Pechoracaris Dzik & Ivantsov & Deulin 2004, GEN. NOV.

<p> PECHORACARIS <b>GEN. NOV.</b></p> <p> <i>Type species: A. aculicauda</i> sp. nov.</p> <p> <i>Diagnosis:</i> Hoplostracan with very long spine-like telson without furca, elongated carapace reaching fifth pleomere; pleopods transformed into spines.</p> <p> <i>Etymology:</i> Derived from the Pechora River region, where the fossils were found, and Latin <i>caris</i> (shrimp).</p> <p> <i>Affinities:</i> The most striking aspect of this arthropod is its single caudal spine (Figs 3, 5). In this respect it somewhat resembles the enigmatic ‘trilobitomorph’ <i>Burgessia bella</i> Walcott, 1912 from the famous Middle Cambrian Burgess Shale of British Columbia (Hughes, 1975). Such affinity is unlikely, however, as the new Russian arthropod shows strongly sclerotized mandibles, which indicates its advanced crustacean affinities.</p> <p> Probably the closest relative of <i>Pechoracaris aculicauda</i> is ‘ <i>Elymocaris</i> ’ <i>urvantsevi</i> Dunlop, 2002 from roughly coeval strata of the Severnaya Zemla archipelago. Although the presence of a medial dorsal plate and rostral plate is claimed in the original description (Dunlop, 2002), the evidence for this seems rather weak. ‘ <i>E.</i> ’ <i>urvantsevi</i> shows a similar shape of the carapace to the new archaeostracan, covering all but the last three segments of the abdomen. Its spinose furca is normally developed, but is significantly shorter than the telson spine.</p> <p> Among the archaeostracans, an elongated caudal spine and reduced furca are known in the Early Devonian <i>Heroldina</i> and <i>Aristozoe</i>, and in the Early Carboniferous <i>Sairocaris</i>. The giant <i>Heroldina rhenana</i> (Broili, 1928) from the Hunsrück Slate of Germany, reaching up to 60 cm in length, is different from the Russian crustacean in the presence of a large rostral plate and dorsal hinge of the carapace (Bergström <i>et al</i>., 1989; Bartels <i>et al</i>., 1998). In its strongly elongated last abdominal segment, <i>Heroldina</i> resembles <i>Aristozoe regina</i> Barrande, 1972 from the Konĕprusy Limestone of Bohemia (Chlupac˘, 1963) and <i>A. virga</i> Chlupac ˘, 1970 from the earliest Devonian Lochkov Limestone. Another Bohemian aristozoid, <i>Pygocaris schuberti</i> Perner 1916 from the Lochkov Limestone, had a thin cuticle (Chlupac˘, 1963) but still does not show even a remote similarity to the Russian form. Archaeostracans with somewhat reduced furca, elongated medial spine and possibly lacking separate rostral plate are known from as far back in the geological past as the Middle Ordovician (Hannibal & Feldmann, 1997).</p> <p> The hoplostracan <i>Sairocaris elongata</i> (Peach, 1882), that notably co-occurs with <i>Anthracophausia</i> in the Early Carboniferous Glencartholm Volcanic Beds of Scotland, has a very short carapace, exposing posterior thoracic segments (Schram, 1979). If the Russian form is truly related to <i>Sairocaris</i>, a carapace reduction took place in the evolution of the lineage.</p>Published as part of <i>Dzik, Jerzy, Ivantsov, Andrey Yu. & Deulin, Yuriy V., 2004, Oldest shrimp and associated phyllocarid from the Lower Devonian of northern Russia, pp. 83-90 in Zoological Journal of the Linnean Society 142 (1)</i> on pages 84-85, DOI: 10.1111/j.1096-3642.2004.00121.x, <a href="http://zenodo.org/record/4687299">http://zenodo.org/record/4687299</a&gt

Archangeliphausia SPINOSA 2004, SP. NOV.

ARCHANGELIPHAUSIA SPINOSA SP. NOV. <p>(FIGS 2–4, 5B)</p> <i>Holotype:</i> Specimen PIN 4983/1a (Figs 2A, 4B). <p> <i>Type horizon and locality:</i> Dark-grey claystone from a depth of 4255.0– 4262.7 m, Lower Devonian (Lochkovian?). Borehole Medynskoye 1, Timan-Pechora region of polar Russia.</p> <p> <i>Material:</i> Sixty more or less complete compressions.</p> <p> <i>Diagnosis:</i> As for the genus.</p> <p> <i>Description:</i> The largest specimen, PIN 4983/35, probably belongs to this species (Fig. 2B). It measures 12.5 mm in length from the carapace rostrum to the end of the telson. The smallest reasonably complete specimen is PIN 4983/37 (Fig. 2C) with an estimated length of <i>c</i>. 6.5 mm. The size of most specimens is close to the mean between these values. As the specimens are mostly complete skeletons, not exuvia, the dominance of larger individuals may reflect the structure of the original population at its repeated catastrophic extinctions.</p> <p>Three basal segments of the 1st antenna are preserved in specimens PIN 4983/18 and 25. The proximal segment is approximately three times longer than the third one, while the second segment is intermediate in length (Fig. 5B). Of the 2nd antenna only the scaphocerite is preserved in a few specimens, the most complete being those of PIN 4983/2, 18, and 24 (Fig. 3A). The scaphocerite is oval, represented only by an organic film on the rock surface and its margins are not easy to trace.</p> <p>The carapace has a sharp, relatively short rostrum, the ocular sinus being clearly visible in specimens PIN 4983/24A and B. The lower margin of the carapace, well preserved in holotype specimen PIN 4983/1a, has a very narrow band (Figs 2A, 4A). Being thicker, this band would have strengthened the cuticle. It is calcified and shows openings of pore canals; the posterior margin is hardly discernible except in the isolated dorsoventrally compressed carapace of specimen PIN 4983/43.</p> <p>Laterally compressed sternites of thoracic segments are preserved in many specimens. The boundaries between the segments are discernible some distance dorsally of the sternites. All segments except for the first are recognizable in the specimen associated with the holotype (Figs 2A, 4B). They disappear at approximately half the height of the body, which probably corresponds to the limit of connection of the body with the carapace.</p> <p>No remnants of the apparently weakly calcified thoracopods are preserved. Some faint marks may correspond to pleopods, but they are completely undefined morphologically.</p> <p>The pleosomites increase gradually in length posteriorly, the 6th pleomere being very much longer than the preceding ones. Their pleura are somewhat expanded posteriorly to form oval lobes. The lobe of the 5th pleuron appears to extend almost to the midlength of the 6th pleosomite. All pleura bear sharp spines at their ventral tips, best preserved in specimens PIN 4983/31 and 24b (Fig. 3G).</p> <p>The 6th pleosomite has almost parallel sides when, as in PIN 4983/36, compressed dorsoventrally (Fig. 3F). There is a kind of hinge connection with the basal segment of the uropods.</p> <p>The telson is best preserved in PIN 4983/28 (Figs 2E, 4C), although its parts are recognizable in several other specimens. Its sides are gently convex but almost parallel to each other. The posterior margin bears about eight indistinct indentations probably corresponding to bristle bases. The surface, as preserved in some stronger sclerotized fragmentary specimens (e.g. PIN 4983/32; Fig. 3B), is externally smooth. The rami of the uropods were strongly sclerotized only along their external margins. This prevents delineation of their shapes, but they were probably rather wide.</p>Published as part of <i>Dzik, Jerzy, Ivantsov, Andrey Yu. & Deulin, Yuriy V., 2004, Oldest shrimp and associated phyllocarid from the Lower Devonian of northern Russia, pp. 83-90 in Zoological Journal of the Linnean Society 142 (1)</i> on pages 86-87, DOI: 10.1111/j.1096-3642.2004.00121.x, <a href="http://zenodo.org/record/4687299">http://zenodo.org/record/4687299</a&gt

Figure 2 in Oldest shrimp and associated phyllocarid from the Lower Devonian of northern Russia

Figure 2. Archangeliphausia spinosa sp. nov. A, holotype (PIN 4983/1a: right) and associated specimen (PIN 4983/1b). B, largest specimen found (PIN 4983/35), with relatively thick cuticle. C, juvenile specimen (PIN 4983/37). E, specimen with dorsoventrally compressed telson and uropods (PIN 4983/28; see also Fig. 4C). D, posterior part of abdomen with well preserved 6th pleosomite and telson (PIN 4983/8).Published as part of <i>Dzik, Jerzy, Ivantsov, Andrey Yu. & Deulin, Yuriy V., 2004, Oldest shrimp and associated phyllocarid from the Lower Devonian of northern Russia, pp. 83-90 in Zoological Journal of the Linnean Society 142 (1)</i> on page 87, DOI: 10.1111/j.1096-3642.2004.00121.x, <a href="http://zenodo.org/record/10114602">http://zenodo.org/record/10114602</a&gt

Figure 3 in Oldest shrimp and associated phyllocarid from the Lower Devonian of northern Russia

Figure 3. Archangeliphausia spinosa sp. nov. A, specimen with oblique dorsoventrally compressed carapace and well preserved scaphocerite of 2nd antenna (PIN 4983/2). B, specimens with partially preserved telson and uropods (PIN 4983/ 32a, b). C, specimens with partially preserved telson and uropods (PIN 4983/12a, b). D, posterior part of abdomen with well preserved 6th pleosomite (PIN 4983/4a). E, posterior part of abdomen with well preserved pleura (PIN 4983/39). F, dorsoventrally compressed 6th pleosomite and partial uropods (PIN 4983/36). G, specimen with well preserved spinose pleura (PIN 4983/31).Published as part of <i>Dzik, Jerzy, Ivantsov, Andrey Yu. & Deulin, Yuriy V., 2004, Oldest shrimp and associated phyllocarid from the Lower Devonian of northern Russia, pp. 83-90 in Zoological Journal of the Linnean Society 142 (1)</i> on page 88, DOI: 10.1111/j.1096-3642.2004.00121.x, <a href="http://zenodo.org/record/10114602">http://zenodo.org/record/10114602</a&gt