Matskási István (szerk.): A Magyar Természettudományi Múzeum évkönyve 80. (Budapest 1988)

Pálfy, J.: Middle Triassic rhynchonellids from the Balaton Highland (Transdanubian Central Range, Hungary)

Variability: The size, the costation and the height of the fold vary (Fig. 14). During growth first blunt costae occur which later get sharper along with the fold becoming higher. Due to this ontogenetic development, most of the specimens from Felsőörs are considered to be immature. Remarks — Among the modern authors GAETANI (1969) provided the most detailed description of the species with rich illustration, including several serial transverse sections. His material from Lombardia also shows great morphological variability. In GAETANI'S collection even the extremely folded "cynocephalous" forms occur as well. GAETANI pointed out that ontogeny is the most probable cause for these morphological variations. Distribution: GAETANI (1969) observed the stratigraphical range of this species to be confined to the Trinodosus Zone. In SIBLIK'S (1971a) opinion the species is most abundant in the Illyrian substage, but he mentioned its occurrence in Pelsonian faunas as well. In the Balaton Highland Piarorhynchella trinodosi occurs at the higher level of the Balatonicus Zone (in the Aszófő sequence), it is more abundant in Felsőörs in the uppermost part of the Pelsonian and is also recorded from the Illyrian strata. — Geographically the species was also reported from the Southern Alps, Eastern Alps, the West Carpathians and the Himalaya. Family Wellerellidae LIKHAREW, 1956 Genus Trigonirhynchella DAGYS, 1963 Trigonirhynchella attilina (BITTNER, 1890) (Plate 2: fig. 5, Plate 3: fig. 7; Fig. 15) 1890 Rhynchonella Attilina sp. n. — BITTNER: p. 16, pi. 37: fig. 1-8. 1933 Rhynchonella Attilina BITTN. — MILOSAVLJEVIC : p. 210, pl. 1 : fig. 9. 1971 "Rhynchonella" attilina BITTNER — SIBLIK: p. 178, pi. 20: fig. 1, Fig. 13. 1972 "Rhynchonella" attilina BITTNER — SCHOLZ: pl. 8. fig. 9. Material: 329 specimens from the Forrás Hill near Felsőörs, mostly well-preserved, but usually silicified shells. Two specimens from Aszófő. Dimensions: The data measured of the largest specimen are the following : length = 9 mm width = 7 mm, thickness = 6 mm. The average is approximately L — 8, W = 6 and Th — 4,5 in mm. There is very little variation in size. Description — External characters: Small-sized shell, subtrigonal in outline. The anterior margin is almost semicircular. The postero-lateral margins are straight or slightly convex, they meet each other at an angle of 45-50°. Both valves are equally convex, in some cases the shell has a globose appearance. Maximum width and thickness are reached at the middle of the valves.. The posterior part of the lateral commissure is straight, it divides a faintly developed planarea into two equal parts. The anterior commissure is rectimarginate, no fold or sinus can be observed, but it has zig-zag deflexions due to the costation. The number of costae is 6 to 9. The costae occur at about the mind-length and become stronger toward the anterior margin. Their profile is rounded, the width of the costae and the intervals are equal. The posterior part of the shell is smooth. The beak is small and erect. The pedicle opening is submesothyridid. Internal characters (Fig. 15): Pedicle valve: the delthyrial cavity is subquadrate between well developed, almost parallel dental plates. The dental plates are widely set and ventrally shorter, than dorsally. The umbonal cavities are narrow and elongated. No pedicle collar has been observed. The teeth are of medium size, deeply inserted in the brachial valve only in the plane of articulation. Denticula have not been perceptible. Brachial valve: The hinge plates are horizontal. The inner socket ridge as well as the crural bases are strong. The dorsal median septum is short, reduced. The crura are of prefalcifer type. Remarks — The type-locality of this species is Felsőörs, where it is one of the most prevalent members of the brachiopod assemblage. Previously "Rhynchonella''' attilina was not associated with any modern genus. The study of the internal characters by serial