Lower Ordovician – Silurian
Lophospira is an extinct genus of epifaunal herbivores
Identification in Hand Sample:
- Outer whole face flattened
- Ornament sinous spiral cords with tubercles at shoulder
- Closely coiled whorls
- Elevated spires
- Very small umbilicus
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- The genus Lophospira was proposed by Whitfield (1886), who recognized that four previously defined North American fossil gastropod species were morphologically distinct enough to be removed from the genus Murchisonia. Three of these species, Murchisonia milleri, M. ventricosta, and M. variosa, had been described by Hall (1847). Salter (1859) described a fourth, M. helicteres. Whitfield noted that as compared to Murchisonia sensu stricto the newly defined lophospirids:
1. Are coiled more tightly around the axis;
2. Display a smaller degree of whorl overlap;
3. Display one or more carinae, and always a carinated periphery;
4. Display a thin, serrated projection on the periphery of many specimens;
5. Have a variable sinus or notch in the outer lip at the periphery, but not necessarily a slit;
6. Frequently display a tendency to uncoil in later whorls;
7. Never display a solid columella, but rather a small umbilicus.
Whitfield also mentioned that the apertures of Murchisonia sensu stricto differ from those of Lophospira, but offered no details.
- However, in Lophospira each carination appears to maintain its position relative to the sutures. The aperture of L. tropidophorus is nearly circular with no indication of a sinus or other angulation, and with a diameter that was much larger than that of the whorl itself (yet, cf. Fischer, 1887, p. 847, who made note of a sharply notched aperture). While very few completely defined apertures are present in the collection of lophospirids from the Platteville Formation, a re-entrant of some depth and form, varying among the species, would have been a very obvious feature.
Caster, Dalve & Pope (1961):
- In the Cincinnatian, only a few genera of snails are common. Strangely, the shells of certain genera, for example Cyclonema, are usually found complete; whereas only the internal molds of other genera, Lophospira, are commonly found. This undoubtedly reflects an original difference in the physical or chemical structure of the shell.
Treatise on Invertebrate Paleontology, Part I (1960) (Under Pleurotomaria):
- Trochiform, moderately high to depressed, anomphalous to broadly phaneromphalous, gradate, with outer whorl face flattened, at least in earlier growth stages; selenizone moderately broad, near mid-whorl; ornament sinuous spiral cords with tubercles at shoulder and in some species at margin of base.
Grabau & Shimer (1909)
- Shells with more or less elevated spires; closed coiled whorls except in senescent (phylogerontic) species. Whorls angular, generally with several carinae of which the central one forms a strong keel and is marked by an obtusely rounded peripheral “band” which is often marked with spirals of which the central one is heaviest. Umbilicus nearly always present. Outer lip notched but without slit. Ordovicic – Devonic.
Ulrich & Scofield (1897):
- Shells with more or less elevated spires; whorls closely coiled throughout or only in the upper part, the last often exhibiting a tendency to become disconnected; whorls angular on the periphery and bearing from one to five distinct carinae; central or peripheral keel strongest and most prominent, carrying the band, which is obtusely rounded, or more or less distinctly trilineate, with the median line heavier and more prominent than the other two; axis rarely, if ever, solid; an umbilicus, usually of very small size, nearly always present. Inner lip generally thickened, often slightly twisted, turning around the umbilicus so as to form a kind of hollow pillar. Outer lip more or less deeply notched, but the center of the notch, which lies at the peripheral angle, is never prolonged into a slit. Surface marking parallel with the apertural edge; occasionally cancellated by fine spiral lines.