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-A304-FF97-424C-FDA5B3B5FBF9 |
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treatment provided by |
Felipe |
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scientific name |
Lissodus sp. |
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Lissodus sp. Morphotype 4
Fig. 5B, C View Fig .
Diagnosis.—Isolated microscopic hybodontoid teeth. Enameloid crown, labio−lingually compressed teeth with five to seven cusps, main cusp with a strong labial buttress extending into the base; median crest from lateral edge to lateral edge forming a diamond over each pointed cusp apex; ornamented lingually with vertical ridges which curve medio−lingually towards the crown−base interface; lateral cusps also have vertical ridges many of which culminate in strong nodes. Base is sub−triangular with the central angle at the main labial buttress; ventral surface slightly concave, more so ventro−labially; lingually slightly convex with deep furrows normal to the crest; short labial base incorporating the labial crown buttress extension.
Material.—Two figured, isolated specimens, TCD.36771, 72, three other isolated specimens, TCD.36770, TCD.36773, 74.
Description.—The length along the median crest of the crown ranges from 0.71 mm to 1.24 mm (base only, 1.03 mm to 1.13 mm); the lingual height ranges from 0.45 mm to 0.74 mm (crown only, 0.13 mm to 0.42 mm). The lingual surface of the crown appears to curve labially in most instances with the main cusp set slightly off−centre; the main cusp has a vertical ridge from the pointed apex bifurcating into two sharp ridges forming a gentle lingual buttress; the lateral cusps on the lingual surface generally have pointed crests from which strong vertical ridges descend and curve medio−lingually; the linguo−lateral edges tend to curve labially. Labially, the main cusp extends into a laterally compressed buttress which overhangs the base and extends into it, the lateral cusps tend to curve labially and are ornamented by vertical ridges which culminate in nodes at the crown−base interface. The lingual crown−base interface is marked by a horizontal ridge and groove, with only a groove visible on the labial side. The base on the lingual surface drops sharply from the crown−base interface, fans out to a platform and then drops again to the ventral margin, this surface has up to seven expanded pits and furrows; the labial surface is short, one−third the length of the lingual surface and dominated by the medio−labial extension of the labial crown buttress with four to five expanded pits on the surface. Ventrally the base is sub−triangular; the area under the lingual base appears as a sloping platform; there is a deep cavity under the labial buttress—these two areas appear to be separated by a horizontal ridge; pits occur on the surface.
Discussion.—Morphotype 4, although similar to Morphotype 1, is more triangular than elongate and in most instances the prominent labial buttress that initiates at the mid to lower crown level extends into the upper level of the labial base; also a number of minor buttress or large nodes occur along the labial surface.
Age, locality, and lithology.—Kilbride Limestone Formation, Polygnathus mehli conodont Biozone, Ivorian (probably Freyrian), late Tournaisian, Dinantian. Disused quarry, near Nobber, Co. Meath (N 845 848); crinoidal limestone.
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