly as on the lateral side. The part lying ventral to the mandibular sensory canal is thickened. Along the dorsal margin of the thickened portion, within the rostral part of the dentary, there are at least two oval depressions (Fig. 4.2) corresponding to the ‘shallow depressions’ of Nielsen (Reference Nielsen1942, p. 165).

There is a series of three bones medially adjoining the dorsal margin of the dentary (Fig. 4.2). The most posterior of these elements, which extends caudally until the surangular, represents the prearticular. The lingual surface of the prearticular is equipped with a row of small teeth in its anterior part, which are slightly smaller than the teeth on the dentary. The two bones rostral to the prearticular are the coronoids. The posterior coronoid is only slightly longer than the prearticular, while the anterior coronoid is shorter than the posterior one. The suture between the prearticular and the posterior coronoid is distinctly indented. The medial surfaces of both coronoids are smooth ventrally, whereas dorsally these bones are armed with minute teeth. Most dorsally, there is a single row of larger teeth, of comparable size to those on the prearticular. Ventral to the anterior and posterior coronoids is at least one additional element. It corresponds to the ‘bone in the anterior part of the mandible’ of Nielsen (Reference Nielsen1942, fig. 38). This element has a smooth lingual surface. In the living animal, the space delimited by the prearticular and coronoids dorsally, and the thickened lower portion of the dentary and angular ventrally, was occupied by Meckel's cartilage, the most posterior part of which is ossified as the articular. This bone is preserved in situ on both the left and the right mandible (Figs. 2, 3, 4). It is subtriangular in medial aspect and laterally connected to both the angular and surangular. Its dorsal surface is marked by two articulation facets (double jaw joint), best visible on the casts of A/I 4402a and b.

Preopercle and operculogular series

Dorsal to the right maxilla, the upper branch of the corresponding preopercle is preserved (Figs. 2, 3, 4). The posteroventral shank of this bone is not visible. The anterodorsal ramus of the preopercle is roughly triangular in outline, with a deeply concave anteroventral border, and a long, sigmoid dorsal margin, which is anteriorly convex and posteriorly concave. The ventral border of the anterodorsal shank is covered by the maxilla. The anterodorsal portion of the preopercle is elongate and pointed rostrally. The preopercular sensory canal pierces the anterodorsal shank slightly above the rostral tip of the bone and passes through the preopercle near its dorsal margin (Fig. 4.2). The ornamentation is composed of tubercles below the sensory canal, and subvertical striae and tubercles above it.

The operculogular series is mostly complete, but partly disarticulated (Figs. 2–4). The gulars and branchiostegals are found in situ. The gular plates are not well preserved, but seemingly three of them are developed—a narrow median gular and a pair of slightly broader lateral gulars. Posterior to the gular plates is a paired series of ~13 branchiostegal rays on either side. Each branchiostegal ray is elongate and relatively broad, similar to the gular plates. The breadth of the rays successively decreases towards the posterior elements. The gulars and branchiostegals overlap a marginal area of the caudally following element.

Two isolated, oval, plate-like bones are interpreted as the opercles. The left opercle is located ventral and the right opercle dorsal to the rest of the skeleton (Figs. 2, 3). Because the right opercle is poorly preserved, the description is based on the left one, which is exposed in lateral view. The opercle is the largest bone of the operculogular series. It is bounded by convex posterodorsal and anteroventral margins, a straight, short anterior border, and a distinctly convex posteroventral margin. Its anterodorsal end is pointed (the orientation is inferred from comparisons with other species, cf., Nielsen, Reference Nielsen1942). An isolated, plate-like bone in the posteroventral part of A/I 4402 possibly represents the subopercle (Figs. 2, 3). The putative subopercle is about half as large as the opercle and has a trapezoidal shape. It is bounded by gently diverging dorsal and ventral confinements, and subparallel anterior and posterior margins. The posterior border is convex and longer than the anterior one. Dermal ornament of the bones of the operculogular series consists of tubercles. Enlarged tubercles are seen on the anterodorsal part of the opercle, the anterior part of the subopercle, and the gulars.

Circumorbitals, nasals

Immediately anterior to the right preopercle and the postorbital plate of the maxilla are several anamestic bones, the suborbitals (Figs. 2–4). There is one large upper suborbital and four additional, smaller, lower suborbitals, all of which appear to be preserved nearly in situ. The upper suborbital is roughly four-sided, with rounded corners. This bone is bounded by long dorsal and ventral margins, which run subparallel, a straight posteroventral border, and a deeply convex anterior confinement. The four lower suborbitals have polygonal outlines. All suborbitals are ornamented with tubercles, although each of them is marked by narrow unornamented regions along some of their margins.

Anterior to the right maxilla and suborbitals are several, serially arranged bones belonging to the right infraorbital series. The most posterior of these elements is identified as the jugal (Figs. 2–4). This bone is somewhat higher than long and roughly four-sided. It is confined by short, straight dorsal and anteroventral margins, a long, convex posterior border, and a short, concave anterodorsal margin. The infraorbital sensory canal traverses the jugal nearer to its anterodorsal margin than to its posterior border. The area caudal to the sensory canal is ornamented with coarse tubercles, whereas the part anterior to it is smooth. An elongate, canal-bearing element, located anteroventral to the jugal, probably belongs to the infraorbital series (Fig. 4.1). In vivo, this element may have been situated dorsal to the jugal. The lateral surface of this infraorbital bone is divided into an unornamented dorsal (originally anterior?) part and a ventral (originally posterior?) portion ornamented with large tubercles. The ventral part is pierced by a sensory canal. Anteroventral to the infraorbital bone is a much larger, rostrocaudally elongate element: the lachrymal (Figs. 2, 4). The subquadrangular lachrymal is bounded by long dorsal and ventral margins, and short anterior and posterior borders. Caudally, the lachrymal still articulates with the anterior process of the maxillary bone. The lachrymal lacks ornamentation, but a distinct longitudinal crest on its lateral surface possibly indicates the course of the infraorbital sensory canal. Several minute teeth are developed on the ventral surface of the lachrymal, similar to those on the anterior process of the maxilla. Anterodorsal to the lachrymal is a smaller, slightly dislocated bone, which we interpret as the antorbital (Fig. 4.1). The antorbital is plate-like and its lateral surface, now facing anterodorsally, is covered with coarse tubercles. The medial surface is smooth and marked by a thickened portion along the now posteroventrally located margin, which contains a sensory canal. Two small, thin bones dorsal to the lachrymal may pertain to elements of the sclerotic ring (Fig. 4.1). The two bones still articulate with each other. Both show an elongate, somewhat rectangular outline. Their lateral surface is mostly smooth, but marked by a single line of small but distinct tubercles along their dorsal margin. In the rostral area, there is a single, plate-like element, interpreted as the right nasal, which is traversed by a sensory canal, the supraorbital canal (Fig. 4.1). The trapezoidal nasal is divided into two portions: a stout posterior part, covered with coarse tubercles, and a thinner anterior part, which is smooth.

Dermal skull roof

A patch of articulated bones in the caudal region of part a (Fig. 2) is tentatively interpreted as the posteriormost part of the dermal cranial roof. Two symmetrically arranged fragments, situated posterolaterally on the putative dermal skull roof, show distinct ornamentation composed of mainly anteroposteriorly aligned striae and some tubercles along the posterior border. These two bone fragments are identified as the caudal portions of the dermopterotics. Two much smaller elements, wedged between the dermopterotics, possibly correspond to the parietals. Posterior to the left dermopterotic are several smaller, plate-like bones, a large lateral and about two smaller, medial elements, which would correspond to the extrascapulars. The parietal and extrascapulars are covered with tubercles.

Hyoid and branchial arches

Several scattered, elongate ossifications in the anterior region of A/I 4402 correspond to bones of the hyoid and branchial arches. A fragment of the right hyomandibula is preserved between the right supracleithrum and the right posttemporal (Figs. 2, 3). The hyomandibula consists of an anterior and a posteroventral shank that meet in an obtuse angle. The most rostral and most ventral extremities of this bone are missing. An opercular process is not developed, but the posterodorsal margin of the angled portion bears a very low, blade-like protrusion. An elongate, triangular element attached to the upper part of the lateral surface of the anterior shank corresponds to the dermohyal. The dermohyal is ornamented with tuberlces (Fig. 3.3). The ceratohyal, preserved dorsal to the left mandible (Fig. 2), is an elongate, plate-like bone with an hourglass-shaped outline. Its anterior margin runs perpendicular to the longitudinal axis of the bone, whereas the posterior termination is inclined. A weak, sigmoid longitudinal groove is observed on the ceratohyal, corresponding to the groove for the afferent hyoid artery (cf., Nielsen, Reference Nielsen1942, fig. 43).

Several rod-like bones preserved predominantly in the cranial area of the fossil belong to the gill arches. Two elongate elements, lying on the branchiostegal rays (A/I 4402b; Fig. 3), are dorsoventrally compressed and show a furrow along their longitudinal axis. Their morphology suggests that they are ceratobranchials. A shorter element with a similar morphology, possibly an epibranchial, is situated rostral to the left pectoral fin (Fig. 2).

Shoulder girdle

Most elements of the dermal shoulder are disarticulated, with those from the right side of the shoulder girdle now located close to the right pectoral fin, whereas the bones from the left side are found near the left pectoral fin (Figs. 2, 3). Both posttemporals are present. The large posttemporal consists of a broad, dorsally convex external plate, and a medioventral process. The plate-like part has a roughly triangular outline, being confined by a long, convex posteromedial border, a slightly shorter, straight lateral margin, and a short, straight anterior border. The transitions between these margins are rounded. The dorsal surface is covered with tubercles, which gain in size towards the broad anterior end of the bone. The tubercles are, to some degree, anteroposteriorly aligned and may occasionally change into short, longitudinal striae. The canal for the lateral line can be traced near the lateral margin. The ventral process is incompletely preserved, but its proximal portion is seen on the left posttemporal in A/I 4402a, and the right one in A/I 4402b (Fig. 3.3). The medial process issues in proximity to the lateral margin of the plate-like part. The supracleithrum is a dorsoventrally broad, plate-like bone. It is bounded by a long and slightly convex posterior margin, a long, gently concave anterior border, and more or less convex dorsal and ventral borders. A pore line on the external side of both supracleithra, running from the middle of the posterior confinement of the bone and traversing obliquely in anterodorsal direction, indicates the course of the lateral line canal. The canal left the bone near its dorsal end. It traversed the ossification center of the supracleithrum, situated on the longitudinal axis of the bone, close to its dorsal end. The external surface of the supracleithrum is convex and ornamented with round to oblong tubercles, arranged in lines radiating from the ossification center.

The cleithrum is bounded by a straight ventral border, a long, concave anterodorsal margin, and a long, sigmoid posterior border, which is convex dorsally and concave in its ventral portion (the concavity indicating the place of insertion of the pectoral fin). The anterior branch of the cleithrum, now directed caudally, is slightly shorter and more slender than the upper one. The external surface of the cleithrum is distinctly convex. A few coarse tubercles are visible on the ventral edge of the lower division of the cleithrum (Fig. 3), but the ornamentation of the remaining areas is not preserved. The endochondral shoulder girdle is not detectable. Whereas the right clavicle is preserved nearly in situ (Fig. 2), the left one is found next to the anterior end of the left cleithrum (Figs. 2, 3). The clavicle has a triangular outline in dorsoventral aspect, with long and straight medial and lateral margins, and a short, straight posterior border. The external (ventral) surface is convex and ornamented with tubercles, which increase in coarseness towards the broad caudal end of the bone.

Paired fins

The exoskeletal parts of both pectoral fins are preserved in situ (Figs. 2, 3). The left pectoral fin is distally more complete than the right one. The fin is fairly large, three-sided and, based on the manner of preservation, was oriented horizontally in the living animal. It has a long, convex anterior border and a nearly straight basal margin. About 27 fin rays are in the right pectoral fin (cast of A/I 4402a). Ornamentation of the fin rays consists of a few longitudinal ridges. All lepidotrichia are segmented, with the most basal segment always distinctly longer than the following ones. The basal segments are longer in the ventral hemitrichia (A/I 4402b; Fig. 3) than they are in the dorsal hemitrichia (A/I 4402a; Fig. 2). The leading edge of the pectoral fin is made of several rays. Bifurcation (at least one or two times each) is observed in the distal part of the fin rays, both on the lepidotrichia terminating at the anterior fin margin (except for the first three rays) and the lepidotrichia terminating at the posterior fin margin. The anterior margin of the fin is armed with two long basal fulcra (A/I 4402b) and numerous, distally adjoining, smaller fringing fulcra. The series of fringing fulcra is seemingly interrupted by terminal lepidotrichia segments (see Fig. 2.3), thus exhibiting Pattern B of Arratia (Reference Arratia2009). A slender, scaled lobe is developed at the base of the right pectoral fin (A/I 4402a). The fin endoskeleton is poorly preserved.

Only the left pelvic fin is preserved and seen in situ in A/I 4402a (Fig. 2). It is mostly complete, but the pelvic girdle is not visible. The fin has a triangular shape, being confined by gently convex anterior and posterior borders, and a relatively long, straight basal margin (nearly as long as that of the pectoral fin). About 23 lepidotrichia are counted (cast of A/I 4402a). All lepidotrichia are composed of short segments, with the basal segment of each fin ray not being significantly longer than the following ones. As far as can be seen, the seventh fin ray and all the posteriorly following ones terminating at the caudal margin of the fin are distally bifurcated at least once. The leading edge of the fin is formed by six unbranched rays, which become gradually longer (Fig. 2.2). They are lined with an incompletely preserved series of fringing fulcra (probably showing Pattern B of Arratia, Reference Arratia2009).

Unpaired fins

The unpaired fins are incompletely preserved and shifted from their in vivo positions. A patch of lepidotrichia and some pterygiophores located in the posterior part of A/I 4402a are tentatively interpreted as belonging to the anal fin and its endoskeletal support (Fig. 2). Our interpretation is based on the proximity of these elements to a large patch of scales (now located posterior to the pelvic fin) that probably comes from the ventral body region. Sixteen anal fin rays are preserved, each of which is made up of several short segments. Branching is not observed, probably related to the incomplete preservation of the fin. Very few fringing fulcra are visible along the leading margin of the fin. Several lepidotrichia located between the pectoral and pelvic fins probably pertain to the dorsal fin (Figs. 2, 3). Their segmentation pattern is similar to that of the putative anal fin.

A large patch of lepidotrichia preserved near the anal fin is identified as the ventral lobe of the caudal fin (A/I 4402a, Fig. 2) due to the greater stoutness of the fin rays compared to those of the other fins. The distal parts of the ventral caudal lobe are missing. Up to 20 lepidotrichia are preserved, all of which consist of several short segments. The basal segment of each lepidotrichium is always the longest one. At least the five most posterior fin rays are distally branched either once or twice. The leading edge of the ventral caudal lobe is made of at least eight gradually longer rays, which are covered with fringing fulcra of Arratia's (Reference Arratia2009) Pattern B. Additionally, there are two basal fulcra. A further patch of lepidotrichia anterolateral to the ventral caudal lobe possibly belongs to dorsal lobe of the caudal fin (A/I 4402a, Fig. 2). It is composed of seven very fine fin rays, all of which are made of numerous short segments and that are dichotomized up to three times distally.

Squamation

The trunk of A/I 4402 (Figs. 2, 3) was covered with mostly rhombic scales arranged in oblique vertical rows. On some isolated rhombic scales (Fig. 2.3), a small dorsal peg is visible (peg-and-socket articulation). Scales from the dorsal/ventral body portions are much longer than deep and those on the flanks less so (as seen on the large articulated patch of scales between the pelvic fin and the presumed anal fin). On some scales, the ornamentation of the free field consists of rostrocaudally oriented striae (Fig. 2.4). Scales preserved at the base of the caudal fin show smooth free fields. The posterior margin of the rhombic scales is either denticulated or straight (Fig. 2.3, 2.4). On the medial side, the scales are thickened centrally along their dorsoventral axis.

Several specialized scales are observed. An accumulation of broad, ellipsoid ridge scales is found just anterior to the left pectoral fin (Figs. 2, 3). These ridge scales, which may have been associated with the nearby dorsal fin, are pointed at their posterior end and characterized by a convex external surface. Further, more lanceolate ridge scales are found near the base of the putative anal fin and the area between the two patches of caudal fin rays (Fig. 2). The lanceolate ridge scales may have been associated with the anal fin in vivo. Ridge scales were seemingly only regionally developed along the ventral midline: a section of the ventral midline, preserved between the pectoral fins and the left pelvic fin (A/I 4402a, Fig. 2), clearly lacks ridge scales. At least one large, unpaired basal fulcrum (sensu Patterson, Reference Patterson1982) is preserved close to the putative patch of dorsal caudal fin rays (Fig. 2). This fulcrum, which belonged to the anterior margin of the upper caudal lobe, has an elongate habitus, with a pointed posterior end, and bifid, acute anterior terminations.

Jaws

Only some skull bones of NMMNH P-57422 can be identified with certainty. Of the upper jaw, mainly the left palatoquadrate, with the impressions of its lingual dermal cover, as well as both maxillae are preserved. The left palatoquadrate (Figs. 5, 6.1) is a three-sided element, with a long, gently concave ventral margin, a short, convex posterior border, and a long anterodorsal margin, whose outline is obscured by a patch of scales. Whether an articular fossa for the basipterygoid process is developed or not can thus not be determined. The most posterior and most anteroventral portions of the palatoquadrate are both curved laterally. The pars quadrata of the palatoquadrate has a subtriangular outline, but its anterior margin is difficult to trace. The ventral part of the medial surface of the palatoquadrate was covered by at least two serially arranged bones, the ectopterygoid and dermopalatine (Figs. 5, 6.1). Their boundaries are imperfect. Dorsal to the ectopterygoid are the impressions of numerous, small polygonal plates of varying sizes, (‘entopterygoid plates,’ cf. Acrorhabdus bertili Stensiö, Reference Stensiö1921). Unlike the adjacent scales, the ‘entopterygoid plates’ do not overlap each other, but rather form a mosaic cover on the lingual side of the palatoquadrate. Both maxillae are visible. The right maxilla is fragmentary, but evidently consisted of an elongate rostral process and a plate-like postorbital portion (Figs. 5, 6.2). The rostral process is incomplete anteriorly and was probably much longer in vivo (in comparison with the size of the palatoquadrate). A fragment of the postorbital plate of the left maxilla is seen posteroventral to the right maxilla. Its medial surface is marked by the imprint of the internal (horizontal) lamina. The ventral border of the postorbital blades of both maxillae are lined with numerous, minute, pointed teeth (Fig. 6), best visible on the silicone cast.

The complete, left branch of the lower jaw is located ventrally to the pectoral fin, and a fragment of the right lower jaw is preserved dorsal to the left one (Fig. 5). The lower jaw is composed of at least two bones: the large dentary anteriorly, and the much smaller angular posteriorly. Their mutual boundary is not well visible. The external surface of the left lower jaw is weathered, but the general outline is still visible. It has a long, sigmoid dorsal margin, which is concave anteriorly and weakly convex posteriorly. The long ventral confinement is partially obscured by the ceratohyal, but had a sigmoid shape as well. It is convex anteriorly and posteriorly, and concave in its middle segment. The posterior margin of the left lower jaw branch, formed by the angular bone, is short and convex. The rostral tip of the lower jaw is rounded and curved dorsally and medially. Minute teeth are preserved within the anterior half of the left dentary. The teeth are comparable in size to those on the maxilla. Traces of the mandibular sensory canal are observed on both branches of the lower jaw. The right lower jaw is covered with fine tubercles, which are arranged in anteroposteriorly running lines (silicone cast).

Preopercle and operculogular series.—Dorsal and posterior to the postorbital process of the right maxilla are two canal-bearing bone fragments, separated by a crack, which belong to the preopercle (Figs. 5, 6.2). The preopercle is angled, consisting of a rostrally expanded anterior shank and a short, slender posteroventral shank. The anterior shank is bounded by a rostral margin that appears to be deeply concave, and a convex posterodorsal border. Its ventral margin, bordering the maxilla, is not well preserved. The rostral and posterodorsal margins of the anterior shank taper in an elongate, pointed anterodorsal process (‘neurocranial process;’ Bürgin, Reference Bürgin1992, p. 20). The suture between the preopercle and maxilla is damaged; however, when reconstructed, the posterodorsal border of the anterior preopercular shank and the dentigerous margin of the maxilla run nearly parallel to each other (Figs. 5, 6.2). The preopercular sensory canal pierces the bone through its anterodorsal process and traverses along the longitudinal axes of its two shanks.

A large, plate-like element located next to the right maxilla-preopercle complex corresponds to one of the opercles. The opercle has a slightly elongate, rhomboid outline, with gently convex margins and rounded corners. The bone is seen from its concave medial side. In the now rostrally and dorsally located parts of the opercle, the bone has partially weathered and the impressions of the ornamentation of the external surface are visible (Fig. 6.2). In these regions, the ornamentation consists of tubercles, which are coarse, pointed, and inclined in the same direction. Judging from the orientation of the apices of the tubercles (best seen on the cast), the now anteriorly facing margin corresponds to the posteroventral border of the opercle. Within the anterodorsal part of the bone, now located posteriorly and ventrally, several concentric growth lines are visible.

Hyoid and branchial arches

One of the hyomandibulae is preserved in the anterior region of the fossil (Figs. 5, 7.1). It is composed of an anterior and a posteroventral shank, which meet in an obtuse angle (~155°). A small, dorsally directed processus opercularis is developed at the back of the angled portion of this bone. The dorsoventral width of the anterior shank increases rostrad. The width of the posteroventral ramus is much smaller than that of the anterior shank and remains constant throughout its length. Within the upper part of the anterior shank, there is a distinct groove, running in anteroposterior direction and merging with the upper margin of the anterior ramus just in front of the opercular process. This sulcus may have been associated with the truncus hyomandibularis of the facial nerve (VII), implying that the element in question is the right hyomandibula in medial view. The rostral end of the bone is capped by cancellous bone (‘epiphysis;’ Stensiö, Reference Stensiö1921; Nielsen, Reference Nielsen1942). The left ceratohyal is preserved beneath the left lower jaw (Fig. 5). This elongate, plate-like bone is about half as long as the lower jaw, and bounded by four confinements: a short, straight anterior border, a short posterior margin, a long, slightly S-curved ventral border, and a gently concave dorsal margin. The anterior, dorsal, and ventral borders meet orthogonally, whereas the posterior border is inclined. A groove on the lateral side of the ceratohyal indicates the course of the afferent hyoid artery. A few disarticulated, rod-like bones that are distributed in the anterior region of P-57422 possibly represent elements of the branchial arches.

Shoulder girdle

Most elements of the dermal and endochondral shoulder girdle are not preserved or not identifiable. However, a small bone fragment found close to the base of the right pectoral fin may pertain to either the right cleithrum or the right clavicle (Fig. 5). It is ornamented with tubercles, which are particularly large along the straight ventral margin.

Paired fins

Of both pectoral fins, only the lepidotrichia are preserved, with those of the left pectoral fin lying on top of the right one (Fig. 5). The fin rays of the right pectoral fin are oriented perpendicularly to those of the left one. There are ~16 lepidotrichia in the left pectoral fin, but the original number was higher. With the exception of the first one or two rays, all lepidotrichia are composed of short segments distally, and at least some of them dichotomize. The leading edge of the right pectoral fin is armed with fairly large fringing fulcra (apparently Pattern C; Arratia, Reference Arratia2009). Both pelvic fins are in situ, but the pelvic girdle is covered by the scales. The pelvic fins are small and located halfway between the pectoral and the anal fins (Fig. 5). The right pelvic fin is more complete than the left one. The fin rays ramify distally and are made up of many short segments. We count about eight to nine fin rays in each of the two ventral fins. A few fringing fulcra line the leading edge of the left fin.

Unpaired fins

The anal fin is located closer to the pelvic fins than to the caudal fin (Fig. 5). Only the basal portions of a few fin rays are visible, each consisting of short segments. Fulcra are not visible and the pterygiophores of the anal fin are not exposed. Differing from most coeval actinopterygians, the dorsal fin of P-57422 is not situated at the level of the anal fin, but rather in front of the pelvic fins (Fig. 5). Nevertheless, the dorsal fin inserts at about the same scale row as the anal fin. Considering that the other unpaired fins and the pelvic fins are preserved in situ, despite their fragmentary preservation, it is assumed that the dorsal fin is also still in situ. Only ~12 lepidotrichia of the dorsal fin are preserved, but the original number was higher. All fin rays are evenly segmented, distal bifurcation is not evident. The leading edge of the dorsal fin is equipped with fringing fulcra (probably Pattern C; Arratia, Reference Arratia2009). Regarding the caudal fin, only the basal parts of ~11 lepidotrichia of the ventral lobe are preserved (Fig. 5). The fin rays of the lower caudal lobe are composed of numerous segments, whereas the most basal segment of each fin ray is longer than the distally following ones, which are box-shaped (i.e., with a nearly quadratic outline in lateral view). Fulcra are visible along the ventral margin.

Squamation

The trunk is covered with rhombic scales, arranged in inclined rows (Fig. 5). The squamation is incomplete, but ~48–50 vertical scale rows are counted on the flank between the anterior and caudal ends of the trunk. Whereas the scales on the lateral side of the body are about equally high as long, those occupying a more dorsal or ventral position are distinctly longer than high. The hind margin of the scales is denticulated (Fig. 5.3). Ornamentation of the free field consists of oblique, anteroposteriorly running striae (strongly to weakly developed), which coalesce with the denticles. The striae occasionally show an anastomosing pattern. The anterior part of each scale, which is laterally covered by one or two preceding scales, is wide. A well-developed dorsal peg, which fits into a groove on the medial side of the adjacent scale (peg-and-socket articulation), and an anterodorsal process are only developed on the scales of the anterior body portion (Fig. 5.3), while both are absent on the scales of the posterior trunk region. Anterior to the anal fin, about four enlarged, pre-anal scales are observed, which surrounded the anus in vivo (Fig. 5). In addition, at least two scales covered with strong striae occur next to the pelvic fins. The lateral line cannot be traced with certainty in the scales.

Neurocranium

The neurocranium is exposed in NMMNH P-57423b (Fig. 9.2). Features such as the postorbital process, the anteroventral myodome, or the foramina for the optic and oculomotor nerves may be visible, but are too poorly preserved for a sound description.

Jaws

The left lower jaw is preserved in situ and is complete (Figs. 9, 10). A poorly preserved fragment of the right lower jaw is possibly preserved in the anterior part of the fossil, interpreted as such due to its ornamentation and indicated presence of a sensory canal. The description is based only on the left lower jaw because it is much better preserved. The lower jaw is relatively short and posteriorly deep, with a pronounced and rounded coronoid process. The lateral side, which is well exposed in P-57423a (Figs. 9.1, 10.1), is composed of the dentary, angular, surangular, and possibly the retroarticular. The dentary is the largest of these bones and forms the anterior part of the lower jaw. It is confined by a long, smoothly sigmoid ventral boundary, being anteriorly concave and posteriorly convex, a long dorsal margin that can be divided into a straight (toothed) anterior part and a sigmoid posterior portion forming part of the coronoid process, and a mostly straight posterior border showing only a small indentation at the base of a small posteroventral process. The posteroventral portion of the mandible is mostly formed by the angular. This bone is bounded by deeply convex posterior and ventral margins and a short, straight dorsal border. Ventral to the angular is a narrow element, the retroarticular, whose boundary with the angular is difficult to trace. The posterodorsal part of the lower jaw is formed by the surangular, which makes a rounded posterodorsal margin. This bone shapes the posterior half of the coronoid process. Just anterior to the coronoid process, a small, toothed portion of the prearticular is visible in lateral view (Figs. 9.1, 10.1). The medial side of the lower jaw is exposed in P-57423b (Figs. 9.2, 10.2), showing the lingual surfaces of the dentary, angular, surangular, and retroarticular. The prearticular, preserved in situ (Figs. 9.2, 10.2), has a somewhat triangular shape, being bounded by a short, nearly straight anterodorsal, a longer, concave posterior, and a mostly straight ventral border. It is not known whether coronoids were developed rostral to the prearticular due to the incomplete preservation of this part.

The lateral ornamentation of the dentary, angular, and surangular consists of tubercles, which are coarse along the ventral margins of the angular and dentary. In the posteroventral part of the dentary, a few thick, anteroposteriorly trending striae are developed, too. The retroarticular appears to be smooth. The lingual side of the prearticular is covered with small teeth, which increase slightly in size near the dorsal margin of this element (well visible on the cast of P-57423b; Fig. 10.2). The dorsal border of the dentary bears numerous close-set, conical teeth. The prearticular teeth are also close-set and conical, like those on the dentary. The dentary and angular are both pierced by the mandibular sensory canal, which closely parallels the ventral margins of these bones. The canal opens in pores laterally, well visible in P-57423a (Fig. 9.1). The external surfaces of the dentary and angular face laterally in the dorsal part of these bones, whereas in the more ventral portions the external surface face ventrally (i.e., the ventral part is curved medially). Rostrally, the lower jaw is curved medially.

The upper jaw is very fragmentarily preserved. Presumably, the posterior portion of the left maxilla is seen in situ on both part and counterpart (Figs. 9, 10). The lateral surface of the elongate anterior portion of the right maxilla is probably visible as an imprint on part b (Figs. 9.2, 10.2). This element is curved towards the left side of the animal (i.e., medially), implying that it belonged to the right branch of the upper jaw, thus supporting our interpretation as the right maxilla. The maxilla is short, with a low posterior portion. The lateral surface is covered with fine tubercles. Teeth are not present. Posterodorsally, the right maxilla articulates with an element that is ornamented with horizontal striae. Topologically, this bone may correspond to the supramaxilla (Figs. 9.2, 10.2), although its relatively large size poses doubt on such an interpretation. A slender, elongate bone fragment neighboring the putative left maxilla in P-57423a is tentatively interpreted as the right ectopterygoid (Figs. 9.1, 10.1). This bone cannot belong to the right maxilla because it is situated medially to this element. The anterior portion of the ectopterygoid is bent towards the left side of the skull, hence opposite to the curvature of the adjacent left branch of the lower jaw (thus supporting our view that the bone in question belongs to the right side of the jaw). Minute teeth are developed along the ventral margin of the ectopterygoid (Fig. 10.1). Two fairly small, tooth-bearing elements found disarticulated in the rostral area of the fossil are tentatively interpreted as the premaxilla and dermopalatine, respectively (Fig. 10.1). The premaxilla is small and equipped with at least three teeth that are slightly larger than the rostral teeth of the dentary. The dermopalatine is larger than the premaxilla. It is plate-like and has a subrectangular shape. A row of close-set teeth is developed on its surface (Fig. 10.1). This bone is identified as the dermopalatine due to overall resemblance with the dermopalatine of W. eugnathoides (cf., Olsen, Reference Olsen1984, fig. 13b).

Preopercle and operculogular series.—Several elements posterior and posterodorsal to the jaw bones are identified as parts of the left preopercle (Fig. 9). On the basis of their distribution pattern, we infer that the preopercle consisted mainly of two large, plate-like parts, a dorsal and a ventral one. The ventral portion has a roughly triangular outline, with a long, sigmoid anterior margin (convex dorsally and concave ventrally), a short, convex anterodorsal margin, and a long, convex posterior border. The dorsal extremity of the ventral preopercular plate incorporates at least two smaller elements, which are partially fused to the larger plate (Fig. 9.1). The dorsal preopercular plate is higher than long, and slightly larger than the ventral one (Fig. 9.2). The precise outline of the dorsal plate cannot be deduced due to fragmentary preservation. The preopercular sensory canal is well visible in the ventral plate (Fig. 9.1). The canal runs medially in the narrow, lowermost region, and close to the posterior bone margin in the dorsal region. A segment of this sensory canal can be traced in the dorsal preopercular plate, running close to the caudal bone margin. Two pit lines are faintly visible on the ventral preopercular plate: a dorsal one, corresponding to the horizontal pit line, and a shorter ventral one, interpreted as the vertical pit line (Fig. 9.1). The ornamentation of the preopercular plates consists of tubercles. Some slightly enlarged tubercles are observed in the lowermost area of the ventral bone, especially in vicinity of the sensory canal.

The left opercle, subopercle, and possibly the interopercle are still in situ, whereas the gular plate, branchiostegal rays, and branchiopercle are found dislocated ventral to the cranium (Fig. 9). The opercle, the largest element of the operculogular series, is confined by a long, convex posterodorsal margin, and a straight ventral border. The subopercle, slightly smaller than the opercle, has a long, convex posteroventral border and a straight dorsal margin. The anterior borders of the opercle and subopercle are covered by other cranial bones. The ornamentation of the opercle and subopercle is mostly composed of tubercles, of similar size and with a comparable density as those on the preopercle. The tubercles increase in size in the anterodorsal part of the opercle. A small portion of the left interopercle may be seen anteroventral to the subopercle (Fig. 9.1); the remaining part of this element is covered by the ventral preopercular plate. At least three branchiostegal rays are preserved. Each one has an elongate, subrectangular outline. A single, large element preserved anterior to the left ventral preopercular plate is interpreted as a possible branchiopercle (Figs. 9, 10.2). It is much larger than the branchiostegal rays, with a distinctly convex lateral surface. A large, plate-like fragment anterior to the lower jaw may correspond to the median gular. It probably had an ovoid shape, being somewhat longer than wide. The ornamentation of the branchiostegals and branchiopercle consists of tubercles, which are less densely spaced than on the opercle and subopercle. The gular is densely covered with tubercles. Coarse tubercles and short striae occur near the lateral bone margins.

Hyoid arch

At least the anterior and posterior ceratohyals are preserved, located ventral to the lower jaw (Figs. 9, 10.2). Both ceratohyals are plate-like. The anterior one is imperfect, but seemingly had an elongate shape. It is marked by a conspicuous, reticulated surface structure along its ventral margin (like in W. eugnathoides; cf., Grande and Bemis, Reference Grande and Bemis1998, fig. 416). The posterior ceratohyal has a triangular outline.

Dermal skull roof

The dermal skull roof is very fragmentarily preserved (Fig. 9). A small, bow-shaped bone, being overlapped by one of the premaxillae, could correspond to the rostral, but it is inadequately preserved. An isolated element preserved in the rostral area (Fig. 9.2) contains a seemingly triradiate sensory canal. It possibly pertains to the right nasal (cf., Grande and Bemis, Reference Grande and Bemis1998, fig. 415). The left nasal is possibly preserved in situ, but too incomplete for sound description. Posterior to the left nasal bone are the large, paired frontals. These elements are elongate and consist of a mediolaterally broad postorbital portion, and a slightly narrower anterior segment. Rostrally, the frontals extend to about the level of the center of the orbit. Each frontal is bounded by a long, serrated medial margin, and a straight posterior border. Its anterior confinement is not well visible, but was probably straight. The lateral border of the frontal is, as far as can be seen, anteriorly and posteriorly straight, and sigmoid in its middle portion. A sensory canal carrying bone fragment posterior to the left frontal may pertain to the corresponding parietal. Probably both dermopterotics are preserved in the posterolateral part of the dermal skull roof. The dermopterotic is longer than wide and bears two sensory canals that run perpendicular to one another. One of these canals, belonging to the supratemporal section of the lateral line, is anteroposteriorly oriented and passes over into the dermosphenotic rostrally. In the posterior part of the dermopterotic, a second canal runs in mediolateral direction, seemingly continuing medially through the parietal. Sections of the supraorbital sensory canal are visible within the frontals and the nasal. The ornamentation of the dermal cranial roof, where visible, consists of fairly coarse tubercles, generally larger than those on the bones of the operculogular series. In the posterior part of the skull roof, the tubercles become oblong and occasionally very large.

Circumorbitals

Small, plate-like bones preserved lateral to the dermal cranial roof are interpreted as the dermosphenotic and supraorbitals. A keystone-shaped element that is firmly connected to the left frontal is identified as the dermosphenotic (Fig. 9.2). Two serially arranged bones on the right side of the dermal skull roof, which are slightly larger than the dermosphenotic, correspond to supraorbitals. Another supraorbital, probably from the left side of the head, is dislocated from its original position (Fig. 9.1). The supraorbitals are covered with dense, relatively coarse tubercles similar to those on the dermal skull roof.

Regarding the bones of the infraorbital series, only the right lachrymal is preserved in situ (Fig. 9.2). This bone has a subtriangular shape, being higher than long, and contains a section of a sensory canal. The external surface is covered with fine tubercles. Three elements, now located between the dorsal and ventral preopercular plates, either belong to the infraorbital or suborbital series (Fig. 9). The most posterior of these bones, which is the largest one, was possibly located posteroventrally to the eye in vivo (jugal). Impressions of a sensory canal may be visible on the medial surface of this bone (Fig. 9.2). The two smaller infraorbital bones, now placed just anterior to the former, may have originally framed the ventral or posterior confinements of the orbital opening. The three infraorbital bones share the same conspicuous ornamentation, consisting of coarse tubercles and reticulate ridges. The tubercles on the lateral surface of the three dislocated infraorbital bones are larger than those on the preopercular plates, rendering an allocation of these three elements to the preopercle unlikely.

Shoulder girdle

The pectoral girdle is composed of four dermal bones: posttemporal, supracleithrum, cleithrum, and clavicle. The elements of the left half of the shoulder girdle are in situ, whereas of those of the right side, only the clavicle is preserved and dislocated (Fig. 9). The posttemporal consists of an external plate and a rod-like ventral process, issuing from the medial surface of the plate-like portion, near its lateral margin. The ventral process itself is covered by the adjacent bones, but its base is visible in P-57423a. The plate-like part is longer than wide and has an ovoid outline. Its external surface is covered with tubercles, except for the very anterior region. A sensory canal traverses the bone along its lateral border. Posteroventrally, the posttemporal is still connected to the supracleithrum, laterally covering a small area of the latter. The supracleithrum is a slender, plate-like bone with a trapezoidal shape. It is bounded by long, parallel posterodorsal and anteroventral margins and short, straight posterior and dorsal borders. The external surface of the supracleithrum is covered with tubercles of comparable size to those on the opercle and subopercle. Within its upper portion, the supracleithrum is pierced by a section of the lateral line sensory canal, traversing the bone obliquely in anteroposterior direction (Fig. 9.2).

The large cleithrum, placed ventral to the supracleithrum, has a broadly triangular outline (crescent-shaped). It is confined by a long, concave anterodorsal margin, a short, straight ventral border, and a long, sigmoid posterior margin, being dorsally convex and ventrally concave. The external surface is distinctly bent: the area along its anterodorsal border faces anterolaterally, whereas the posterodorsal and posteroventral regions of the cleithrum face laterally. Most of the lateral surface is ornamented with distinct, dorsoventrally running, interrupted ridges, which show anastomozation. Coarse, rounded tubercles occur in the ventral area. A strong ridge marks the anteroventral part of the medial surface of the cleithrum (preserved as an impression on the left cleithrum of P-57423b; Fig. 9.2). The endochondral shoulder girdle is not visible. The left clavicle is observed still in articulation with the corresponding cleithrum, while the right clavicle is located anteroventral to the branchiopercle. The clavicle is much smaller than the cleithrum and has a rectangular, elongate shape. Its external surface is ornamented with distinct, close-set, anastomozing striae that run perpendicular to the longitudinal axis of the bone, and tubercles locally (similar to W. eugnathoides; Grande and Bemis, Reference Grande and Bemis1998, fig. 416).

The supracleithrum and cleithrum are bordered by a large, deep postcleithrum. Two additional, smaller postcleithra are seen ventral to this element (Fig. 9). The postcleithra are covered with tubercles and vertical ridges, similar to those on the cleithrum. Wedged between the posttemporal and dermal skull roof is another, probably paired element: the extrascapular. The left extrascapular is preserved in situ (Fig. 9.1). This plate-like bone is anteroposteriorly short and of rectangular shape. Posteriorly, it partly overlaps an unornamented area on the left posttemporal. The extrascapular is covered with tubercles, and is traversed by four pore canals that meet in the center of the bone. The posterolateral and anterolateral canals correspond to the lateral line (or otic canal, respectively), whereas the two medially directed branches may belong to the supratemporal commissure, and perhaps to a link with the supraorbital sensory canal, respectively.

Paired and unpaired fins

The pectoral, pelvic, dorsal, and anal fins are preserved in situ, but are not complete (Fig. 8.1, 8.2). The relatively large pectoral fin inserts at the level of the concave lower part of the cleithrum's posterior margin. The radials are not exposed. The lepidotrichia of the pectoral fin are long and segmented, with long proximal and short, box-shaped distal units. The fin rays are distally branched. The ventral (pelvic) fin is placed midway between the pectoral and anal fins. It is short-based and consists of approximately seven fin rays. Each lepidotrichium is long and segmented, with long units at the base and much shorter ones distally. The fin rays are distally bifurcated. A few fringing fulcra are seen along the leading edge of the ventral fin. The anal fin is long-based, comprising ~20 lepidotrichia. The basal lepidotrichial segments of the anal fin are preserved in situ, being relatively long. Several short, box-shaped distal lepidotrichial segments are found scattered nearby. Some lateral scales at the base of the anal fin are missing, exposing a single row of pterygiophores. The exact number of these elements cannot be determined, but they relate as 1:1 to the fin rays. The dorsal fin is located slightly in front of the anal fin, but begins a few scale rows caudal to it (Fig. 8.1, 8.2). Although only a few fin rays are preserved in situ, the dorsal fin was probably long-based, judging from the distribution of in situ preserved basal lepidotrichial segments. The dorsal fin is composed of long fin ray segments at the base and much shorter units distally. The lepidotrichia ramify distally.

Squamation

The body of P-57423 is fusiform and relatively deep, with the maximum dorsoventral depth being found at a level slightly in front of the pelvic fins (Fig. 8). The squamation is composed mostly of rhombic scales, arranged in S-curved, subvertical rows. The course of the lateral line sensory canal can be traced along some scales situated between the shoulder girdle and the anal and dorsal fins. About 45 scale rows are counted along the inferred path of the lateral line (between the supracleithrum and the caudal end of the fossil). The scales on the flanks are slightly larger than those in the dorsal and ventral parts, and the depth of the scales decreases successively towards caudally.

The rhombic scales exhibit a large free field posteroventrally, and narrow, smooth anterior and dorsal areas that are laterally covered by the neighboring scales. The free field of the anterodorsal scales (Fig. 8.3, 8.4) is ornamented with ridges that are mostly oriented parallel to the posterior and ventral margins of the scale. The ridges may be interrupted, especially in the anterodorsal part of the free field. The scales immediately posterior to the postcleithra are ornamented with dorsoventrally directed ridges, similar to those on the postcleithra. In other parts of the body, the free field of the scales is smooth. Most scales do not show a denticulate hind margin, though a few scales on the cast of part b exhibit very weak serrations. A dorsal spine for peg-and-socket articulation and a slightly larger anterodorsal process are developed on scales in the anterodorsal and anteroventral part of the trunk (Fig. 8.3). Both features are seemingly absent on scales posterior to the level of the pelvic fins. At least one specialized scale is found anterior to the anal fin (Fig. 8.1, 8.2). This pre-anal scale has a circular shape and is enlarged compared to the neighboring scales. It is ornamented with concentric ridges.

PIMUZ A/I 4728

This is an incomplete, largely articulated, mid-sized actinopterygian (estimated standard length ~250–300 mm). Part a of specimen A/I 4728 (Fig. 11.1) contains the body (squamation) and some bones of the skull and shoulder girdle, as well as parts of the dorsal and anal fins. Portions of the squamation, fin rays, and several dermal bones are also preserved on a few noncontiguous fragments of the counterpart of the same nodule.

Of the dermal bones of A/I 4728, only the left cleithrum can be confidently identified. It is preserved anterior to the dorsal fin (Fig. 11.1). The cleithrum is bounded by a short, straight anterior margin, a long, convex posteroventral border marked by an indentation at the level of insertion of the pectoral fin, and a long, equably concave anterior confinement. The dorsal extremity of the cleithrum is incomplete. The convex external surface is ornamented with coarse, anastomosing striae, radiating from the center of the cleithrum, which is situated just anterior to the aforementioned indentation. Some striae running parallel to the anterior margin are observed in the anterior part of this element. The other, plate-like bones of A/I 4728 are ornamented with either coarse tubercles or thick, bifurcating striae.

The squamation consists of subvertical rows of large, rhombic scales. Approximately 35 rows are developed along the flanks between the anterior and posterior ends of the fossil. The scales along the flanks in the anterior body portion are about as deep as long, whereas those in the caudal, dorsal, and ventral body regions are much longer than deep. The ornamentation of the free field is preserved predominantly on the scales in the anterodorsal trunk portion. It consists of a few, anteroposteriorly running, gently meandering ridges, which become more distinct near the ventral scale margin.

The dorsal and anal fins of A/I 4728 are both situated in the caudal region of the body and are opposed to each other. The dorsal fin consists of fine lepidotrichia, each composed of a long proximal portion and shorter, elongate distal segments. Bifurcation is observed on some fin rays. It is not possible to count the number of fin rays because they are mostly disarticulated, but they appear to be numerous. The anal fin rays are mostly not visible. About 14 pterygiophores are preserved in situ at the base of this fin, but the posterior part of the fin base is missing. There are a few thin fin ray segments dispersed nearby. Because the dorsal and anal fins are often built similarly in coeval actinopterygians, we infer that the number of lepidotrichia may have exceeded that of the pterygiophores in A/I 4728.

PIMUZ A/I 4727

This specimen is preserved on two halves of a nodule, as part a and part b, respectively, showing the disarticulated remains (dermal bones, scales, fin rays) of a mid-sized actinopterygian (Fig. 11.2). The plate-like dermal bones show rather coarse surface ornamentation. Some of these elements are covered with thick, anastomosing striae, while others exhibit predominantly tubercles. Due to the fragmentary preservation, the dermal bones cannot be identified. The scales of A/I 4727 have a rhombic outline (Fig. 11.3). Some of them are about as deep as long, while others are distinctly longer than high. Many scales show a dorsal peg and a ventral socket on their medial surface. Such a peg-and-socket-articulation is not only developed on the deep scales, probably originating from the anterior flank region, but also on some of the elongate scales, supposedly from the posterior, dorsal, or ventral trunk areas. On many scales, a pronounced anterodorsal process is developed. The hind margin of the scales is usually straight, but at least one scale shows serrations. The free field is smooth. Some lepidotrichia are preserved, consisting of either long segments or shorter, box-shaped segments, frequently still in articulation (Fig. 11.4).

PIMUZ A/I 4731 and PIMUZ A/I 4732

Both specimens require excessive preparation before sound description, but they can be confidently identified as mid-sized actinopterygians based on the exposed skeletal elements. Specimen A/I 4731 shows articulated rhombic scales of comparable size, as in A/I 4728. The scales are subquadrangular. On at least one scale of A/I 4731, there is a small dorsal peg and a similar-sized anterodorsal process. Specimen A/I 4732, on the other hand, shows a dermal bone covered with distinct striae and tubercles. This specimen also preserves the squamation, but it is still enclosed in the matrix.