In doing broader research on three species of Strobeus that occur within the Glenshaw Formation in Western Pennsylvania, I have discovered many excellent plates by former authors. These plates are miniature works of art, capturing details of these fossil gastropods that may not be available in photographs. The art can be a mixed bag, as authors would fill in or invent details that didn’t exist. You’ll often see the overdrawn outlines that show what the specimen would look like if it remained in perfect shape.

Many of these specimens do not have correlating identification numbers, so finding the originals can be next to impossible. However, some rare examples exist, such as when an author illustrates a holotype. This text will review two of these historical plates. The first plate we will examine is one by Charles A. White, published in 1884 as part of a report on the fossil fauna of the “Coal Measures” (Pennsylvanian) in Indiana. The second will be a plate by George H. Girty in 1915 as part of his report on the fossil fauna of the Wewoka Formation of Oklahoma.

White’s Plate 34 from the Year 1884

Plate 34 in White’s report on the Fossils of the Indiana Rocks, No. 3, is an excellent representation of fossil gastropods known today under the genus Strobeus. White assigned all specimens on the plate to the genus Solenisus Meek and Worthen 1860, with the majority given to the subgenus Macrocheilus Phillips 1841.

White wrote that the assignment within the subgenus Macrocheilus was confusing. Unfortunately, an unknown printing error reversed this plate’s genus and subgenus names for Soleniscus (Macrocheilus). This mistake initially made correlation tricky, as I only used the plate. Fortunately, someone caught the error before it appeared on Plate 8 of Proceedings of the United States National Museum, Volume 6, 1883, a loaned version of Plate 34.

Still, White’s base genus for all these was Soleniscus, a situation that Knight proclaimed was the root of many problems across the family, the Subulitidae. In his own words: “For example, differences of opinion as to the true characters of Soleniscus typicus Meek and Worthen formed the basis of several misunderstandings.” Figures 18 and 19 on the following plate represent the type species of Solenisus, Soleniscus typicus.

Plate 34 from the fauna of the Indiana Coal Measures. Published by the Indiana Geological Survey in 1884. Many examples of what is known today as the fossil gastropod Strobeus are shown.
Plate 34 from Fossils of the Indiana Rocks Coal Measures, published by the Indiana Geological Survey in 1884, shows many examples of what is known today as Strobeus.

Later Authors’ Interpretations of White’s Identifications

Between Girty (1915) and Knight (1931), the pair reassigned most of White’s figures to other species, and all but one belonged to a new genus in modern times. White was particular when discussing his doubts about the taxonomic assignment for his figures. For example, he mentioned that Soleniscus (Macrocheilus) fusiformis, S. (M.) newberryi, and S. (M.) planus would be difficult to compare, even with complete collections of all three. Knight (1931) placed all of White’s figures of these three species under Soleniscus (Macrochilina) regularis. White also had doubts about his identification of figures 13 and 14, S. (M.) texanus, and figures 15 and 16, S. (M.) medialis. Girty correlated figures 13 and 14 to S. primogenius, and Knight placed figures 15 and 16 under the same.

Girty (1915) considered Soleniscus ponderosa from this plate a synonym of Sphaerodoma primigenius [sic] by suggesting that they are the same species. He also felt the same about S. texanus; others saw it as a younger (i.e., juvenile) S. ponderosa. Finally, Knight discusses S. ponderosa, calling it one of the largest examples of S. primigenius [sic] yet recovered.

Knight (1931) split White’s Macrocheilus (Soleniscus) ventricosus into two species, with figure 11 going to S. primogenius and figure 12 assigned to S. brevis. White (1881) had created the species S. brevis earlier but did not mention it in the 1884 publication. With the size of these publications and the technology to publish at the time, it’s possible his new species was unknown when making the plates. The last figures, 18 and 19, are copies of the holotype of Soleniscus typicus, thus retaining their name, which is still valid today.

Girty (1915) assigned these species under the genus Sphaerodoma Keyes. Knight (1931) went full circle and reassigned species under Soleniscus (Macrocheilus). It would be interesting to know if Girty and Knight had discussed the matter. They both did extensive reviews that included these species, but 16 years apart. Knight reviewed the Subulitidae, whereas Girty examined the entire fossil fauna of the Wewoka Formation of Oklahoma (353 pages worth). He dedicated 23 whole pages to Sphaerodoma.

Stated Species by White in 1884FigureKnown Today As
Soleniscus? (Macrocheilus) ponderosus1-2Strobeus primogenius
Soleniscus? (Macrocheilus) primigenius3Strobeus primogenius
Soleniscus (Macrocheilus) fusiformis4-6Strobeus regularis
Soleniscus (Macrocheilus) newberryi7-8Strobeus regularis
Solenisus planus9-10Strobeus regularis
Soleniscus (Macrocheilus) ventricosus11Strobeus primogenius
Soleniscus (Macrocheilus) ventricosus12Strobeus brevis
Soleniscus (Macrocheilus) texanus13-14Strobeus primogenius
Soleniscus? (Macrocheilus) medialis15-16Strobeus primogenius
Soleniscus (Macrocheilus) paludinaeformis17Strobeus paludinaeformis
Solenisus typicus18-19Solenisus typicus
Table 1.—Correlation of species by White in 1884 with modern genus assignments.

Girty’s Plate No. 24 from the Year 1915

In 1915, Girty published a monograph of the fossils of the Wewoka Formation of Oklahoma. In the publication, he provided 35 well-detailed fossil plates. The publication was very long, weighing in at 353 pages. Having been published over 100 years ago, it is no surprise that all the species represented on plate XXIV (24) now have new generic assignments. Knight (1931) reassigned most to the genus Soleniscus (Macrocheilus) again, restoring the genus and subgenus White (1884) had used. Over the intervening years, most of these species changed generic names, identifiable as Soleniscus, Polyphemopsis, Sphaerodoma, StrobeusIanthinopsis, and back to Strobeus again after a paper by J. Harper in 1981.

Plate 24 by Girty in 1915.
Plate 24 from Fossils of the Wewoka Formation of Oklahoma, published by the U. S. Geological Survey in 1915.

In figure 13, Girty includes a copy of Conrad’s illustration of Plectosylus primogenius on his plate for use in comparison. Knight agreed with Girty’s figures 14-17, placed Girty’s figures 9 through 12 of S. brevis under S. primigenius, and put figure 8 as Auriptygma simplex. Knight also correlated figure 4 S. ventricosa and 7 S. brevis var as S. paludinaeformis. He placed S. ventricosa under S. paludinaeformis after examining the type specimens authored by James Hall. He concluded that the only apparent difference was their size.

Knight placed figure 8 under Auriptygma simplex. Later in 1936, he changed all North American specimens identified under Auriptygma to a new genus, Leptoptygma. He was enlightened after taking a European trip to view many genotype specimens. Knight was better informed on the relationship between North American examples and their European counterparts since he could study them in person.

Hall (1858) created three new species under the genus Macrocheilus. M. fusiformis, M. ventricosus, and M. paludinaeformis. I’ve included a few figures from Hall’s plate in a graphic below. You can get a rough idea of why Knight (1931) combined M. ventricosus and M. paludinaeformis. Knight concluded that M. paludinaeformis was an adult specimen, whereas M. ventricosus was a juvenile of the same.

Girty considered both S. ponderosa and S. texanus as junior synonyms of S. primogenius and felt that S. texanus was a younger S. ponderosa (=S. primogenius). His identified figures of S. primogenius are still a valid species today. The specimen’s age came into consideration for figures 4 and 7. Knight (1931) placed both of these under S. paludinaeformis, considering them juveniles.

Sphaerodoma intercalaris from figures 1 and 2 is known today as Strobeus intercalaris. Sphaerodoma gracilis, figure 3, is known as Soleniscus gracilis.

Stated Species by Girty in 1915FigureKnown Today As
Sphaerodoma intercalaris1-2Strobeus intercalaris
Sphaerodoma gracilis3Soleniscus gracilis
Sphaerodoma ventricosa4Strobeus paludinaeformis
Sphaerodoma paludiniformis5-6Strobeus regularis
Sphaerodoma brevis var.7Strobeus paludinaeformis
Sphaerodoma brevis8Leptoptygma simplex
Sphaerodoma brevis9-12Strobeus primogenius
Sphaerodoma primigenia13-17Strobeus primogenius
Table 2.—Correlation of species by Girty in 1915 with modern genus assignments.