Junior Synonym Research Articles

Contribution to the taxonomy of Oxytrigona Cockerell, 1917 (Apidae, Meliponini)

The stingless bees of the genus Oxytrigona Cockerell are popularly known as “fire bees”, due to their unique habit of spitting a caustic secretion when disturbed. Currently, this neotropical genus includes 11 valid species distributed from southern Brazil, throughout most of South and Central America, reaching southern Mexico. They are especially diverse in the Amazon, where five species are recorded. Although Oxytrigona exhibits a very distinctive morphology in relation to other stingless bees, species are often difficult to identify, having blurred limits due to intraspecific variation. In the present contribution the taxonomy of Oxytrigona is revisited, based on novel findings since the last taxonomic accounts were made. Oxytrigona tataira (Smith, 1863) is reinterpreted on the basis of new evidence regarding the provenance of its type material. The whereabouts of the type material of Oxytrigona cagafogo (Müller, 1874) sp. ressur. are discussed, and the species is resurrected from synonymy, representing a common bee occurring in the Atlantic rainforest of Brazil. Oxytrigona huaoranii Gonzalez & Roubik, 2008 is considered a junior synonym of Oxytrigona mellicolor (Packard, 1869) syn. nov., and the identity of the species is clarified. The whereabouts of the type material of Oxytrigona flaveola (Friese, 1900) are discussed. Three new species are described: Oxytrigona banana sp. nov. from Brazil and Paraguay; Oxytrigona pallida sp. nov. from northern South America and Central America; and Oxytrigona sauronica sp. nov. from Colombia. Distribution maps and a revised key are provided. Although the taxonomy of Oxytrigona species has been improved, questions remain about some species complexes. Implementation of tools from phylogeography is encouraged in order to improve our understanding of the species boundaries.

Whale Collections and Exhibitions at the Natural History Museum of the University of Pisa (Italy)

The Natural History Museum of the University of Pisa hosts the most important osteological collection of extant cetaceans in Italy as well as one of the most relevant all over Europe. Furthermore, it also preserves a significant palaeontological collection that includes several holotypes and otherwise unique specimens of Archaeoceti (archaic cetaceans), Mysticeti (baleen whales) and Odontoceti (toothed whales). Here, we provide a historical overview of these collections and the corresponding displays, with special attention paid to the origin, development and design of the ‘Archaeocete Hall’ and ‘Cetacean Gallery’. These comprise what may be the largest exhibition worldwide among those dedicated exclusively to cetaceans—one that includes 28 complete skeletons and one skull belonging to 27 extant species as well as fossils of nine extinct species. Our review also reveals that the museum exhibitions feature the oldest known specimen of Mesoplodon bowdoini and the type specimen of Ziphius savi, the latter being a validly described species that is currently regarded as a junior synonym of Ziphius cavirostris. Also significant is the display of several holotype specimens of fossil species such as the protocetid archaeocete Aegyptocetus tarfa, the balaenid baleen whales Balaena montalionis and Balaenula astensis, and the monodontid Casatia thermophila. The Archaeocete Hall and Cetacean Gallery are highly appreciated by visitors as well as perused by the museum’s educational team. The online archiving of 3D models of many of the MSNUP specimens on the open-access digital repository Sketchfab and their subsequent dissemination through the Wikimedia platforms has led to the creation of a major osteological resource—one that is broadly accessible to internet users worldwide.

Are aeolian ichnofacies distinctive and useful? An analysis of trace fossil assemblages from Cretaceous aeolian facies in northern Patagonia, Argentina

In this paper, Cretaceous trace fossil assemblages are reported from aeolian facies within four units from Patagonia, Argentina, to evaluate the usefulness of the aeolian ichnofacies concept. From oldest to youngest, studied units comprise the Agrio (Valanginian-Hauterivian), Cerro Barcino (Aptian-Cenomanian), Candeleros (Cenomanian), and Allen (Campanian-Maastrichtian) formations. Twenty one ichnotaxa were recorded, including ten of invertebrate origin (Archaeonassa fossulata, Arenicolites tenuis, Beaconites isp., Digitichnus laminatus, Edaphichnium lumbricatum, cf. Octopodichnus isp., Palaeophycus tubularis, Skolithos linearis, Taenidium barretti, and an unidentified arthropod trackway), seven tetrapod footprints and burrows (Avipeda isp., Brasilichnium isp., cf. Chelonipus isp., Reniformichnus katikatii, two types of indeterminate footprints, and burrow fills) and four rhizolith types. Entradichnus meniscus (formerly used as eponym of an aeolian ichnofacies) is considered a junior synonym of Taenidium barretti. Common ichnotaxa in aeolian and fluvial sequences like Taenidium barretti, Skolithos linearis and Palaeophycus tubularis are facies-crossing ichnotaxa and should not be used to distinguish ichnofacies. Trace fossil assemblages and ichnofabrics from aeolian dune, dry interdune and wet interdune facies are interpreted in terms of the potential producers and their palaeoecological and palaeoenvironmental constraints. This procedure is more informative than the ichnofacies approach in aeolian deposits. Based on a literature review of 32 examples of trace fossil assemblages from Cretaceous aeolian sequences worldwide, we conclude that the most distinctive ichnotaxa occur in aeolian dunes, including Brasilichnium, Farlowichnus, lacertoid footprints, Octopodichnus and Paleohelcura. It is recommended to abandon the usage of the Chelichnus, Entradichnus and Entradichnus-Octopodichnus ichnofacies, which are poorly defined in terms of recurrence and environmental significance or based on uncharacteristic or unavailable ichnotaxa. We propose a new definition of the Octopodichnus ichnofacies, diagnosed by the presence of subequant tetrapod footprints in quadrupedal trackways and/or selected arachnid /insect trackways. This ichnofacies is a taphofacies recorded from the Permian to the Cretaceous, and probably extends to the Cenozoic.

Lost & Found - Rediscovery of H. Hauffen’s Carychium material in the Dominik Bilimek Collection, BOKU University, including a contemporary assessment within the genus Zospeum (Gastropoda, Ellobioidea, Carychiinae)

The syntypes of Carychium reticulatum Hauffen, 1856 and Carychium bidentatum Hauffen, 1856, thought to be lost to science, have been rediscovered in a recent inventory of the shell collection of Domink Bilimek (1813–1884) at the University of Natural Resources and Life Sciences in Vienna, Austria (BOKU). In this work, we present (1) the historical context of the Dominik Bilimek and Heinrich (also: Henrik) Hauffen collections and (2) provide a contemporary image dataset of Hauffen’s original material while considering today’s taxonomic understanding of the genus Zospeum. We clarify the taxonomic status of the syntypes by using light microscopy, Scanning Electron Microcopy (SEM) and 3D X-ray Micro-CT data in conjunction with Hauffen’s original illustrations and compare them to contemporary investigations of their closest congeners. Analysis of Zospeum reticulatum (Hauffen, 1856) is supported by historical documentation from Heinrich Hauffen’s original annotations and Bilimek’s diary entries, as well as from individual collection labels in Hauffen’s own script (verified by archive material from the Archive of the National Museum of Slovenia, NMS). Hauffen’s descriptions are based on apertural morphology and shell microstructure. Our re-investigation of Zospeum reticulatum provides corroborating evidence supporting its assignment to Zospeum spelaeum (Rossmaessler, 1839) while that of Carychium bidentatum corroborates its status as junior synonym of Zospeum costatum (Freyer, 1855).

Review of Chinese species of genus Paramritodus Xue & Zhang (Hemiptera: Cicadellidae) with description of a new species

The Chinese leafhopper species of the genus Paramritodus Xue & Zhang are reviewed. One new species, Paramritodus concavicaudus Zhang sp. nov., is described and illustrated from southwest China. Additionally, Paramritodus flavocapitatus (Cai & He, 2001) is proposed as a junior synonym of Paramritodus pistacious (Huang & Maldonado Capriles, 1992). A key to the species of the genus is also provided.

Lost but not forgotten: Rediscovery of the Ukrainian Lepidurus middendorffii (Braem, 1893) (Branchiopoda: Notostraca) through integrative taxonomy

Abstract The taxonomy of the notostracan LepidurusLeach, 1819 is complicated by a large number of synonymised species and extensive intraspecific variability in many relevant characters. We demonstrate, based on an integrative taxonomic approach, that the Ukrainian populations of Lepidurus are not conspecific with any currently accepted Lepidurus species and assign them to the previously synonymised species Lepidurus middendorffiicomp. nov. (Braem, 1893). This species exemplarily highlights the problems in the taxonomy of Lepidurus. The species was originally described as Apus extensus var. middendorffii (Braem, 1893), but L. extensus is a junior synonym of Lepidurus lubbocki (Brauer, 1873), which is currently treated as a subspecies of Lepidurus apus (Linnaeus, 1758). Our molecular genetic analyses based on mitochondrial COI, 12S, 16S, and nuclear 28S, which included published data, suggest the presence of further, possibly cryptic species that await formal recognition and stress the importance for a more extensive revision of Lepidurus. The original type specimens of L. middendorffii, previously stored at the Museum of Natural History (Wrocław University, Wrocław, Poland), are lost and a neotype is designated. Lepidurus middendorffii is characterised by the dorsal organ position between the ocular tubercle margins, the sharp carapace sulcus spines, the long supra-anal plate with many median spines, a telson length to carapace length ratio 0.18–0.35, and differs by > 9% uncorrected COI p-distances from all other Lepidurus species.

Synopsis of Akamboja (Coleoptera: Phengodidae): new species, synonym, new records and remarks on abdominal morphology for the genus

Akamboja Roza et al., 2017 (Phengodidae: Mastinocerinae) was described to include five species, all from Atlantic Forest, which are characterized by having ten segmented antennae, biflabellate from antennomeres IV-VIII, and with fused flabellae on antennomere IX. The genus comprises six species today, including one from Ilha Grande (Angra dos Reis, Rio de Janeiro State, Brazil) with the IX antennomere flabellae not fused. In this paper, we describe seven new species based on specimens from seven entomological collections: Akamboja ganhoae sp. nov., Akamboja kumagaiae sp. nov., Akamboja microphthalmus sp. nov., Akamboja peckorum sp. nov., Akamboja piauiensis sp. nov., Akamboja planautensis sp. nov., and Akamboja wittmeri sp. nov. These new species include new biome records for Brazil (Cerrado, Caatinga and Amazonia), and the first species of the genus from Venezuela and Argentina. The seven new species fit in the genus diagnosis, but presents an antennal morphological variation in the flabellae of the antennomere VIII-IX: fusion of flabellae in antennomeres IX, in both antennomeres VIII and IX, or the absence of any fusion in any flabellae. Based on this variation, we propose an updated diagnosis for the genus. We also discuss and propose Akamboja caparaoensis Roza et al., 2017 as a new junior synonym of Akamboja cleidae Roza et al., 2017, and provide new distributional records for A. minimum Roza et al., 2017 and A. insularis Roza et al., 2018. Additionally, we describe for the first time in the genus the abdominal membranous projection present in several Mastinocerinae, but previously ignored, as well as the morphology of tergites IX, and X, and sternite IX.

Manica shanyii (Hymenoptera: Formicidae: Myrmicinae) is not Manica

The Holarctic genus Manica Jurine, 1807 are mysterious and primitive ants from the tribe Myrmicini of the subfamily Myrmicinae. A new species (Manica shanyii He et al., 2024) from China has recently been described, which was the first documented appearance of the genus and a new species in China. In this study, the key features of M. shanyii are compared with Manica species and the related genus Myrmica Latreille, 1804. Morphological features are demonstrated here, which makes it possible to divide two close genera Manica and Myrmica. After studying the specimens of this species, we transfer Manica shanyii He et al., 2024 to Myrmica shanyii (He et al., 2024), comb. nov. Also, to comply with the nomenclature rules, we propose to consider Manica parasitica (Creighton, 1934), syn. nov., as a junior synonym of Manica bradleyi (Wheeler, 1909).

Revision of Janeirona Distant, 1911 (Hemiptera: Pentatomidae: Ochlerini) with the description of four new species from Brazil

Janeirona Distant, 1911 is a Neotropical pentatomid genus restricted to South America that was recently transferred from Pentatominae to Ochlerini (Discocephalinae). Janeirona was described for one species, and during the 20th century other five species were allocated in the genus. In this study we redescribe Janeirona and its known species, and propose two new synonyms: Serdia stali Kormilev, 1956 as junior synonym of Janeirona insignis Distant, 1911, and Janeirona asaroana Brailovsky, 1988 as junior synonym of Janeirona costalimai (Pirán, 1962). We describe four new species: Janeirona aurea Sampaio & Campos sp. nov., Janeirona flavipes Sampaio & Campos sp. nov., Janeirona roellae Sampaio & Campos sp. nov., and Janeirona stenosa Sampaio & Campos sp. nov.. An identification key to the species and distribution maps are given.

The non-flowering plants of a near-polar forest in East Gondwana, Tasmania, Australia, during the Early Eocene Climatic Optimum.

The Cenozoic Macquarie Harbour Formation (MHF) hosts one of the oldest and southernmost post-Cretaceous fossil plant assemblages in Australia. Coinciding with the Early Eocene Climatic Optimum (EECO) and predating the breakup of Australia from Antarctica, it offers critical data to study the diversity and extent of the Austral Polar Forest Biome, and the floristic divergence between Australasia and South America resulting from the Gondwana breakup. The micromorphology and macromorphology of new fossil plant compressions from the MHF were described and systematically analyzed. Previously published non-flowering plant records were reviewed and revised. Macrofossil abundance data were provided. The flora was compared with other early Paleogene assemblages from across the Southern Hemisphere. Twelve species of non-flowering plants were identified from the macrofossil record. Conifers include Araucariaceae (Araucaria macrophylla, A. readiae, A. timkarikensis sp. nov., and Araucarioides linearis), Podocarpaceae (Acmopyle glabra, Dacrycarpus mucronatus, Podocarpus paralungatikensis sp. nov., and Retrophyllum sp.), and Cupressaceae (Libocedrus microformis). Dacrycarpus linifolius was designated a junior synonym of D. mucronatus. Further components include a cycad (Bowenia johnsonii, Zamiaceae), a pteridosperm (Komlopteris cenozoicus, Umkomasiaceae), and a fern (Lygodium dinmorphyllum, Schizaeaceae). The fossil assemblage represents a mixed near-polar forest with a high diversity of conifers. The morphology and preservation of several species indicate adaptations to life at high latitudes. The coexistence of large- and small-leaved conifers implies complex, possibly open forest structures. Comparisons with contemporaneous assemblages from Argentina support a circumpolar biome during the EECO, reaching from southern Australia across Antarctica to southern South America.

Complementary description of three Amblyseius species (Acari: Mesostigmata; Phytoseiidae) and keys to the world species of duncansoni and largoensis species subgroups

Three phytoseiid species: Amblyseius excelsus Chaudhri, Akbar and Rasool, A. adhatodae Muma, and A. isuki Chant and Hansell, collected from Pakistan, are re-described with more detailed descriptions and illustrations. The species, A. bajulus Chaudhri, Akbar and Rasool, is considered as junior synonym of A. isuki instead of A. obtusus (Koch). The identification keys to the world species of duncansoni and largoensis species subgroups are presented.

Pseudomystus tuberosus, a new species of catfish from central Borneo (Actinopterygii: Bagridae)

Pseudomystus tuberosus, a new species of bagrid catfish from the Kahayan River drainage in south central Borneo, is described in this study. It can be distinguished from all congeners in having a strongly humped dorsal profile (vs. dorsal profile weakly humped or without hump), as well as its head and flanks covered with rounded tubercles (vs. smooth or with capillaceous epithelial projections). Pseudomystus tuberosus most closely resembles P. vaillantii, but can be further distinguished from it in having a smaller eye (8% HL vs. 9–12) and a slenderer caudal peduncle (5.5–6.0% SL vs. 6.8–8.1). The identity of P. carnosus, described from southern Sumatra, is also discussed, and the species treated as a junior synonym of P. moeschii.

The first records of Microprosthema pernambucensis (Bochini, Cunha, Terossi & Almeida, 2020) and Odontozona addaia Pretus, 1990 from the tropical eastern Atlantic (Decapoda: Stenopodidea)

Two species of stenopodidean shrimps are newly recorded from the tropical eastern Atlantic, each representing considerable extensions to their previously known biogeographical ranges. The shrimp genus Chicosciencea Bochini, Cunha, Terossi & Almeida, 2020, is confirmed as a junior synonym of Microprosthema Stimpson, 1860. Microprosthema pernambucensis (Bochini, Cunha, Terossi & Almeida, 2020), previously only known from northeastern Brazil, is reported for the first time from the tropical eastern Atlantic based on material collected in subtidal lava tubes on the coast of Sal, Cabo Verde, and re-illustrated in view of the limited original description. Odontozona addaia Pretus, 1990, previously only known from the Mediterranean Sea, is herein reported from the Atlantic Ocean proper, based on specimens from the same habitat, also in Cabo Verde.

Revision of the genus Bryodemina Hull (Diptera, Bombyliidae, Lomatiinae) with descriptions of two new Neotropical species

The New World genus Bryodemina Hull is revised. Two new species are herein described and illustrated: Bry. enigmatica sp. nov. from Brazil and Bry. ayalai sp. nov. from Venezuela. The results of a detailed morphological study, based on types and material deposited in many collections of the world, shows that Brachydemia Hull should be considered as a junior synonym of Bryodemina Hull, syn. nov. and Bra. latisoma Hull as junior synonym of Bra. hedickei (Paramonov), syn. nov. Illustrations of the external morphology of adults and male and female terminalia for all valid species are presented. A distribution map including all examined records, an identification key to species together with a preliminary biogeographic discussion are also added.

New generic name for a small Triassic ray-finned fish from Perledo (Italy)

Our new study of the species originally included in the genus Allolepidotus led to the taxonomic revision of the halecomorph species from the Triassic of Perledo, Italy. The morphological variation revealed by the analysis of the type material is sufficient to confirm four different taxa represented in the Perledo Formation. We correct the misunderstanding about the type species of Allolepidotus, which is A. ruppelii and not “A.” bellottii as considered in the literature over the past two decades. The latter species was originally placed in the genus Semionotus. Fossils from the Kalkschieferzone of Besnasca/Ca' del Frate (Viggiù-Varese, Italy) and Meride (Ticino, Switzerland) which were referred to Allolepidotus, rather represent a species of Eoeugnathus. Therefore, we transfer the species Semionotus bellottii to that genus and propose the new combination E. bellottii. The second and only other species originally included in the genus Allolepidotus is transferred here to the new genus Perledovatus. The holotype of P. nothosomoides new comb. has been mechanically prepared, revealing additional anatomical information that allows to place this taxon in the halecomorph family Subortichthyidae. The other halecomorph species named from the Perledo Formation, Pholidophorus oblongus and Pholidophorus curionii, have been treated as junior synonyms of E. bellottii, but our analysis indicates that they represent distinct separate taxa. However, due to the loss of the type specimens, it is not possible to decide whether they might have been conspecific with other ray-finned fishes from the Middle Triassic of the Alps.

The identities of Pinnotheres villosulus Guérin-Méneville, 1832, P. edwardsi De Man, 1887, and P. trichopus Tesch, 1918, with description of a new Indo-West Pacific genus of pinnotherid crab (Decapoda: Brachyura: Pinnotheridae)

Abstract Nepinnotheres villosulus (Guérin-Méneville, 1832) [Guérin-Méneville, 1829–1837] [type locality: Timor] and Nepinnotheres edwardsi (De Man, 1887) [type locality: Mergui Archipelago], as currently understood, are both reportedly widespread in Southeast Asia and northern Australia, and unique in the genus in having females densely covered by a setal tomentum that completely obscures the surfaces of the carapace and pereiopods. Based on the limited information contained in the type accounts, N. edwardsi and N. villosulus appear indistinguishable, but this cannot currently be confirmed by comparing type material because the holotype of N. villosulus, the senior name, is lost. A neotype is therefore designated for N. villosulus to fix its identity and taxonomic status as a senior synonym of N. edwardsi. In addition to the unique setation pattern of female N. villosulus, males of the species also present important differences from those of male Nepinnotheres sensu stricto. Pinnotheres trichopusTesch, 1918 [type locality: Elat, Great Kei Island, Indonesia], is also shown to be a junior synonym of P. villosulus. Moreover, recent molecular phylogenetic analyses determined that N. villosulus is phylogenetically distant from Nepinnotheres sensu stricto. As such, we establish a new genus for N. villosulus.

Assessment of the diversity of the family Sillaginidae in the Indian Ocean with emphasis on the taxonomic identity of Sillago sihama

The present study contributes to the taxonomy of the family Sillaginidae, with comments on the distribution of its species in the Indian Ocean and an emphasis on the taxonomy and distribution of Sillago sihama. Thirty described and putative species with Indian Ocean distribution are listed, and a distribution range for each species is provided based on published data and results from the present study. A comprehensive phylogenetic analysis of the barcoding portion of the mitochondrial COI gene is provided together with three approaches for molecular species delimitation, which includes 44 to 47 genetic lineages (depending on the species delimitation approach used) in the family Sillaginidae, 33 of them applying to described species and also 8 putative species, formerly misidentified as S. sihama. Inclusion of specimens from South Africa, Iran, Pakistan, India, Bangladesh and the southern Red Sea (type locality) reveals one genetic lineage representing the true Sillago sihama. Distribution of the species is confined to the Red Sea and the Indian Ocean, and other records under the name S. sihama are based on misidentifications. Several undescribed species identified as S. sihama are distributed in the Indo-West Pacific region and closely resemble S. sihama, but are not identical with this species and can be identified as members of different evolutionary lineages. Two species, S. sihama and S. soringa, reported from Bangladesh, represent the easternmost record of both species. These two species are described in detail, including swimbladder morphology. The study also shows that specimens from India identified as Sillago ingenuua McKay, 1985 are nested within a lineage previously referred to as S. ingenuua A, but are different from the lineage S. ingenuua B, representing a confirmed record of the clade S. ingenuua in the northern Indian Ocean. Comments on misidentifications of S. sihama from the Indian Ocean and western Pacific are provided. Furthermore, we propose that Sillago erythraea should be resurrected from its synonymy with S. sihama. As Sillago suezensis is identical with the former species, it becomes a junior synonym of S. erythraea.

Crassatella rubrolineata Turton, 1932, as a replacement name for Crassatella sowerbyi Lamy, 1917 non Wood, 1871 (Bivalvia, Crassatellidae), and a revision of Wood’s subspecies of C. sowerbyi

Resolving and disambiguating the many names given to fossil and Recent Crassatellidae is sometimes a knotty problem, exacerbated by the subtle differences between taxa and many applications of simple descriptive specific epithets (‘sulcata’, ‘rostrata’, ‘compressa’ etc.) leading to homonyms requiring resolution. The common decision to (perhaps) soften the blow of replacing someone’s name by erecting an eponym as a replacement to honour them has led to further unresolved homonyms and taxonomic ambiguities. One such case is addressed here. In this paper I resolve the homonymy of Crassatella sowerbyi Wood with Crassatella sowerbyi Lamy by replacing Lamy’s name with the available junior synonym C. rubrolineata Turton. Further, I revise the suite of taxa considered by Wood to be of subspecific rank within C. sowerbyi: I synonymise C. s. var. obesa with C. sowerbyi, and elevate C. s. var. semilaevis and C. s. var. hantoniensis to full specific rank. Detailed descriptions and illustrations are provided for all species.

Redescription of the type of Cormocephalus brasiliensis Humbert & Saussure, 1870 (Chilopoda, Scolopendromorpha, Scolopendridae), with taxonomic remarks on the species

ABSTRACT Cormocephalus brasiliensis Humbert & Saussure, 1870 has been described based on a single damaged specimen and without detailed information or illustrations. Since then, there has been no further detailed treatment of the taxon. Here, C. brasiliensis is redescribed in detail and illustrated based on the type material plus extra material from Brazil, Colombia, Panama and Ecuador; a diagnosis for the species is provided; its distribution is updated and expanded, with new records for some states in Brazil. The relationships between C. brasiliensis and C. edithae González-Sponga, 2000, C. ungulatus (Meinert, 1886) and C. impressus unimarginatus Bücherl, 1941 are analyzed; both C. ungulatus and C. impressus unimarginatus are junior synonyms of C. brasiliensis. The presence of the latter within the Neotropical subclade called the ‘guildingii-subgroup’ is examined and confirmed.

Molecular Systematics and Type-material-based Redescription of Metarhadinorhynchus lateolabracis, With Taxonomic Revisions of Metarhadinorhynchus, Indorhynchus, and Neotegorhynchus (Acanthocephala: Palaeacanthocephala).

Molecular phylogenetics has been improving the acanthocephalan systematics, yet numerous taxa remain unexplored. The palaeacanthocephalan Metarhadinorhynchus Yamaguti, 1959 and its type species M. lateolabracis Yamaguti, 1959 are such to-be-explored taxa. We aim to refine (i) the systematic placement, (ii) the morphological circumscription, and (iii) the taxonomic components of the genus. We also aim to examine the taxonomic status of the species that have been assigned to the genus. Morphological observations on newly collected specimens as well as the type material of Metarhadinorhynchus lateolabracis were conducted. Also, molecular phylogenetic analyses with maximum-likelihood method and Bayesian inference were performed based on freshly collected specimens. Nominal species that have at least once been assigned in Metarhadinorhynchus, as well as a related form, Gorgorhynchus lateolabri Yin and Wu, 1984, are taxonomically re-evaluated based on literature information. Our re-examination of the type material of M. lateolabracis revealed that the number of cement glands is six, instead of eight as described and illustrated in the original description. In the resulting phylogenetic tree, M. lateolabracis was nested in Isthmosacanthidae. Gorgorhynchoides Cable and Linderoth, 1963 was found to be a junior synonym of Metarhadinorhynchus. Taxonomic re-evaluations of six nominal species that have once belonged in Metarhadinorhynchus led to modifications of generic diagnoses for Indorhynchus Golvan, 1969 and Neotegorhynchus Lisitsyna, Xi, Orosová, Barčák, and Oros, 2022. Metarhadinorhynchus has been assigned to Leptorhynchoididae (Echinorhynchida), but our study now locates it in Isthmosacanthidae (Polymorphida). We propose 13 new combinations of specific names in Metarhadinorhynchus and three in Indorhynchus. Metarhadinorhynchus lateolabri (Yin and Wu, 1984) comb. nov. may be synonymous with M. orientalis (Wang, 1966) comb. nov.