Turbo insectus Conrad, 1835

Timothy Conrad’s description of the Paleozoic gastropod Turbo insectus in 1835 was an open and shut case. In his historic, single sentence description, he described and figured a new species of the genus Turbo. His was the first report of North American marine fossils of the Pennsylvanian age. His was also the final report of T. insectus itself, with no future author describing recovered specimens as this species, at least with evidence.

Twenty years later in the year 1855, Joseph Norwood and Henry Pratten of the Illinois Geological Survey published a report on eight new species of Carboniferous fossils. In their report, they designated Pleurotomaria carbonaria as a new species. Either Turbo insectus was not known to them or Norwood and Pratten did not think it was related. Either way, it was not mentioned in their text. It was reported from Illinois and said to be rare to find at the locality.

It’s hardly surprising that Turbo insectus has been ignored. Even if the authors of P. carbonaria had reviewed Conrad’s illustration, there were problems with it. If his original illustration was drawn from a specimen of what is now known as Shansiella carbonaria, it was either of a misshapen specimen or it was poorly illustrated. In Figure 1, you can clearly see the difference in outline between the two. Several authors have compared the two over the years. Each of them has suspected that the two might be the same species.

Figure 1. Outline of Turbo insectus compared to Pleurotomaria carbonaria
Figure 1. Outline comparison of A, Turbo insectus and B, Pleurotomaria carbonaria. Note the difference in the final whorl profile. A is very tall in comparison to the wider, flat-topped final whorl in B. The number of spiral ribs is lower in A, which may indicate that it is a much smaller specimen than B.

The discovery of Turbo insectus by Edward Miller

Turbo insectus was recovered by Edward Miller, an assistant railway engineer. As he was employed in constructing the Allegheny Portage Railroad, he would spend his leisure time examining the rocks in the area. Using large excavating equipment to clear room for the infrastructure needed to lift railcars over the Allegheny Mountains had the side effect of exposing the hidden underlying geology. Miller, being an engineer rather than a geologist, gave his fossils to well-known paleontologists and paleobotanists of the day to describe and illustrate.

In Timothy Conrad’s paper, he reported five new species, all recovered from the same area. He also listed additional species that were found in the same stratum. This greatly helps the case of possibly correlating T. insectus with S. carbonaria, as familiar Pennsylvanian marine fossils were recovered alongside it. These included the well-known gastropods Worthenia tabulate (called Turbo by Conrad) and Strobeus primogenius (which Conrad called Stylifer) — it should be pointed out that these two gastropods are the only fossils Conrad described and named in the paper that are recognized as valid species today.

Photography was uncommon in use for much of anything in 1835, let alone for documenting recovered fossils. Conrad published the specimens given to him by Miller using drawings. One standard practice today for naming a new species is to thoroughly describe and illustrate it. Also, an author deposits the holotype specimen in an institution that allows others to review it. A manuscript that contains a name, a description, a figure, an identification number for the holotype, its collection location, and the name of the formation it occurred in are all part of the process. It’s important to be accurate and to make sure you are not describing a species that has already been declared.

All of the standards of today were not being used in 1835. The specimen is currently lost, perhaps retained by Conrad, Miller, or presented to a friend after its publication. It may have been handed down within their families or simply tossed out at some later date. It is all speculation. As far as science knows, Conrad’s new gastropod species Turbo insectus was discovered and disappeared in 1835. Since the specimen is missing, this makes any sort of official correlation with other fossils very difficult.

The International Commission on Zoological Nomenclature (ICZN), the world authority on taxonomic naming rules, would not be created for another sixty years

Four Authors Make a Correlation with T. insectus and S. carbonaria

The following four outstanding authors have made comments about the speculated similarity of these two published species. Their writings in 1910, 1937, 1964, and 2016 have kept the notion alive that these two species are possibly one and the same.

Percy E. Raymond was the first curator of invertebrate fossils at the Carnegie Museum of Natural History, and later chief paleontologist for the Geological Survey of Canada (Harper, 2016). George H. Girty was among the top paleontologists working for the USGS in his time and was known for his thoroughness in his work. Myron T. Sturgeon was a lifetime Pennsylvanian period researcher, producing several publications for the Pennsylvanian fossil fauna in Ohio, to the point where the period has by far the most publications from the state of Ohio. John A. Harper is a retired geologist for the Pennsylvania Geological Survey and is a noted expert in Mississippian period gastropods, writing several manuscripts about the class Gastropoda.

Percy E. Raymond mentions Turbo insectus

Percy E. Raymond published a list of fossil fauna for the Allegheny Formation and Conemaugh Group in Western Pennsylvania. In his research, he referenced Conrad’s report as part of his work. Raymond (1910, p. 145) wrote “These first fossils, described by Conrad in 1835, are Turbo tabulata (Worthenia tabulata), Stylifer primogenia (Sphaerodoma primogenia), and Turbo insectus, a shell similar to, if not the same as Pleurotomaria carbonaria in his discussion about the Brush Creek limestone. Raymond’s photograph of P. carbonara can be found in Figure 2-C.

Figure 2. Historical Specimens of T. insectus and Shansiella carbonaria
Figure 2. Historical specimens of T. insectus and Pleurotomaria carbonaria. A, Turbo insectus as illustrated by Conrad in 1835; B, Pleurotomaria carbonaria as illustrated by Norwood and Pratten in 1855; C, P. carbonaria by Raymond in 1910; D, P. carbonaria by Morningstar in 1922; E, Shansiella carbonaria by Hoare in 1967.

George H. Girty Believes the Pair to be Congeneric

Girty’s comparison of T. insectus and P. carbonaria came in 1937. Yin had only recently coined the name Shansiella, but P. carbonaria had not yet been reassigned to that genus. Girty’s discussion was similar to Raymond’s, a quick sentence comparing the two, giving a solid suggestion that the two were the same, or at the very least, belonged under the same genus.

Oddly enough, Girty referenced Turbo insectus as Pleurotomaria insecta, but I know of no other publication where T. insectus was reassigned to this genus. “The same is equally, or even more true of P. insecta, which Conrad described under the genus Turbo, but which I can scarcely doubt is a species at least congeneric with P. carbonaria.” (Girty, 1937, p. 211). It seems that Girty adjusted the name as well. He used insecta instead of insectus, but this was to match the gender of the genus, a required practice with Latin names.

Myron T. Sturgeon Proposes a Solution for Turbo Insectus

In his review of 40 specimens of Shansiella carbonaria from the Putnam Hill and Vanport limestones of eastern Ohio, Sturgeon ended his remarks with a paragraph on the similarity of Turbo insectus with Shansiella carbonaria. His was the longest discussion on the matter, where he states “In 1835 T. A. Conrad (p. 267, pl. 12, fig. 4) named, crudely figured, and briefly described a gastropod species as Turbo insectus from the Brush Creek Member near Bens Creek, Pennsylvania. Conrad’s figure of T. insectus resembles Shansiella carbonaria, a fact which Raymond (1910, p. 145; 1911, p. 85) has already noted. If topotype material should eventually prove T. insectus and S. carbonaria to be the same, Conrad’s name has precedence over Norwood & Pratten’s, and the name of this species will have to become S. insectus (Conrad).” (Sturgeon, 1964, p.210).

He proposed a path for the resolution of the name. If good Shansiella carbonaria material were to be recovered from the Ben’s Creek locality, then Shansiella carbonaria would become Shansiella insectus.

However, Sturgeon wrote this in 1964. At least 56 years have passed since his writing, and it has now been 185 years since Conrad’s inadequate description and illustration were published. The species S. carbonaria has existed for 165 years and has been written about in numerous publications and is labeled as such in a number of museum collections. Changing the name at this point could be counterproductive and confusing, so at least someone would likely object to this change in modern times.

John A. Harper’s Manuscript about the First Pennsylvanian Marine Invertebrate Fossil Locality in North America

John A. Harper has been an incredible resource for me to learn about local fossils, especially invertebrates found in the Glenshaw Formation. His 2016 paper about the historic Ben’s Creek locality is by far the most comprehensive review of the locality. He writes about the economic history and the geologic setting, reviews each of Conrad’s fossil finds, and discusses finds by three authors, Conrad, Raymond, and Leidy.

Harper’s review is important as he clearly states that Conrad’s illustration shares no similarities to any other Pennsylvanian gastropod from North America. Harper has long written about gastropods and specializes in Mississippian gastropods, however has spent the majority of his time living and working overtop of Pennsylvanian age rocks. He has written papers on several finds in the Glenshaw Formation, including the first Pennsylvanian aged report of a cephalopod aptychus in the Appalachian Basin.

The work is also important as it shows correlation with the other associated finds that Conrad, Raymond, and Leidy made at the location, therefore placing Turbo insectus in the company of other fossils commonly found with Shansiella carbonaria. Harper’s plate in the article, Figure 7, is a detailed comparison of each author’s illustrations vs modern photographed specimens. “Turbo insectus (Figure 7C) has not been described, illustrated, or documented since Conrad’s original report. Given that Conrad’s lithographs are probably fairly accurate, it is possible that it was based on a distorted specimen of Shansiella carbonaria (Norwood and Pratten) (shown on the right in Figure 7C for comparison). Shansiella, like Worthenia, is one of the more recognizable fossils found in Pennsylvanian marine faunas throughout North America. I know of no other Pennsylvanian gastropod from North America that comes even close to Conrad’s illustration of Turbo insectus.” (Harper, 2016, p. 9).

Conclusion

It certainly is no secret that the nomen dubium Turbo insectus is possibly the same fossil as Shansiella carbonaria. All of the published aforementioned authors have considered the possibility of correlation, showing that the two might be the same species. The problems still exist. The specimen or illustration is distorted, and the original material is missing. But, with time comes difficulties. Since the problems have been long-unsolved, and no authors have recovered published material from the location for over 100 years, it seems that the door is closed for species synonymization. Sturgeon suggested a path for fixing the problems at hand, but it may now be too late.

References