14 research outputs found
Figure 3 in Oldest shrimp and associated phyllocarid from the Lower Devonian of northern Russia
No full textFigure 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 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) on page 88, DOI: 10.1111/j.1096-3642.2004.00121.x, http://zenodo.org/record/468729
Figure 2 in Oldest shrimp and associated phyllocarid from the Lower Devonian of northern Russia
No full textFigure 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 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) on page 87, DOI: 10.1111/j.1096-3642.2004.00121.x, http://zenodo.org/record/468729
Archangeliphausia Dzik & Ivantsov & Deulin 2004, GEN. NOV.
No full textARCHANGELIPHAUSIA GEN. NOV. <p> <i>Type species: A. spinosa</i> sp. nov.</p> <p> <i>Diagnosis:</i> A generalized anthracophausiid with abdominal pleura bearing a single small spine on their ventral margin.</p> <p> <i>Etymology:</i> Derived from the latinized name of Arkhangelsk and <i>phausis</i> (Greek = shine).</p> <p> <i>Affinities:</i> Brooks (1962) indicated a recessed ‘eye socket’ of the proximal segment of peduncle of antennules as the diagnostic character of his Anthracophausiidae. This feature is not represented in the new genus, which is quite generalized in this respect and may have been anatomically close to the Devonian eocaridids, as indicated also by the long abdominal pleura. However, the more general aspects of <i>Anthracophausia</i> listed by Brooks (1962) - weak sclerotization of generally smooth carapace, margins reinforced with an unusually narrow band, a short rostrum, and lateral flattening of the body due to compression - fit well the Russian material.</p> <p> The Carboniferous species of <i>Anthracophausia</i> reveal dramatically different outlines of abdominal pleura from those in the Russian species. In <i>A. strongi</i> Brooks, 1962, from the Late Carboniferous Mazon Creek fauna of Illinois, the pleural lobes of the abdominal tergites are broadly rounded. In <i>A. dunsiana</i> from the Early Carboniferous Glencartholm Volcanic Beds of Scotland they narrow to form a sharp apex (Schram, 1979). In the new species, rounded lobes are armed with short spines, which seems to be enough to substantiate its taxonomic distinction. Another possible difference between the Russian form and the Carboniferous species of <i>Anthracophausia</i> is the increasingly posterior orientation of the abdominal pleural lobes towards the telson (although not easily discernible because of strong flattening of the specimens). In fact, the faint parabolic lines visible on the paratype of <i>A. strongi</i> (Brooks, 1962; pl. 48: 3) may also indicate a similar shape of the posterior pleural lobes in that species. Some gradient in the shape of pleural lobes is also observable in <i>A. dunsiana</i>.</p> <p> All these distinguishing characters are probably primitive (plesiomorphic) and the new genus is probably transitional between the benthic Eocarididae and typical Carboniferous Anthracophausiidae. It may represent the beginning of the lineage of <i>Anthracophausia</i>. Because of the significant time and morphological distance it seems practical, however, to separate them at the generic level.</p> <p> The Anthracophausiidae probably gave rise to the Recent euphausiaceans, closest to the ancestry of Eumalacostraca among the extant orders (Jarman <i>et al.,</i> 2000). The identified distinction of the anthracophausiids in respect to the euphausiaceans is invariably connected with their basal position in the evolutionary tree: the wide telson, lack of hinge-like connection between the first pleotergite and the carapace, and ventrally extended lobes of the carapace.</p> <p>The Late Carboniferous anthracophausiids are considered near-shore marine filter feeders (Schram, 1981). Offshore eumalacostracan communities are inadequately known, with the available evidence restricted to the British late Early Carboniferous, the low diversity community being represented there by schooling species preserved in great numbers of individuals probably as an effect of mass killing (Schram, 1981).</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 page 86, DOI: 10.1111/j.1096-3642.2004.00121.x, <a href="http://zenodo.org/record/4687299">http://zenodo.org/record/4687299</a>
Pechoracaris Dzik & Ivantsov & Deulin 2004, GEN. NOV.
No full text<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>
Pechoracaris ACULICAUDA 2004, SP. NOV.
No full textPECHORACARIS ACULICAUDA SP. NOV. <p>(FIGS 1, 5 A)</p> <i>Holotype:</i> PIN 4983/21b (Fig. 1D) <p> <i>Type horizon and locality:</i> Dark-grey claystone from between 4255.0 and 4262.7 m, Early Devonian (Lochkovian?). Borehole Medynskoye 1 in the Timan-Pechora region of polar Russia.</p> <p> <i>Material:</i> Thirty relatively complete specimens and many more fragments.</p> <p> <i>Diagnosis:</i> As for the genus.</p> <p> <i>Etymology:</i> Derived from Latin <i>acus</i> (needle) and <i>cauda</i> (tail), referring to the form of the telson.</p> <p> <i>Material:</i> Sixty relatively well preserved specimens, mostly with abdomen.</p> <p> <i>Description:</i> The carapace lacks any hinge or separate dorsal plates, as visible in slightly obliquely compressed specimens. The lower margin frequently shows a narrow strengthening belt, probably a little thicker than the rest of the cuticle, perhaps representing a doublure. In specimens PIN 4983/20 and 4983/7, minute sparsely distributed denticles are recognizable near the posterior end of the carapace at its margin. Two somewhat more prominent spines arm the ventro-posterior lobe of the carapace in PIN 4983/1d. The anterior end of the carapace narrows parabolically and is a little pointed, as shown by PIN 4983/8a. The carapace length in the studied material ranges from 2.5 mm to 4.7 mm (Fig. 1B). In most specimens dark crushed mandibles are visible across the compressed carapace near its anterior end (Fig. 1F). Appendages of the abdomen are transformed into paired sharp spines (Fig. 1D), somewhat longer than their segments. The caudal spine is definitely much longer than the carapace (Fig. 1E) but its exact length is difficult to trace in the fossils, the spine being either exfoliated or hidden in the sediment.</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 page 85, DOI: 10.1111/j.1096-3642.2004.00121.x, <a href="http://zenodo.org/record/4687299">http://zenodo.org/record/4687299</a>
Discussion of ‘First finds of problematic Ediacaran fossil <i>Gaojiashania</i> in Siberia and its origin’
No full textY. Cai & H. Hua comment: Zhuravlev, Gámez Vintaned & Ivantsov (2009) reported the problematic Ediacaran fossil Gaojiashania annulucosta in Siberia and they considered that this is the first find of Gaojiashania outside China, since Gaojiashania had previously only been reported from the Gaojiashan Member of the middle Dengying Formation in the Ningqiang area, southern Shaanxi Province, South China. However, we believe that the so-called Siberian Gaojiashania was mis-identified, and what was described as Gaojiashania annulucosta by Zhuravlev, Gámez Vintaned & Ivantsov (2009) is more appropriately ascribed to Shaanxilithes ningqiangensis, another problematic Ediacaran fossil that has also been known from the Gaojiashan Member in Shaanxi Province of South China (Chen, Chen & Lao, 1975; Xing et al. 1984), as well as the stratigraphically equivalent Taozichong Formation in Guizhou Province (Hua, Chen & Zhang, 2004) and the Jiucheng Member (Dengying Formation) in Yunnan Province of South China (Zhu & Zhang, 2005), the Zhoujieshan Formation in Qinghai Province (Shen et al. 2007), and the Zhengmuguan Formation in Ningxia Hui Autonomous Region of North China (Shen et al. 2007).</jats:p
Archangeliphausia SPINOSA 2004, SP. NOV.
No full textARCHANGELIPHAUSIA SPINOSA SP. NOV. (FIGS 2–4, 5B) Holotype: Specimen PIN 4983/1a (Figs 2A, 4B). Type horizon and locality: Dark-grey claystone from a depth of 4255.0– 4262.7 m, Lower Devonian (Lochkovian?). Borehole Medynskoye 1, Timan-Pechora region of polar Russia. Material: Sixty more or less complete compressions. Diagnosis: As for the genus. Description: 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 c. 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. 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. 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. 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. No remnants of the apparently weakly calcified thoracopods are preserved. Some faint marks may correspond to pleopods, but they are completely undefined morphologically. 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). 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. 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.Published as part of 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) on pages 86-87, DOI: 10.1111/j.1096-3642.2004.00121.x, http://zenodo.org/record/468729
First macrobiota biomineralisation was environmentally triggered
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Why large and diverse skeletons first appeared
ca
550 Ma is not well understood. Many Ediacaran skeletal biota show evidence of flexibility, and bear notably thin skeletal walls with simple, non-hierarchical microstructures of either aragonite or high-Mg calcite. We present evidence that the earliest skeletal macrobiota, found only in carbonate rocks, had close soft-bodied counterparts hosted in contemporary clastic rocks. This includes the calcareous discoidal fossil
Suvorovella,
similar to holdfasts of Ediacaran biota taxa previously known only as casts and moulds, as well as tubular and vase-shaped fossils. In sum, these probably represent taxa of diverse affinity including unicellular eukaryotes, total group cnidarians and problematica. Our findings support the assertion that the calcification was an independent and derived feature that appeared in diverse groups where an organic scaffold was the primitive character, which provided the framework for interactions between the extracellular matrix and mineral ions. We conclude that such skeletons may have been acquired with relative ease in the highly saturated, high alkalinity carbonate settings of the Ediacaran, where carbonate polymorph was further controlled by seawater chemistry. The trigger for Ediacaran biomineralization may have been either changing seawater Mg/Ca and/or increasing oxygen levels. By the Early Cambrian, however, biomineralization styles and the range of biominerals had significantly diversified, perhaps as an escalating defensive response to increasing predation pressure. Indeed skeletal hardparts had appeared in clastic settings by Cambrian Stage 1, suggesting independence from ambient seawater chemistry where genetic and molecular mechanisms controlled biomineralization and mineralogy had become evolutionarily constrained.
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The cuticle of the enigmatic arthropod Phytophilaspis and biomineralization in Cambrian arthropods
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