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Diambonia discuneata

Strophomenata - Strophomenida - Leptestiidae

Leangella discuneata was named by Lamont (1935). Its type specimen is H.M.L 1982, a shell, and it is a 3D body fossil.

It was recombined as Diambonia discuneata by Williams (1962), Cocks (1970) and Rasmussen et al. (2012); it was recombined as Leangella (Leangella) discuneata by Candela and Harper (2014).

Sister species lacking formal opinion data

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Synonymy list
YearName and author
1935Leangella discuneata Lamont pp. 315 - 316 figs. pl. 7, figs 17–19
1962Diambonia discuneata Williams pp. 173 - 174 figs. Pl. XVI, figs. 25-28
1970Diambonia discuneata Cocks p. 157 figs. pl. 1, figs 9–10.
1977Leangella discuneata Mitchell
2012Diambonia discuneata Rasmussen et al. pp. 27 - 28 figs. Plate 5, figures 15–20
2014Leangella (Leangella) discuneata Candela and Harper pp. Supplement 1

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phylumBrachiopodaCuvier 1805
subphylumRhynchonelliformeaWilliams et al. 1996
classStrophomenataWilliams et al 1996
orderStrophomenidaOpik 1934
superfamilyPlectambonitoideaJones 1928
familyLeptestiidaeOpik 1933
genusDiamboniaOpik 1933

If no rank is listed, the taxon is considered an unranked clade in modern classifications. Ranks may be repeated or presented in the wrong order because authors working on different parts of the classification may disagree about how to rank taxa.

A. Lamont 1935Shell small, tumid, sub-triangular, concavo-convex. Ventral valve highly inflated along median line, but laterally somewhat depressed; cardinal angles produced, sub-cylindrical; beak moderately swollen, slightly overhanging the area which lies in the plane of the valve. Internally there is a stout elongated tooth on each side of the triangular delthyrium. Supporting the teeth are two dental lamellae which run forward and outward to join the ridge bounding the muscle-scars. The muscle impressions occupy a quarter of the length and a little less than a third of the width of the valve; the didiictor pits are broad, subtriangular in outline, and rather deeply sunk; they are separated by a marked septum; the anterior ridge bounding the musclescars varies from emarginate to almost straight. Faint short vascular ridges arise from the antero-lateral angles of the muscle impressions. In front of the muscular region, a sharp-edged high median septum originates and runs forward for about 2 mm. along the median line.
A. Williams 1962Elongately semi-oval Diambonia about three-quarters as long as wide, with a slightly carinate pedicle valve about two-fifths as deep as long; radial ornamentation very finely parvicostellate, divided into wide sectors by a median and 2 pairs of divergent thickened and conspicuous costae radiating from the umbo; ventral muscle-scar subcordate, about three-fifths as long as wide, and extending anteriorly for about one-quarter of the length of the pedicle valve, diductor scars subpetaloid, giving rise to a pair of slightly divergent vascula media and separated medianly by a strong partition that passes posteriorly into a small, oval, elevated adductor platform bearing a thin median ridge, ventral median septum high and narrow arising a short distance in front of the muscle-field and extending anteriorly for about onequarter of the length of the valve; lophophore platform about as long as wide, elevated, and cleft anteromedianly with free, pointed, antero-lateral margins extending forward for over one-half of the length of the valve, raised lateral edges subparallel, strongly developed almost to the widely divergent socket ridges; subperipheral rim sharply defined as a pair of lateral curves, concave towards each other and meeting as a narrowly pointed elevation antero-medianly.
C. M. O. Rasmussen et al. 2012Small, strongly concavoconvex with an alate rectangular outline. Maximum width at acute cardinal extremities. Ventral valve unevenly convex with a bulbous umbo that projects slightly posterior of hingeline. Strongest convexity towards anterior margin. Ventral interarea apsacline, slightly curved. Delthyrial angle wide. Dorsal valve essentially flat until at anterior margin where the shell rises vertically to become deeply concave in profile. Interarea hypercline. Ornament of five widely spaced, accentuated costae on an otherwise smooth exterior. Growth lines developed close to anterior margin.

Ventral interior with large, widely spaced and divergent teeth. Dental plates not present. Ventral muscle field strongly impressed, divided by strongly developed ventral median septum that elevates anteriorly. High muscle bounding ridges clearly separate adductor from diductor muscle fields.