Aeduellidae ROMER , 1945

Štamberg, Stanislav, 2021, Actinopterygians Of The Broumov Formation (Permian) In The Czech Part Of The Intra-Sudetic Basin (The Czech Republic), Fossil Imprint 77 (1), pp. 73-101 : 92-97

publication ID 10.37520/fi.2021.008

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Aeduellidae ROMER , 1945


Aeduellidae ROMER, 1945

Text-figs 14–17 View Text-fig View Text-fig View Text-fig View Text-fig

M a t e r i a l. A total of 20 specimens ( DP 4307 , G 58, NM-M 4910 , NM-M 4911 a, b, NM-M 4912 , NM-M 4913 , NM-M 4914 , NM-M 4921 , NM-M 4930 , NM-M 4931 ,

P 30942, P 30948, P 64650, P 64651, P 64662, P 64678, P 64692, P 64886, P 64892, P 80169, P 80179) from the Otovice Limestone Horizon (Olivětín Member) of the IntraSudetic Basin, from the localities Otovice “Černý potok”, Otovice “Stěnava”, Otovice “Chmelnice” .

D e s c r i p t i o n. A small but robust body of fusiform shape ( Text-fig. 14a View Text-fig ) with a total length up to 16–20 cm with dorsally arched trunk (DP 4307). The skull length is 20 % of the total body length, and the body length/depth ratio is about 3.5. Significant differences in the shape of the body are exhibited in specimen NM-M 4931 ( Text-fig. 14b View Text-fig ) which is described at the end of the description of Aeduellidae .

Skull roof ( Text-fig. 15b, c, d View Text-fig ). The skull is rounded anteriorly and the skull roof bones are preserved on specimen

NM-M 4910. The frontal is of oblong shape with a straight anterior and lateral edge. The interfrontal suture is slightly wavy. The length of the bone is only 1.6 times its width and 1.1 times the length of the parietal. The frontal borders laterally with the dermosphenotic and dermopterotic. The parietal is square shaped or narrower than where its length. The anteroposteriorly elongated dermosphenotic forms a lateral projection lateroposteriorly and, together with the dermopterotic, borders the frontal laterally. The dermopterotic is of oblong shape, narrowing posteriorly. One pair of narrow lateromedially elongated extrascapulars meet in the midline posteriorly to the right and left parietals. All bones of the skull roof exhibit sculpture formed of short ridges and tubercles (NM-M 4910, P 64892). The traces of the sensory canals are clearly visible. A supraorbital sensory canal passes along the lateral edge of the frontal, it bends in the posterior region of the bone laterally and traverses to the dermopterotic. The supraorbital sensory canal continues diagonally across the dermopterotic towards the infraorbital sensory canal. The infraorbital sensory canal is traceable along the lateral edge of the dermopterotic and it traverses to the dermosphenotic in an anterior direction. The pores in a transverse orientation on the extrascapulars indicate the course of the occipital sensory canal connecting the sensory canals of the right and left sides of the skull. Right and left parietals carry middle and posterior pit lines, and their courses on the two parietals are not identical, the middle pit line is directed anterolaterally on the right parietal. The pit lines on the parietals are not found in the posterolateral region of the parietals as in Paramblypterus , but are shifted more medially.

Jaws ( Text-fig. 15a View Text-fig ). The maxilla (G 58, P 64678, NM-M 4930 ) has a typical aeduellid shape with a triangular shaped posterior part and narrow but strong anterior suborbital part. The maxilla is slightly bent and anterior part of the maxilla slightly rises upwards. The length of the maxilla is twice its depth in the posterior part. A strip of tubules from tubular teeth forms the ventral edge of the maxilla. The length of the maxilla on specimen P 64678 is 19 mm and the length of the tubules of the tubular teeth is 1 mm, they are terminated by a 0.2 mm long acrodine tip. The tubules of the tubular teeth are covered with a thin lateral lamella similarly as in other Aeduellidae ( Štamberg 2020) .

Opercular apparatus ( Text-fig. 16 View Text-fig ). The operculum is conspicuously elongated in a dorsoventral direction (NM-M 4910, P 64662). The dorsal third of the operculum bends anteriorly at an angle of 30° (angle of bend formed by anterior margins of the dorsal and ventral branches of the operculum). The high operculum is narrowed at the dorsal end, the largest anteroposterior dimension is located along the ventral edge of the bone.

The suboperculum on P 30948 is trapezoidal in shape. The dorsal edge of the suboperculum slopes significantly anteriorly and therefore the posterior margin of the suboperculum is twice deeper than the anterior margin. The ventral border of the bone is slightly convex. The sculpture on the ventral region of the outer surface consists of two rows of long ridges parallel with the ventral edge of the bone. The long ridges become several short ridges and tubercles in a dorsal direction.

Body and squamation ( Text-figs 14 View Text-fig , 17 View Text-fig ). The whole specimen, DP 4307, with arched back measures 16 cm of the total body length, but the fragments of bodies with squamation (P 64662, NM-M 4912) suggest body remains certainly reaching 20 cm out of the total body length. The specimens from the Otovice limestone are usually significantly deformed. The shape of the body and corresponding ratio of the length and depth of the body were calculated for specimen DP 4307. The ratio of the total body length to its depth is 3.5 and ratio of the total body length to the length of the skull is about 5.

The pelvic fin is situated midway between the skull and anal fin. The base of the fin extends over 4 scale rows and consists of 15 lepidotrichia. Minute scales with serrations on their posterior margin occur along the posterior part of the pelvic fin base (DP 4307). The anterior border of the fin is protected by the terminal pointed segments of 4 anterior lepidotrichia in combination with several fringing fulcra.

The anal fin base extends over 7 scale rows and a row of small denticulated scales were observed along the anal fin base in some specimens (P 80169, DP 4307). The anal fin consists of 24 lepidotrichia, of which the first five reaches the anterior border of the fin and their terminal segments form protection of the anterior edge of the fin.

The dorsal fin base extends over 7 scale rows (P 80169), it begins in the middle of the total body length, and its whole base is vertically just in front of the start of the anal fin base. Three large stout ridge scales precede the dorsal fin and a relatively large field of minute scales is located along the dorsal fin base (P 80169).

The caudal peduncle is strong ( DP 4307 , P 64650) . The dorsal and ventral lobes of the caudal fins together form an angle of 53°, the dorsal lobe forms an angle of 23°–24° with the horizontal plane, and the ventral lobe forms an angle of 30° ( DP 4307 , P 64650) with the horizontal plane. The dorsal lobe is twice the length of the ventral lobe. The ventral lobe consists of 14 segmented lepidotrichia and more than 60 segmented lepidotrichia constitute the dorsal lobe (P 64650) . Segments of the lepidotrichia of all fins are very strong and short with sigmoid contact edges. The segments divide longitudinally dichotomously from the basal segment. The leading edges of the paired and unpaired fins are protected by the pointed terminal segments of the lepidotrichia in combination with fringing fulcra. The number of fringing fulcra on the anterior edge of the fins increases with age of the individual. From the short and strong segments of lepidotrichia it is possible to deduce that specimens of total body length 15 cm were adult.

The scales on the lateral side of the body are of oblong shape, also large and deep. They overlap one another by onefifth in an anteroposterior direction. The scales bearing pores of the lateral sensory line are slightly smaller than the scales located below the lateral sensory line. The deepest scales are in the anterior region of the body in two rows under the lateral sensory line. The individual of total body length 16 cm has scales in the region between the pelvic and anal fins in the row immediately below the lateral sensory line of depth 4–4.2 mm. Paramblypterus rohani or Bourbonnella hirsuta with the same total body length have scales half the depth in the same area. Peg and socket articulation is well developed. On the surface there is a combination of fine ridges along the posterior and ventral edges of the scale (P 80168, P 64892, P 64662) which protrude into the fine serration on the posterior margin of the scales and also as pointed tubercles on the posterior surface of the scales. Serration on the posterior edge of the scales and tubercles on the surface of the scale protrude into the fine spines (P 80179, DP 4307; Text-fig. 17a, b View Text-fig ), the posterior area of the scale was extremely thorny. Fine spines are well developed along the entire posterior edge of the scales in the anterior region of the body (NM-M 4912, NM-M 4914), and they cover two thirds of the posterior edge of the scales in the region between the pelvic and anal fins. Fine spines border the posterior edge of the flank scales dorsally from the anal fin base (P 64650, P 80169). Irregularity in the squamation can be observed in specimen NM-M 4912 which exhibits scales twice the height as the surrounding ones, which is repeated in several rows ( Text-fig. 17c, d View Text-fig ). Large scales are preserved in the 14 th, 16 th, 17 th and 19 th rows. These large scales are always twice the size as the scales in the row in front of them. They are always joined without any sutures. It is clear that these scales grew independently when the individual was in the juvenile stage and did not coalesce until a later stage of growth.

There are 6 scales above the lateral line in a row of scales in front of the anal fin and 9 scales below the lateral line. The scale count of specimen DP 4307 is

23 ––––––––––––––––– 36 8 22 34

Specimen NM-M 4931 ( Text-fig. 14b View Text-fig ) demonstrates obvious differences as regards body shape and scale count. The body, including squamation and fins, is well preserved; on the contrary, the bones of the head are completely missing. The specimen has a slender body, 18 cm of the total body length. The ratio of the total body length to its depth is 4.6. The morphology of the fins and scales, including a serration which forms fine spines on the posterior edge of the scales, is the same as in the aeduellid describe above. The lateral side of the body, similarly as in NM-M 1912, bears scales twice the size of the neighbouring scales. They occur in the fourteenth and twentieth rows just below the lateral sensory line. The dorsal fin is moved slightly anteriorly relative to the above described specimen DP 4307 ( Text-fig. 14a View Text-fig ). The dorsal fin begins before the middle of the total body length and has the entire the level anteriorly to the anal fin base. The forward displacement of the dorsal fin may be caused by slight deformation of the specimen during fossilization since the inclination of the scale row in front of the anal fin is 50°, whereas in the previously described specimen, DP 4307, the scale rows are more upright and their inclination is 65°. Also the caudal peduncle is longer than in DP 4307. The dorsal lobe of the caudal fin forms an angle of 24° with the horizontal plane, the ventral lobe of the caudal fin makes an angle of 15° with the horizontal plane. The scale count can be determined unambiguously. It is

27 ––––––––––––––––– 37 7 24 35

and shows a slight difference compared to the previous one. It is not yet possible to decide whether the different features found so far are a manifestation of species differences or only differences caused during the fossilization processes.

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