Aeduella, WESTOLL, 1937

Štamberg, Stanislav, 2018, Actinopterygians Of The Permian Locality Buxières-Les-Mines (Bourbon- L’Archambault Basin, France) And Their Relationship To Other Early Actinopterygians, Fossil Imprint 74 (3 - 4), pp. 245-291 : 271-285

Aeduella blainvillei (AGASSSIZ, 1833)

Text-figs 25–35

D i a g n o s i s. After Heyler (1969; emended). Body fusiform reaching a total length of 20 cm. The parietal small and always longer than it is wide. The frontal large and wide; the width of the bone is 1.6–2 times its length. The dermosphenotic with prominent posterolateral process. Pentagon shaped rostro-postrostral with conspicuous tubercles on its outer surface. Orbit is large. The crescent shaped anterior supraorbital inserted between the orbit and the nasal. Variability in the fusion of the parietal. Supraorbital may or may not be fuse with the dermosphenotic and may or may not reach to the nasal. There may be five or six extrascapulars, many supraorbitals, and horizontal fragmentation of the preoperculum. The maxilla with triangular maxillary plate which is low posteriorly. The ratio of the length of the maxilla to its depth is on average from 3 to 3.5. The operculum and suboperculum are very high, ornamented with flat tubercles on their surface. Very oblique suture between the operculum and suboperculum. The suboperculum has conspicuously sloping and concave dorsal margin. Only one branchiostegal ray is present. The medial gular is elongated in anteroposterior direction, and it is significantly more slender anteriorly. The cleithrum is of ovoid shape. There maybe five or six extrascapulars. The pectoral fin inserts on the scaly lobe. The anal fin has a short base. Segments of lepidotrichia are short, but large with sigmoid sutures. The main lateral line extends, in some specimens, to the caudal inversion which is gradual. A short accessory lateral line is present dorsally behind the skull. Scale count:

22±1 37±1 7/8 22±1 35±1

D e s c r i p t i o n. The material consists of specimens ranging from juveniles with a total length of 36 mm (D 26.11.95.2) to adults with a length of 180 mm (D 20.03.99.6). The trunk is dorsally arched, and its greatest depth is at the level just anterior to the pelvic fin. The ratio between total length of the body in the adult specimens to height is about 3.2, and the ratio between total length of the body to head length is about 5–5.5. The skull is rounded anteriorly, but does not extend anteriorly.

Head. Snout. To date, a complete rostral region of the skull has not been found, but isolated bones or fragments are evident in the available material. The rostro-postrostral (in the sense of Heyler 1969) is in the shape of a pentagon ( Text-fig. 26c ) as in D 11.02.95.6; MHK 82787. The posterior margin of the bone is convex, and it fills the space created anteriorly in the concave anterior border of the right and left frontals. The outer surface of the rostro-postrostral is decorated with tubercles, which in the anterior region of the bone are very conspicuous but further back are less pronounced. The posterior part of the rostro-postrostral is without sculpture. In specimens from Buxières-les- Mines, laterally from the rostro-postrostral is the anterior supraorbital which is well preserved in several specimens (D 20.03.99/6; MHK 82784; MHK 82782; MHK 82787). This bone, which is wedged between the nasal and the orbit, is crescent shaped and the posterior concave border abuts the orbit anteriorly ( Text-fig. 26d ). The bone is conspicuously decorated with long ridges parallel to the posterior border of the bone. In the anterior direction the ridges are gradually shortened, and only isolated tubercles are present along the anterior border. The bone forms several conspicuous sinuses anteriorly where the pores of the supraorbital sensory canal are located. These supraorbital sensory canal pores are on the boundary line between the anterior supraorbital and nasal. The studied specimens from Buxières-les-Mines also contain bones which represent a coalescence of the nasal with the anterior supraorbital. A coalescence of the nasal with the anterior supraorbital is usual. The anterior supraorbital was previously described as the antorbital by Westoll (1937: figs 2, 4) in Aeduella blainvillei from Muse. The anterior supraorbital is also present in many specimens of Aeduella blainvillei from Muse described and figured by Heyler (1969). Heyler (1969) considered this bone to be the nasal, but several figures ( Heyler 1969: figs 48, 50, 56, 57, 91, 92) demonstrate the anterior supraorbital combined with the nasal to produce a single unit. The rostral region composed of the medial rostro-postrostral, paired nasal, and paired anterior supraorbital was described by

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Štamberg (2007, 2010b) in aeduellids Bourbonnella hirsuta, Neslovicella rzehaki and Neslovicella elongata. It is clear that the configuration of the rostral region bones in Aeduella blainvillei from Muse, Aeduella from Buxières-les-Mines, Bourbonnella hirsuta, Neslovicella rzehaki and Neslovicella elongata is similar to the rostral region in Amblypteridae ROMER, 1945 . Blot (1966) described the anterior supraorbital in addition to the nasal and postrostral in the rostral region in Paramblypterus decorus, Heyler (1969) and Štamberg (1976) in Paramblypterus rohani ( HECKEL, 1861), Dietze (1999) in Paramblypterus duvernoy ( AGASSIZ, 1833) and Štamberg (2013b) in Amblypterus latus ( AGASSIZ, 1833). The coalescence of the anterior supraorbital with the nasal to produce one unit was documented in Paramblypterus duvernoy by Dietze (1999).

Skull roof. The frontal, parietal, dermosphenotic, dermopterotic and the extrascapular series which form the skull roof are preserved in several specimens.

The oblong frontal is the largest bone in the skull roof ( Text-figs 25 , 26a, b, g ). The frontal is relatively wide; the width of the bone is 1.6–2 times its length (MHK 82784, MHK 82787, D 04.11.05.11). The interfrontal suture is straight, the lateral suture which borders with the dermosphenotic is also straight or slightly undulating anteriorly ( Text-fig. 26a, b, g ). The short posterior part of the frontal’s lateral suture borders with the dermopterotic. The posterior border of the frontal has a conspicuous notch at the point where the supraorbital canal passes from the frontal to the dermopterotic. The anterior border of the frontal slopes medially, and this concave area is filled by the rostro-postrostral. The exposed surface of the frontal is ornamented with inconspicuous flat tubercles. The infraorbital sensory canal crosses over the frontal from the lateral corner of the frontal’s anterior margin in a posterior direction close to its lateral margin, and traverses to the dermopterotic in the lateral part of the frontal’s posterior margin. ( Text-fig. 26a, g ) .

The parietal ( Text-figs 25 , 26a, b, e, f ) is narrow, oblong in shape, and is always longer than it is wide (MHK 82785; MHK 82804; D 04.11.05.19). The borders of the parietal are almost straight, not conspicuously undulating. The right and left parietals are always narrower than the frontals. The sculpture on the exposed surface is not conspicuous, and is formed by flat tubercles as on the frontal. Two sensory pit lines, namely the medial pit line and posterior pit line are very prominent on the bone posterolaterally. The dermopterotic borders the parietal laterally and a series of extrascapular bones posteriorly .

A triangular dermosphenotic borders the frontal laterally ( Text-figs 25 , 26a, b ). It is extended in an antero-posterior direction, narrows anteriorly and is posteriorly (BX 07.09.97; D 04.11.05.19; MHK 82784; MHK 82787). The bone has a characteristic shape, and it forms a prominent process posterolaterally. The infraorbital sensory canal passes to the dermosphenotic from the dermopterotic, and subsequently bends ventrolaterally and traverses across the lateral process of the dermosphenotic, around the posterior border of the orbit .

The dermopterotic is oblong in shape. An extentsion in the antero-posterior direction is preserved on specimens D 04.11.05.19, BX 07.09.97; MHK 82784 ; MHK 82787 . The courses of the sensory canals on the dermopterotic are of great importance. The infraorbital sensory canal traverses from the dermosphenotic in a posterior direction along the lateral border of the dermopterotic, and from there it traverses posteriorly to the bones of the extrascapular series. The continuation of the supraorbital sensory canal is also present as well as the infraorbital sensory canal. The supraorbital sensory canal traverses from the frontal, and it anastomoses with the branch of the supraorbital sensory canal in the posterior area of the dermopterotic ( Text-fig. 25 ).

The series of extrascapular bones is partly preserved in D 04.11.05.19. They form a strip of small bones posterior to the parietals and dermopterotics. It is not possible to distinguish the exact number of extrascapular bones. The infraorbital canal runs from the dermopterotic to the extrascapulars and it divides into the supratemporal branch interconnected with the infraorbital sensory canals of the right and left sides of the skull and continues posteriorly to the supracleithrum as the lateral sensory line.

The formation of the skull roof and course of the sensory canals are a distinguishing feature of the Aeduellidae . A parietal which narrows markedly towards the frontal was figured by Heyler (1969) for both Aeduella blainvillei, Decazella vetteri and Bourbonnella guilloti, by Štamberg (2007) in Neslovicella rzehaki and Bourbonnella hirsuta and by Štamberg (2010b) in Neslovicella elongata. The shape of the dermosphenotic is also a distinguishing feature. The dermosphenotic in Carboniferous and Permian actinopterygians is usually triangular in shape, narrows anteriorly and broadens in a posterior direction so that the bone is widest at its posterior part ( Amblypterus , Paramblypterus ). The dermosphenotic of Aeduellidae have a similar shape, but with a prominent ventro-lateral process along the infraorbital sensory canal, and a narrowing posteriorly. The dermosphenotic extends less than the frontal, but in dimensions it is the second largest bone of the skull roof. It differs from the bones of the skull roof in the Amblypteridae in which the dermopterotic is the second largest bone in the skull roof after the frontal. Previously Westoll (1937) and Heyler (1969) stressed the importance of the course of the sensory lines in Aeduellidae . Supraorbital sensory canal passes across the frontal and traverses onto the dermopterotic where it anastomoses with the infraorbital canal. However, the passing of the supraorbital canal from the frontal to the parietal is the most common condition in other Permo-Carboniferous actinopterygians. The supraorbital sensory canal marks not only the pit line on the dermopterotic anteriorly, but it continues and posteriorly anastomoses with the infraorbital canal ( Text-fig. 25 ). The termination of the supraorbital sensory canal was described ( Heyler 1969, Poplin and Dutheil 2005) as being a pit line only. It is now clear that the canal anastomoses with the infraorbital sensory canal on the dermopterotic similarly as in Decazella vetteri ( Heyler 1969). Only two pit lines, namely the middle and posterior, are present on the parietal, whereas in most Permo- Carboniferous actinopterygians the presence of three pit lines is documented on the parietal. These typical features of the sensory lines in Aeduellidae were documented in the material from Buxières-les-Mines. The same supraorbital canal course as in Aeduellidae was described byBlot (1966), Heyler (1969), Štamberg and Zajíc (1994) and Štamberg (2016a) in the family Igornichthyidae HEYLER, 1977 .

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Cheek bones. The large orbit is surrounded by the anterior supraorbital anteriorly and by the dermosphenotic dorsally. In addition a small triangular shaped supraorbital forms part of the border of the orbit dorsally. This supraorbital bone is situated along the lateral margin of the dermosphenotic anterior to the ventrolateral process of the dermosphenotic ( Text-figs 25 , 26a, b ). It is uncertain if this small bone is always present. Heyler (1969: figs 48, 49, 54, 55 etc.) figured a triangular shaped supraorbital in some specimens of Aeduella blainvillei from Muse and in Bourbonnella guilloti, but this bone is missing in other specimens of Aeduella blainvillei and other members of the Aeduellidae .

The preoperculum is very small (D 04.11.95.19; MHK 82784). It is narrow ventrally, and broadens in a dorsoanterior direction. The bone is only slightly anteriorly inclined but does not divide into two branches ( Text-fig. 25 ). This differs from the peropercular condition of Progyrolepis heyleri , Amblypteridae , and others. The preopercular sensory canal runs along the dorso-posterior margin of the preoperculum. There is a short branch off the preopercular canal that forms the horizontal pit line. The shape of the

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preoperculum is the same as in Aeduella blainvillei from Muse. Small rounded postorbital bones located anterior to the preoperculum are partly preserved so it is not possible to state the number or illustrate their exact position.

Jaws. The maxilla is preserved in many specimens (BX 04.11.97.58; BX 07.09.97; BX 28.09.96; D 04.11.95.6; D 20.03.99.6; D 26.11.95.7; MHK 82770; MHK 82803 and others). The basic feature of the maxilla is the triangular shape of the posterior portion. The maxilla is pointed anteriorly, and it continuously broadens in a posterior direction so that the bone is deepest posteriorly. The ventral margin of the maxilla is slightly convex, and sometimes the maxilla is slightly bent anteriorly ( Heyler 1969: fig. 126D). The majority of trianguloid maxillary plates extend in a dorsal or dorso-posterior direction to form a process (Text- figs 27a, b, 28a–c). This process has been recorded in the majority of maxillaries, but is missing in some ( Text-figs 27 c–e, g, 28d–f). This process was not recorded by Heyler (1969) in the specimens of Aeduella blainvillei from Muse, and Heyler (1969, 2000) considered this difference to be the character that defined a different taxon. Posteriorly, the maxilla is not very deep, and the ratio of the length of the maxilla to its depth is a factor of great variability that varies from 2.5 (MHK 82770; Text-fig. 28a, c) to 4 (D 04.11.95.6). The ratio is on average from 3 to 3.5. I believe the presence or absence of the maxillary plate extension in a dorsal or dorso-posterior direction reflects the variability in range of Aeduella blainvillei. The ventral margin of the maxilla bears minute teeth attached to tubules ( Text-fig. 29 ). One maxilla from an adult specimen (D 04.11.95.6) in medial view

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Text-fig. 28. Aeduella blainvillei ( AGASSIZ, 1833). Maxilla. Scale bars 5 mm. a – photograph (whitened) and c drawing of the left maxilla in lateral view. MHK 82770. b – posterior part of the right maxilla in lateral view. D 11.02.95, whitened. d – right maxilla in lateral view . MHK 82792. e – left maxilla of juvenile specimen in lateral view. G 4/2. f – right maxilla of juvenile specimen in lateral view. BX 07.09.97 .

exhibits a conspicuous horizontal lamina along the ventral border of the maxilla. The maxilla bears inconspicuous flat tubercles especially on the ventral half of the exposed surface of the bone.

The lower jaw is usually badly preserved ( Text-fig. 27a, b ). It is a weak bone (BX 04.11.97.58) that is slightly bent anteriorly. The pores of the mandibular sensory canal are arranged in a line in a postero-anterior direction (D 20.03.99).

Dentition. The dentition, consisting of tubular teeth, is an important feature of Aeduella blainvillei. The tooth consists of the tubule with a small tooth-cusp distally. The same teeth are on the upper and lower jaws, but especially well preserved are those on the maxilla. The whole tubule is laterally overlapped by the thin bone lamina of the maxilla, and only the small tooth-cusp protrudes above the jaw edge. This type of dentition was previously well described by Heyler (1969), but isolated maxillary bones from Buxièresles-Mines make it possible to compare teeth from different stages of ontogenetic development. Tubular teeth from a juvenile specimen consist of a short strong tube with a small tooth-cusp mounted distally. Text-fig. 29c, d shows a maxilla of length 12 mm which represents a juvenile specimen smaller than 80 mm in total body length. A tubular tooth from this specimen (G 4/1) is 0.16 mm long and 0.05 mm wide. Similar teeth can be seen from another juvenile specimen, G 4/ 2 in Text-fig. 29a, b . Adult specimens with a maxilla of length 21 mm have very long, thin tubules. The tubules are overlapped laterally by the thin maxilla lamina, and are traceable laterally on the maxilla in the form of vertically arranged ridges ( Text-fig. 29e, f ). Only very small tooth-cusps protrude along the ventral edge of the maxilla. Adult specimen G 6 ( Text-fig. 29e, f ) has tubules 0.58 mm long and only 0.06 mm wide.

The operculo-gular series. The bones of the operculogular series reflect the general characteristics of Aeduellidae . The series consists of the operculum, suboperculum, branchiostegal ray and lateral and medial gulars.

The operculum is a large bone significantly elongated in a dorsoventral direction and in which the dorsal one third of the bone bends in an anterior direction. The operculum is twice as deep as it is long. The angle of the bend, which forms the anterior margins of the dorsal and ventral branches of the operculum, varies notably. An angle of 145°–150° is most common (MHK 82791; MHK 82771; MHK 82775; MHK 82776), but angles of around 160 °

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were also recorded in slightly deformed operculars (BX 01.08.97.1; MHK 82771; MHK 82773). The operculum is rounded and narrower dorsally, it has a straight border ventrally which usually forms an angle of 90° with the anterior and posterior borders of the operculum. However, the ventral margin in some specimens is oblique and forms an acute angle with the anterior margin of the operculum. This character adds to the variability of the operculum. The operculum exhibits easily recognizable concentrically arranged incremental lines which are usually combined with

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fine lines forked radially from the ossification centre which is situated anteriorly in the area where the operculum bends ( Text-figs 30 , 31a, b , 32f, g ). Incremental lines and radially arranged lines are most well developed in young specimens. The exposed surface of the operculum bears flat tubercles orientated in a posterior direction. The opercular bones from Buxières-les-Mines are very similar in shape to those of Neslovicella elongata ( Štamberg 2010b: fig. 6) but are

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slightly different from these bones in Aeduella blainvillei from Muse. Heyler (1969) figured two types of Aeduella blainvillei opercula from Muse. One type is characterized by its regularly round posterior shape ( Heyler 1969: figs 58, 77C, E), the second type is distinguished by its irregularly bent posterior border which forms a hump ( Heyler 1969: figs 45, 53, 79). Specimens from Buxières-les-Mines exhibit opercular bones with a hump, and moreover narrow in a dorsal direction. Their clearly visible bend in the upper third of the bone is always present. The opercular bones from Buxières-les-Mines are also slightly deeper than their length compared to these bones in Aeduella blainvillei from Muse. The ratio of the depth of the operculum to its length in Aeduella blainvillei from Muse is 1.35–1.72 but in the same bones from Buxières-les-Mines the ratio is 1.75–2.15. Heyler (1969, 2000) previously pointed out the differences between these bones from Muse and Buxières-les-Mines, and he argued that this ratio taken together with some differences in the shape of the maxilla, should lead to the specimens from Buxières-les-Mines being assigned to a new species of Aeduellidae . The dermal bones of the operculogular series document large variability within these bones, and I am convinced that the observed differences in shape of the operculum are a demonstration of the variability within these bones in the range of species of Aeduella blainvillei rather than a defining character of a new taxon.

The suboperculum ( Text-figs 31 c–h, 32f, g) is trapezoidal in shape and is conspicuous elongated in a dorsoventral direction (BX 07.09.97; D 30.08.98; D 4.11.95(19); MHK 82769; MHK 82786). The suboperculum is unusually deep, and its ventral margin reaches to the level of the ventral margin of the maxilla. The dorsal border of the suboperculum slopes

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significantly anteriorly, and therefore the posterior margin of the suboperculum is 1.3–1.9 times deeper than the anterior margin. The depth of the suboperculum in its posterior region is twice its length. The shape of both the suboperculum and the operculum exhibit great variability which is most striking when considering the depth of the anterior margin of the suboperculum. The ratio of the depth of the anterior margin of the suboperculum to the suboperculum length fluctuates between 0.55 and 0.71 ( Text-fig. 31e, f ). The exposed surface of the suboperculum is ornamented with backward pointing flat tubercles. Some of the bones exhibit a narrow fold medially, directed along the bone’s ventral margin without any sculpture ( Text-figs 31e, f , 32f ). This narrow strip of the suboperculum ventral margin was overlapped by the dorsal margin of the branchiostegal ray. The suboperculum is ventroanteriorly thickened with a scraped surface which serves for attachment of the muscles. The ventroanterior corner is the ossification centre of the suboperculum. The conspicuously sloping and concave dorsal margin of the suboperculum is one of the distinguishing characteristics of Aeduella blainvillei. An anteriorly sloping dorsal margin can also be observed in Spinarichthys dispersus, Neslovicella rzehaki or Neslovicella elongata ( Štamberg 1988, 2007, 2010b), but not to such an extent as in Aeduella blainvillei. The suboperculum dorsal margin in Bourbonnella ( Heyler 1969, Poplin 2001, Štamberg 2007, Mickle 2011), Decazella ( Heyler 1969) or Puertollanichthys ( Forey and Young 1985) is straight or only slightly concave.

Branchiostegal ray. Only one branchiostegal ray is present ventrally to the suboperculum (D 04.11.95.19; D 20.03.99.6; MHK 82782; MHK 82791; MHK 82794). Larger numbers of branchiostegal rays are not present due to the lack of space caused by the extreme depth of the suboperculum which reaches ventrally to the level of the maxilla ventral margin ( Text-figs 27a, b, c , 32a, b, f, g ). The presence of only one branchiostegal ray in Aeduella blainvillei is also a diagnostic feature of this species. The branchiostegal ray is rectangular in shape and bears a large hyoid process that projects anteriorly ( Text-figs 27a, b , 32a, b, f ). The exposed surface of the branchiostegal ray is decorated with flat bumps pointing backwards. The hyoid process and narrow strip along the anterior margin of the bone is without sculpture, and was covered by the lateral gular. The hyoid process, devoid of sculpture, is unusually well developed with a variable large projection which points forwards under the medial margin of the lateral gular ( Text-fig. 32f ). The pronounced anterior projection on branchiostegal rays is described as the hyoid process by Pearson and Westoll (1979) in Cheirolepis and similarly by Gardiner (1984) in Mimipiscis toombsi. The branchiostegal ray projection in Mimipiscis toombsi or Cheirolepis is only a small extension of the ray anteriorly, but in Aeduella blainvillei this projection is very pronounced. Moreover, overlapping of the ventral margin of the suboperculum by the dorsal margin of the branchiostegal ray was documented, and conversely the anterior margin of the branchiostegal ray without sculpture is overlapped by the lateral gular. This arrangement of the branchiostegal ray and suboperculum is unusual in the Permo-Carboniferous actinopterygians and usually the suboperculum and following branchiostegal rays overlap in an anterior direction ( Text-fig. 32f ). Similar variance in the direction of overlap of the branchiostegal rays was described by Selezneva (1985) in Evenkia eunotoptera BERG, 1941.

Gular lateral and gular medial. Paired lateral gulars and one medial gular fill the space between the right and left lower jaws. The lateral gular (D 09.11.96.9; MHK 82782; MHK 82791; MHK 82804; MHK 82807) is rhombic in shape, elongated in an anteroposterior direction, and is twice as wide as it is long ( Text-figs 27a, b, d , 32f ). The lateral gulars are overlapped by the medial gular anteromedially, but the right and left lateral gulars do not overlap each other medially. The lateral gular overlaps the branchiostegal ray posteriorly. The exposed ventral surface of the bone is ornamented with flat tubercles and ridges similarly as in other bones of the operculo-gular series. A pronounced pit line lies mid length on the lateral gular and a little nearer to the lateral side of the bone. The rhombic medial gular (D 20.03.99.6; D 09.11.96.9; BX 04.11.97.58; MHK 82788; MHK 82787; MHK 82800; MHK 82807) is conspicuously elongated in an anteroposterior direction. The bone is more than twice as long as it is wide, and significantly more slender anteriorly. The exposed ventral surface of the bone bears a few flat tubercles or short ridges. A prominent pit line forms slots in the form of a V in the centre of the bone. The region of the bone anterior to the pit lines is always longer than the posterior region in the medial gular. The shape of the medial gular and particularly its slender anterior region are characteristic for Aeduella blainvillei .

Dermal bones of the shoulder girdle. The posttemporal, supracleithrum, cleithrum and clavicle form the shoulder girdle dermal bone series.

The posttemporal of oval shape is only partly preserved (MHK 82796; MHK 82808), but the fragments suggest a large bone as was figured by Heyler (1969: figs 91, 92, 96B) .

The supracleithrum is a narrow bone and in a dorsoventral direction markedly extended, tapering ventrally ( Text-fig. 33 d–f). The bone length is always less than one third the depth of the bone.A prominent projection developed dorsally joins the supracleithrum to the posttemporal. The lateral margin of the posttemporal overlaps the dorsal margin of the supracleithrum including its dorsal projection. The anterior margin of the bone which is overlapped by the operculum is markedly concave. The supracleithrum is rounded ventrally, and does not reach the ventral margin of the operculum.The lateral surface of the supracleithrum bears ridges which are arranged predominantly in a dorsoventral direction. The lateral sensory canal starts anteriorly to the dorsal process, passes diagonally through the dorsal third of the bone towards the posterior margin, and traverses to the scale as the main lateral sensory line. In medial view, the supracleithrum is reinforced in the area around the lateral sensory canal by two crests ( Text-fig. 33e, f ). The anterior margin of the supracleithrum is strengthened by the anterior crest (crista anterior) and the posterior crest (crista posterior) passes across the dorsal half of the bone. Both crests begin at the vaulted sensory canal ( Text-fig. 33e, f ). The strengthening of the medial side of the supracleithrum is very similar to that described by Štamberg (2007: fig. 21) in Neslovicella rzehaki.

The cleithrum ( Text-fig. 33 a–c) is very frequently preserved as an isolated bone or as part of a skull (BX 12, MHK 82768; MHK 82782). The bone consists of two branches, namely the lateral branch and ventral branch. The lateral branch is enlarged in an anteroposterior direction and elongated in a dorsoventral direction. It has an elliptical shape in lateral view, and dorsally tapers into a long process that reaches one third of the height of the operculum. Its a b

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anterior margin is conspicuously concave and forms the posterior boundary of the branchial cavity. The exposed lateral surface is ornamented with stout ridges apart from the area which is anteriorly overlapped by the operculum and suboperculum. The cleithrum is ventrally curved in a medial direction and forms the ventral branch which anteriorly borders with the clavicle. A cleithrum with much enlarged lateral branch is typical for Aeduella blainvillei, and the same form was described by Štamberg (2007, 2010b) in Neslovicella rzehaki and Neslovicella elongata.

The clavicle is preserved as an isolated bone on specimen MHK 82789 ( Text-fig. 33g ). The bone consists of a short and relatively wide horizontal branch and very deep narrow dorsal branch. The exposed area of the horizontal branch of the clavicle is ornamented .

Body. Adult specimens reach 16 cm of the total body length ( Text-fig. 35d ). The trunk is anteriorly arched. The total body length is estimated to be 3.2 times the deepest part of the body and 5.1 times the length of the skull (MHK 82806; MHK 82809). In younger specimens such

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as D 07.06.98.10 with a length of 80 mm ( Text-fig. 35c ) it represents the deepest part of the body and the ratio of the length of the skull to the total body length is 4.7. In juvenile specimens with a total body length 38–47 mm, the ratio between the total body length and the length of the skull is 3.8–4.2. No measurements of the deepest part of the body in juvenile specimens have been reported as squamation is developed along the lateral sensory line only and in the dorsal part of the body it is missing. Heyler (1969: tableau I, II) gave a figure for depth of the body in juvenile specimens ( Heyler 1969: pl. 37, figs 1, 2) based on unclear evidence. Measurements of adult and juvenile specimens lead to two conclusions: first, that the depth of the trunk during the course of growth increases in proportion to the total body length, and second, the length of the skull during growth of the specimen decreases in proportion to the total body length. Juvenile specimens have a well-developed large operculum in the skull ( Text-fig. 35a, b ).

Fins. The pectoral fin is only fragmentarily preserved. The lepidotrichia are segmented along their entire length.

The pelvic fin is situated in the middle between the pectoral and anal fins, and the base of the dorsal fin begins directly above the end of the pelvic fin.

The anal fin is triangular in shape. The base of the fin extends over a length of 8–9 scale rows. The fin contains approximately 21 segmented lepidotrichia (D 03.11.96.14; MHK 82796). The leading edge of the anal fin is protected by terminal segments of lepidotrichia in combination with fringing fulcra .

The dorsal fin is triangular in shape. The base of the fin extends over a length of 11 scale rows (D 04.11.95.19), and the fin contains 22 segmented lepidotrichia. The longest lepidotrichia in the dorsal fin of adult specimens contains more than 25 segments.

The caudal fin is attached to a strong caudal peduncle. Well-developed dorsal and anal lobes of the caudal fin produce an angle of 50°–55°. The dorsal lobe is 1.6–1.8 times as long as the ventral lobe. The ventral lobe contains 15 lepidotrichia which in adult specimens have at least 30 short robust segments in the longest lepidotrichia. The dorsal lobe contains no less than 50 lepidotrichia. The ventral lobe of the caudal fin is protected, as is the anterior border of other fins, by terminal segments of lepidotrichia in combination with the fringing fulcra ( Text-fig. 34f ).

Changes in the shape and number of segments in the lepidotrichia can also be recored during growth of an individual. The both anal and dorsal fins contain 21 or 22 lepidotrichia, the longest lepidotrichia contain at least 25 segments, and similarly, the ventral lobe of the caudal fin has 15 lepidotrichia with at least 30 short robust segments. While the number of lepidotrichia in the fins of juvenile and adult specimen is the same, however the number and shape of segments in juvenile specimens differ significantly. The segments in juvenile specimen D 26.11.95.2, with a total body length of 36 mm, are very slender and there are only four segments in the longest lepidotrichia of the pelvic fin, five segments make up the lepidotrichia of the dorsal fin, and the longest lepidotrichia in the ventral lobe of the caudal fin consists of seven segments. The number of segments increases with growth of the individual. Specimen D 07.06.98 which is 80 mm in total body length has 12 segments in the longest lepidotrichia of both the anal and dorsal fins. These conclusion agree with the data published by Heyler (1969: 147) for Aeduella blainvillei and Štamberg (2007, 2010b) for Neslovicella rzehaki and Neslovicella elongata.

Squamation. The scales on the anterior part of the trunk along the lateral sensory line are of oblong shape and are serrated posteriorly. The serrations occupy 2/3 of the posterior margin (MHK 82790; MHK 82801). The scale count is :

22

------------------ 36

8 21 32

Six scales are above the lateral sensory line and six scales are below it in the oblique scale range in front of the pelvic fin base in juvenile specimen D 04.11.95.20. In front of some fins are large ridge scales. Four ridge scales precede the dorsal fin. Their shape is variable depending on the age of the specimen. Ridge scales in juvenile specimens are slender and elongated in an anteroposterior direction ( Text-fig. 34a ). Only the first scale is entire, those following are produced by a coalescence of two scales. The scales grow together gradually during growth of the specimen ( Text-fig. 34b ), and the scales gradually broaden ( Text-fig. 34c, d ). Large paired ridge scales precede the base of the anal fin. These scales protect the dorsal margin of the caudal peduncle and two ridge scales cover the ventral margin of the caudal peduncle. Distinctive microsculpture characterises the scales of Aeduella blainvillei. Typically this consists of tubercles with a circular base which are arranged at regular distances (Textfig. 34g, h). These tubercles are similar to the short ridges forming the microsculpture of Progyrolepis heyleri scales and are typical for ganoine surfaces. The tubercles forming the microsculpture of Aeduella blainvillei have the same shape and arrangement as those forming the scale microsculpture of Paramblypterus duvernoy (personal observation), and the scales of Aeduella blainvillei and Paramblypterus duvernoy cannot be distinguished on the basis of their microsculpture at present. Monitoring the microsculpture of scales is very important as already Meunier et al. (1986), Gayet and Meunier (2001) demonstrated in recent and fossil genera of Lepisosteiformes and Polypteriformes . The shape and arrangement of microtubercles can also be used for determination of isolated scales of Permo- Carboniferous actinopterygians as shown in the comparison of microtubercles of Progyrolepis heyleri ( Text-figs 23b , 24 ), “ Elonichthys ” sp. ( Štamberg 2016b), Igornichthys bohemicus ŠTAMBERG, 2016 ( Štamberg 2016a), Spinarichthys dispersus ( Štamberg 2016b) and others. This comparison of scale microsculpture in the above mentioned species shows differences in shape and arrangement of microtubercles.

Figures

Text-fig. 25. Aeduella blainvillei (AGASSIZ, 1833). a, b – drawing and photograph of the skull. MHK 82784. Scale bars 5 mm. Abbreviations: Clei – cleithrum; Dsph – dermosphenotic; Dpt – dermopterotic; Fr – frontal; ioc – infraorbital canal; lsc – lateral sensory canal; Mx – maxilla; Op – operculum; Pa – parietal; Pop – preoperculum; popc – preopercular canal; Pt – posttemporal; Sbo – suborbital;Scl – supracleithrum; Soant – anterior supraorbital; Sorb – supraorbital; soc – supraorbital canal; Sop – suboperculum.

Text-fig. 26. Aeduella blainvillei (AGASSIZ, 1833). a, b – drawing and photograph (whitened) of the skull roof in dorsal view. MHK 82787. Scale bars 5 mm. c, d, e, f, g – isolated bones of the rostral part and the skull roof. The arrow indicates the front for all bones. Scale bar represents 5 mm for all bones. c – rostro-postrostral. MHK 82788. d – right supraorbital anterior in lateral view. MHK 82782. e – left parietal in dorsal view with two pit lines. MHK 82804. f – right parietal in dorsal view with two pit lines. MHK 82785. g – right frontal in dorsal view with pores of the supraorbital sensory canal. MHK 82767. Abbreviations: Dsph – dermosphenotic; Fr – frontal; ioc – infraorbital canal; Pa – parietal; pl – pit line; Rpr – rostropostrostral; soc – supraorbital canal; Sorb – supraorbital.

Text-fig. 27. Aeduella blainvillei (AGASSIZ, 1833). Scale bars 5 mm. a, b – photograph and drawing of the gulars, branchiostegal ray, suboperculum and maxilla in lateroventral view. MHK 82807. c – right suboperculum and maxilla in lateral view. MHK 82797. d – lateral gular in ventral view, right maxilla and branchiostegal ray in lateral view. MHK 82784. e – right maxilla in lateral view. MHK 82792. f – right maxilla in lateral view. G 4/1. g – left maxilla in lateral view. G 5. Abbreviations: Gul – lateral gular; Gum – medial gular; Md – mandible; Mx – maxilla; pl – pit line on the lateral and medial gulars; Par – parasphenoid; Rbr – branchiostegal ray; Sop – suboperculum.

Text-fig. 29. Aeduella blainvillei (AGASSIZ, 1833). a – anterior part of left maxilla of juvenile specimen in lateral view. The maxilla is 9 mm long. Arrows delimit the fragments of tubular teeth figured at b of this Text-fig. Specimen G 4/2. Scale bar 1 mm. b – fragments of short strong tubules of tubular teeth. The teeth-cusps are broken. G 4/2. Scale bar 100 μm. c – anterior part of left maxilla of juvenile specimen. The maxilla is 12 mm long. Frame marks the view at d of this Text-fig. G 4/1. Scale bar 1 mm. d – isolated short tubular tooth of juvenile specimen. Tubule of the tooth is short and strong. It is terminated apically by the tooth-cusp. G 4/1. Scale bar 100 μm. e – anterior part of left maxilla of adult specimen in lateral view. The maxilla is 21 mm long. Tubular teeth with long tubules are covered from lateral side by maxillary bone and only short teeth-cusps project on the ventral edge of the maxillary. The arrows indicate the positioning of the tubular tooth on the maxillary. G 6. Scale bar 1 mm. f – middle part of the ventral edge of the same maxilla as at a of this Text-fig. with isolated tubular tooth (marked by the frame) which is figured at higher magnification at g of this Text-fig. G 6. Scale bar 1 mm. g – isolated tubular tooth of adult specimen partially overlapped by the sediment. The tooth consists of very long slender tubules which are terminated by small sharply pointed tooth-cusp. G 6. Scale bar 100 μm.

Text-fig. 30. Aeduella blainvillei (AGASSIZ, 1833). A set of opercular bones showing their variability in bending and an example of their ventral border. Scale bars 5 mm. a – photograph and b – drawing of the right operculum in lateral view. MHK 82776. c – photograph and d – drawing of the right operculum in lateral view. MHK 82791. e – photograph (whitened) and f – drawing of the left operculum in lateral view. BX 01.08.97.1. g – photograph (whitened) and h – drawing of the right operculum in lateral view. MHK 82771. i – right operculum in lateral view. MHK 82771. j – right operculum in lateral view. BXM 080. k – left operculum in lateral view. D 04.10.98, whitened. l – left operculum in lateral view. MHK 82768, whitened.

Text-fig. 31. Aeduella blainvillei (AGASSIZ, 1833). A set of opercular and subopercular bones showing their variability. Scale bars 5 mm. a – left operculum in lateral view. MHK 82773. b – left operculum in lateral view. MHK 82775. c – left suboperculum in lateral view. MHK 82769. d – left suboperculum in lateral view. MHK 82786. e – left suboperculum in lateral view. G 3/1. f – left suboperculum in lateral view. G 3/1. g – right suboperculum in lateral view. BX 07.09.97. h – right suboperculum in lateral view. G 3/2.

Text-fig. 32. Aeduella blainvillei (AGASSIZ, 1833). Scale bars 5 mm. a – right branchiostegal ray in lateral view. BX 07.09.97. b – right branchiostegal ray in lateral view. D 20.03.99.6. c – medial gular with pit lines in the form of a V. BX 07.09.97. d – drawing. e – photograph of medial gular. G 2. The arrow indicates the front of the bones on the figures a, b, c, d, e. f – restoration of the mutual position of the operculum, suboperculum and branchiostegal ray in lateral view and lateral gular and medial gular in ventral view. g – operculo-gular series of juvenile specimen in lateral view. D 0411.95.19. Abbreviations: Gul – lateral gular; Op – operculum; Rbr – branchiostegal ray; Sop – suboperculum.

Text-fig. 33. Aeduella blainvillei (AGASSIZ, 1833). Dermal bones of the shoulder girdle. Scale bars 5 mm. a – right cleithrum in lateral view. MHK 82768. b – drawing and c – photograph (whitened) of right cleithrum in medial view. MHK 82771. d – right supracleithrum in medial view. MHK 82770. e – drawing and f – photograph (whitened) of left supracleithrum in medial view. G 1. g – right clavicle in lateral view. MHK 82784. Abbreviation: ca – crista anterior; cp – crista posterior; lsc – lateral sensory canal; sclp – process of supracleithrum.

Text-fig. 34. Aeduella blainvillei (AGASSIZ, 1833). a – ridge scales in front of the dorsal fin of a juvenile specimen (total length of the body 38 mm). D 03.11.96.14. Scale bar 1 mm. b – ridge scales in front of the dorsal fin of a juvenile specimen (total length of the body 40 mm). D 26.11.95.7. Scale bar 5 mm. c – ridge scales in front of the dorsal fin of a subadult specimen (total length of the body 80 mm). D 07.06.98.10. Scale bar 5 mm. d – ridge scales in front of the dorsal fin of an adult specimen (total length of the body 145 mm). MHK 82809. Scale bar 5 mm. e – part of the dorsal lobe of the caudal fin. MHK 82809, whitened. Scale bar 5 mm. f – part of the ventral lobe of the caudal fin with fringing fulcra along its anterior edge. MHK 82809, whitened. Scale bar 5 mm. g – microtubercles on a scale from the lateral side of the body. Microtubercles on this and the following snaps have a round shape, and are arranged in rows. MHK 82790. Scale bar 50 μm. h – Microtubercles on a scale from the lateral side of the body. MHK 82805. Scale bar 50 μm.

Text-fig. 35. Aeduella blainvillei (AGASSIZ, 1833). Scale bars 10 mm. a – juvenile specimen. D 03.11.96.14. b – juvenile specimen. D 26.11.95.2. c – subadult specimen. D 07.06.98.10. d – adult specimen. MHK 82809.

Text-fig. 23. Progyrolepis heyleri POPLIN, 1999. a – a scale from the middle part of the lateral side of the body with conspicuous ridges arranged diagonally across the scale. MHK 82831, whitened. Scale bar 1 mm. b – small tubercles which form the microsculpture on the scale have elliptical base, antero-posteriorly elongated, and are arranged diagonally in the same direction as the ridges on Text-fig. 23a. MHK 82831. Scale bars 100 μm. c, d – photograph and drawing of a scale with a pore of the lateral sensory line. D 08.02.98.10.4/4, whitened. Scale bar 1 mm. e – drawing of a scale from the middle part of the lateral side of the body. D 04.11.95.10. Scale bar 1 mm. f – drawing of a scale from the anterior region of the body above the lateral sensory line. D 05.09.98. Scale bar 1 mm. g – drawing of a scale from the lateral side of the body between the lateral sensory line and the base of the pelvic fin. D 18.13.96.7. Scale bar 1 mm. h – drawing of a scale from the abdominal region of the body in front of the pelvic fin. BX 31.05.99.49. Scale bar 1 mm. i – large basal fulcra from the dorsal rim of the caudal peduncle. BX 28.01.99.8. Scale bar 5 mm.

Text-fig. 24. Progyrolepis heyleri POPLIN, 1999. Scales from the dorsal part of the body which exhibit ridges arranged diagonally across the scale plus microtubercles. MHK 82829. a – whole scales. The frame marks the view at b of this Text-fig. Scale bar 1 mm. b – sector of the surface with some ridges and microtubercles. Scale bar 100 μm. The frame marks the view at c. c – sector of the surface with microtubercles slightly extended diagonally. Scale bar 50 μm.