Original article Late Silurian trilobites from the Nuratau and Turkestan ranges, Uzbekistan and Tajikistan § Trilobites du Silurien supérieur des chaînes du Nuratau et du Turkestan, Uzbekhistan et Tadjikistan Olga Ivanova a , Robert M. Owens b, * , Irina Kim a , Leonid E. Popov b a OAO ‘Regionalgeologiya’, Eshonguzar, Zangiatinskiy Rayon, Tashkentskaya oblast 702050, Uzbekistan b Department of Geology, National Museum of Wales, Cardiff CF10 3NP, Wales, United Kingdom Received 27 March 2007; accepted 3 June 2009 Available online 4 October 2009 Abstract Silurian trilobites of Ludlow and Pr ˇídolí age are described from sections in southern Uzbekistan and from adjacent parts of Tajikistan. They belong to 22 species (10 named and 12 under open nomenclature) distributed among 13 genera belonging to the families Proetidae, Tropidocoryphidae, Aulacopleuridae, Scharyiidae, Cheiruridae, Encrinuridae and Odontopleuridae. The following new species are described: Interproetus pentaxus, Paleodechenella turkestanica, P. zaaminicus, Cromus tamchii and Leonaspis nuratensis. The generic associations from the mid Ludlow bear a striking resemblance to coeval ones from Bohemia, and include genera otherwise known only from that region or from adjacent parts of central Europe. The trilobite faunas from the late Ludlow and Prˇídolí series are much less diverse and are dominated by genera of the Warburgellinae (Tropidocoryphidae), which include one species common to Vaigatch Island in the Russian Arctic, and Podolia, Ukraine. The closest links of the diverse central Asian mid Ludlow faunas are therefore to central Europe, whilst the sparser younger Ludlow and Prˇídolí faunas, such as they are, suggest closer links to Baltica. # 2009 Elsevier Masson SAS. All rights reserved. Keywords: Trilobita; Silurian; Central Asia; Systematics; Palaeobiogeography Résumé Nous décrivons les trilobites siluriens d’âge Ludlow et Prˇídolí provenant de coupes situées dans le Sud de l’Uzbekhistan et les secteurs proches du Tadjikistan. Ils appartiennent à 22 espèces (10 nommées et 12 laissées en nomenclature ouverte) distribuées dans 13 genres au sein des familles Proetidae, Tropidocoryphidae, Aulacopleuridae, Scharyiidae, Cheiruridae, Encrinuridae et Odontopleuridae. Les nouvelles espèces suivantes sont décrites : Interproetus pentaxus, Paleodechenella turkestanica, P. zaaminicus, Cromus tamchii et Leonaspis nuratensis. Les associations génériques du Ludlow moyen montrent une forte ressemblance avec celles, contemporaines, de Bohème, incluant des genres connus jusqu’à présent de cette seule région ou de régions voisines d’Europe centrale. Les faunes de trilobites des séries du Ludlow supérieur et du Pr ˇídolí sont beaucoup moins diversifiées ; elles sont dominées par des genres de Warburgellinae (Tropidocoryphidae) incluant une espèce également identifiée sur l’île Vaigatch (Russie arctique) et en Podolie (Ukraine). Les liens les plus étroits des faunes diversifiées du Ludlow moyen d’Asie centrale sont donc avec l’Europe centrale, alors qu’en l’état, les faunes moins diversifiées du Ludlow supérieur et du Pr ˇídolí suggèrent des liens plus étroits avec la Baltica. # 2009 Elsevier Masson SAS. Tous droits réservés. Mots clés : Trilobita ; Silurien ; Asie centrale ; Systématique ; Paléobiogéographie 1. Introduction Silurian trilobites from southern Tien-Shan, which includes the Nuratau and Turkestan ranges, were described originally in two monographs by Weber (1932, 1951). During the last Geobios 42 (2009) 715–737 § Corresponding editor: Gilles Escarguel. * Corresponding author. E-mail address: [email protected](R.M. Owens). 0016-6995/$ – see front matter # 2009 Elsevier Masson SAS. All rights reserved. doi:10.1016/j.geobios.2009.09.001
Transcript
Original article
Late Silurian trilobites from the Nuratau and Turkestan ranges,Uzbekistan and Tajikistan§
Trilobites du Silurien supérieur des chaînes du Nuratau et du Turkestan,Uzbekhistan et Tadjikistan
Olga Ivanova a, Robert M. Owens b,*, Irina Kim a, Leonid E. Popov b
a OAO ‘Regionalgeologiya’, Eshonguzar, Zangiatinskiy Rayon, Tashkentskaya oblast 702050, Uzbekistanb Department of Geology, National Museum of Wales, Cardiff CF10 3NP, Wales, United Kingdom
Received 27 March 2007; accepted 3 June 2009
Available online 4 October 2009
Abstract
Silurian trilobites of Ludlow and Prídolí age are described from sections in southern Uzbekistan and from adjacent parts of Tajikistan. Theybelong to 22 species (10 named and 12 under open nomenclature) distributed among 13 genera belonging to the families Proetidae,Tropidocoryphidae, Aulacopleuridae, Scharyiidae, Cheiruridae, Encrinuridae and Odontopleuridae. The following new species are described:Interproetus pentaxus, Paleodechenella turkestanica, P. zaaminicus, Cromus tamchii and Leonaspis nuratensis. The generic associations from themid Ludlow bear a striking resemblance to coeval ones from Bohemia, and include genera otherwise known only from that region or from adjacentparts of central Europe. The trilobite faunas from the late Ludlow and Prídolí series are much less diverse and are dominated by genera of theWarburgellinae (Tropidocoryphidae), which include one species common to Vaigatch Island in the Russian Arctic, and Podolia, Ukraine. Theclosest links of the diverse central Asian mid Ludlow faunas are therefore to central Europe, whilst the sparser younger Ludlow and Prídolí faunas,such as they are, suggest closer links to Baltica.# 2009 Elsevier Masson SAS. All rights reserved.
Keywords: Trilobita; Silurian; Central Asia; Systematics; Palaeobiogeography
Résumé
Nous décrivons les trilobites siluriens d’âge Ludlow et Prídolí provenant de coupes situées dans le Sud de l’Uzbekhistan et les secteurs prochesdu Tadjikistan. Ils appartiennent à 22 espèces (10 nommées et 12 laissées en nomenclature ouverte) distribuées dans 13 genres au sein des famillesProetidae, Tropidocoryphidae, Aulacopleuridae, Scharyiidae, Cheiruridae, Encrinuridae et Odontopleuridae. Les nouvelles espèces suivantes sontdécrites : Interproetus pentaxus, Paleodechenella turkestanica, P. zaaminicus, Cromus tamchii et Leonaspis nuratensis. Les associationsgénériques du Ludlow moyen montrent une forte ressemblance avec celles, contemporaines, de Bohème, incluant des genres connus jusqu’àprésent de cette seule région ou de régions voisines d’Europe centrale. Les faunes de trilobites des séries du Ludlow supérieur et du Prídolí sontbeaucoup moins diversifiées ; elles sont dominées par des genres de Warburgellinae (Tropidocoryphidae) incluant une espèce également identifiéesur l’île Vaigatch (Russie arctique) et en Podolie (Ukraine). Les liens les plus étroits des faunes diversifiées du Ludlow moyen d’Asie centrale sontdonc avec l’Europe centrale, alors qu’en l’état, les faunes moins diversifiées du Ludlow supérieur et du Prídolí suggèrent des liens plus étroits avecla Baltica.# 2009 Elsevier Masson SAS. Tous droits réservés.
Mots clés : Trilobita ; Silurien ; Asie centrale ; Systématique ; Paléobiogéographie
0016-6995/$ – see front matter # 2009 Elsevier Masson SAS. All rights reserveddoi:10.1016/j.geobios.2009.09.001
1. Introduction
Silurian trilobites from southern Tien-Shan, which includesthe Nuratau and Turkestan ranges, were described originally intwo monographs by Weber (1932, 1951). During the last
30 years extensive geological mapping and exploration of theseareas, which lie in the Uzbek and Tajik parts of southern Tien-Shan, has generated new collections. Of these, some Ludlowand Prídolí species of Proetidae were described by Ivanova(1991), and figures with brief descriptions of 13 speciesdistributed among eight genera from the Wenlock, Ludlow andPrídolí series were given by Ivanova (in Kim et al., 2008). Inthis paper, 22 species belonging to 13 genera from the Ludlowand Prídolí series are described.
Silurian strata crop out widely in the Turkestan and Nuratauranges. Those of Llandovery and early Wenlock age are mostlygraded siliciclastic and pyroclastic deposits with interbeddedgraptolitic mudrocks, and are interpreted as having beendeposited on slopes within an intra-oceanic island arc (Korenet al., 1986); for the most part they lack any distinctive benthicfaunal assemblages. Younger (mid to late) Wenlock, Ludlowand Prídolí strata are predominately carbonates, whichoriginated probably on shallow island shelves.
In South Tien-Shan trilobites form a relatively minorcomponent of late Silurian shallow marine benthic assem-blages, which are dominated by corals and rhynchonellifor-mean brachiopods. However, some provide distinctbiogeographical signatures, linking them with contempora-neous faunas, particularly those from Bohemia. This allows notonly more detailed correlation of the upper Silurian sequencesbetween these regions, but also contributes to the understandingof the complex geological history of the numerous small crustalfragments and remnants of Palaeozoic volcanic arcs that areincorporated into the tectonic collage of what is now CentralAsia.
2. Geological and geographical setting
The Nuratau and Turkestan ranges form the westerncontinuation of the complex orogenic system of South Tien-Shan. The most recent detailed account of the Palaeozoicgeology and tectonics of the region is that of Biske (1996). The
Fig. 1. Outline map of central Uzbekistan and adjacent areas showing the posit
Silurian (Wenlock to Prídolí) deposits in the region aresubdivided into four regional stages: Merishkor (Wenlock),Kurgan, Tamchi (both Ludlow), and Rabkash (Prídolí), and intonumerous local lithostratigraphic units (for details see Kimet al. in Shakubov and Dalimov, 1998; Abduazimova, 2001;Kim et al., 2008). The Silurian trilobites described below werecollected from three principal sections (Shaly Sai and AkkayaMountain, northern Nuratau Range, and Myk Sai, Zaaminsuriver basin, Turkestan Range), from several isolated localities inUzbekistan, and from the Isfara section in Tajikistan (Fig. 1).
2.1. The Nuratau range
Upper reaches of Shaly Sai. This section is located on thesouthern slope of Dzhalpak Mountain, about 3.35 km north-eastof the village of Chashmazrak (Figs. 1 and 2). The Siluriansequence is represented here by the Khatynbulak Formation(Merishkor and Kurgan regional stages, upper Wenlock – lowerLudlow), which is composed mostly of clastic rocks, whichhave yielded the graptolites Monograptus deubeli (Suess) andMonograptus ludensis Murchison, with some brachiopod-bearing limestone units in the middle part. The ChaltashFormation (upper Ludlow-Prídolí) is subdivided into the ShalyMember, which comprises alternating units of massive andbedded limestone, with some beds of sandstone in the lower andmiddle part of the sequence, and the Chashmazrak Member,which comprises pure, micritic-sparry limestones. The forma-tion contains an abundant and diverse brachiopod fauna,associated with numerous tabulate and rugose corals, stroma-toporoids, trilobites and echinoderms. The Silurian deposits areoverlain conformably by the Lower Devonian DzhalpakFormation (Kim et al. in Shakubov and Dalimov, 1998; Kimand Larin, 1966).
In the Shaly Sai section (668 270 1000 E, 408 240 4600 N),trilobites occur in the lower part (Units 3–8) of the ShalyMember and in Unit 14 of the Chashmazrak Member (Fig. 2).Units 3 and 4, close to the base of the Shaly Member, which
ion of localities in the Nuratau and Turkestan ranges mentioned in the text.
O. Ivanova et al. / Geobios 42 (2009) 715–737 717
comprise a sequence of sparry, argillaceous limestone withlenses of argillite (samples 707-2, 773, II-4/1), have yielded thefollowing trilobite assemblage: Aulacopleura aff. koninckii(Barrande), Lacunoporaspis postromanowskyi (Ivanova), Hed-stroemia? sp. B, Leonaspis nuratensis sp. nov., Youngia aff.alaica Weber and Cromus tamchii sp. nov. Sphaerexochusmirus Beyrich appears in the bioclastic limestone of Unit 6(sample II-6/1), where it co-occurs with the brachiopodsAtrypella and Gypidula. A moderately diverse trilobiteassemblage also occurs in the bioclastic and pelmatozoanlimestones of Units 7–8 (samples II-7/1, II-7/2, II-8/2, II-8/3and II-8/6), where it includes L. postromanowskyi, Scharyiasp. B, Interproetus pentaxus sp. nov., Leonaspis nuratensissp. nov., Pseudocheirurus aff. beyrichi (Barrande) and S. mirus.No trilobites have been found between this part of the sectionand the base of the Chashmazrak Member, where in themicritic-sparry limestones of Unit 14 (Fig. 2) rare disarticulatedtrilobites referred to Hedstroemia sp. A, Prionopeltis? sp. B,Warburgella? sp. and P. aff. beyrichi occur in samples II-14/1,II-14/5 and II-14/30 in association with the brachiopodsStriispirifer isfarensis, Alaskospira dunbari and Atrypoideacamelina.
Akkaya Mounta. The Silurian sequence exposed on thewestern slope (678 060 1000 E, 408 240 2500 N), south-west of thevillage of Farish (Figs. 1, 3 and 4) is represented by carbonatedeposits of the Akkaya Formation (Kim et al. in Shakubov andDalimov, 1998; Abduazimova, 2001). Its lower part, belongingto the Kurgan Regional Stage (upper Ludlow), comprisesmostly massive, and some bedded limestones, which areinterpreted as having been deposited in an outer shelfenvironment (BA-4). It contains abundant brachiopods,echinoderms and ostracods. The middle part, referred to theTamchi Regional Stage (upper Ludlow) is composed mostly ofdolomites, with coquinas of Conchidium at the top. The upperpart (Rabkash Regional Stage, Prídolí) is a sequence of micriticand biosparitic limestone with some beds of carbonate breccia;it was deposited presumably on the slope of a large organicbuild-up, and contains an abundant and diverse brachiopodfauna. Trilobites are present only in the lower part of theAkkaya Formation (Kurgan Regional Stage), where in thelowermost part (Unit 1, samples VIII-3 and VIII-4) they arerepresented by Prionopeltis cf. praecedens Boucek,P. akkajensis Ivanova, Scharyia sp. A, Sphaerexochus mirusBeyrich and Youngia aff. alaica Weber. Their diversityincreases slightly in Unit 2 (samples VIII-7, VIII-9, VIII-10and VIII-11), from where P. cf. praecedens, P. akkajensis,P. rara Ivanova, Leonaspis nuratensis sp. nov., Pseudocheir-urus aff. beyrichi (Barrande), S. mirus, Y. aff. alaica andCromus tamchii sp. nov. have been recorded. Rare trilobites(P. cf. praecedens and S. mirus) were also recovered frombedded calcareous dolomites (sample VIII-12) at the base of thepredominantly massive dolomites of Unit 3.
2.2. The Turkestan range
Myk Sai. In the western Turkestan Range, trilobites of lateSilurian age occur sporadically in the Zaamin Formation
exposed in the Zaamin river basin (688 230 4000 E, 398 380 4500 N;Fig. 5). The Silurian part of this formation comprises siltstonesinterbedded with bioclastic and argillaceous limestones; it restsunconformably on Cambrian deposits, and has a basal bed ofconglomerate and quartzose sandstone about 20 m thick (Kimet al. in Shakubov and Dalimov, 1998; Abduazimova, 2001).The overlying carbonates have yielded the conodont Ozarko-dina crispa (Walliser, 1964), suggesting a late Ludlow age forthe base of the formation. The uppermost part of the ZaaminFormation is comprised mostly of argillaceous limestone andbelongs to the Lower Devonian Kunzhak Regional Stage. Thetrilobites described herein were collected (samples 609-5, 610/2, XX-7, 525/11) from a section in the middle part of theZaamin Formation, situated about 2 km upstream from themouth of Myk Sai, the western tributary of the Ettkichu River(Fig. 6). They are represented by Paleodechenella turkestanicasp. nov., P. zaaminica sp. nov. and Warburgella tcherkesovaeMaksimova. The latter species also occurs in the LowerDevonian part of the formation (sample 612). None of theelements of the co-occurring medium diversity faunas ofstromatoporoids, tabulate corals and brachiopods allows aprecise definition of the position of the Ludlow-Prídolíboundary in this section.
2.3. Isfara River, south Fergana, Tajikistan
In the eastern part of the Turkestan Range the upper Silurianis represented by the thick, shallow water carbonate sequenceof the Isfara Formation (Ludlow-Prídolí, Tamchi-Rabkashregional stages). The only trilobite locality studied from thisformation is situated on the left bank of Rabkash Sai (708 350
0000 E, 398 550 0000 N), an eastern tributary of the Isfara river,where a few specimens of Paleodechenella turkestanica sp.nov. were collected from a unit of nodular, argillaceouslimestone about 6.7 m thick (samples 22/315, 22/345) in themiddle part of the Isfara Formation (167-174 m above the base)belonging to the lower Rabkash Regional Stage.
3. Palaeobiogeographical affinities of the fauna
The trilobite faunas from the Chaltash Formation (lateLudlow and Prídolí series) of the Shaly Sai section, and fromthe Akkaya Formation (late Ludlow Series) of AkkayaMountain include species of Prionopeltis, Cromus, Interproe-tus, Pseudocheirurus, Leonaspis, Scharyia and Sphaerexochus.All of these genera occur in the Ludlow Kopanina Formation ofBohemia, and among them Prionopeltis and Cromus in theLudlow are known otherwise only from sections in the HarzMountains, Germany and in the Carnic Alps, Austria. As awhole, the faunas of the Chaltash and Akkaya formations showsome similarity in generic composition to the Prionopeltisarchiaci and Prionopeltis striata – Scharyia nympha assem-blages recognized in Bohemia by Chlupác (1987). In any event,they show a close connection with Ludlow-Prídolí faunas thatoccur in central Europe in terranes interpreted to have occupiedperi-Gondwanan locations. In the Silurian, Leonaspis isrestricted to peri-Gondwanan terranes, reported from Morocco,
O. Ivanova et al. / Geobios 42 (2009) 715–737718
Fig. 3. Generalised geological map of the Akkaya Mountain area in the Nuratau Range, showing the position of the principal Silurian (Ludlow) section.
O. Ivanova et al. / Geobios 42 (2009) 715–737 719
Bohemia and Australia, but is absent from Laurentia andBaltica (Ramsköld and Chatterton, 1991). These distributionssuggest that the complex of central Asian terranes was at thistime linked faunally with peri-Gondwanan regions, even if theyoccupied a quite wide latitudinal range (e.g. Cocks and Torsvik,2002).
The sparse Ludlow and Prídolí trilobite faunas from theZaamin Formation of the Turkestan Range, and from theIsfara Formation of south Fergana are restricted toWarburgellinae (Warburgella and Paleodechenella). Thesefew taxa find their closest counterparts in Baltica, where theyhave been found in Vaigatch Island in the Russian Arctic, andin Podolia, Ukraine. One species, Warburgella tcherkesovaeis apparently common to central Asia, Vaigatch Island andPodolia. Such occurrences suggest that the central Asianterranes in which these faunas occur may have been separatedby no great distance from Baltica during late Ludlow andPrídolí times.
4. Systematic palaeontology
Terminology follows Whittington and Kelly in Kaesler(1997), but with modifications to that relating to cephalic
Fig. 2. Generalised stratigraphical column of the Silurian (Ludlow-Prídolí) sequehorizons and ranges, together with ranges of significant conodonts and graptolites
border furrows discussed by Owens (2006). The bulk of thecollections, including nearly all of the specimens described andfigured herein, as well as all occurrences not referred to byspecific museum numbers, are deposited in the Museum of theGeological Committee of Uzbekistan, Tashkent (MGCU);small reference collections, together with casts of all originalshave been deposited in the National Museum of Wales, Cardiff(NMW). The trilobite collections described by Weber (1932,1951) are deposited in the Central Geological Research andExploration Museum, St Petersburg (CNIGR). Olga Ivanovaand Robert Owens are responsible for the systematicdescriptions.
Family PROETIDAE Hawle and Corda, 1847Subfamily PROETINAE Hawle and Corda, 1847Genus Lacunoporaspis Yolkin, 1966Type species: Lacunoporaspis contermina Yolkin, 1966,
from Devonian, Emsian Stage, Kireevsk Formation, GornyAltai, Siberia.
Lacunoporaspis postromanowskyi (Ivanova, 1991)Fig. 7(1–4)1991. ‘Proetus’ postromanowskyi Ivanova, p. 130, pl. 1, figs.
9, 10.
nce in the Shaly Sai section in the Nuratau Range, showing trilobite-bearing.
Fig. 4. Generalised stratigraphical column of the Silurian (Ludlow) sequence in the Akkaya section in the Nuratau Range, showing trilobite-bearing horizons andranges, together with that of the conodont Ozarkodina crassa.
O. Ivanova et al. / Geobios 42 (2009) 715–737720
2008. Lacunoporaspis postromanovskyi (Ivanova) – Ivanovain Kim et al., p. 114, pl. 99, Figs. 1–3.
Figured material: MGCU 9/977, cranidium, MGCU 6/814,MGCU 10/997, pygidia, all from type stratum and type locality,samples II-7/2 and Yolkin collection 70202. Also reported fromsample II-7/1.
Diagnosis: Lacunoporaspis with elongated, pointed glabella65% as wide across base of L1 as long (sag.); short (sag.)preglabellar field a little over 50% sagittal width of anteriorborder; palpebral lobe 25-30% length of glabella; pygidiumwith well-defined border, eight axial rings and six pairs ofpleural ribs; surface of glabella finely granulose.
Description: Cranidium moderately convex. Glabella elon-gated, 65% as wide across base of L1 as long (sag.). Three pairs ofweakly incised lateral glabellar furrows. S1 deeper than others,geniculate, dying out before reaching S0, defining subquadrateL1, which is weakly convex; short anterior branch, which may ormay not be confluent with rest of S1. S2 and S3 gently curved,
inclined posteriorly, S2 more so than S3; both run into axialfurrow. S4 represented by small ovate depression a short distanceto anterior of S3, and isolated from axial furrow. Occipital furrowmore or less transverse, curving gently forwards behindposterolateral corners of preoccipital glabella. Occipital ringretains constant width (sag., exsag.), with pair of prominentlateral lobes. Small occipital tubercle present.
Short (sag.) preglabellar field defined by deep furrows, and isa little over 50% width (sag.) of anterior border, which isapproximately 15% length (sag.) of glabella. Preocular facialsutures moderately divergent, with b falling more or lessexsagittally in front of g. Palpebral lobe is between 25–30%sagittal length of glabella, with its mid point (exsag.) situatedslightly anterior to abaxial end of S1. Librigena, hypostoma andthorax unknown.
Pygidium semicircular, moderately convex. Narrow axiswith eight rings and a terminal piece, with deep ring furrowsthat become progressively shallower towards posterior.Prominent apodemal pits on flanks of each ring. Pleural fieldwith six pairs of ribs, which terminate laterally at inner edge ofborder. More posterior ribs have shallower pleural andinterpleural furrows than anterior.
Fig. 5. Generalised stratigraphical column of the Silurian (Ludlow-Prídolí) sequence of the Myk Sai section in the western Turkestan Range, showing trilobite-bearing horizons and ranges.
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Surface of cranidium and pygidium with finely granulosesculpture.
Remarks: The diagnosis of this species has been modifiedto take account of its transfer from Proetus to Lacunoporaspis.It is similar to L. romanowskyi (Weber, 1932), but it has aproportionately wider anterior border, and a smaller number ofpygidial axial rings (eight compared to 10–11) and pleural ribs(six compared to seven; cf. Fig. 7(1–4) and Weber, 1932: pl. 2,figs. 31, 36–39; Weber, 1951: pl. 3, figs. 3, 15). Also similar arespecimens from the Ludlow of the Wieda valley, HarzMountains, Germany, described by Kegel (1927: p. 634,pl. 32, figs. 1–5) as Proetus conspersus (Angelin, 1854). Thesebelong to Lacunoporaspis, but not to L. conspersa, and aresimilar to L. postromanovskyi in the configuration of thecranidium and in the number of pygidial axial rings and pleural
ribs. They appear to differ in having a proportionately widerglabella and less well-defined pygidial border.
Subfamily CRASSIPROETINAE Osmólska, 1970Genus Hedstroemia Pribyl and Vanek, 1978Type species: Proetus delicatus Hedström, 1923, from
Description: Pygidium convex, semicircular in outline.Axis strongly convex, almost semicircular in cross section,
Fig. 6. Generalised geological map of the area of Myk Sai and the Ettkichu valley in the Zaaminsu river basin, western Turkestan range, showing the location of theprincipal Silurian sections and trilobite localities.
O. Ivanova et al. / Geobios 42 (2009) 715–737722
gradually tapering posteriorly, flanked by narrow and shallowaxial furrows; anteriorly occupies almost one third pygidialwidth. 10–11 narrow (sag., exsag.) axial rings, each with a rowof large granules, defined by shallow ring furrows. Pleural fieldgently convex with eight pairs of pleural ribs divided intoanterior and posterior pleural bands of approximately equalwidth, each bearing a row of granules. Distal end of eachanterior pleural band slightly inflated. Interpleural furrowsmuch shallower and narrower than pleural furrows, bothterminating close to inner edge of narrow pygidial border,which is defined by broad, shallow furrow.
Cephalon and thorax unknown.Remarks: These pygidia are similar to that of H. sourdoughi
Ludvigsen and Tripp, 1990 from the uppermost Ludlow RoadRiver Formation, Prongs Creek, Yukon, Canada in generalproportions and in surface sculpture. The latter differs in havingfewer axial rings (eight) and pleural ribs (six).
Description and remarks: Two pygidia bear a broadresemblance to those of Hedstroemia species, but the axis isnarrower than is typical for this genus; it comprises 13 well-defined axial rings and a short terminal piece. The pleural fieldhas seven pairs of ribs, with a suggestion of a swelling on thedistal end of the anterior pleural band. The border is well-defined, with the pleural ribs truncated at its adaxial edge. Thesurface sculpture comprises very fine granules. The swollen
distal end of the anterior pleural bands is a characteristic ofHedstroemia (see Owens, 2006: p. 123), and these specimensare possibly attributable to this genus. Other parts of theexoskeleton are required for this to be confirmed.
Family TROPIDOCORYPHIDAE Pribyl, 1946Subfamily TROPIDOCORYPHINAE Pribyl, 1946Genus Prionopeltis Hawle and Corda, 1847Type species: Phaeton archiaci Barrande, 1846, from
Remarks: This genus has been recorded mainly fromcentral Europe (Bohemia and Harz Mountains; see Snajdr,1980: p. 135), where it has a comparatively short range in theupper part of the Ludlow Series and throughout the PrídolíSeries, possibly ranging upwards into the Lower Devonian(Alberti, 1981: p. 179). Snajdr (1980: p. 135) listed 11 namedspecies, nine from Bohemia and two from the Harz Mountains.A twelfth, in open nomenclature, from the Llandovery ofBohemia, based on one librigena was also described by Snajdr(1980: p. 146); its attribution to Prionopeltis cannot beconfirmed, and it could belong to any of a number oftropidocoryphid genera. von Gaertner (1930: p. 218) reportedP. incisa Kegel, 1927 from the upper part of the Ludlowsequence in the Carnic Alps, and Alberti (1981: p. 185, table 2)noted the presence of specimens of P. cf. octaschista Kegel,1927 in Yolkin’s collections from central Asia and the Altai.Ivanova (1991: pp. 131–133) described three species fromUzbekistan, two new, and a third attributed to P. praecedensBoucek.
Prionopeltis akkajensis Ivanova, 1991Fig. 8(1–4)
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1991. Prionopeltis akkajensis Ivanova, p. 133, pl. 1, figs. 1, 2.2008. Prionopeltis akkajensis Ivanova in Kim et al., p. 116,
pl. 99, figs. 12–15.Holotype: MGCU 14/814, cranidium (Fig. 8(3)), Ludlow
Series, Kurgan Regional Stage, lower member of AkkayaFormation (sample VIII-7), Akkaya Mountain, northernNuratau Range, Uzbekistan.
Material: NMW 2004.21G.279, cranidium, MGCU 15/814,NMW 2004.21G.280, pygidia, all from type locality(samples VIII-10, VIII-11, VIII-7). Also recorded fromsample VIII-9.
Diagnosis (modified from Ivanova, 1991: p. 133): Glabella80% as wide (tr.) as long (sag.), well-rounded anteriorly andscarcely constricted laterally; preglabellar field about 40%sagittal length of glabella; anterior border narrow, a little under30% sagittal length of preglabellar field; pygidium 60% as long(sag.) as wide (tr.), with long, narrow axis with 13–15 rings and12 pairs of pleural ribs terminating in short spines.
Description: Cranidium weakly convex. Glabella tongue-shaped with well-rounded frontal lobe, 80% as wide (tr.) acrossL1 as long (sag.), and defined by narrow axial and preglabellarfurrows; barely constricted laterally. Three pairs of lateralfurrows; S1 arcuate, deep at midlength and directed obliquelybackwards and shallowing at either end where it runs into axialand occipital furrows. S2 weakly impressed, almost straight,slightly backwardly curved and widening a little adaxially. S3similar to S2, but a little shorter (tr.), almost transverse.Occipital furrow narrow, almost transverse medially andlaterally curving gently behind L1. Occipital ring about 25%sagittal length of, and marginally wider (tr.) than preoccipitalglabella, with weakly defined lateral lobes and a small mediantubercle. Preglabellar field wide, 40% sagittal length ofglabella. Anterior border furrow shallow, weakly impressedmedially and deepening laterally. Anterior border narrow, alittle under 30% sagittal length of preglabellar field, and gentlyconvex. Preocular facial sutures strongly divergent.
Librigena, hypostoma and thorax unknown.Pygidium 60% as long (sag.) as wide (tr.). Axis long and
narrow, comprised of 13–15 rings defined by comparativelywide, transverse ring furrows, and terminating in a shortpostaxial ridge. Pleural field with 12 pairs of pleural ribs,terminating in short spines. Pleural furrows extend for most oflength of rib, terminating a short distance from the distal end.Interpleural furrows shallow and narrow adaxially, deepeningand widening close to the distal ends of pleurae.
Remarks: This species is closely comparable to Priono-peltis archiaci Barrande in glabellar outline, and in theproportional widths (sag.) of the anterior border andpreglabellar field (Fig. 8(1, 3); Snajdr, 1980: pl. 24, figs. 1,7, 10). The pygidium is distinguished immediately by its largernumber of marginal spines (10 in P. akkajensis compared tousually 7, but range of 6–9 in P. archiaci), which are shorterthan those of P. archiaci (Fig. 8(2, 4); Snajdr, 1980: pl. 24,figs. 3, 5, 8, 12–14).
Prionopeltis rara Ivanova, 1991Fig. 7(9–10)
1991. Prionopeltis rarus Ivanova, p. 132, pl. 1, figs. 3, 4.2008. Prionopeltis rara Ivanova in Kim et al., p. 115, pl. 99,
Series, Kurgan Regional Stage, lower member of AkkayaFormation (sample VIII-9), Akkaya Mountain, northernNuratau Range, Uzbekistan.
Material: MGCU 19/814, pygidium, from type locality(sample VIII-11).
Diagnosis (modified from Ivanova, 1991: p. 132): Crani-dium with preglabellar area approximately 55% sagittal lengthof glabella, which is weakly constricted opposite g, and haswell-rounded anterior margin. Pygidium with elongated axiswith 10 rings and a terminal piece, and seven pleural ribsterminating in short spines.
Description: Glabella 75% length (sag.) of cranidium,narrowing in front of L1 to well-rounded frontal lobe, definedby narrow axial furrows. Markedly constricted at front end ofL1. S1 narrow, oblique, isolated from both axial and occipitalfurrows, defining ovoid L1. Occipital furrow narrow, curvinggently forwards laterally. Occipital ring slightly wider (tr.) thanpreoccipital glabella, and 30% its length (sag.), maintainingconstant width laterally. Preglabellar field broad, 30% length(sag.) of glabella. Anterior border about 40% length (sag.) ofpreglabellar field, inclined gently upwards towards anteriormargin, defined by broad, shallow anterior border furrow.Preocular facial sutures moderately divergent, turning stronglyadaxially from b.
Librigena, hypostoma and thorax unknown.Pygidium almost semicircular, 60% as long (sag.) as wide
(tr.), with a convex, conical axis with 10 rings and a terminalpiece, continuing as a postaxial ridge terminating at posteriormargin. Pleural field of low relief, with seven pairs of pleuralribs terminating in short spines. Posteriormost pair of ribs verypoorly defined. Pleural furrows deep, closer to posterior than toanterior margin of each rib, terminating close to end of pleuralspine. Interpleural furrows narrow, shallow adaxially anddeepening markedly distally.
Remarks: This species resembles P. archiaci (Barrande)from the Ludlow of Bohemia, but is distinguished in having aproportionately broader anterior border, a narrower S1, andshorter, broader pygidial spines.
pl. 1, figs. 5, 6.2008. Prionopeltis cf. praecedens Boucek - Ivanova in Kim
et al., p. 116, pl. 99, figs. 8, 9.Figured material: MGCU 16/814, cranidium and MGCU
17/814, pygidium, from Ludlow Series, Kurgan RegionalStage, lower member of Akkaya Formation, Akkaya Mountain,northern Nuratau Range (samples VIII-4 and VIII-7). Alsoreported from sample VIII-12.
Description: Glabella approximately 75% as wide acrossL1 as long (sag.). Weakly constricted laterally in front of S1,hardly narrowing forwards to evenly rounded frontal lobe. S1
geniculate, narrowing and deepening distally, dying out beforereaching occipital furrow; defines subquadrate L1. S2sigmoidal. Occipital furrow narrow, deepening and curvingslightly backwards behind L1. Occipital ring long (sag.), almost25% sagittal length of preoccipital glabella and about samewidth (tr.), with a small median tubercle situated closer to itsposterior margin. Preglabellar field as wide (sag.) as sagittal
extends to posterior margin. Axial furrows deep, well defined.Pleural field with five pairs of pleural ribs, each terminating as ashort, flattened spine. Anteriormost pair of spines slightly largerthan posterior ones, strongly curved posteriorly. Pleural furrowsdeep, situated closer to posterior edge of each rib andterminating close to the end of the pleural spine. Interpleuralfurrows very shallow adaxially, deepening distally, situatedcloser to a posterior margin of pleural ridges.
Remarks: Ivanova (1991: p. 131) attributed these specimensto Prionopeltis praecedens (see Snajdr, 1980: pl. 25, figs. 14–21)from the Ludlow Series of Bohemia, but further comparison withthe latter shows that they differ from this species in their narrowerS1, broader anterior border (60% length of preglabellar field,compared to 35–40% for P. praecedens), longer pygidialmarginal spines and a shorter, more rapidly tapering pygidialaxis. A different species is clearly represented, but the presentmaterial is insufficient to name it.
Description: Glabella moderately convex, broadly bell-shaped, about 75% as wide (tr.) across occipital ring as long(sag.), with rounded frontal lobe. S1 deep medially, shallowingat either end and directed strongly backwards, defining ovoidL1. Occipital furrow narrow, curving gently forwards anddeepening laterally, behind L1. Occipital ring wider (tr.) thanpreoccipital glabella and about 22% of its sagittal length. Shortfurrow running forwards into occipital furrow a little abaxial ofS1 partially defines lateral occipital lobe.
Preglabellar field 25–30% sagittal length of glabella, withprominent transverse preglabellar ridge occupying its anteriortwo thirds. Anterior border wide, 70–80% length (sag.) ofpreglabellar field, with prominent terrace ridges and defined bydeep, broad anterior border furrow. Preocular facial suturesstrongly divergent.
Sculpture of fine granules and very fine terrace ridgesbecoming more pronounced on posterior part of glabella.
Remarks: These cranidia resemble those of Prionopeltisspecies in their general configuration, but the principaldistinguishing feature is the transverse preglabellar ridge, acharacter not present in species hitherto assigned to this genus.It may not be of generic significance, because in Warburgella,for example, it is present in some species, and not in others (e.g.Owens, 1973: pl. 13, figs. 11, 13 and pl. 14, fig. 3). Informationon the rest of the exoskeleton is necessary before the affinitiesof these cranidia can be assessed fully, and pending this they areattributed with question to Prionopeltis.
Remarks: In their general morphology, including thestrongly divergent preocular facial sutures and the occipitalring markedly wider (tr.) than the preoccipital glabella, thesecranidia resemble those of Prionopeltis? sp. A, but they lack atransverse preglabellar ridge. Instead, the presence of a borderfurrow running close to the anterior end of the glabella, and adeeper epiborder furrow defining the border roll immediatelydistinguishes these specimens from both Prionopeltis? sp. Aand from the Prionopeltis species described above. Apart fromthis last character and the transversely broad occipital ring, theyresemble Prionopeltis rara in overall proportions. Fullassessment of their generic affinity must await further material.
Subfamily CORNUPROETINAE Richter, Richter andStruve in Moore, 1959
Genus Interproetus Snajdr, 1977Type species: Proetus intermedius Barrande, 1846, from
Interproetus pentaxus sp. nov.Fig. 7(13–22) and 8(5–8)1991. Interproetus intermedius ovalifrons (Hawle and
Corda) – Ivanova, p. 134, Pl. 1, Figs. 7, 8.Etymology: Greek pentaxos, fivefold, with reference to the
five pygidial axial rings.Holotype: MGCU 8/814, cranidium (Fig. 7(22)), from
Ludlow Series, Tamchi Regional Stage, Chaltash Formation,Shaly Member (sample 776), Abartkan, 2 km NE of GavalbetMountain, Shaly district, northern Nuratau Range, Uzbekistan.
Paratypes: MGCU 7/814, 1/977, NMW 2004.21G.298-99cranidia; MGCU 2/977, librigena; MGCU 3/977, 4/977, 5/977,hypostomata; MGCU 6/977, 7/977, 8/977, 10/814, NMW2004.21G.296, NMW 2008.3G.10, pygidia, from LudlowSeries, Tamchi Regional Stage, Chaltash Formation, ShalyMember, from the type locality (samples 776, 777, 70199) andShaly Sai (samples II-7/2 and II 8/3, 707/2).
Diagnosis: Glabella subcylindrical, scarcely constrictedlaterally; anterior cephalic border strongly convex; hypostomawith coarse terrace ridges; pygidial axis with five rings plusterminal piece, anteriorly 26–30% width (tr.) of pygidium.
Description: Glabella subrectangular, 75–80% as wide (tr.)across occipital ring as long (sag.), scarcely constrictedlaterally, and tapering very gently forwards. Three pairs ofweakly defined lateral glabellar furrows, of which S1 is longest(tr.); S2 evenly curved posteriorly, S3 short and transverse.Occipital furrow narrow, curving gently forwards behind L1.Occipital ring with small median tubercle, slightly wider (tr.)than preoccipital glabella, with pair of very shallow furrowspartially defining lateral occipital lobes.
Preglabellar field narrow, 25–30% length (sag.) of anteriorborder and depressed well below level of anterior border andfrontal lobe of glabella. Anterior border broad and convex, withprominent terrace ridges. Preocular facial sutures slightlydiverging, curved evenly adaxially from b. Palpebral lobe long,about 35% sagittal length of glabella, with an exsagittal linethrough d falling abaxially of b. Eye with narrow eye socle.Librigenal field broad, gently convex. Lateral border similar to
O. Ivanova et al. / Geobios 42 (2009) 715–737 727
anterior, with well-marked terrace ridges running along itsouter half. Deep lateral border furrow continues onto genalspine as median furrow, dividing it into wider outer half andnarrower inner half.
Hypostoma elongate, with width across anterior wings about80% its sagittal length. Anterior and posterior wings extendinglaterally for about equal distance. Anterior lobe of middle bodymore or less parallel sided behind anterior wings. Small,backwardly oblique maculae isolated from lateral borderfurrow. Posterior lobe of middle body crescentic. Anteriorborder gently convex forwards, posterior and lateral bordersconcave. Prominent, coarse terrace ridges form an elongateBertillon pattern on middle body.
Pygidium transverse, with length (sag.) ranging from 40–
48% anterior width. Axis convex, relatively narrow, anteriorly26–30% width of pygidium; comprises five well-defined ringsand a terminal piece. Pleural field broad, very gently convex,with four pairs of pleural ribs, the posteriormost pair ill-defined.Pleural and interpleural furrows sub-parallel. First pleuralfurrow deep and narrow, succeeding two shallower, but deeperthan interpleural furrows. All extend close to pygidial margin.
Sculpture of fine terrace lines and granules.Remarks: Snajdr (1980) described a series of Interproetus
species from the Wenlock and Ludlow series of Bohemia, andadditional ones are known from the Wenlock Series of Wales(Owens, 1973; Thomas, 1978), from the late Wenlock orLudlow series of Ireland (Siveter, 1989) and from the LudlowSeries of Morocco (Alberti, 1969). I. pentaxus sp. nov. isdistinguished immediately from most of these in possessingfive rings on the pygidial axis, in contrast to the more usual four.Only I. peraticus (Owens, 1973) – see Thomas (1978: pl. 11,figs. 7, 9, 11, 12, 14–16, 20) – has five, and the fifth is onlyindistinctly indicated (Thomas, 1978: pl. 11, fig. 16). In termsof other characters, such as width (sag.) of preglabellar field,size of eye, width of librigenal field and proportions of thepygidium and pygidial axis, I. pentaxus sp. nov. is similar toI. intermedius intermedius (Barrande, 1846) from the Ludlowof Bohemia (see Snajdr, 1980: pl. 45, figs. 15–19). Ivanova(1991: p. 134) included the Uzbek material in I. intermediusovalifrons (Hawle and Corda, 1847) (see Snajdr, 1980: pl. 46,figs. 1–14), also from the Ludlow of Bohemia but furthercomparison revealed differences including: a more weaklyconstricted glabella; more inflated cephalic anterior border;fewer, coarser terrace ridges on the hypostome and, inparticular, five rather than four pygidial axial rings.
nov. sp., p. 197–198, Pl. 1, Figs. 1–9.1983. Warburgella tcherkesovae Maksimova – Yolkin, p. 36,
Pl. 7, Figs. 1–3.
2008. Warburgella tcherkesovae Maksimova – Ivanova inKim et al., p. 116, pl. 99, figs. 16–18.
Holotype: CNIGR 1/10321, cranidium, Prídolí Series,Greben Regional Stage, Vaigach Island, Arctic Russia (figuredin Maksimova, 1970: pl. 1, fig. 1; Yolkin, 1983: pl. 7, fig. 1).
Material from Uzbekistan: MGCU 3/884, MGCU 38/977,MGCU 39/977, pygidia from Prídolí Series, Rabkash RegionalStage, lower member of Zaamin Formation (sample 525/11),Myk Sai, left bank of the Ettkichu river, Turkestan Range,Uzbekistan. Also reported from Zaamin Formation, KunzhakRegional Stage (sample 612), Myk Sai.
Remarks: These pygidia agree in all their characters withthose in the type material of this species figured by Maksimova(1970: pl.1, figs.1–6) and by Yolkin (1983: pl. 7, figs. 2, 3), andthere is no reason to suppose that they are not conspecific. Bothoccurrences are of approximately the same (Prídolí) age.W. tcherkesovae has also been reported (Yolkin, 1983: p. 37)from the Prídolí Series of Podolia, Ukraine. Yolkin (1983:pp. 36, 37) considered Warburgella (Anambon) jelli Landrumand Sherwin, 1976 from the Derriwong Beds (late Prídolí –
early Lochkovian) of New South Wales to be a junior subjectivesynonym of W. tcherkesovae, and although the material of theformer species (Landrum and Sherwin, 1976: p. 1, figs. 1–13) ispoorly preserved, the cranidium appears to differ from that ofW. tcherkesovae in having a shallower anterior border furrowand less divergent preocular facial sutures, and the pygidium isproportionately shorter (sag.). Until further material of W. (A.)jelli becomes available to enable a fuller comparison, we retainboth species.
Warburgella? sp.Fig. 9(9)Material: Cranidium MGCU 37/977 from the Prídolí
Description: Cranidium moderately convex, about 70% aswide (tr.) at occipital ring as long (sag.). Frontal lobe wellrounded. S1 inclined strongly backwards, defining narrow(tr.) L1. S2 short, straight, almost transverse, occupying notmore than one third of glabellar width. Occipital furrowtransverse, narrow and deep. Occipital ring with a pair ofweek lateral occipital lobes. Preglabellar field 15% sagittallength of glabella, with weak preglabellar ridge. Anteriorborder furrow narrow, distinct. Anterior border 60% length(sag.) of preglabellar field, weakly convex. Sculpture of finegranules.
Remarks: This cranidium differs from typical representa-tives of Warburgella in having a narrow (tr.) L1 and in theglabella being almost parallel-sided. The former character findsits closest parallels in W. rugulosa eureka Alberti, Haas andOrmiston, 1972 (pl. 1, figs. 1–4, 6) from the basal Lochkovianof Nevada, but this taxon has a much wider (sag.) anteriorborder and forward-tapering glabella. The question as towhether the present specimens belong to Warburgella requiresmore material for its resolution.
Paratypes: MGCU 29/977, pygidium, from type horizonand locality (sample 22-345); MGCU 1/884, 28/977, cranidia;MGCU 27/977, 30/977, 31/977, 32/977, pygidia, from Tamchi-Rabkash regional stages, Zaamin Formation, lower member(samples 525/11, 609/5, 610/2), Myk Sai, left bank of theEttkichu river, Turkestan Range, Uzbekistan.
Diagnosis: Paleodechenella with frontal glabellar lobetransverse; S1 dies out before reaching occipital furrow;marked intramarginal zone separating border and epiborderfurrows, which are both weak; pygidium elongate, with 13–14axial rings; pleural fields with five or six pairs of ribs, thosebehind second pair progressively more effaced.
Description: Cephalon semicircular. Preoccipital glabellabroadly bell-shaped, more or less parallel sided at L1, thentapering rapidly towards anterior; frontal lobe with transverseanterior margin. Three pairs of lateral glabellar furrows. S1deep, deepest at mid-length and directed obliquely backwardsbut not fusing with occipital furrow. L1 rhomboidal. S2 short,inclined obliquely backwards, subparallel with S1. S3 veryshort, opposite g, at narrowest part of the glabella. Occipitalfurrow narrow, curved gently forwards sagittally and againbehind L1. Occipital ring as wide (tr.) as posterior part ofpreoccipital glabella, with pair of weakly defined lateraloccipital lobes and with small median tubercle. Preglabellarfield very narrow, where intramarginal zone widens (sag,exsag.) slightly. Intramarginal zone distinct, separating borderand epiborder furrows, which are both weak. Anterior borderroll gently convex in cross section, about same width asintramarginal zone sagittally. Preocular facial sutures divergewith b a broad curve. Palpebral lobe large, about half length(sag.) of glabella; g situated well out abaxially from anexsagittal line drawn through b. Postocular facial suture with eplus z as a wide angle, close to axial furrow; intersection withposterior cephalic margin about half way from axial furrow tolateral margin of cephalon.
Eye large, about 70% length of glabella, its posterior end ashort distance in front of posterior border furrow. Field oflibrigena rather narrow, with a prominent break in slope atborder furrow on adaxial edge of intramarginal zone, the latterof approximately equal width to lateral border roll. Epiborderfurrow broad and shallow, posterior border furrow deeper andbroader. Long, narrow genal spine with median furrow deep andbroad anteriorly, narrowing and dying out towards posterior endof spine.
Pygidium elongated, semielliptical in outline. Stronglyconvex, narrow axis about 25% pygidial width (tr.), terminatinga short distance from the posterior border and bearing from 13
to 14 narrow rings which become progressively weakerposteriorly. Pleural field gently convex with up to five flattenedpleural ribs. First three pairs of pleural furrows narrow andwell-marked, terminating at inner edge of border, moreposterior ones effaced and barely visible. First three pairs ofinterpleural furrows very shallow and weak, subparallel topleural; more posterior ones effaced. Prominent pygidial borderconvex in cross section.
Sculpture of fine pits, interspersed with weak rugae onglabella.
Remarks: P. turkestanica sp. nov. differs from bothP. waigatchensis (Maksimova, 1970: pl. 2, figs. 1–3) andP. novozemelica (Maksimova, 1970: pl. 1, figs. 29–32) from theLudlow Grebensk Horizon of Vaigatch Island and NovayaZemlya in having a glabella with a transverse anterior margin, awider intramarginal zone and a proportionately narrowerpygidium in which the more posterior ribs are effaced.
Paleodechenella zaaminica sp. nov.Fig. 9(13–16)Etymology: From Zaaminsu, near the type locality.Holotype: MGCU 33/977, cranidium (Fig. 9(13)), Tamchi-
Rabkash regional stage, lower member of Zaamin Formation(sample 619/1), Myk Sai, left bank of the Ettkichu river,Turkestan Range, Uzbekistan.
Paratypes: MGCU 34/977, 35/977, 36/977, pygidia, allfrom type stratum and type locality.
Diagnosis: Glabella bell-shaped, narrowest opposite g, withtransverse anterior margin; S1 deep, extending almost tooccipital furrow; S2 long, shallow and subparallel to S1; broadintramarginal zone with border and epiborder furrows bothshallow and marked by change in slope; very large palpebrallobe, 60% as long as sagittal length of glabella; pygidiumelongate, broadly triangular with narrow axis comprised of 11–
12 rings.Description: Glabella bell-shaped, 70% as wide (tr.) as long
(sag.), widest half way along palpebral lobe, with a distinctwaist opposite g, and widening again in front of this point;frontal margin transverse. Three pairs of oblique, subparallellateral glabellar furrows. S1 deep, meeting axial furrow justanterior of widest point of glabella, and dying out beforereaching occipital furrow. S2 situated a short distance behind g,a little shorter than S1. S3 very short, situated opposite g.Occipital furrow narrow and more or less transverse. Occipitalring 20% sagittal length of preoccipital glabella, with smallmedian tubercle. Furrow defining lateral occipital lobe runs intooccipital furrow opposite a depression running backwards fromdistal end of S1.
Preglabellar field narrow, with shallow border furrowrunning a short distance in front of frontal lobe of glabella.Intramarginal zone about twice width (sag.) of preglabellarfield. Epiborder furrow of similar depth to border furrow.Narrow anterior border roll slightly raised. Preocular facialsutures describe wide, even curve, with b directly in front of g(exsag.). Large, broad (tr.) palpebral lobe of sub-semicircularoutline, 60% as long (exsag.) as sagittal length of glabella.
Pygidium elongate, sub-triangular, approximately 85% aslong (sag.) as wide (tr.). Narrow axis anteriorly 25% width (tr.)of pygidium, terminating at posterior border and bearing from11 to 12 rings, defined by weak ring furrows. Pleural fieldsdeclined evenly towards margin, with six pairs of pleural ribs,which become more weakly defined towards posterior. Firsttwo or three pleural furrows narrow, incised; more posteriorones weak or effaced. Interpleural furrows all weak, moreanterior ones marked by low, narrow ridge abaxially. Pleuralribs truncated at inner edge of well-defined, gently convexborder.
Surfaces of cranidium and pygidium finely pitted.Remarks: P. zaaminica sp. nov. is distinctive in having a
broad intramarginal zone, and in having rather long S2, and inthe very large palpebral lobe. One of the pygidia (Fig. 9(14))has what appears to be a mucro, but there is no trace of one onother specimens (Fig. 9(15, 16)). Because the posterior part ofthe border is damaged on this specimen, its apparent presence islikely to be preservational.
Family AULACOPLEURIDAE Angelin, 1854Genus Aulacopleura Hawle and Corda, 1847Type species - Arethusa koninckii Barrande, 1846, Wenlock
Remarks: This specimen closely resembles A. koninckii,but differs in that: the cephalic anterior border furrow is notdeflected anteriorly medially; the preocular facial sutures areslightly more divergent; the fixigenae are wider (tr.), with thedistance between the margin of the palpebral lobe and the axial
O. Ivanova et al. / Geobios 42 (2009) 715–737 731
furrow being 90% of the transverse width of the frontal lobe ofthe glabella, compared to a value of 75% in A. koninckii; and thelibrigenal fields are proportionately narrower. Commoncharacters include the subrectangular preoccipital glabella,prominent, transverse eye ridges and rather short, narrow genalspines. Similar differences can be seen in A. koninckii haueriFrech, 1887 from the upper Wenlock Orthocerenkalk of theCarnic Alps. Santel (2001: pp.120–121, pl. 5, figs. 1–8)concluded that the latter is probably not distinguishable asa separate subspecies. The Uzbek specimen represents anew species, but there is insufficient material to name itformally.
Adrain and Chatterton (1995: p.327) give the mediallydeflected anterior border furrow as a diagnostic character ofAulacopleura, and in lacking it, it could be argued that thepresent specimen does not belong to this genus, but to theclosely related Songkania, which is known from the Llandoveryof SW China, NW Canada and N Greenland. However, othercharacters, especially the subrectangular preoccipital glabellaand the prominent transverse eye ridges are characteristic ofAulacopleura, not Songkania, and show that the formerincludes species lacking the medially deflected anterior borderfurrow, contrary to the opinion of Adrain and Chatterton.
Family SCHARYIIDAE Osmólska, 1957Genus Scharyia Pribyl, 1946Type species: Proetus micropygus Hawle and Corda, 1847,
Scharyia sp. AFig. 10(3)Material: MGCU 26/814, pygidium, from Ludlow Series,
Kurgan Regional Stage, lower member of Akkaya Formation(sample VIII-4), Akkaya Mountain, northern Nuratau Range,Uzbekistan.
Description: Pygidium semielliptical, without clearlydefined border. Axis narrow, conical, 65% length (sag.) ofpygidium, flanked laterally by deep axial furrows and bearingsix rings defined by sigmoidal ring furrows which are broad andshallow axially, but deepening and narrowing distally. Pleuralfield with five pairs of pleural ribs with pleural and interpleuralfurrows of about equal depth. Small granule on adaxial end ofeach posterior pleural band. Anterior and posterior pleuralbands extend onto poorly defined, gently concave border, withthose anterior pleural bands situated towards posterior ofpygidium extending farther towards margin and terminating inpointed ends.
Surface sculpture finely granulose.Remarks: This pygidium bears a broad resemblance to that
of Scharyia nympha Chlupác from the Prídolí Series ofBohemia (Chlupác, 1971: pl. 23, figs. 4–6), especially in therather short (sag.) axis and finely granulose sculpture.Compared to Scharyia sp. A, S. nympha has more axial rings(7–8), and the border is better defined, at least on largerspecimens, and the pleural ribs do not extend onto it in the sameway. A new species is clearly represented, but there isinsufficient material to name it formally.
Scharyia sp. BFig. 10(2)Material: MGCU 27/814, pygidium from Ludlow Series,
Description: Pygidium elongate semielliptical, with weaklydefined border separated from pleural field by abrupt change inslope. Axis narrow, conical, 70% length (sag.) of pygidium,defined by shallow axial furrows, with six axial rings and an endpiece. Inter-ring furrows sigmoidal, deepening laterally. Pleuralfield moderately convex with five pairs of pleural ribs, andanterior pleural band of sixth, terminating at inner edge ofborder. Pleural furrows deepen and widen distally, terminatingnear inner edge of border with exception of first, whichcontinues towards pygidial margin. Small granule on adaxialend of each pleural rib, larger granule abaxial of this on second,third and fourth ribs. Distal ends of third to sixth anteriorpleural bands swollen, clavate. Distinct isolated node on borderarea opposite each rib.
Surface sculpture granulose, with a row of conspicuousgranules on each axial ring.
Remarks: This species, with the swollen abaxial ends of theanterior pleural bands of the more posterior pygidial pleuralribs, and the isolated nodes on the border area, is distinct fromall others, and is a second new species of Scharyia, althoughthere is insufficient material at hand to name it.
Family CHEIRURIDAE Hawle and Corda, 1847Subfamily CHEIRURINAE Hawle and Corda, 1847Genus Pseudocheirurus Prantl and Pribyl, 1947Type species: Cheirurus beyrichi Barrande, 1846, Ludlow
Pseudocheirurus aff. beyrichi (Barrande, 1846)Fig. 10(7)2008. Pseudocheirurus strabo (Weber) – Ivanova in Kim
et al., p. 117, pl. 99, fig. 25.Figured material: MGCU 30/814, cranidium from Prídolí
Series, Rabkash Regional Stage, Chaltash Formation, Chas-hmazrak Member (sample II-14/30), Shaly Sai, northernNuratau Range. Also recorded from II-7/2, II-8/3 (ShalyGorge) and VIII-7 (Akkaya Mountain).
Description: Glabella elongated, 65–70% as wide (tr.) aslong (sag.), scarcely widening forwards. Three pairs of deep, sub-parallel lateral furrows, inclined obliquely backwards at a lowangle. S1 merge axially to form broad, shallow furrow thatmerges laterally with occipital furrow, which is narrow andgently curved backwards behind L1, which is transversely sub-triangular. S2 similar to S1, extending 80% distance from axialfurrow to sagittal line. S3 of similar depth and length. Frontallobe 40–45% sagittal length of glabella, its anterior part steeplydeclined in lateral view. Occipital ring slightly raised above levelof posterior part of preoccipital glabella, and about as wide (tr.) asdistance across L1. Fixigena incompletely preserved, flattenedwith pitted surface. Small palpebral lobe opposite L3.
Librigena, hypostoma, thorax and pygidium unknown.Remarks: This specimen differs from species of Cheirurus
(e.g. C. insignis Beyrich, 1845, and C. centralis Salter, 1853;
O. Ivanova et al. / Geobios 42 (2009) 715–737732
see Lane, 1971, text-fig. 3a, c, f, and pl. 1, figs. 1, 3–6, 9, 11, 12respectively) in having the glabella more or less parallel-sided,in having much longer lateral glabellar furrows and a wider (tr.)L1. In all these characters it accords with Pseudocheirurusbeyrichi (Barrande, 1846), and differs only in the relativeproportions of the glabella, which is longer and narrower (cf.Horny and Bastl, 1970: pl. 14, fig. 7). It is assigned here toPseudocheirurus as P. aff. beyrichi. A cranidium from theWenlock/Ludlow Akkan Limestone of Ak-Kerme Bay, W endof Lake Balkhash, Kazakhstan, figured by Weber (1951: pl. 6,fig. 1) as Cheirurus beyrichi is similar to the specimen fromShaly Sai, and also belongs to Pseudocheirurus, but the glabellais proportionately shorter and wider than in either P. beyrichiand P. aff. beyrichi. Two undescribed species are evidentlyrepresented by the central Asian material, but further specimensare required before they can be characterized sufficiently to benamed formally. Ivanova (2008: p. 117) attributed thisspecimen to Pseudocheirurus strabo, but the figures of thecranidium from Fergana, upon which this species is based(Weber, 1932: pl. 2, fig. 18a, b; 1951: pl. 6, fig. 14a, b) show aforwardly expanding glabella, indicating that it should beplaced in Cheirurus (as for example by Weber, 1951: p. 35 andby Lane, 1971: p. 11), and not Pseudocheirurus.
Youngia aff. alaica Weber, 1932Fig. 11(13)2008. Youngia alaica Weber - Ivanova in Kim et al., p. 117,
pl. 99, fig. 30.Material: MGCU 36/814, cranidium. Ludlow Series,
Tamchi Regional Stage, Chaltash Formation, Shaly Member(sample II-6/2), Shaly Sai. Also reported from samples VIII-4,VIII-9 and VIII-11, Akkaya.
Description: Glabella inflated, estimated to be about 80% aslong (sag.) as wide (tr.). Two pairs of lateral furrows. S1 deep,curved postero-medially, dying out before reaching occipitalfurrow; S2 shallower, about half length of S1, its adaxial endcurved slightly backwards. Occipital furrow of similar depth toS1; only lateral part of occipital ring behind L1 preserved.Surface of entire glabella and occipital ring coarsely granulose.
Remarks: The figured specimen is similar to Y. alaicaWeber from the Ludlow-Prídolí of the Alai Range, southernKyrgyzstan. As far as can be judged by comparison withWeber’s (1932: pl. 1, fig. 38) figure, our specimen appears to bemore coarsely granulose, and L1 slightly narrower (exsag.). Itdiffers from Y. uralica Tchernyshev, 1893 (see Weber, 1951:pl. 6, figs. 4, 9) from the region of the Is and Vyia rivers, easternslope of the Urals, in having much deeper S1 and S2, a narrower(exsag.) L1 and much coarser granulose sculpture.
Figured material: MGCU 32/814, cranidium, and MGCU33/814, pygidium, from Ludlow Series, Kurgan RegionalStage, lower member of Akkaya Formation (samples VIII-10and VIII-7), Akkaya (also reported from samples VIII-4, VIII-9and VIII-12); MGCU 34/814, pygidium, from Ludlow Series,Tamchi Regional Stage, Chaltash Formation, Shaly Member(sample II-6/1), Shaly Sai (also reported from sample II-7/1).All from northern Nuratau Range, Uzbekistan. This speciesoccurs also in: the Akkan Formation of the west Lake BalkhashRegion, Kazakhstan; the upper Silurian of the Urals andSaiany-Altai Region, SW Siberia, Russia; and the upperSilurian of Kyrgzstan, Britain and Bohemia.
Diagnosis: See Thomas (1981: p. 63).Remarks: Weber (1951: pp. 39–40, pl. 6, figs. 6, 10, 20)
described specimens of this species from the Lake BalkhashRegion and South Tien-Shan. These, and the specimens fromUzbekistan figured here conform to the diagnosis of S. mirusgiven by Thomas (1981: p. 61) except that one pygidium(Fig. 10(5)) has a more strongly constricted terminal piece thando others (Fig. 10(6)). It may represent intraspecific variability,but a larger sample size is required for this to be confirmed.
(sample VIII-7), Akkaya; all from northern Nuratau Range,Uzbekistan.
Diagnosis: Cromus with large, sparse tubercles on glabella;prominent, rounded lateral glabellar lobes; pygidium with atleast 20 narrow (exsag.) axial rings which shallow to becomealmost obsolete axially; extreme posterior part of axis tapersalmost to a point; 11 pairs of non-spinose pleural ribs.
Description: Glabella broadly pyriform, expanding for-wards anterior of S2. S1–S4 pit-like, of similar depth andlength. L1 narrow (exsag.), L2–L4 ovoid, almost isolated frommedian part of glabella. Occipital furrow narrow but distinct,arching gently forwards sagittally. Occipital ring widens(exsag., sag.) towards median part. Fixigena broad (tr.), andcomparatively narrow (exsag.), fixigenal field terminating inacute genal angle. Glabella covered with large, rather sparsetubercles of varying size; fixigena with tubercles interspersedwith fine pits. Occipital ring and posterior cranidial bordersmooth.
Librigena, hypostoma and thorax unknown.Pygidium sub-triangular with a long, weakly convex (tr.)
axis anteriorly occupying about one quarter pygidial width (tr.),with at least 20 rings, posteriormost ill-defined and difficult tocount. Axially, rings become almost obsolete as they crossbroad, smooth sagittal zone. Axial furrows narrow and shallow,becoming almost obsolete towards posterior, pointed end ofaxis. Pleural fields gently convex, flattened adaxially, declininggently towards margin. 11 pairs of non-spinose pleural ribs,separated by narrow pleural furrows. Posteriormost pair curvesgently round narrow, raised postaxial area. Surface of pygidiumsmooth.
Remarks: C. tamchii sp. nov. is similar to C. beaumonti(Barrande, 1846) from the Ludlow Kopanina Formation,Bohemia, but is distinguished in having L2-L4 ovoid andsemi-isolated instead of lobate (compare Fig. 10(10) andSnajdr, 1985: pl. 7, figs. 9, 10; pl. 8, figs. 1, 2). In this characterthey are like those of C. bohemicus Barrande, 1852 also fromthe Kopanina Formation (see Snajdr, 1985: pl. 6, figs. 2–4, 6).Additional contrasts between C. beaumonti and C. tamchii sp.nov. are the latter’s sculpture of interspersed pits and granuleson the librigena, and its larger number of pygidial axial rings(ca. 20, compared to 13–16) which are much finer and shorter(tr.).
The characters of C. tamchii sp. nov. combine those presentin such species as C. beaumonti, C. intercostatus andC. bohemicus – for example the lateral glabellar lobes,density of cephalic tubercles and number of pygidial axialrings are comparable with the latter two, whilst the non-spinose pygidial margin are shared with the former. Snajdr(1985: p. 23) used some of these characters to separateC. beaumonti and similar species from Cromus, and assignedthem instead to Encrinuraspis Webby, Moors and Mclean,1970 (type species: E. optimus, from the Ordovician(Caradoc) of New South Wales, Australia). Strusz (1980:p.11) considered these genera synonymous, whilst Ludvigsenand Tripp (1990: p. 22) used Cromus in a similar way toStrusz, but retained Encrinuraspis with reserve. For thereasons given above, we include all the above taxa in Cromus.
The status of Encrinuraspis, and its relationship with theSilurian species placed in Cromus must await a fullphylogenetic analysis of these and related species.
A pygidium from the Ludlow Series of Sarty-Salik, nearUra-Tyube, Tajikistan, figured by Weber (1951: p. 32, pl. 5, fig.18) as Encrinurus beaumonti var. novaki Frech? belongs toCromus, and is similar to that of C. tamchii sp. nov. in having 11non-spinose pleural ribs and at least 20 axial rings, but in thiscase they are deeper axially, and extend across the axis.
Remarks: These specimens differ from C. tamchii sp. nov.in the following ways: the glabella expands forwards morerapidly; the pygidium is proportionately narrower and has fewer(9) pleural ribs, and fewer (ca. 15–16) axial rings with deeperring furrows with a narrower sagittal smooth band. They aresimilar to the specimens described by Weber (1951: p. 31, pl. 5,figs. 6, 9, 12) as Encrinurus beaumonti var. lozvensis (which wehere consider to be a species of Cromus) from the WenlockSeries of the Lozva River region, eastern slope of the Urals,which have 10 pleural ribs and ca. 15 axial rings, although thelatter has proportionately wider (tr.) pleural fields. Thecranidium of C. lozvensis (Weber, 1951: pl. 5, fig. 12) is toopoorly preserved for comparison.
Family ODONTOPLEURIDAE Burmeister, 1843Subfamily ODONTOPLEURINAE Burmeister, 1843Genus Leonaspis Richter and Richter, 1917Type species: By original designation. Odontopleura
Leonhardi Barrande, 1846, from Ludlow Series, KopaninaFormation, Dlouhá hora near Beroun, Czech Republic.
Leonaspis nuratensis sp. nov.Fig. 11(1–12)Etymology: From the Nuratau Range.Holotype: MGCU 60/977 cranidium (Fig. 11(9)), Ludlow
Paratypes: MGCU 61/977, MGCU 63/977, cranidia,MGCU 58/977, partial thorax and pygidium, MGCU 69/977,pygidium from type locality; MGCU 66/977, pygidium fromsame locality, Shaly Member (sample II-8/3); MGCU 70/977,pygidium, from same locality, Shaly Member (sample 707/2);MGCU 67/977, pygidium, from same locality (sample 70202);MGCU 65/977, 64/977, cranidia, MGCU 62/977, cranidiumand partial thorax, MGCU 68/977, pygidium and partial thorax,and MGCU 71/977, pygidium, all from Shaly Member,Abartkan (sample 70199); MGCU 57/977, cranidium andMGCU 59/977, pygidium from same locality (sample 776).
O. Ivanova et al. / Geobios 42 (2009) 715–737 735
Diagnosis: Frontal lobe of glabella narrow (tr.); fixigenaeopposite g wide, between 24% and 33% width of glabella (tr.);preocular facial sutures converge typically at between 88 and108; major pygidial border spines weakly tapering.
Description: Cranidium with almost transverse anteriormargin, which is surmounted with row of small tubercles.Glabella with narrow (tr) frontal lobe, with gently convexanterior margin. L1 depressed, elongated with the longer axisdirected more or less exsagittally. On some specimens (e.g.Fig. 11(1–2)) it is divided transversely into two, a longerposterior part and a small, ovate anterior part. L2 prominent,more convex than L1 and suboval. Both L1 and L2 joined tomedian part of glabella by short, depressed, backwardly obliqueridge. S1 and S2 deep, pit-like. Occipital ring as wide (tr) aspreoccipital glabella across L1, with occipital furrow broad andshallow in its median section, deep and pit-like laterally. Smalllateral occipital lobes, slightly adaxial of L1. Posterior marginbackwardly curved. Axial furrow very shallow alongside L1,but slightly deeper at S2. Frontal lobe of glabella, and L1 andL2 with small tubercles; subdued tubercles on posterior part ofglabella. Median occipital tubercle present.
Fixigena gently convex and broad, between 24% and 33%width (tr.) of glabella opposite g. Palpebral lobe backwardlyplaced, opposite occipital furrow. In front of it, eye ridgedirected straight forward before curving strongly adaxiallyopposite S1. Preocular facial sutures converge between 88 and108. Postocular sutures directed abaxially at a little over 908 topreocular branch, curving backwards more strongly near baseof genal spine. Narrow, transverse cranidial posterior furrow.Librigena with convex border with at least 12 marginal spines,and with row of at least five small tubercles on border itself.Similar small tubercles present on genal field.
Hypostoma unknown.No complete thorax known, and axial region poorly
preserved on available specimens. Pleura with broad principalpleural ridge, separated from anterior accessory ridge by deep,narrow furrow, and from posterior accessory ridge by change inslope. Long, backwardly directed pleural spines present on twoposteriormost segments (Fig. 11(6)). Single tubercle presentabout mid-way along each principal pleural ridge.
Pygidium ranges from 26% to 38% as long (sag.) as wide(tr.), with axis comprising two rings and a terminal piece. Axialfurrow shallow adjacent to first ring, but deeper at second,shallowing again around posterior end of axis. Flat pleural areacrossed by prominent raised ridge which runs from first axialring into major border spine. Three shorter marginal spinesanterior of major spine, and two pairs inside it. Major spinenarrow-based, and tapering gently backwards; other spinesmore strongly tapering into long, narrow points. Sparsetubercles present on pygidium, in particular in the antero-lateral border region and on the axial rings. A single tubercle ispresent on the ridge running into the major border spine, in aposition analogous to those on thoracic principal pleural ridge.
Remarks: L. nuratensis sp. nov. accords with the revisedgeneric concept of Leonaspis defined by Ramsköld andChatterton (1991: p. 357), but is distinguished immediatelyfrom all other species by having a much wider (tr.) fixigena
opposite g. The value for this species ranges from 24% to 33%,far in excess of that (up to 16%) given by Ramsköld andChatterton as characterizing Leonaspis. Since other charactersof L. nuratensis sp. nov. (e.g., angle of convergence of preocularfacial sutures 108 or less; two pairs of border spines betweenmajor border spines; eyes set far posteriorly) are all consistentwith assignment to Leonaspis, the presence of broad fixigenae,a character involving proportion, is no reason to exclude it fromthe genus.
Most species of Leonaspis are of Devonian age, and besidesL. nuratensis sp. nov. only four are known from the Silurian.The type species, L. leonhardi, from the Kopanina Formation(Ludlow) of Bohemia, differs from L. nuratensis sp. nov. inhaving a wider frontal glabellar lobe, narrower fixigenae andmore tapered major pygidial spines (cf. Bruton, 1968: pl. 2,figs. 6–8, 10). L. grouensis Alberti, 1970 (p. 131, pl. 19, fig. 7)from the Lower Ludlow Shoul Limestone of Morocco is knownonly from the cranidium, which differs from that ofL. nuratensis sp. nov. in similar ways to L. leonhardi (widerfrontal glabellar lobe, narrower fixigenae). L. ezellina Snajdr,1983 (p. 177, pl. 2, figs. 6, 7) from the Pozáry Formation(Prídolí), Bohemia, is distinguished from L. nuratensis sp. nov.in these same cranidial characters, and has more tapering majorborder spines on the pygidium. ‘Leonaspis sp. n. sp.’ of Santel(2001: p.137, pl.6, fig. 3) from the Ludlow of the Carnic Alps isbased on one small, presumably immature pygidium in whichthe posterior region between the major spines is narrower thanthat of L. nuratensis sp. nov.
Acknowledgements
We are grateful to Dr Derek J. Siveter whose thorough reviewmuch improved the original manuscript. Amanda Valentineprepared casts for the collections of the National Museum ofWales and Dr Christian Baars translated German texts.
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