Assignment of nomen protectum status to Eugnathus [ = Furo] orthostomus Agassiz, 1842

ABSTRACT

Triggered by the need to clarify the taxonomic and phylogenetic relationships of multiple Late Jurassic species presently assigned to the genus Furo, the taxonomic status of the widely accepted type species F. orthostomus (Agassiz, 1842) was revised. It was found to be a junior synonym of Lepisosteus dentosus Koenig, 1825, and Eugnathus speciosus Agassiz, 1839, two names that despite their availability have not been used for a valid taxon after 1899. Therefore, for the sake of maintaining stability, this contribution shows that the conditions of Article 23.9 ‘Reversal of precedence’ of the Code have been met, and as a result, the younger valid name Eugnathus [= Furo] orthostomus Agassiz, 1842, has priority over its older synonyms Lepisosteus dentosus Koenig, 1825, and Eugnathus speciosus Agassiz, 1839.

INTRODUCTION

Ray-finned fishes presently represent over 50% of total vertebrate taxonomic diversity. Most modern ray-finned fishes are teleosts (∼99.85%; Fricke et al., 2023), while other actinopterygian clades are restricted to a few remnant species. Of these clades, the Halecomorphi is currently represented by only two species of the genus Amia. However, halecomorphs were highly diverse during the Mesozoic and, thus, they are very well represented with abundant fossils, in particular during the Jurassic. The alpha taxonomy of Jurassic halecomorphs is relatively well documented, but their phylogenetic diversity remains incompletely understood (López-Arbarello et al., 2020). This is mainly due to the scarcity of studies regarding the phylogenetic relationships of several key taxa, for example, the species classified in the genus Furo.

The generic name Furo was erected by Gistel (1848) to replace Eugnathus Agassiz, 1839, which was preoccupied by Eugnathus Schoenherr, 1834, a curculionid arthropod. From the Upper Triassic to the Upper Jurassic, there are currently 14 species classified in this genus. However, it is likely that they are not monophyletic (Ebert, 2019, 2020a, b, 2021; Ebert et al., 2020; Lambers, 1998). All of these species need further study, and their referral to Furo will depend on their affinities with the type species of the genus. Furo orthostomus (Agassiz, 1842) has been widely accepted as the type species based on the works of Woodward and Sherborn (1890) and Woodward (1895a). However, our research has revealed a conflict of priority with the names Lepisosteus dentosus Koenig, 1825, and Eugnathus speciosus Agassiz, 1839. This note aims to explain the matter regarding the type species and its holotype specimen.

Institutional Abbreviations—NHMUK, The Natural History Museum, London, U.K.; OUMNH, Oxford University Museum of Natural History, Oxford, U.K.

SYSTEMATIC PALEONTOLOGY

Subclass ACTINOPTERYGII Cope, 1887

Series NEOPTERYGII Regan, 1923

Superdivision HOLOSTEI Müller, 1845

Division HALECOMORPHI Cope, 1871

Order OPHIOPSIFORMES Ebert, 2018

Family FURIDAE Jordan, 1923

FURO Gistel, 1848

1836 Eugnathus Agassiz in Egerton, Phil. Mag. VIII, p. 368 [nomen nudum]

1839 Eugnathus Agassiz, Poiss. Foss., Feuilleton, p. 118 [preoccupied].

1848 Furo, Gistel, Nat. Thierr. 1848, p. 9.

Type Species––Eugnathus [ = Furo] orthostomus Agassiz, 1842.

Diagnosis––Several species are currently classified in Furo, but most of them need thorough revision and phylogenetic analysis. A generic diagnosis will not be possible until these studies are completed.

Currently Referred Species––Pending taxonomic revision of the genus, the Late Triassic F. trottii (Balsamo-Crivelli, 1839), F. hermesi (Bellotti in De Alessandri, 1910), and F. insignis (Kner, 1866); the Early Jurassic F. philpotiae (Agassiz, 1839), F. altus (Woodward, 1895a), F. normandica Wenz, 1965, and F. fasciculatus (Agassiz in Woodward, 1895b); and the Late Jurassic F. microlepidotus (Agassiz, 1833), F. latimanus (Agassiz, 1834), F. angustus (Münster, 1842), F. longiserratus (Agassiz, 1843), and F. aldingeri (Heimberg, 1949) (Table 1).

FURO ORTHOSTOMUS (Agassiz, 1842)

TABLE 1. Current taxonomic status and taxonomic history of the species classified in the genus Furo Gistel, 1848.

Original name	Synonym	Taxonomic status	References
Triassic taxa
Lepidotes trottii Balsamo-Crivelli, 1839	Furo trottii (Balsamo-Crivelli, 1839)	Nomen dubium	López-Arbarello et al. (2014)
Eugnathus insignis Kner, 1866	Furo insignis (Kner, 1866)	Valid	López-Arbarello et al. (2023)
Eugnathus hermesi Bellotti in De Alessandri, 1910	Furo hermesi (Bellotti in De Alessandri, 1910)	Nomen dubium	This work
Early Jurassic taxa
Lepisosteus dentosus Koenig, 1825	Furo orthostomus (Agassiz, 1842)	Nomen oblitum	This work
Eugnathus orthostomus Agassiz, 1842	Furo orthostomus (Agassiz, 1842)	Nomen protectum	This work
Eugnathus speciosus Agassiz, 1839	Furo orthostomus (Agassiz, 1842)	Objective synonym of Lepisosteus dentosus Koenig, 1825	Woodward (1895b), Woodward and Sherborn (1890), this work
Eugnathus philpotiae Agassiz, 1839	Furo philpotiae (Agassiz, 1839)	Valid	Ebert (2019)
Eugnathus minor Agassiz, 1839	Furo philpotiae (Agassiz, 1839)		Ebert (2019)
Lissolepis serratus Davis, 1884	Furo philpotiae (Agassiz, 1839)		Ebert (2019)
Eugnathus polyodon Agassiz, 1839	Furo philpotiae (Agassiz, 1839)		Ebert (2019)
Eugnathus altus Woodward, 1895a	Furo altus (Woodward, 1895a)	Potentially valid	Woodward (1895b)
Eugnathus hastingsiae Agassiz, 1843	Furo hastingsiae (Agassiz, 1843)	Nomen dubium	Ebert (2019)
Eugnathus fasciculatus Agassiz in Woodward, 1895b	Furo fasciculatus (Agassiz in Woodward, 1895b)	Potentially valid	Woodward (1895b)
Furo normandica Wenz, 1965	Furo normandica Wenz, 1965	Valid	Ebert (2019), Ebert et al. (2020)
Late Jurassic taxa
Uraeus microlepidotus Agassiz, 1833	Furo microlepidotus (Agassiz, 1833)	Valid	Ebert (2019), Lambers (1998)
Pholidophorus latimanus Agassiz, 1834	Furo latimanus (Agassiz, 1834)	Valid	Ebert (2019), Lambers (1998)
Histionotus reclinis Eastman, 1914	Furo latimanus (Agassiz, 1834)		Ebert (2019)
Pholidophorus angustus Münster, 1842	Furo angustus (Münster, 1842)	Valid	Ebert (2019), Lambers (1998)
Pholidophorus elongatus Münster, 1842	Furo angustus (Münster, 1842)		Ebert (2019), Lambers (1998)
Pholidophorus muensteri Giebel, 1848	Furo angustus (Münster, 1842)		Ebert (2019), Lambers (1998)
Pholidophorus longiserratus Agassiz, 1843	Furo longiserratus (Agassiz, 1843)	Valid	Ebert (2019), Lambers (1998)
Pholidophorus brevivelis Wagner, 1863	Furo longiserratus (Agassiz, 1843)		Ebert (2019), Lambers (1998)
Eugnathus vetteri Heineke, 1906	Furo longiserratus (Agassiz, 1843)		Ebert (2019)
Eugnathus aldingeri Heimberg, 1949	Furo aldingeri (Heimberg, 1949)	Valid	Ebert (2019), Lambers (1998)

1825 Lepidosteus? [sic] dentosus Koenig, Icon. Foss. Sect., pl. 12, fig. 140 [nomen oblitum].

1839 Eugnathus speciosus Agassiz, Poiss. Foss., Feuilleton, p. 118, pl. 57 [nomen oblitum; objective synonym of Lepisosteus dentosus Koenig, 1825].

1842 Eugnathus orthostomus Agassiz, Poiss. Foss., Feuilleton, p. 136, pl. 57a. [nomen protectum]

1890 Eugnathus orthostomus, Woodward & Sherborne, pp. 78–79, 111

1895 Eugnathus orthostomus, Woodward, pp. 291, 293; fig. 34; pl. 4, fig. 1; pl. 5, fig. 1

1965 Furo orthostomus Wenz, p. 145.

Additional synonyms in Table S1.

Holotype—NHMUK PV P.465 (Fig. 1).

FIGURE 1. Furo orthostomus (Agassiz, 1842), holotype NHMUK PV P.465 (Natural History Museum, 2023).

Referred Specimens—OUMNH PAL J.03029 and PAL J.03030 (Syntypes of Lepisosteus dentosus; Fig. 2A, B), NHMUK PV P.509, PV P.559, PV P.870, PV P.865, PV P.2019, PV P.2027, PV P.3576, PV P.3633a, PV P.3633b, PV P.3633c, PV P.38120, PV P.3634, PV P.3641, PV OR.38119, PV OR.38120.

FIGURE 2. Lepisosteus dentosus Koenig, 1825, syntypes. A, specimen OUMNH PAL J.03029; B, specimen OUMNH PAL J.03030 (GB3D Type Fossils Online Database, 2013–2023); C, original illustration of the specimens modified from Koenig (1825:fig. 140; not to scale).

Diagnosis—see Ebert (2019).

Locality, Horizon, and Age—Lyme Regis, Dorset, U.K., Sinemurian, Lower Jurassic.

DISCUSSION

The species originally included in Eugnathus [ = Furo] in the 12° Livraison of the Recherches sur les Poissons fossiles (p. 118 and pl. 56, 58) that was published in April 1839 (Quendstedt, 1963) are: E. speciosus Agassiz, 1839, E. philpotiae Agassiz, 1839, E. minor Agassiz, 1839, and E. polyodon Agassiz, 1839. Later on, Agassiz added E. orthostomus Agassiz, 1842, and E. chirotes Agassiz, 1842, in the 14° Livraison (Tab. 57a, b; p., 136), which was published in January–June of 1842 (Quendstedt, 1963).

Probably unaware of the exact publication date of the two nominal taxa, Woodward and Sherborn (1890) synonymized E. speciosus and E. orthostomus, with the latter name being deemed the senior synonym (Table 1). The authors included the name Lepisosteus dentosus Koenig, 1825, in this synonymy. Koenig (1825) misspelled the generic name as “Lepidosteus” in an unjustified emendation of the original spelling Lepisosteus La Cepède, 1803, which was permanently corrected by Briggs (1961).

According to the Code, Lepisosteus dentosus Koenig, 1825, is an available name because it was published and accompanied with an illustration of two specimens (OUMNH PAL J.03029 and OUMNH PAL J.03030; Fig. 2C) which are therefore syntypes (ICZN, 1999: Arts. 1.3, 10–12). These syntypes are exactly the same specimens figured by Agassiz (1839) to represent his nominal taxon Eugnathus speciosus Agassiz, 1839, and, thus, the latter name is an objective synonym of Lepisosteus dentosus Koenig, 1825. Consequently, attending to the principle of priority (ICZN, 1999: Art. 23) the combination Furo dentosus (Koenig, 1825) is the senior synonym for the species also denoted with the names E. speciosus, and F. orthostomus, and has priority over the other names. However, applying Article 23.9 ‘Reversal of precedence’ of the Code, and confirming the synonymy proposed by Woodward and Sherborn (1890) and sustained by later authors (Ebert, 2019; Woodward, 1895b), we preserve the name Furo orthostomus (Agassiz, 1842) for the type species of Furo Gistel, 1848.

As far as we have been able to trace in the published literature the senior synonyms Lepisosteus dentosus Koenig, 1825, and Eugnathus speciosus Agassiz, 1839, have never been used as valid names after 1899, thus satisfying the requirement in Article 23.9.1.1 of The Code (ICZN, 1999) (see all references to this species found in the literature published since 1890 in Table S1). Instead, the junior synonym Furo orthostomus has been used as the valid name for the species represented by OUMNH PAL J.03029 and OUMNH PAL J.03030, as indicated in at least 26 scientific works from 16 different authors since 1975 (Table S1), i.e., during the last 50 years and spanning more than 10 years, thus satisfying the requirements in Article 23.9.1.2 of The Code (ICZN, 1999). Therefore, the conditions in Article 23.9.1 are met and with this publication, we give the younger valid name Eugnathus orthostomus Agassiz, 1842, which becomes a nomen protectum, precedence over the older names Lepisosteus dentosus Koenig, 1825, and Eugnathus speciosus Agassiz, 1839, which become nomina oblita.

Woodward and Sherborn (1890) not only proposed the aforementioned synonymy, they also fixed Eugnathus [ = Furo] orthostomus as the type species of the genus. Eugnathus [ = Furo] orthostomus is not listed among the names originally included in Eugnathus Agassiz, 1839, but Eugnathus speciosus is one of them. Therefore, as long as the synonymy between these taxa is maintained and the junior synonym Furo orthostomus is the valid name for the species, the fixation of the latter as the type species is accepted.

Among the other species originally included in the genus, F. philpotiae (Agassiz, 1839) is the only one still treated as valid. The other two names, F. minor (Agassiz, 1839) and F. polyodon (Agassiz, 1839) are considered junior synonyms of F. philpotiae (Ebert, 2019; Woodward, 1895a) (Table 1).

THE SPECIES OF FURO

This contribution formally establishes the precedence of the valid name Furo orthostomus, type species of the genus, over its older synonyms, but does not intend to revise the taxonomic composition of Furo. This taxonomic note is the necessary first step towards a systematic revision of the various taxa currently attributed to this genus. To facilitate such revision, this section concisely summarizes the present state of knowledge and taxonomic history of the species classified in Furo, as outlined in Table 1.

The stratigraphically oldest species classified in Furo Gistel, 1848 (= Eugnathus Agassiz, 1839) has been found in the Upper Triassic. The species Lepidotes trottii Balsamo-Crivelli, 1839, Middle Triassic of Perledo, Italy, was referred to Eugnathus [ = Furo] by De Alessandri (1910). In the most recent revision of the species, Lombardo (2001) indicates that the type specimen which was stored at Museo Civìco di Storie Naturale di Milano was lost during World War II. Lombardo (2001) described and referred to Furo trottii (Balsamo-Crivelli, 1839) a single specimen housed in the Civico Museo Insubrico di Storia NaturaÌe di Induno Olona (Varese, northern Italy), MCSNIO P456 from the Kelkschieferzone (Meride Limestone, upper Ladinian) of Ca’ del Frate (Viggiù, Varese). MCSNIO P456 differs from the type specimen of Furo trottii (Balsamo-Crivelli, 1839), which is figured in De Alessandri (1910:tab. V, fig. 3) in several features that are described by Balsamo-Crivelli (1839) and Bellotti (1857). Among them, the dorsal fin was almost completely contained between the pelvic and anal fins in the holotype, but it expands opposite to the anal fin in MCSNIO P456. Lombardo (2001) describes at least 15 dorsal fin rays in MCSNIO P456, but there are only 13 in the holotype according to Bellotti (1857) and De Alessandri (1910). More precisely, De Alessandri (1910) distinguishes the species by a combination of features, including the origin of the dorsal fin almost in correspondence with the insertion of the pelvic fins, whereas the anal fin originates at the eighth soft ray of the dorsal fin. Although the specimen is incompletely preserved, the anal fin originates very close to the origin of the dorsal fin in MCSNIO P456 (Lombardo, 2001:pl. 2A). According to López-Arbarello et al. (2014), MCSNIO P456 resembles most closely Archaeosemionotus connectens Deecke, 1889, and might represent a species of that genus. López-Arbarello et al. (2014) considered the available descriptions of the lost holotype of Furo trottii (Balsamo-Crivelli, 1839) insufficient and regard the species as a nomen dubium.

Eugnathus hermesi Bellotti in De Alessandri, 1910, is another species from Perledo that has been referred the genus Furo (= Eugnathus). The species is only known through the work of De Alessandri, which is based on the type specimen only. As in the previous case, the specimen was housed at Museo Civìco di Storie Naturale di Milano but was lost during World War II (Lombardo, pers. comm., April 26, 2023).

The third Triassic species of Furo [ = Eugnathus] is Eugnathus insignis Kner, 1866, from the Norian of Seefeld, Austria. Woodward (1895a) referred this species to Caturus, but a recent study excluded it from the latter genus and from the superfamily Caturoidea, emphasizing the need for a thorough revision (López-Arbarello et al., 2023).

Ten species of Furo [ = Eugnathus] have been named from the Lower Jurassic: E. speciosus Agassiz, 1839, E. philpotiae Agassiz, 1839, E. minor Agassiz, 1839, E. polyodon Agassiz, 1839, E. orthostomus Agassiz, 1842, E. serratus Davis, 1884, E. altus Woodward, 1895a, and E. hastingsiae Agassiz, 1843, from the Sinemurian of the Lias Group in the U.K.; the somewhat younger F. normandica Wenz, 1965, from the Toarcian of La Caine, Normandy, France; and the very imperfectly known E. fasciculatus Agassiz in Woodward, 1895b, from the Toarcian of Whitby, U.K.

Eugnathus speciosus Agassiz, 1839 (nomen oblitum), is a synonym of Furo orthostomus (Agassiz, 1842). According to Ebert (2019), F. minor and F. serratus are junior synonyms of F. philpotiae, and F. hastingsiae is a nomen dubium. Furo normandica is only known from its holotype and the referral of this species to the genus Furo has been questioned (Ebert, 2019; Ebert et al., 2020). Furo altus, and F. fasciculatus have not been studied since Woodward (1895a, b) and are very poorly known.

Recent taxonomic revisions of several Late Jurassic species previously referred to Furo have led to the creation of several new genera, whose phylogenetic relationships remain unknown (Ebert 2019, 2020a; Lane & Ebert, 2012, 2015). Similarly, the other Late Jurassic species of Furo might represent different genera and are in need of revision (Ebert, 2019, 2020a, b; Lambers, 1998): F. microlepidotus (Agassiz, 1833), F. latimanus (Agassiz, 1834), F. angustus (Münster, 1842), F. longiserratus (Agassiz, 1843), F. aldingeri (Heimberg, 1949).

SUPPLEMENTARY FILE(S)

Supplementary File 1.docx: studied material and Table S1.

AUTHOR CONTRIBUTIONS

A.L.A. designed the project, analyzed the data and drafted the manuscript, A.L.A. and M.E. gathered the data, and edited the manuscript.

DATA AVAILABILITY STATEMENT

The data that support the conclusions of this study are available in the manuscript.

DISCLOSURE STATEMENT

No potential conflict of interest was reported by the author(s).

ACKNOWLEDGMENTS

We are grateful to E. Bernard (NHMUK) and E. Howlett and E. Nicholls (OMUNH) for their assistance with collections visits and historical information. Special thanks are due to the editor Juan Liu and four anonymous reviewers for their thorough and rigorous reviews that led to a significant improvement of the manuscript. This research was supported by DFG grant LO1405/8-1 to A.L.A.