Enigmatic Arthropod Research Articles

The enigmatic arthropod Duraznovis gallegoi from the Late Triassic of Argentina is a cicadomorphan head (Insecta: Hemiptera: Auchenorrhyncha)

Recently, Lara et al. (2020a, b) described a new fossil taxon, Duraznovis gallegoi, based on two specimens from the Upper Triassic Potrerillos Formation at Quebrada del Durazno, Cuyana Basin of Argentina. This fossil is considered to be an enigmatic arthropod closely resembling the living and fossil representatives of xiphosurans (Chelicerata) and notostracans (Branchiopoda), two completely different arthropod groups with convergent body plans. Some distinctive combination of features, however, makes the systematic position of these specimens indeterminate (Lara et al., 2020a, b).

First African thylacocephalans from the Famennian of Morocco and their role in Late Devonian food webs

Thylacocephalans are enigmatic arthropods with an erratic Palaeozoic and Mesozoic fossil record. In many of the few localities where they occur, they are quite abundant. This also holds true for the Famennian Thylacocephalan Layer in the Maider (eastern Anti-Atlas of Morocco), a small epicontinental basin hosting some strata with taphonomic properties of a conservation deposit yielding exceptionally preserved gnathostomes and non-vertebrates. In a thin argillaceous interval in the earliest middle Famennian, thylacocephalans occur in such great numbers that they became eponyms of this unit. Therein, we discovered a new taxon of thylacocephalans, Concavicaris submarinus sp. nov., which represent the oldest records of thylacocephalans from Africa. In the CT-imagery, the holotype of Concavicaris submarinus sp. nov. revealed anatomical details including its eyes, appendages and other soft parts. Sedimentary facies and faunal composition of the Thylacocephalan Layer suggest that these animals populated the water column above the low-oxygen sea floor. Thus, thylacocephalans likely represented an important component of the diet of chondrichthyans and placoderms, which are quite common as well. The abundance of thylacocephalans in other conservation deposits like the Cleveland Shale (USA) and the Gogo Formation (Australia) underline their pivotal role in Late Devonian pelagic food webs.

New thylacocephalans from the Early Triassic Paris Biota (Bear Lake County, Idaho, USA)

Two new genera and species of thylacocephalans (Arthropoda, Thylacocephala), Parisicaristriassica Charbonnier and Ligulacarisparisiana Charbonnier, are described from the early Spathian Paris Biota. These new occurrences are the first reports of thylacocephalans from Triassic rocks in North America. They considerably enlarge the spatiotemporal distribution of these enigmatic arthropods and highlight their relatively high generic richness during the Early Triassic. It also confirms that the Triassic was the taxonomically richest period for Thylacocephala.

First Carboniferous thylacocephalan from Europe and its significance for the understanding of functional morphology of Concavicarididae Schram, 2014

Thylacocephala Pinna, Arduini, Pesarini & Teruzzi 1982 are among the most enigmatic arthropods. Their fossil record is very patchy both geographically and stratigraphically. In this paper we describe the first thylacocephalan known from the Carboniferous (Mississippian) of Europe,Concavicaris viktorynisp. nov. Until now Carboniferous representatives of Thylacocephala were know exclusively from the U.S.A. We discuss the stratigraphic and geological context of occurrence of this new species as well as form and function of the unique carapace micro- and macro-ornamentation. A shape and assumed function of the characteristic lirae on theC. viktorynisp. nov. carapace present an important supporting argument for the supposed free-swimming or pelagic mode of life in thylacocephalans. Palaeobiogeographical and evolutionary aspects of surprisingly rich but local occurrence of thylacocephalans in the Lower Carboniferous of the Moravian karst are discussed. Possible sympatric evolution from its predecessorConcavicaris incolais also pointed out.

The cuticle of the enigmatic arthropodPhytophilaspisand biomineralization in Cambrian arthropods

Lin, J.-P., Ivantsov, A.Y. & Briggs, D.E.G. 2011: The cuticle of the enigmatic arthropod Phytophilaspis and biomineralization in Cambrian arthropods. Lethaia, Vol. 44, pp. 344–349. Many non-trilobite arthropods occur in Cambrian Burgess Shale-type (BST) biotas, but most of these are preserved in fine-grained siliciclastics. Only one important occurrence of Cambrian non-trilobite arthropods, the Sinsk biota (lower Sinsk Formation, Botomian) from the Siberian Platform, has been discovered in carbonates. The chemical compositions of samples of the enigmatic arthropod Phytophilaspis pergamenaIvantsov, 1999 and the co-occurring trilobite Jakutus primigenius Ivantsov in Ponomarenko, 2005 from this deposit were analysed. The cuticle of P. pergamena is composed of mainly calcium phosphate and differs from the cuticle of J. primigenius, which contains only calcium carbonate. Phosphatized cuticles are rare among large Cambrian arthropods, except for aglaspidids and a few trilobites. Based on recent phylogenetic studies, phosphatization of arthropod cuticle is likely to have evolved several times. □arthropod cuticle, Burgess Shale-type preservation, fossil-diagenesis, phosphatization.

An annotated catalogue of the tongue worms (Pentastomida) held in the Museum für Naturkunde Berlin

An annotated catalogue of the type and non-type material belonging to the enigmatic arthropod group Pentastomida (tongue worms) in the Museum fur Naturkunde Berlin is presented. Aspects of human infection, current ideas on their affinities and some recent developments in the study of these animals are briefly reviewed. Types of eight species have been recorded: Raillietiella affinis Bovien, 1927, Raillietiella bicaudata Heymons & Vitzthum, 1935, “Pentastomum ” javanicum Bovien, 1927, Raillietella kochi Heymons, 1926, Elenia lialisi Heymons, 1939a, Raillietiella mabuiae Heymons, 1922, Raillietella shipleyi Heymons, 1926 and Cephalobaena tetrapoda Heymons, 1922. Five of these types are currently considered valid species. According to the literature, type material from Elenia travassosi (Heymons, 1932) should be in Berlin, but could not be traced during the present review and may have to be considered lost. A further twenty-six non-type species were recorded, plus specimens assigned to two names currently regarded as nomina dubia. This yields a total of 31 currently valid species in Berlin, representing nearly 25 % of the known world fauna. Much of the Berlin material derives from the important Richard Heymons collection, but significant historical specimens collected in Brazil in the early nineteenth century by Johann Natterer was also discovered during the course of this project. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

JURACYCLUS POSIDONIAE N. GEN. AND SP., THE FIRST CYCLOID ARTHROPOD FROM THE JURASSIC

The cycloids represent an enigmatic arthropod group of probably crustacean affinity, occurring mostly in the younger Paleozoic, from the early Carboniferous up to the Late Triassic (Schram et al., 1997). Superficially, cycloids strikingly resemble crabs and were thought to have had a similar lifestyle, becoming extinct when crabs started to radiate. Recently, the existence of a Late Cretaceous cycloid, Maastrichtiocaris rostratus Fraaije et al., 2003, from the Maastrichtian of the Netherlands, proved that cycloids did not go extinct at the end of the Triassic as believed for a long time, but survived much longer, co-occurring with crabs. Due to obvious collecting bias and the incompleteness of the fossil record of arthropods with relatively delicate carapaces in general, neither Jurassic nor Early Cretaceous representatives have been reported hitherto. However, from the Lower Jurassic Posidonienschiefer (‘Posidonia Shale’) of southwestern Germany—famous for its excellent fossil preservation, not only of marine vertebrates and large crinoids living on driftwood, but also many other invertebrate groups (Riegraf et al., 1984; Urlichs et al., 1994)—now a single specimen of a cycloid is recorded and described herein. Although this record helps link the bias between the Triassic and the Late Cretaceous occurrences, the characters of the specimen differ strongly from those of other cycloids, thus requiring the erection of a new genus and species. In Europe, cycloids are mainly known from the German Triassic (e.g., Meyer, 1838, 1844, 1847; Seebach, 1857; Bill, 1914; Muller, 1955; Trumpy, 1957; Linck, 1961; Meischner, 1963; Zorn, 1971; Oosterink, 1986), and from the Triassic of the Alps (Schafhautl, 1863; Reuss, 1867; Trauth, 1918; …

Cambrian origins and affinities of an enigmatic fossil group of arthropods.

Euthycarcinoids are one of the most enigmatic arthropod groups, having been assigned to nearly all major clades of Arthropoda. Recent work has endorsed closest relationships with crustaceans or a myriapod-hexapod assemblage, a basal position in the Euarthropoda, or a placement in the Hexapoda or hexapod stem group. Euthycarcinoids are known from 13 species ranging in age from Late Ordovician or Early Silurian to Middle Triassic, all in freshwater or brackish water environments. Here we describe a euthycarcinoid from marine strata in Argentina dating from the latest Cambrian period, extending the group's record back as much as 50 million years. Despite its antiquity and marine occurrence, the Cambrian species demonstrates that morphological details were conserved in the transition to fresh water. Trackways in the same unit as the euthycarcinoid strengthen arguments that similar traces of subaerial origin from Cambro-Ordovician rocks were made by euthycarcinoids. Large mandibles in euthycarcinoids are confirmed by the Cambrian species. A morphology-based phylogeny resolves euthycarcinoids as stem-group Mandibulata, sister to the Myriapoda and Crustacea plus Hexapoda.

MAASTRICHTIOCARIS ROSTRATUS NEW GENUS AND SPECIES, THE FIRST CRETACEOUS CYCLOID

Since the description of the first cycloid from the Carboniferous of Yorkshire, England (Phillips, 1835) the Cycloidea have been placed in many different groups within the Arthropoda. These include agnostid trilobites (Phillips, 1835), xiphosure merostomes (Packard, 1872; Oosterink, 1978), limuloid-like crustaceans (Woodward, 1905), decapod brachyurans (Trauth, 1918), branchiurans (Hopwood, 1925), copepods (Clark, 1989), and maxillopodan crustaceans (Schram et al., 1997). Glaessner (1928) considered that the Cycloidea might be derived from the Paleozoic Phyllocarida. More recently Vannier and Babin (1995) postulated the enigmatic arthropod, Hanadirella known from the Ordovician of Saudi Arabia and France, as a possible ancestor of the cycloids. However, cladistic analysis (Schram et al., 1997) indicates that the Cycloidea possibly belong within the Crustacea as a sister group of the Copepoda. The Cycloidea were, heretofore, known from beds extending from the early Carboniferous until the late Triassic. They are found in Austria, Belgium, Bosnia, Central Asia, France, Germany, Ireland, Italy, Russia, Netherland, the U.K. and the U.S.A. (Glaessner, 1969; Schram et al., 1997). One of the youngest cycloids previously known, Halicyne cf. H. agnota von Meyer, 1847, was reported from the Muschelkalk of Winterswijk, in Netherland (Oosterink, 1978; 1986). However, in the course of the ongoing investigations of the Maastricht Formation in the Maastrichtian type area, southern Limburg, Netherland, three specimens of what clearly seem to be cycloids have come to light. The distinctive anatomy of these fossils, all from the Meerssen Member (IVf4) of the ENCI quarry, require erection of a new genus and species. ### Class MaxillopodaDahl, 1956 Order Cycloidea Glaessner, 1928 Family Cyclidae Packard, 1885 Genus Maastrichtiocaris new genus #### Diagnosis Carapace oval; with relatively broad, flat …

New Euthycarcinoids and an Enigmatic Arthropod from the British Coal Measures

Two new species of euthycarcinoids (Arthropoda), Kottixerxes anglicus sp. nov. and Smithixerxes pustulosus sp. nov., are described from the Coal Measures of Westhoughton, Lancashire and Coseley, West Midlands (Westphalian A and B respectively). Both genera are previously known from Mazon Creek, USA (Westphalian D). An additional, enigmatic arthropod with possible euthycarcinoid affinities, Arthrogyrinus platyurus gen. et sp. nov., is described from Coseley. Hypotheses concerning the phylogenetic position of euthycarcinoids are critically reviewed.