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Replacement names for two species of Orthacanthus Agassiz, 1843 (Chondrichthyes, Xenacanthiformes), and discussion of Giebelodus Whitley, 1940, replacement name for Chilodus Giebel, 1848 (Chondrichthyes, Xenacanthiformes), preoccupied by Chilodus Müller & Troschel, 1844 (Actinopterygii, Characiformes)
expand article infoLoren E. Babcock‡
‡ The Ohio State University, Columbus, United States of America

Corresponding author: Loren E. Babcock ( babcock.5@osu.edu )

Academic editor: Bruno Melo
© 2024 Loren E. Babcock.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation: Babcock LE (2024) Replacement names for two species of Orthacanthus Agassiz, 1843 (Chondrichthyes, Xenacanthiformes), and discussion of Giebelodus Whitley, 1940, replacement name for Chilodus Giebel, 1848 (Chondrichthyes, Xenacanthiformes), preoccupied by Chilodus Müller & Troschel, 1844 (Actinopterygii, Characiformes). ZooKeys 1188: 219-226. https://doi.org/10.3897/zookeys.1188.108571
ZooBank: urn:lsid:zoobank.org:pub:B6BBB2F0-B9FF-4E76-B354-3D7CF36310C9
Open Access

Abstract

Three species assigned to the same nominal genus of Paleozoic xenacanthiform shark have been combined with the name Orthacanthus gracilis (Chondrichthyes, Xenacanthiformes, Orthacanthidae). Orthacanthus gracilis (Giebel, 1848), which was originally combined as Chilodus gracilis Giebel, 1848, is the senior synonym; it has priority over both Orthacanthus gracilis (Newberry, 1857), which was originally combined as Diplodus gracilis Newberry, 1857, and Orthacanthus gracilis Newberry, 1875a. Proposed species-group replacement names are Orthacanthus lintonensis nom. nov. for O. gracilis (Newberry, 1857) and Orthacanthus adamas nom. nov. for O. gracilis Newberry, 1875a. Chilodus gracilis Giebel, 1848 is designated as the type species of Chilodus Giebel, 1848; this species becomes the type species for Giebelodus Whitley, 1940, which is a replacement name for Chilodus Giebel, 1848 (preoccupied by Chilodus Müller & Troschel, 1844, Actinopterygii). Giebelodus Whitley, 1940 is a junior subjective synonym of Orthacanthus Agassiz, 1843.

Key words

Carboniferous, Chilodontidae, headstander, junior homonym, Orthacanthidae, shark

Introduction

Three species of xenacanthiform sharks described from Carboniferous strata have been assigned to the same nominal genus and combined with the name Orthacanthus gracilis (Chondrichthyes, Xenacanthiformes, Orthacanthidae), either originally or subsequently. The basionym of the senior synonym, in its original combination, Chilodus gracilis Giebel, 1848, is homonymous with the name of an extant species of characiform fish, Chilodus gracilis Isbrücker & Nijssen, 1988 (Actinopterygii, Characiformes, Chilodontidae). Chilodus is a genus-group name that was proposed for two different nominal genera. One is a genus of characiform fish (Müller and Troschel 1844: 85–86) and the other is a genus of extinct xenacanthiform shark (Giebel 1848: 352).

The purpose of this paper is to clarify, detangle, and stabilize the nomenclature of these genus-group and species-group names.

Nomenclatural history

Species-group names of fossil xenacanthiform sharks that have been combined as Orthacanthus gracilis are as follows:

  1. Chilodus gracilis Giebel, 1848 (Fig. 1A), reassigned to Orthacanthus Agassiz, 1843 by Boy and Martens (1991) and Hampe (1994, 2003). According to Articles 23.3.5, 52, 57, and 60.3 of the International Code of Zoological Nomenclature (International Commission on Zoological Nomenclature 2000), this species has priority over two species named by Newberry (1857, 1875a) (see below) that have the name Orthacanthus gracilis originally or after recombination.
  2. Diplodus gracilis Newberry, 1857 (Fig. 1B), reassigned to Orthacanthus by Hampe (1994, 2003). It is a junior secondary homonym of Orthacanthus gracilis (Giebel, 1848) when both species are treated as valid species of Orthacanthus Agassiz, 1843 (Hampe 1994: 56–63). To remove the homonymy, the name Orthacanthus lintonensis nom. nov. is proposed as a new replacement name for Diplodus gracilis (Newberry, 1857).
  3. Orthacanthus gracilis Newberry, 1875a (Fig. 1C). This species is a junior secondary homonym of Chilodus gracilis Giebel, 1848 when C. gracilis Giebel, 1848 is placed in Orthacanthus Agassiz, 1843 (Hampe 1988, 1994, 2003; Boy and Martens 1991: figs 1, 8). To remove the homonymy, the name Orthacanthus adamas nom. nov. is proposed as a new replacement name for Orthacanthus gracilis Newberry, 1875a.

Proposals of Chilodus as a genus-group name are as follows:

  1. Chilodus Müller & Troschel, 1844 was erected for an extant characiform fish with Chilodus punctatus Müller & Troschel, 1844 (Actinopterygii, Characiformes, Chilodontidae) as the type species, by monotypy.
  2. Chilodus Giebel, 1848 was erected for an extinct Paleozoic xenacanthiform shark (Chondrichthyes, Xenacanthiformes, Orthacanthidae), embracing two species, Chilodus tuberosus Giebel, 1848 (Fig. 1D) and Chilodus gracilis Giebel, 1848 (Fig. 1A).

The type species of Chilodus Giebel, 1848, designated here for nomenclatural stability, is Chilodus gracilis Giebel, 1848. It is the best-known species and the only one that Giebel (1848) included in Chilodus that is represented by a known, existing type specimen (Hampe 1994; Fig. 1A). Designation of this species as the type species follows Recommendation 69A of the Code (International Subcommission on Zoological Nomenclature 2000). The other species originally included in Chilodus Giebel, 1848, C. tuberosus Giebel, 1848, was synonymized by Giebel (1849) with Lamna carbonaria Germar, 1844 (Fig. 1E); but see Romanovski (1857), who retained the combination C. tuberosus Giebel, 1848. Here, L. carbonaria, including C. tuberosus as a junior subjective synonym, is recombined as Orthacanthus carbonarius (Germar, 1844).

Figure 1. 

Original 19th century figures of Carboniferous-age xenacanthiform shark fossils from Saxony-Anhalt, Germany, and Ohio, USA A Orthacanthus gracilis (Giebel, 1848), tooth, holotype (Geiseltalmuseum Halle, GTM 1095), two views; reproduced from Giebel (1849: pl. XXIX, fig. 2a, b), 7.7 mm long. Wettin-Schichten, Wettin/Saalegebiet, Saxony-Anhalt, Germany B Orthacanthus lintonensis nom. nov., replacement name for Diplodus gracilis Newberry, 1857a, two teeth, syntypes (repository unknown); reproduced from Newberry (1875a: pl. LVIII, figs. 3, 3a), ca 5 and 13 mm long. Upper Freeport Coal, Allegheny Group, Diamond Coal Mine, Linton, Ohio, USA C Orthacanthus adamas nom. nov., replacement name for Orthacanthus gracilis Newberry, 1875a, dorsal spine, illustration is a composite based on syntypes (Orton Geological Museum, OSU 4467A, 4467B); reproduced from Newberry (1875a, pl. LIX, fig. 7), ca 71 mm long. Upper Freeport Coal, Allegheny Group, Diamond Coal Mine, Linton, Ohio, USA D Orthacanthus carbonarius (Germar, 1844), two teeth, syntypes (repository unknown) of Chilodus tuberosus Giebel, 1848; reproduction of Giebel (1849: pl. XXIX, figs. 1, 1a, 1b as), length unknown. Wettin-Löbejun, Saxony-Anhalt, Germany E Orthacanthus carbonarius (Germar, 1844), tooth, syntype (repository unknown) of Lamna carbonaria Germar, 1844; reproduced from Germar (1844: pl. 1, fig. 1), ca 20 mm long. Presumably from Saxony-Anhalt, Germany.

Whitley (1940: 243) proposed the name Giebelodus as a replacement name for Chilodus Giebel, 1848 because the genus-group name is preoccupied by Chilodus Müller & Troschel, 1844. Following Article 67.8 of the Code (International Commission on Zoological Nomenclature 2000), C. gracilis Giebel, 1848 automatically becomes the type species of Giebelodus Whitley, 1940.

Chilodus gracilis Giebel, 1848 is here assigned to Orthacanthus, and Giebelodus Whitley, 1940 is thus a junior subjective synonym of Orthacanthus Agassiz, 1843.

Uses of the combination Chilodus gracilis are as follows:

  1. Chilodus gracilis Giebel, 1848 (Chondrichthyes, Xenacanthiformes, Orthacanthidae), a fossil shark described from the Carboniferous of Germany.
  2. Chilodus gracilis Isbrücker & Nijssen, 1988 (Actinopterygii, Characiformes, Chilodontidae), an extant freshwater characiform fish also known as the graceful headstander, described from Trovão, Río Aaupés, Amazonas, Brazil.

Chilodus gracilis Isbrücker & Nijssen, 1988 is not a junior homonym of C. gracilis Giebel, 1848 because, according to the exception in Art. 57.8 of the Code, and the related example, homonymy between identical species-group names in combination with homonymous generic names having the same spelling but established for different nominal genera is to be disregarded (International Commission on Zoological Nomenclature 2000).

Systematics

Class Chondrichthyes Huxley, 1880

Subclass Elasmobranchii Bonaparte, 1838

Superorder Euselachii Hay, 1902

Order Xenacanthiformes Berg, 1955

Family Orthacanthidae Heyler & Poplin, 1990 (see van der Laan 2018)

Genus Orthacanthus Agassiz, 1843

Orthacanthus gracilis (Giebel, 1848)

Fig. 1A

Chilodus gracilis Giebel, 1848: 352–353.

Chilodus gracilis: Giebel 1849: 70, pl. XXIX, fig. 2.

Pleuracanthus sp.: Gocht 1955: pl. VIII, fig. 5.

Orthacanthus -Typ UG: Schneider 1985: 91–92, fig. 2.

Orthacanthus carbonarius (Germar, 1844): Schneider 1988: pl. 1, fig. 4.

Orthacanthus gracilis (Giebel, 1848): Boy and Martens 1991: figs 1, 8.

Orthacanthus gracilis: Hampe 1994: 56–63, figs 1–5.

Orthacanthus gracilis: Hampe 2003: 209–210.

Holotype

Tooth; Geiseltalmuseum Halle, GTM 1095, previously illustrated by Giebel (1849: pl. XXIX, fig. 2) and Hampe (1994: Fig. 1a–c).

Type locality

Slate of the Wettin-Schichten (Carboniferous) from Wettin, north of Halle, Saale area, Saxony-Anhalt, Germany.

Remarks

The basionym Chilodus gracilis Giebel, 1848 is designated herein as the type species of Chilodus Giebel, 1848. Whitley (1940: 243) proposed Giebelodus as a replacement name for Chilodus Giebel, 1848 (preoccupied by Chilodus Müller & Troschel, 1844), and C. gracilis Giebel, 1848 is thus the type species of Giebelodus. Following Boy and Martens (1991) and Hampe (1994, 2003), Giebelodus gracilis (Giebel, 1848), which is known only from teeth, is referred to the genus Orthacanthus Agassiz, 1843.

Orthacanthus lintonensis nom. nov.

Fig. 1B

Diplodus gracilis Newberry, 1857: 99.

Diplodus gracilis: Newberry 1873: 334–336.

Diplodus gracilis: Newberry 1874: 330–331.

Diplodus gracilis: Newberry 1875a: 45, pl. LVIII, figs 3, 3a.

Diplodus gracilis: Newberry 1875b: 45, pl. LVIII, figs 3, 3a.

Xenacanthus gracilis (Newberry, 1857): Olson 1946: 290–291.

Xenacanthus compressus (Newberry, 1857): Hotton 1952: 496, 499.

Orthacanthus compressus (Newberry, 1857): Hook and Baird 1986: table 2.

Orthacanthus gracilis (Newberry, 1857): Hampe 1988: 292.

Orthacanthus compressus: Hook and Baird 1988: table 1.

Orthacanthus gracilis: Hampe 1994: 63.

Orthacanthus compressus: Johnson 1999: 243–245.

Orthacanthus gracilis: Hampe 2003: 209–210.

Syntypes

Teeth, repository unknown, previously illustrated by Newberry (1875a: 45, pl. LVIII, figs 3, 3a; 1875b:45, pl. LVIII, figs 3, 3a).

Type locality

Upper Freeport Coal (Carboniferous), from the Diamond Coal Mine, Linton, Jefferson County, Ohio, USA.

Etymology

The species refers to Linton, Ohio, the type locality.

Remarks

The new species-group name Orthacanthus lintonensis nom. nov. replaces Diplodus gracilis Newberry, 1857, which after recombination as Orthacanthus gracilis (Newberry, 1857) is a junior secondary homonym of Orthacanthus gracilis (Giebel, 1848).

Detailed study of xenacanthiform materials from the Linton Lagerstätte is needed, and the type specimens need to be re-examined. Much of the systematic work on fish taxa described from Linton after 1900 has involved non-type specimens. Indeed, most published illustrations of Linton fish types are line-art drawings (e.g. Newberry 1873, 1874, 1875a, 1875b; herein, Fig. 1B, C), often with generous “restoration;” few of the types, even the ones whose repositories are known, have been photographically illustrated. Pending restudy of the type specimens of xenacanthiform sharks from the Linton Lagerstätte, O. lintonensis nom. nov. is proposed here as an available name that can compete in priority with other names, not as a junior synonym of any other species (compare Hotton 1952; Hook and Baird 1986; Johnson 1999).

Orthacanthus adamas nom. nov.

Fig. 1C

Orthacanthus gracilis Newberry, 1875a: 56–57, pl. LIX, fig. 7.

Orthacanthus gracilis: Newberry 1875b: 56–57, pl. LIX, fig. 7.

Orthacanthus gracilis: Cope 1881: 163.

Pleuracanthus (Orthacanthus) gracilis: Case 1900: 701, pl. I, fig. 4.

Orthacanthus gracilis: Morningstar 1924: 53.

Xenacanthus gracilis (Newberry, 1875a): Olson 1946: 287.

Xenacanthus gracilis: Hook and Baird 1986: 179, table 2.

Xenacanthus gracilis: Hook and Baird 1988: table 1.

Orthacanthus gracilis: Hampe 2004: 209.

Syntypes

Two dorsal spines, Orton Geological Museum, The Ohio State University, Columbus, Ohio, USA (OSU) 4467A, 4467B, previously illustrated as a composite by Newberry (1875a: pl. LIX, fig. 7; 1875b: pl. LIX, fig. 7).

Type locality

Upper Freeport Coal (Carboniferous), from the Diamond Coal Mine, Linton, Jefferson County, Ohio, USA.

Etymology

Adamas (Latin, diamond), in allusion to the Diamond Coal Mine, where the species was first collected.

Remarks

The new species-group name Orthacanthus adamas nom. nov. replaces Orthacanthus gracilis Newberry, 1875a, which is a junior homonym of Orthacanthus gracilis (Giebel, 1848). Newberry (1875a: pl. LIX, fig. 7; 1875b: pl. LIX, fig. 7) illustrated this species with a composite figure based on syntypic dorsal spines. This species should not be confused with the other xenacanthiform species from Linton bearing the species epithet gracilis, based on teeth, and also referred to Orthacanthus, as discussed above. Replacement names for both taxa will reduce potential confusion. Cope (1881) and Case (1900) extended the stratigraphic range of this species into the Permian.

Acknowledgements

I am indebted to the reviewers, R. van der Laan, B. Sidlauskas, M. Kottelat, and an anonymous reviewer, plus the academic editor B.F. Melo, for insightful and helpful reviews and comments that have substantially improved this manuscript.

Additional information

Conflict of interest

The author has declared that no competing interests exist.

Ethical statement

No ethical statement was reported.

Funding

No funding was reported.

Author contributions

Writing – original draft: LEB.

Author ORCID

Loren E. Babcock https://orcid.org/0000-0002-9324-9176

Data availability

All of the data that support the findings of this study are available in the main text.

References

  • Agassiz L (1843) Recherche sur les Poissons fossiles. Vol. 3. Contenant l’Histoire de l’Ordre des Placoïdes. Petitpierre, Neuchâtel: 157–390.
  • Berg LS (1955) Classification of Fishes, both Recent and Fossil (2nd ed., revised by Pavolvsky EN). Travaux de l’Institute Zoologique de l’Académie des Sciences de l’URSS 20, 286 pp.
  • Bonaparte CL (1838) Selachorum tabula analytica. Nuovi Annali delle Scienze Naturali 1(2): 195–214.
  • Boy JA, Martens T (1991) Zur Problematik chronostratigraphischer Korrelationen im mitteleuropäischen Rotliegend (?oberstes Karbon – Perm). Newsletters on Stratigraphy 25(3): 163–192. https://doi.org/10.1127/nos/25/1991/163
  • Case EC (1900) The vertebrates from the Permian bone bed of Vermilion County, Illinois. The Journal of Geology 8(8): 698–729. https://doi.org/10.1086/620866
  • Cope ED (1881) Catalogue of the Vertebrata of the Permian formation of the United States. American Naturalist 15(2): 162–164.
  • Germar EF (1844) Fischüberreste [Piscium reliquiae] In Germar EF Die Versteinerungen des Steinkohlengebirges von Wettin und Löbejün im Saalkreise. Heft [Fasciculus] 1: 1–3. [Petrificata Stratorum Lithanthracum Wettini et Lobejuni in Circulo Salae.] [C.A. Schwetschke und Sohn, Halle.] https://doi.org/10.5962/bhl.title.169070
  • Giebel CG (1848) Die Fische der Vorwelt, mit steter Berücksichtigung der lebenden Fische. In Giebel CG Fauna der Vorwelt mit steter Berücksichtigung der lebenden Thiere. Erster Band: Wirbelthiere. Dritte Abtheilung: Fische, Brockhaus, Leipzig, 467 pp. https://doi.org/10.5962/bhl.title.24938
  • Giebel CG (1849) Fischüberreste [Piscium reliquiae]. In: Germar EF (Ed.) Die Versteinerungen des Steinkohlengebirges von Wettin und Löbejün im Saalkreise [Petrificata Stratorum Lithanthracum Wettini et Lobejuni in Circulo Salae. ] Heft [Fasciculus] 6: 69–79. C.A. Schwetschke und Sohn, Halle.
  • Gocht H (1955) Acanthodierstacheln und andere Fischreste im Unteren Rotliegenden bei Manebach. Hallesches Jahrbuch für mitteldeutsche Erdgeschichte 2: 110–111.
  • Hampe O (1988) Über die Bezahnung des Orthacanthus (Chondrichthyes: Xenacanthida; Oberkarbon-Unterperm). Paläontologische Zeitschrift 62(3/4): 285–296. https://doi.org/10.1007/BF02989499
  • Hampe O (1994) Neue Erkenntnisse zur permokarbonischen Xenacanthiden-Fauna (Chondrichthyes: Elasmobranchii) und deren Verbreitung im südwestdeutschen Saar-Nahe-Becken. Neues Jahrbuch für Geologie und Paläontologie. Abhandlungen 192(1): 53–87.
  • Hampe O (2003) Revision of the Xenacanthida (Chondrichthyes: Elasmobranchii) from the Carboniferous of the British Isles. Transactions of the Royal Society of Edinburgh. Earth Sciences 93(3): 191–237. https://doi.org/10.1017/S0263593300000419
  • Heyler D, Poplin C (1990) Systematics and relationships among the Xenacanthiformes (Pisces, Chondrichthyes) in the light of Carboniferous and Permian material. Acta Musei Reginaehradecensis Series A, Scientiae Naturales 22 [for 1989]: 69–78.
  • Hotton N III (1952) Jaws and teeth of American xenacanth sharks. Journal of Paleontology 26(3): 489–500.
  • Huxley TH (1880) On the application of the laws of evolution to the arrangement of the Vertebrata, and more particularly of the Mammalia. Proceedings of the Zoological Society of London 43: 649–662.
  • Isbrücker IJH, Nijssen H (1988) Review of the South American characiform fish genus Chilodus, with description of a new species, C. gracilis (Pisces, Characiformes, Chilodontidae). Beaufortia 38(3): 47–56.
  • Johnson GD (1999) Dentitions of late Palaeozoic Orthacanthus species and a new species of? Xenacanthus (Chondrichthyes: Xenacanthiformes) from North America. Acta Geologica Polonica 49(3): 215–266.
  • Morningstar H (1924) Catalogue of type fossils in the Geological Museum of The Ohio State University. The Ohio Journal of Science 24: 31–64.
  • Newberry JS (1857) Descriptions of several new genera and species of fossil fishes from the Carboniferous strata of Ohio. Proceedings of the Academy of Natural Sciences. Vol. 8 [for 1856]: 96–100.
  • Newberry JS (1873) Descriptions of fossil fishes. Report of the Geological Survey of Ohio. Volume I. Geology and Palaeontology. Part II. Palaeontology, 247–355.
  • Newberry JS (1874) Beschreibung der fossilen Fische. Bericht über die Geologische Aufnahme von Ohio. I. Band. Geologie und Paläontologie. II. Theil. Paläontologie: 247–350.
  • Newberry JS (1875a) Descriptions of fossil fishes. Report of the Geological Survey of Ohio. Volume II. Geology and Palaeontology. Part II. Palaeontology, 1–64.
  • Newberry JS (1875b) Beschreibung fossiler Fische. Bericht über die Geologische Aufnahme von Ohio. II. Band. Geologie und Paläontologie. II. Theil. Paläontologie: 1–64.
  • Olson EC (1946) Fresh- and brackish-water vertebrate-bearing deposits of the Pennsylvanian of Illinois. The Journal of Geology 54(5): 281–305. https://doi.org/10.1086/625364
  • Romanovski G (1857) Ueber die Verschiedenheit der beiden Arten: Chilodus tuberosus Gieb. und Dicrenodus okensis Rom. Bulletin de la Société impériale des Naturalistes de Moscou 30(2): 290–295.
  • Schneider J (1985) Elasmobranchier-Zahntypen (Pisces, Chondrichthyes) und ihre stratigraphische Verbreitung im Karbon und Perm der Saale-Senke (DDR). Freiberger Forschungshefte C 400: 90–100.
  • Schneider J (1988) Grundlagen der Morphogenie, Taxonomie und Biostratigraphie isolierter Xenacanthodier-Zähne (Elasmobranchii). Freiberger Forschungshefte C 419: 71–80.
  • Whitley G (1940) The Nomenclator Zoologicus and some new fish names. The Australian Naturalist 10(7): 241–243.
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