The articulated skeleton of the male specimen which is described above exhibits meristic characters that are very similar to those of the species Tinca furcata Agassiz, from the Middle Miocene (Badenian) of Öhningen (Gaudant, 1980), and of the more or less coeval Tinca micropygoptera Agassiz from Steinheim am Albuch (Gaudant 1989): the vertebral column includes 37 vertebrae (22 + 15), against 35–37 (generally 20–21 + 15–16) in T. furcata, and 35–38 (19–21 + 15–17) in T.
micropygoptera; the dorsal fin is composed of 12 rays (8 branched), supported by 9 pterygiophores, against 10–13 (7–9 branched) and 9 pterygiophores in T. furcata, and 10–12 (7–8 branched) and 8–9 pterygiophores in T. micropygoptera; the anal fin consists of 11 rays (8 of them being probably branched), supported by at least 7 pterygiophores, instead of 9–11 (7–8 branched) and 8 pterygiophores in T. furcata, and 9–11 (8–9 branched) and 8–9 pterygiophores in T. micropygoptera.
However, it should be noted that the maximum height of the body of the best preserved specimen from Höwenegg is included 3.5 times in the standard length, a situation which is similar to that known in Tinca furcata Agassiz, whereas this ratio is generally less than 1/4 in Tinca micropygoptera (Agassiz). For this reason, the tenches from Höwenegg may be considered as probably belonging to the species Tinca furcata Agassiz.
Family SILURIDAE Cuvier, 1817
Genus Silurus Linnaeus, 1766
Silurus joergi n. sp.
(Figs. 10, 11, 12, 13, 14)
Short diagnosis: Silurus of moderate size having a vertebral column is composed of about 50 vertebrae (about 13 + 37) behind the Weberian apparatus. Anal fin having about 45 rays.
Holotype articulated skeleton SMNK-PAL.6662, kept in the Staatliches Museum für Naturkunde Karlsruhe.
Origin of the name: Species dedicated to Dr. Ernst Jörg (1917–1977), former director of the Landessammlungen für Naturkunde Karlsruhe, who was active from 1951 to 1963, together with Heinz Tobien, in excavating the maar of Höwenegg and initiated the study of its fish fauna.
Material: This genus is documented by two complete specimens, and some fragments including a cleithrum with the pectoral spine in connexion. Additionally, a well-preserved head of a young fish, which is curated in the palaeontological collections of the Staatliches Museum für Naturkunde, Stuttgart, was found during the excavations made in June, 2005 (R. Böttcher in litt.).
The length of this head (SMNS 95177) reaches about 40 mm (Fig. 10). Although it is rather strongly crushed, it shows the two elongate dentaries (Dent) exhibiting the pores of the mandibular sensory canal. On their oral edge, no tooth is preserved. The oral process of the maxillaries (Mx) is covered with several longitudinal rows of small tooth sockets. Of the mesethmoid (Mesethm), one can see the typical shape of its anterolateral processes. The left frontal (Fr) may be partly observed by its ventral surface. The massive articular head of the hyomandibular (Hmd) is visible. The operculum (Op) is triangular; its maximum width, which reaches about two-third of the maximum height, is situated in its upper part. The anteroventral part of its lateral surface is ornamented with ridges radiating from the anterodorsal part of the bone. The right cleithrum (Cl), which is arch-shaped, articulates with the pectoral spine (Pect sp.), which exhibits small denticulations on its upper part.
A rather well-preserved specimen which has been prepared by the transfer method into an epoxy resin is the best preserved silurid skeleton found at Höwenegg (SMNK-PAL.6662; Fig. 11). It has a standard length of 355 mm. The head length is included about 4.5 times in standard length, whereas the maximum height of body is included 5 times in the same measurement. The head is rather elongate, its height being included about two times in its length.
The vertebral column consists of about 50 vertebrae; 37 of them are postabdominal. The caudal fin, which is incompletely preserved, is small.
Of the dorsal fin, only two rays are visible. Although the anal fin is destroyed, it is possible to estimate its composition because its endoskeleton is composed of about 45 pterygiophores.
A strong spine is present in the pelvic fin. It is ornamented with a row of small tubercles.
A second, almost complete, specimen has been transferred onto Lackfilm (SMNK-PAL.6661; Fig. 12). It shows the ventral side of a large head, which is dorsoventrally compressed. It has a length of about 90 mm. The ventral arms of the cleithra and the parasphenoid are exposed on the ventral surface. In front of the first abdominal vertebrae, the main component of the Weber apparatus is present. Its ventral surface is characterized by the presence of a long and rather narrow longitudinal ventral fossa.
An incomplete right cleithrum is fossilized in connection with a robust pectoral spine, which is ornamented by a row of tubercles (SMNK-PAL.6663; Fig. 13).
Additionally, a fragment of a left cleithrum (SMNK-PAL.6664) shows on its mesial surface the characteristic arch-shaped articular socket, which is penetrated by the articular process of the pectoral spine.