Cenozoic cyclostomatous bryozoans from the Qom ...

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N. Jb. Geol. Paläont. Abh. 283/1 (2017), 109–118Article Stuttgart, January 2017

Cenozoic cyclostomatous bryozoans from the Qom Formation (Chahriseh area northeast of Isfahan, central Iran) Kamil Zágoršek, Mehdi Yazdi and Ali Bahrami With 2 figures

Abstract: The Dizlu and Bagh Sections in the Oligocene – early Miocene Qom Formation (northeast of Isfahan, central Iran) has yielded a rich association of Bryozoa including eleven species belonging to the order Cyclostomata. The description of these eleven species (including three new species (Exidmonea baghi sp.n., Nevianipora isfahani sp.n. and Polyascosoecia iranica sp.n.) increase the knowledge with respect to the faunal diversity within the Qom Formation. Key words: Qom Formation, Bryozoa, Cyclostomata, Miocene, new species.

1. Introduction

2015). Bryozoans, especially cyclostomes, which occur in high quantity, have, however, not been studied in detail apart from an analysis of species growing on larger foraminifera (Berning et al. 2009).

Qom Formation: The Qom Formation was established by Furrer & Soder (1955) based on the type locality near the city of Qom, situated northeast of the province of Isfahan in Central Iran. The formation represents one of the best studied areas in Iran of Oligocene to Miocene age, mainly because of its high importance as an oil reservoir basin (Mostofi & Gansser 1957; Abaie et al. 1964). This led to the stratigraphy and the structural geology of this formation being studied by numerous authors (among others e.g., Rahaghi 1980; Schuster & Wielandt 1999; Torabi 2003; Daneshian & Ramezani Dana 2007; Reuter et al. 2009; Behforozi & Safari 2011; Mohammadi et al. 2011, 2013; Mohamm MADI & Safari 2015). The Qom Formation has yielded a highly diverse fauna, mainly consisting of corals (Schuster & Wielandt 1999; Schuster 2002a, b), molluscs (Harzhauser 2004) and foraminifers (Yazdi et al. 2012; Nouradini et al. 2014), which attest to the Late Oligocene to Early Miocene age of the Formation (Nouradini et al.

Geological setting: Three Cenozoic lithostratigraphic formations can be distinguished in central Iran. Firstly, the Lower Red Formation (LRF) is late Eocene-early Oligocene in age and consists of red to brownish continental thick siliciclastic sediments (Mohammadi et al. 2015). Overlying the LRF is the Qom formation of Oligocene-Miocene age containing mainly near-shore, shelf sediments. The thickness of the Qom Formation varies due to the morphology of the basement and different sedimentation rates (Aghanabati 2006). The third, Upper Red Formation consists of disconformable layers of red continental sediments of middle Miocene age (Aghanabati 2006). The Qom formation can be divided into six lithologic units (Furre & Soder 1955; Gansser 1955; Bozorgnia 1966; Daneshian & R amezani Dana 2007). According to Aghanabati (2006), who provided the most

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110 K. Zágoršek et al.

Fig. 1.

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Cenozoic cyclostomatous bryozoans from the Qom Formation 111

recent detailed research, the characteristics of the units are as follows: – Unit A consists of 40 to 85 m massive, thickly bedded, sandy limestone containing diverse foraminifers (milliolids, rotalids and textulariids), and represents near-shore conditions of Chattian age. – Unit B consists of 260 m thick sequence of marls, sandy marls with coarse grained layers containing mainly a rich macrofauna and the foraminifers Miogypsina sp., Miogypsinoides complanata, Rotalia viennotti, Globoquadrina sp. and Globorotalia opima opima. The age of this unit is proposed to range from the Oligocene to the early Miocene. – The next unit C (often divided into C1, C2, C4 and C4 subunits) represents 300-500 m thick layers of marls and marly limestone with local coral patch reefs. The Rupelian – Aquitanian age is indicated by presence of Miogypsinoides sp., Globigerina bulloides, Operculina cf. complanata and Anomalina rostrata. – Unit D consists of 20 to 40 m thick gypsum and red shale layers lacking any fossil content and is probably Rupelian – Aquitanian in age. – Unit E is the thickest unit ranging from about 80 to 650 m and consist of an alternation of green marls and marly limestone with gypsum. The fossils are restricted to the foraminifers Globigerinoides triloba triloba, Globigerinoides sacculifera, Globigerinoides bispherica, Robulus vertex, Cibicides ungerianus and Cibicides dutemplei, indicating Rupelian – Aquitanian age. – Unit F is 180 to 320 m thick and is formed by limestone intercalated by marly limestone beds with the occurrence of bryozoans and the foraminifera Neoalveolina melocurdica, Peneroplis evolutus, Dentritina rangi, Meandropsina anahensis, Acervulina sp. and Archaias sp.. The age is indicated as Rupelian – Aquitanian. The sedimentary sequence of the Qom Formation was deposited on the NE margin of the Tethyan Seaway (Daneshian & Ramezani Dana 2007; Reuter et al. 2009; Mohammadi et al. 2013), mainly in the Sanandaj-Sirjan structural zone in the Esfahan-Sirjan basins (Schuster & Wielandt 1999; Mohammadi et al. 2015). The Qom Formation was, however, also reported from the Urumieh-Dokhtar magmatic arc (intra-arc), as well as from the Sanandaj-Sirjan fore-arc and Central Iranian back-arc basins (Mohammadi et al. 2013).

Studied sections: The bryozoans were studied from three sections, one from Dizlu and two from Bagh (Fig. 1) in the Chahriseh area within Qom Formation unit F (Aghanabati 2006). The Chahriseh area is situated in NE Isfahan district around the village of the same name (GPS coordinates of the village are 32°59’36.24” N; 52°05’52.38” E). The Dizlu Section is situated south west of Chahriseh village. The upper part of the section yielded rich bryozoans assemblages (Yazdi et al. 2012). The GPS coordinates of the base of the Dizlu Section are 33°00’8.86” N and 52°02’22.56” E, those from the top of the section are 33°00’13.46” N and 52°02’26.15” E. The Bagh (#1 and #2) Sections are situated south of Chahriseh village (Nouradini et al. 2015) very close to each other. The base of Bagh Section #1 has GPS coordinates 32°56’54.96” N and 52°00’37.34” E, the top 32°56’53.22” N and 52°00’40.95” E. The position of the base of Bagh Section #2 is 32°57’8.09” N and 52°00’57.01” E, the top is at 32°57’3.08” N and 52°00’52.87” E. There are practically no differences in outcropped lithological sequence and faunal content between the sections Bagh #1 and #2. Therefore only one lithological log is displayed in Figure 1. The total thickness of sediments in Qom Formation changes laterally due to the different shape of basement and different deposition rates of clastic material transported into the basin. The studied sections comprise of a thick succession of marine marls, limestone, gypsum and siliciclastic deposits (Reuter et al. 2009). The Bagh Sections are represented predominantly by carbonate ramp deposits with limestone intercalated by subordinate siliciclastic beds in its lower part (Fig. 1). The Dizlu Section consists mainly of fossiliferous limestone with marly layers (Aghanabati 2006). The Qom Formation in the Chahriseh area is very rich in fossils. Besides the foraminifers which confirm the Oligo-Miocene age of the sediment (Nouradini et al. 2015), rich assemblages of corals (Schuster 2002), scleractinian corals (Yazdi et al. 2012), echinoids (Nouradini et al. 2014), molluscs, brachiopods, serpulids and bryozoans indicate shallow marine conditions. Cyclostomatous bryozoans have not been studied before even though they are highly abundant and well preserved in these sections. The present study will serve to fill this lack of knowledge.

Fig. 1. The studied locality. Sketch of the geographical position of the Chahriseh area, Dizlu and Bagh1 and 2 Sections, lithostratigraphical columns of Dizlu and Bagh1 Sections with sample numbers (washed and picked).

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Fig. 2.

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2. Material and methods

Remarks: The preserved fragment shows all characteristic features of this species, which are the presence of additional apertures situated between the pairs of fascicles, in the middle of the frontal side of the colony, and fascicles formed of three to five autozooecia. The species is often reported from the Miocene of the Paratethys (Zágoršek 2010), but also from the Oligocene of Latdorf in Germany (Zágoršek & Gordon, 2014). Gonozooids have never been reported in this species.

The material was washed in water and cleaned ultrasonically prior to taking pictures. SEM photos were taken using the Hitachi S-3700N SEM at the National Museum Prague. Measurements were made using software incorporated into command software of this microscope. The studied material is stored within the Natural History collection in the North Bohemian Museum in Liberec, Czech Republic (SCML).

Occurrence: Latdorf, Oligocene (Zágoršek & Gordon, 2014); Dizlu Section, Rupelian – Aquitanian; Paratethys, Miocene (Zágoršek 2010).

3. Systematic description The systematic arrangement of described bryozoans follows mainly the bryozoan web page (www.bryozoa. net) edited by Phil Bock (last update 2016) based on Bassler (1953) and Hayward & Ryland (1985, 1998 and 1999). The systematics of Cyclostomata additionally takes into consideration the papers of Taylor & McKinney (2006), Vávra (1977) and Zágoršek (2010).

Exidmonea baghi sp.n. Fig. 2A-C v. 2013 Exidmonea sp. – Zágoršek & Gordon p. 596, fig. 1A Diagnosis: Colony erect, delicate branching, rarely bifurcating with triangular transverse section. Autozooecial tubes arranged in fascicles of three to five apertures, the fascicles are parallel to each other. Gonozooecium situated on the frontal side, very large, spread over four fascicles with a flat frontal wall and its ooeciopore situated at the margin. No kenozooecia.

Phylum Bryozoa Ehrenberg, 1831 Class Stenolaemata Borg, 1926 Order Cyclostomata Busk, 1852 Suborder Tubuliporina Milne Edwards, 1838 Family Tubuliporidae Johnston, 1838 Genus Exidmonea David, Mongereau & Pouyet, 1972

Holotype: The specimen illustrated in Fig. 2A & C from the Bagh #1 Section; SCMLP number 2/2016: Pa 910. Paratypes: 2 specimens from the Bagh #1 Section; SCMLP numbers P 2/2016: Pa 911 and P 2/2016: Pa 912.

Diagnosis: See Zágoršek (2010).

Derivatio nominis: Due to the occurrence in the Bagh Section.

Exidmonea giebeli (Stoliczka, 1862)

Locus typicus: Bagh #1 Section; washed out material, not exact bed recognized.

v. 2010 Exidmonea giebeli (Stoliczka, 1862). – Zágoršek p. 28, pl. 6, figs. 1-3 (cum syn.) v* 2014 Exidmonea giebeli (Stoliczka, 1862). – Zágoršek & Gordon p. 543, fig. 1B

Stratum typicum: Rupelian – Aquitanian Measurements: (in micrometers = µm; x = average) Length of the colony: 4700-2800; x = 3800 Width of the colony: 514-480; x = 508

Material: One large fragment from Dizlu Section without gonozooecium.

Fig. 2. A – holotype of Exidmonea baghi sp.n., scale bar 1 mm. B – paratype of Exidmonea baghi sp.n., scale bar 1 mm. C – holotype of Exidmonea baghi sp.n., detail of ooeciopore, scale bar 100 µm. D – Exidmonea partschii (Reuss, 1848), scale bar 1 mm. E – holotype of Nevianipora isfahani sp.n., scale bar 1 mm. F – detail of the gonozooecium in holotype of Nevianipora isfahani sp.n., scale bar 100 µm. G – detail of the gonozooecium of the paratype of Nevianipora isfahani sp.n., scale bar 100 µm. H – Mecynoecia pulchella (Reuss, 1847) , scale bar 1 mm. I – Frondipora parva Zágoršek, 2010, scale bar 1 mm. J – Ybselosoecia typica (Manzoni, 1878), scale bar 1 mm. K – holotype of Polyascosoecia iranica sp. n. with extended gonozooecium, scale bar 1 mm. L – lateral view of the paratype of Polyascosoecia iranica sp. n., scale bar 1 mm. M – Hornera cf. frondiculata Lamouroux, 1821, scale bar 1 mm. N – Disporella cf. hispida (Fleming, 1828), scale bar 1 mm. O – Disporella cf. radiata (Savigny & Audouin, 1826), scale bar 1 mm.

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Length of observable fixed autozooecial wall: 486-571; x = 506 Width of autozooecia: 112-150; x = 146 Diameter of autozooecial aperture: 108-143; x = 138 Gonozooecium width: 628-507; x = 556 Gonozooecium length: 1742-1538; x = 1638 Diameter of oeciopore: 79

terial from Paratethyan Vienna Basin (Vávra 1977) and unpublished results from Přemyslovice, Hluchov and Rousínov. The only difference is a somewhat shorter gonozooecium in the Paratethyan material, which is spread over two to three fascicles. But the arrangement of the ooeciopore and the general habitat of the colonies (only encrusting Exidmonea in the Paratethys) are identical.

Description: Colony erect, delicate branching, rarely bifurcating with triangular transverse section. Autozooecial tubes arranged only on two sides of the triangle, in fascicles. There are three to five apertures in each fascicle, parallel or slightly alternating to each other. Apertures circular to square on the top of the short peristomes. Fixed part of the autozooecial wall evenly perforated by small pseudopores. Gonozooecium situated on the frontal side, very large, usually spread over four to five fascicles. The frontal wall is very flat and granular. The ooeciopore situated in the margin, below the distalmost fascicle, circular without peristome. No kenozooecia.

Occurrence: Dizlu Section, Rupelian – Aquitanian; Vienna basin, Miocene (Vávra 1977).

Family Diaperoeciidae Canu, 1918 Genus Nevianipora Borg, 1944 Colony erect, delicate branching, often bifurcated. Apertures only in one side, arranged chaotically, or in slight fascicles. Gonozooecium small, irregular, ooeciopore attached to one autozooecial aperture. Kenozooecia absent.

Comparison: The specific feature of the newly described species is the size and shape of the gonozooecium. No species of Exidmonea have gonozooecia as large as the described new species. The usual gonozooecia are spread over two to three fascicles (while in the new species it is spread over more than four fascicles) and the frontal wall is convex, such that the whole gonozooecium is more globular. The described specimens are identical to those described and illustrated by Zágoršek & Gordon (2013) as Exidmonea sp. from the Miocene of Turkey. The size of the gonozooecium and flat frontal wall is identical with the described species.

Nevianipora isfahani sp.n. Fig. 2E-G Diagnosis: Colony narrow, apertures in pairs or single arranged chaotically. Gonozooecium spread over four to eight apertures. Ooeciopore larger than aperture. Holotype: The specimen illustrated in Fig. 2E, from the Dizlu Section, SCML number P 2/2016: Pa 913. Paratypes: 2 specimens from the Dizlu Section, SCML numbers P 2/2016: Pa 914 and P 2/2016: Pa 915.

Occurrence: Bagh Sections and Başyayla, Turkey (Zágoršek & Gordon 2013).

Etymology: Due to the presence near the city of Isfahan (central Iran).

Exidmonea partschii (Reuss, 1847) Fig. 2D

Locus typicus: Dizlu Section, washed out material, not exact bed determinable.

*1847 Diastopora partschii. – Reuss p. 52, pl. 7, figs. 16, 17 v. 1977 Idmonea partschii. – Vávra p. 56

Stratum typicum: Rupelian – Aquitanian deposits. Measurements: (in micrometers = µm; x = average) Length of the colony: 1809-2268; x = 2080 Width of the colony: 468-608; x = 506 Length of observable fixed autozooecial wall: 293-406; x = 388 Width of autozooecia: 80-106; x = 98 Diameter of autozooecial aperture: 76-98; x = 88 Gonozooecium width x length: 640 x 2106

Type: Lost. Not found within the Reuss collection deposited in the Natural History Museum Vienna (Zágoršek, personal investigation 2016). Material: Three colonies from Dizlu Section, two with gonozooecium. Diagnosis: Colony encrusting, with triangular transverse section. Autozooecial tubes arranged in fascicles of three to five apertures, the fascicles are arranged alternatively to one another. Gonozooecium situated on the frontal side, large, spread over three to four fascicles with slightly convex frontal wall. Oeciopore approximately in the distal third of the gonozooecium, attached to one fascicle, oval without peristome.

Description: Colony erect, delicate branching, often bifurcating, the distance between bifurcated branches about 1.8 mm. Apertures are thin-rimmed and round to oval, arranged chaotically, usually single, rarely in pairs or in bigger clusters. Peristomes of lateral autozooids are longer than those of the median autozooids. Pseudopores abundant, rounded. Gonozooid large, penetrated by 8 to 10 autozooidal peristomes and perforated by larger pseudopores than the rest of the colony. Ooeciopore attached to the one zooidal aperture,

Remarks: Colonies identical with previously described ma-

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making it semicircular. The part of the semicircle belonging to the zooid slightly smaller than that belonging to the ooeciopore.

Remarks: The gonozooecium is very characteristic, enlarged over five autozooecial tubes, with small ooeciopore, about half the diameter of an autozooecial aperture with short ooeciostome, slightly curved proximally.

Comparison: The most similar species is Nevianipora rugosa (Osburn) having, however, denser rows of zooids. Nevianipora floridana (Osburn) has smaller apertures than the newly described species. A large gonozooecium that is perforated by more than eight autozooids and with an ooeciopore attached to the autozooid is not found in any of the known species of Nevianipora.

Occurrence: Dizlu Section, Rupelian – Aquitanian; Paratethys, Miocene (Zágoršek 2010).

Suborder Fasciculina D’Orbigny, 1853 Family Frondiporidae Busk, 1875 Genus Frondipora Link, 1807

Remarks: The presence of erect, delicate branching colonies, with narrow oval cross section and apertures arranged chaotically only on one side suggest the placement in the genus Nevianipora.


Frondipora parva Zágoršek, 2010 Fig. 2I

Occurrence: Dizlu Section, Rupelian – Aquitanian.

Family Entalophoridae Reuss, 1869 Genus Mecynoecia Canu, 1918

v. *2010 Frondipora parva sp.n. – Zágoršek p. 33, Pl. 21, Fig. 1-7


Material: More than five colonies from Dizlu Section, three of them with developed gonozooecium.

Mecynoecia pulchella (Reuss, 1847) Fig. 2H

Remarks: The specimens from the Dizlu Section show all specific features, even preserving the frontal wall of the gonozooecium. The gonozooecium is spread over three to four fascicles, the frontal wall is flat, with the slit-like ooeciopore situated distally from one of the fascicle, without peristome.

v. *1847 Cricopora pulchella m. – Reuss p. 40, Pl. 6, Fig. 10 v. 2010 Mecynoecia pulchella (Reuss, 1847). – Zágoršek p. 32, Pl. 17, Fig. 1-8 (cum syn.)


Material: Two colonies from Dizlu Section bed d1 and d2 with enlarge apical part.

Genus Polyascosoecia Canu, 1920

Remarks: The apical part is more enlarged as usually exhibited in material from the Central Paratethys (Zágoršek, 2010). This feature, however, might be affected by higher temperatures in the Tethyan Seaway compared to the Paratethys.



Polyascosoecia iranica sp.n. Fig. 2K-L

Family Plagioeciidae Canu, 1918 Genus Ybselosoecia Canu & Lecointre, 1933

Diagnosis: Colony erect, delicate branching, rarely bifurcating with a triangular to trapezoidal transverse cross section. About three autozooecial tubes per fascicle. Additional one aperture occurs outside of the regular fascicle, which is shifted slightly proximally. Autozooecial tubes perforated by large pseudopores. Frontal kenozooecia (‘mesopores’) very abundant. Dorsal side of the colony flat with one type of kenozooecium (vacuoles?). Gonozooecium large, situated on the frontal side of the colony close to a bifurcation with flat frontal wall. Ooeciopore not observed.


Ybselosoecia typica (Manzoni, 1878) Fig. 2J 2010 Ybselosoecia typica (Manzoni, 1878). – Zágoršek p. 31, Pl. 15, Fig. 1-5 (cum syn.)

Holotype: The specimen illustrated in Fig. 2K, from the Dizlu Section, SCML number P 2/2016: Pa 916.

Material: Altogether 4 specimens were studied from Dizlu section in detail and documented by SEM, but only a single one with preserved gonozooecium.

Paratypes: 2 specimens from the Dizlu Section, SCML numbers P 2/2016: Pa 917 and P 2/2016: Pa 918.

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Etymology: Due to the occurrence in Iran.

gonozooecium is much enlarged which might indicate that the specimen belongs to another species. Without a thorough revision of all Cenozoic hornerids, the establishment of new species seems senseless. Moreover, the poor preservation of the studied specimens and absence of ooeciopore does not allows detailed description of all important structures, mainly on the frontal side of the colony.

Locus typicus: Dizlu Section from washed out material, no exact layer determined. Stratum typicum: Oligocene to Miocene deposits. Measurements: (in micrometers = µm; x = average) Length of the colony: 4636-2437; x = 3527 Width of the colony: 367-556; x = 458 Length of observable fixed autozooecial wall: 265-397; x = 331 Width of autozooecia: 61-106; x = 85 Gonozooecium width x length: 689 x 3510


Suborder Rectangulata Waters, 1887 Family Lichenoporidae Smitt, 1867 Genus Disporella Gray, 1847

Description: Colony delicate branching, rarely bifurcating with a triangular to trapezoidal transverse cross section. About three autozooecial tubes per fascicle on two sides of the triangle (or trapezoid). Additional one aperture occurs outside of the regular fascicle, which is shifted slightly proximally. Autozooecial tubes perforated frontally by large pseudopores. Frontal kenozooecia (‘mesopores’) rare, fixed wall of the autozooecial always observable. Dorsal side of the colony flat with one type of kenozooecium (vacuoles?). Gonozooecium large, spread above more than five fascicles, situated on the frontal side of the colony close to a bifurcation. Frontal wall flat evenly perforated by numerous small pseudopores. Ooeciopore not observed.


Disporella cf. hispida (Fleming, 1828) Fig. 2N ?2010 Disporella cf. hispida (Fleming, 1828) – Zágoršek 2010 p. 39, pl. 36, figs. 2-5 (cum. syn.) Material: Two colonies found in the Dizlu Section. Remarks: The development of the fascicles is weaker compared to the material from the Paratethys. Moreover, the preservation of the colonies is poor, and not good enough to observe all of the important features. Therefore the specimens cannot be classified to species level with certainty.

Comparison: The most similar species is Polyascosoecia cancellata Canu 1920 as revised by Zágoršek (2010), which differs mainly in having much smaller gonozooecia (spread over not more than three fascicles), in having more a convex frontal wall (unlike P. iranica sp.n. which has a very flat frontal wall), and in the presence of numerous frontal kenozooecia (the fixed autozooecial wall of P. cancellata is not observable).


Occurrence: Dizlu Section, Rupelian – Aquitanian in age.

Disporella cf. radiata (Savigny & Audouin, 1826) Fig. 2O

Suborder Cancellata Gregory, 1896 Family Horneridae Smitt, 1867 Genus Hornera Lamouroux, 1821

v. 2010 Disporella cf. radiata (Savigny & Audouin, 1826). – Zágoršek p. 40, pl. 38, figs. 1-3 (cum syn.)

Diagnosis: See Zágoršek 2010

Material: Only one specimen without gonozooecium has been found in the Dizlu Section.

Hornera cf. frondiculata Lamouroux, 1821 Fig. 2M

Remarks: Autozooecial tubes arranged in uniserial, very long fascicles occupying the margin of the colony. The material described from Paratethys has fascicles developed more closely to the central area. The general habitus and arrangement of the autozooecial tubes in uniserial fascicles suggesting the classification to this genus with formal assignment to the species D. cf. radiata.

v. 2010 Hornera cf. frondiculata Lamouroux, 1821. – Zágoršek p. 35; pl. 26, figs. 3-13 (cum syn.) Material: A common species which occurs in both sections. More than 10 specimens were studied, but only a few show gonozooecia.


Remarks: The problem of this species identification is discussed by Zágoršek (2010), which is fully followed here. The

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4. Discussion and conclusion

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A rich association of bryozoans from the Qom Formation yielded eleven species belonging to the order Cyclostomata including three new species (Exidmonea baghi sp.n., Nevianipora isfahani sp.n. and Polyascosoecia iranica sp.n.). The most comparable assemblage of cyclostomatous bryozoans occurs in Mut Basin, middle Miocene, Central Anatolian Plateau, southern Turkey (Zágoršek & Gordon, 2013), having six common species: Exidmonea baghi sp.n., Exidmonea giebeli (Stoliczka, 1862), Mecynoecia pulchella (Reuss, 1847), Ybselosoecia typica (Manzoni, 1878), Hornera cf. frondiculata Lamouroux, 1821 and Disporella cf. radiata (Savigny & Audouin, 1826). The common presence of Exidmonea baghi sp.n. in both localities may indicate the origin of this species in the Esfahan-Sirjan Basin in the early Miocene and its expansion into the Mut Basin during the middle Miocene. The absence of this species in the Paratethys may indicate its tropical origin and restriction only to tropical environments, or the closure of the Iranian gateway as indicated by Harzhauser et al. (2007) and Reuter et al. (2009). The other species are also abundant in many localities in the Central Paratethys (Zágoršek 2010), even though only some of them are formally classified. The absence of well-preserved gonozooecia limits the precise taxonomy especially of cyclostomatous bryozoans, which are generally poor in morphological characters and often lack many characteristic features. The faunal association studied in the Qom Formation, however, often show developed gonozooecia and therefore allow their precise determination. Based on bryozoans and other fossils (e.g. Behforouzi & Safari 2011), the studied sequence is interpreted as indicative of a tropical, normal marine environment. The absence of data concerning other tropical bryozoan assemblages in the Tethyan Ocean may explain the relatively high number of new species within the cyclostomatous bryozoans in the studied sections (from eleven species, three are new to science). Acknowledgments The authors are grateful to the Department of Geology, Faculty of Science, University of Isfahan for their support. We thank Dr. Homayon Safaei for preparing satellite photos of the studied area. We are also thankful to the James Nebelsick for his editorial work for our manuscript and to Bjorn Berning for valuable comments.

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Stocklin, J. & Setudehni, A. (1977): Stratigraphic Lexicon of Iran. – 2nd edition, Report No. 18: 376 pp., Tehran (Geological Survey of Iran). Torabi, H. (2003): Stratigraphy of Oligocene–Miocene sediments (Qom formation), West Ardestan–North Naein. – Unpublished PhD thesis, University of Isfahan, Iran, 280 pp. Vávra, N. (1977): Bryozoa tertiaria. – In: Zapfe, H. (Ed): Catalogus Fossilium Austriae – Vb/3: 1-189; Vienna. Yazdi, M., Parvanenejad Shirazi, M., Rahiminejad, A.H. & Motavalipoor, R. (2012): Paleobathymetry and paleoecology of colonial corals from the Oligocene–early Miocene (?) Qom Formation (Dizlu area, central Iran). – Carbonates and Evaporites, 06: 395-405. Zágoršek, K. (2010b): Bryozoa from the Langhian (Miocene) of the Czech Republic. – Acta Musei Nationalis Pragae, (B), 66 (1-4): 1-255. Zágoršek, K. & Gordon, D.P. (2013): Late Tortonian bryozoans from Mut Basin, Central Anatolian Plateau, southern Turkey. – Acta Palaeontologica Polonica, 58 (3): 595-607. Zágoršek, K. & Gordon, D.P. (2014): Revision of the Oligocene bryozoan taxa described by Stoliczka (1862), with the description of a new genus of Bryocryptellidae. – Geodiversitas 36 (4): 541-564. Manuscript received: November 28th, 2016. Revised version accepted by the Tübingen editor: December 22th, 2016. Addresses of the authors:

Kamil Zágoršek, Department of Geography, Technical University of Liberec, Studentská 2, CZ-461 17 Liberec, Czech Republic; e-mail: [email protected] Mehdi Yazdi, Department of Geology, Faculty of Science, University of Isfahan, Iran; e-mail: [email protected] Ali Bahrami, Department of Geology, Faculty of Science, University of Isfahan, Iran; e-mail: [email protected]

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