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Planalvus cailliaudi
Taxonomy
Cryptonella cailliaudi was named by Barrois (1889) [Cryptonella ? cailliaudi.
Type is a recently designated lectotype.]. Its type specimen is MHNN-B-A-(f)-01),, a shell (complete shell), and it is a 3D body fossil.
It was recombined as Planalvus cailliaudi by Racheboeuf et al. (1994).
It was recombined as Planalvus cailliaudi by Racheboeuf et al. (1994).
Synonymy list
| Year | Name and author |
|---|---|
| 1889 | Cryptonella cailliaudi Barrois pp. 149-151 figs. Pl. 10 f. 4 |
| 1994 | Planalvus cailliaudi Racheboeuf et al. pp. 455 - figs. 1.20-.127, 8 |
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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.
†Planalvus cailliaudi Barrois 1889
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Diagnosis
| Reference | Diagnosis | |
|---|---|---|
| P. R. Racheboeuf et al. 1994 | Planalvus with equidimensional to slightly elongated biconvex to dorsibiconvex shell. Ventral sulcus starting in anterior fourth of adult shell.
Shell very small, subequidimensional to slight-ly elongated, subcircular to ovate outline, biconvex to dorsi-biconvex; maximum width from one-third to half shell length; maximum thickness attained about mid-length. Anterior com-missure slightly uniplicate. Outer surface with irregularly spaced growth lines. Ventral valve moderately convex in lateral profile, broad and very shallow sulcus originating in anterior fourth of adult shell. Gently curved beak, not prominent, truncated by circular mesothyrid to permesothyrid foramen. Convex and poorly defined pseudoareas, apsacline. Ventral valve thick-shelled, lacking dental plates and apical lateral cavities. Central pedicle cavity wide and subcircular. Cyr-tomatodont, convergent teeth relatively short, stout. Muscle field poorly differentiated. Dorsal valve equal to or slightly more convex than ventral, with greatest curvature in posterior third, close to umbo, di-rected ventrally over delthyrium. Poorly defined median fold gently uniplicate in adult shell. Cardinal plate heavily thickened, subtrapezoidal, ventrally concave, lacking apical perforation or ventral cavity under plate (Figure 8). Wide and flat, or slightly convex ventrally, conjunct inner hinge plates present. Outer hinge plates reduced, difficult to discern from inner socket ridges. Crural bases prominent near anterior edge of cardinal plate. Laterally high inner socket ridges slightly overhang sockets. Crura project anteroventrally from anterior margin of cardinal plate, reaching close to ventral valve, recurved posterodorsally, then anteriorly producing spiral cones of up to six whorls. Lateral branches of jugum almost perpendicular to dorsal part of primary lamellae, developing into jugal arch in form of widening U; jugum projected anteriorly as short saddle, extended ventrally as thin stem and bifurcating into accessory lamellae. Muscle scars poorly differentiated and sep-arated by low myophragm. |