Lissodus sp.
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publication ID |
https://doi.org/ 10.5281/zenodo.13514789 |
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persistent identifier |
https://treatment.plazi.org/id/03DF87A9-A302-FF9B-4106-F8BEB31BF967 |
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treatment provided by |
Felipe |
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scientific name |
Lissodus sp. |
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Lissodus sp. Morphotype 1
Fig. 3 View Fig .
Diagnosis.—Isolated microscopic hybodontoid teeth. Linguo−labially compressed with enameloid crown; up to eleven non−differentiated cusps (average six to seven); prominent median crest extending from lateral edge to lateral edge widening over each cusp and contracting between, with a wider and higher median cusp which expands on the labial side to a prominent labial buttress and a minor lingual buttress. Ornamented labially and lingually by medially curving ridges; labial nodes may occur at the crown−base interface. Ventral base is elongate, usually concave with a horizontal ridge centrally; a basal canal usually appears beneath the labial buttress area; lingual surface is a convex crescent with up to seven expanded pits or furrows; labial surface short with expanded pits or furrows.
Material.—Five figured isolated specimens, TCD.36752–54, TCD.35757, 58. Ten other isolated specimens, some complete, TCD.35755, 56, TCD.36759–64, TCD.36781, 82.
Description.—The length along the median crest ranges from 0.72 mm to 1.38 mm; the labio−lingual width ranges from 0.12 mm to 0.34 mm for the crown (base, 0.22 mm to 0.56 mm); the height in lingual view is 0.3 mm to 0.56 mm (crown only, 0.3 mm to 0.56 mm). The crown in some specimens is slightly asymmetric with an even number of cusps on one side of the main cusp and an uneven number on the other; the cusps are slightly fan shaped. The lingual crown has a main cusp with a vertical ridge bifurcating half way down, outlining a pyramidal base to the cusp; up to five non−differentiated cusps to either side, each with a ridge (not always along the mid line) from the apex, curving medio−lingually to the crown−base interface which is marked by a double horizontal ridge and groove. The lingual crown equals or slightly exceeds the length of the base; labially a buttress occurs as an extension of the main cusp which in some specimens extends into the base; vertical ridges descend from each of the other cusps culminating in a node, before curving medio−labially. The base is concave, more strongly so under the labial surface, with a horizontal ridge down the centre in many specimens; lingually the surface is long and rises sharply to the crown. It is indented with up to nine expanded pits or furrows and in some specimens longer medially than laterally. The labial side is short (where observed) and concave along the labio−ventral margin with a number of expanded pits or furrows.
Discussion.—The specimens grouped here as Morphotype 1 show a variation in shape: in some specimens a very strong lingual buttress occurs; in others the lingual buttress is poorly developed. Some of the specimens are more arrow shaped in lingual/labial view than others. They have been grouped together on the similarities of the crown form and ornamentation.
Age, locality, and lithology.—(i) Kilbride Limestone Formation, Polygnathus mehli conodont Biozone, Ivorian (probably Freyrian), late Tournaisian, Dinantian. Disused quarry, near Nobber, Co. Meath (N 845 848); crinoidal limestone. (ii) Upper Ballysteen Limestone , Polygnathus mehli conodont Biozone, Ivorian (pre−Freyrian), late Tournaisian, Dinantian. Bore hole 3246/4, 181.6– 252.7 m, Urlingford, Co. Kilkenny ; thinly bedded crinoidal limestone.
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