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A New Record of Adelophthalmus (Eurypterida, Chelicerata) from the Devonian of the South Minusinsk Depression
Abstract
A new species of Adelophthalmus Jordan in Jordan et von Meyer, 1854, A. khakassicus sp. nov., from the Givetian (Middle Devonian) of the Republic of Khakassia (Russia) is described. This is one of the oldest species of the genus. It is also interesting in the unusually large for Adelophthalmus.
... Pterygotidae originated in the Llandovery (early Silurian), went extinct in the Middle Devonian (Tetlie, 2007;McCoy et al. 2015) and were characterized by the possession of a laterally expanded pretelson, with most species having enlarged chelicerae with elongated proximal podomeres (Tetlie & Briggs, 2009). Pterygotids attained a nearly global distribution (Poschmann & Tetlie, 2006;Miller, 2007;Tetlie & Briggs, 2009;Lamsdell & Legg, 2010;Wang & Gai, 2014) and were ecologically diverse predators with a range of visual acuity and a variety of cheliceral morphologies indicating adaptations towards a variety of benthic and actively swimming prey (Anderson et al. 2014;McCoy et al. 2015).The superfamily Adelophthalmoidea represents the most common eurypterids in the Late Palaeozoic, with about 46 species in seven genera (Tetlie, 2007;Shpinev, 2012;Lamsdell et al. 2014;Poschmann, 2015Poschmann, , 2020Shpinev & Filimonov, 2018). Taxonomically they are the second most diverse of all eurypterid clades, after the Pterygotoidea, their putative sister group . ...
... possessing strongly developed lateral epimera on the fourth to twelfth tergites whereas epimera are only observed on the seventh to twelfth tergites in the Euramerican species, even in larger specimens (Kjellesvig-Waering, 1961;Kjellesvig-Waering & Leutze, 1966;Størmer, 1973;Poschmann & Tetlie, 2006;Poschmann, 2015Poschmann, , 2017Poschmann, , 2020. The developed lateral epimera are unlikely to be an ontogenetic difference because epimera can also be observed in the different ontogenetic stages of the closely related Adelophthalmus (Shpinev & Filimonov, 2018). ...
Two new eurypterids, a pterygotid Pterygotus wanggaii n. sp. and an adelophthalmoid Parahughmilleria fuea n. sp., are described from the Early Devonian (Lochkovian) Xiaxishancun Formation of Yunnan province, southwest China. This discovery represents the first record of Parahughmilleria from Gondwana and the first Pterygotus from China. Pterygotus wanggaii n. sp. is characterized by the first primary denticles (d1,d1′) being located on the middle part of the cheliceral ramus and third primary denticles (d3,d3′) elongate, even longer than the first primary denticles. Parahughmilleria fuea n. sp. is differentiated by being a large Parahughmilleria with strongly developed lateral epimera from tergites T4 to T12. These discoveries not only extend the geographical extent of the genera Pterygotus and Parahughmilleria from Euramerica to SW China, but also give insight into the similarity of ecosystem structures across the Early Devonian world. In addition, based on previous studies, the new discoveries further support the hypothesis that eurypterids underwent a crisis during the Silurian–Devonian boundary interval.
... The comparisons would illustrate which (if any) cheliceral morphologies were most effective at shell crushing and whether the gnathobasic structures could have aided in durophagous predation. Braddy et al., 1995Bruton et al., 1969Playford and Lowry, 1966Selden, 1993aShpinev, 2012aShpinev and Filimonov, 2018 ...
Eurypterids, the so-called sea scorpions, are a group of extinct chelicerates with a diversity of over 250 species. Although the group has a distribution across most of the globe, the majority of taxa are known from the northern Hemisphere. Despite the general palaeontological interest in sea scorpions, Gondwanan—specifically Australian—taxa have received little consideration. To rectify this, we collate data on Australian sea scorpion material from the Gogo, Melbourne and Montys Hut formations, the Humevale and Muttama Creek siltstones and the Wilson Creek Shale. The studied material spans the late Silurian to the late Devonian and highlights a rich Pterygotidae fauna, especially in the state of Victoria. We conclude that presently there is insufficient material to erect new taxa. However, further collecting of material—especially the Wilson Creek Shale and the Montys Hut Formation—will uncover more material to aid in understanding the most southern, Gondwanan eurypterids.
Xiphosura are extant marine chelicerates that have displayed apparent morphological conservatism and remarkable survivorship across their~480 Ma fossil record. The easily recognisable features that are known to even the earliest xiphosurans-a crescentic prosoma and often trapezoidal thoracetron (opisthosoma)-have generated debate surrounding their origins and taxonomic significance. This interest resulted in the description of numerous horseshoe crab species during the early to mid-twentieth century, particularly in Russia, that have remained unrevised since their original publications and unconsidered in the light of recent phylogenetic hypotheses. Here, we reexamine the non-belinurid taxa housed within the Chernyshev Central Museum for Geological Exploration in Saint Petersburg. We present the first formal diagnosis of Bellinuroopsis rossicus, erect Shpineviolimulus jakovlevi (Glushenko and Ivanov, 1961) comb. nov., to contain the species formerly described as 'Paleolimulus' jakovlevi and refer Paleolimulus juresanensis to Paleolimulidae incertae sedis. Phylogenetic analysis places S. jakovlevi at the base of Limulina. This position, coupled with a prosomal shield that is notably larger than the thoracetron, and lack of hypertrophied genal spines, suggests that this morphology may represent the ancestral austrolimulid shape. As an extension of this revision, we assessed the general austrolimulid morphological characters and uncovered two possible groups of these bizarre xiphosurids.
The first eurypterid known from Italy is described, as Adelophthalmus piussii n. sp. It comes from the Upper Carboniferous of the Carnic Alps (Friuli, NE Italy). Relationships with related species are discussed. Adelophthalmids are the commonest eurypterids of the late Palaeozoic, at which time the disparity of the order was waning. The new record enhances our knowledge of adelophthalmid distribution and diversity.
The eurypterid Rhenopterus sievertsi Størmer from the Lower Devonian of Germany is redescribed. Based on new morphological data, including the possession of prosomal limbs of Adelophthalmus-type and spatulae on the genital operculum, the species is transferred to Adelophthalmus Jordan, in Jordan and von Meyer and thus is the oldest representative of this geographically and stratigraphically widespread genus. Eurypterus? trapezoides Størmer is recognized as a junior synonym of A. sievertsi.
Standards have been empirically developed to describe various morphological characters of eurypterids. The standards pertain to the following characters: 1) shape of the prosoma; 2) shape of the metastoma; 3) shape of the eyes; 4) position of the eyes; 5) types of prosomal appendages; 6) types of swimming leg paddles; 7) structure of the doublure; 8) differentiation of the opisthosoma; 9) structure of the genital appendages; 10) shape of the telson; and 11) types of ornamentation.
For the first time, a uniform, standardized taxonomy is proposed for classification and identification of most genera. The taxonomy is based on the observation that most higher taxonomic levels for arthropods are based on the structure and arrangement of the appendages. Details of the taxonomy rely on the morphological standards proposed here.
The order Eurypterida Burmeister, 1843, is here defined by the presence of only six pairs of prosomal appendages, the first pair being the chelicera, the next five pairs being the gnathobasic, uniramus legs. Suborders are characterized by the gross morphology of the chelicera. Superfamilies and families are characterized by the use of a single character complex, specifically the structure and arrangement of the second through sixth pairs of prosomal appendages. Genera are recognized by more specific standards.
A new classification of the order Eurypterida is proposed. Three new superfamilies, Kokomopteroidea, Megalograptoidea, and Brachyopterelloidea, and five new families, Brachyopterellidae, Adelophthalmidae, Lanarkopteridae, Erieopteridae, and Hardieopteridae, are proposed.
Two new eurypterid species, Adelophthalmus kamyshtensis sp. nov. and Adelophthalmus dubius sp. nov., are described from the Middle Devonian of Khakassia. The new species are among the earliest known members of the genus Adelophthalmus and the earliest members of this genus known outside Europe and North America.
The distribution and dispersal histories of Eurypterida are examined in a phylogenetic and palaeogeographic context. It is suggested that all the eurypterid clades originated and had most of their evolutionary history on the palaeocontinents of Laurentia, Baltica, Avalonia, the Rheno–Hercynian Terrane and some presence in Siberia. The Siluro–Devonian Stylonurina and the eurypterine superfamilies Eurypteroidea and Waeringopteroidea are confined in their entirety to these continents. The Late Palaeozoic records of Adelophthalmoidea and Hibbertopteroidea in China, South America and Africa can be explained by ‘rafting’ on the continental plates that amalgamated into the supercontinent Pangaea. However, two clades have distributions that suggest abilities to cross open stretches of ocean; the Silurian and Devonian pterygotoids and some Devonian adelophthalmoids. However, one Silurian mixopteroid and the basal swimming form Onychopterella outside the ‘core-area’ suggest the dispersal patterns are more complicated. The pterygotoids might be the only clade whose members frequently undertook oceanic excursions. Since almost all eurypterid evolution took place in Laurentia, Baltica and Avalonia (and some in the Early Devonian of the Rheno–Hercynian Terrane) prior to the Carboniferous, it is unlikely that many taxonomically rich pre-Carboniferous eurypterid faunas will be encountered outside of these palaeocontinents.
A phylogenetic analysis of the monophyletic superfamily Adelophthalmoidea suggests that there is a basal, hitherto unrecognised genus, Eysyslopterus gen. nov., in the clade, on the basis of carapace shape, anterior ornament and eye position. The two comparatively poorly known genera Pittsfordipterus and Bassipterus form a relatively basal clade and are united by their shared possession of elongated eyes and a type A genital appendage consisting of two articles forming a complex distal termination. The genera Parahughmilleria and Nanahughmilleria are represented in the analysis by only one well-known species each and the monophyly of these two genera remains untested. The geologically long-lasting Adelophthalmus is monophyletic and supported by a number of synapomorphies. The clade probably had a marine origin. Most known representatives are brackish (estuarine-deltaic) or freshwater (laminated lacustrine-fluvial) inhabitants, but with a marine influence commonly encountered within the sequences. The fossil record of the clade is relatively poor with a Relative Completeness Index value of between 31 and 34%. However, the fit between phylogeny and stratigraphical occurrences of the taxa analysed is very good (Stratigraphic Consistency Index = 0.73; Gap Excess Ratio = 0.96-0.97). The sister group of Adelophthalmus, the genus Parahughmilleria, is reported for the first time from the Silurian of Lesmahagow, Scotland and these specimens are questionably referred to P. cf. hefteri, previously known only from the Siegenian and Emsian of western Germany and Luxembourg.
Thesis (doctoral)--Université de Paris, 1955.
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