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Heterorthina fairmountensis
Taxonomy
Dalmanella fairmountensis was named by Foerste (1909).
It was recombined as Heterorthina fairmountensis by Schuchert and Cooper (1932).
It was recombined as Heterorthina fairmountensis by Schuchert and Cooper (1932).
Sister species lacking formal opinion data
Synonymy list
| Year | Name and author |
|---|---|
| 1909 | Dalmanella fairmountensis Foerste pp. 216 - 217 figs. pl. 4 f. 2A-C |
| 1932 | Heterorthina fairmountensis Schuchert and Cooper p. 124 |
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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.
†Heterorthina fairmountensis Foerste 1909
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Diagnosis
| Reference | Diagnosis | |
|---|---|---|
| A. F. Foerste 1909 | Shell small, averaging 1"5 millimeters in width, but sometimes attaining a width of 18 millimeters. Shell usually wider posterior to the middle, the lateral edges more or less straightened, but converging anteriorly, suggesting a symmetrical trapezoidal rather than semicircular outline; however, shells with subquadrangular and with semicircular outlines also exist.
Pedicel valve with sides somewhat flattened and sloping away from a more or less distinct median axis of elevation; the latter IS most distinct posteriorly but frequently reaches the anterior margin. Lateral margins of the muscular area divergent as far as the anterior end of the exterior pair of diductor impressions, and then convergent with a sinuous curvature as far as the anteriol margin of the second pair, between which there is a strongly reentrant angle as far as the antenor edge of the adductor impressions. The adductor impressions are oblong and occupy about one-fifth of the width of the muscular area. Brachial valve flattened toward the lateral margins, but slightly convex on each side of the distinct median depression; the latter is narrow near the beak, but widens anteriorly, and produces a distinct abrupt curvature in the outline of the shell when viewed from the anterior side. The strong and rather wide median elevation separating the adductor scars broadens posteriorly between the crural plates, and supports the cardinal process. The latter is divided by a median slit, and often is fairly conspicuous. |
Measurements
No measurements are available
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| Source: g = genus, o = order, c = class, p = phylum, uc = unranked clade | |||||
| References: Nesnidal et al. 2013, Hendy 2009, Aberhan et al. 2004 | |||||
Age range: Maysvillian or 450.20000 to 449.60000 Ma
Collections (12 total)
| Time interval | Ma | Country or state | Original ID and collection number |
|---|---|---|---|
| Late/Upper Ordovician | USA (Ohio) | Heterorthina fairmountensis (78192) | |
| Maysvillian | USA (Ohio) | Heterorthina fairmountensis (72971 72973 72974 72977 72979 72980 72981 72982 72983 72984 73126) |