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1. Introduction
The Persian Gulf is an epicontinental margin basin surrounded by the Zagros Mountains, which form the active margin in the north and the Arabian stable foreland in the south (Falcon, 1969; Purser and Seibold, 1973; Haynes and McQuillan, 1974; Bordenave, 2002; Alavi, 2007; Jahani et al. 2009, 2017; Motamedi et al. 2011; Perotti et al., 2011, 2016). Qeshm Island is composed of NW-SE, W-E, and N-S trending anticlines and synclines with very thick Fars Group deposits (Gachsaran, Mishan, Aghajari, and Bakhtiari Formations) and the presence of 118 salt plugs (Sajadi and Rashidi, 2019). According to the tectonic and sedimentology evidence, Qeshm Island in the Persian Gulf is considered part of the south of the Zagros Mountains. The geological similarities as well as the existing harmony between the anticlines in the Zagros Mountains and Qeshm Island are similar and therefore related geologically to one another. The oil-bearing Zagros Mountains are northwest-southeast-trending from northern Iraq to southeast Iran and have been interpreted as the active zone of the Arabia-Eurasia collision belt (Stöcklin, 1968, Alavi, 2004, Allen et al., 2006). Qeshm is the largest island of the Persian Gulf and is located at the southern end of the folded Zagros Mountains (Figure 1).
Figure 1 Geological map of the investigated areas; A. Terrain map of Iran; B. Geological map of Qeshm Island, Persian Gulf (after Huber, 1977), with three sampled localities; 1=Direstan outcrop near the village; 2= Kendaloo outcrop in NE of the Kendaloo harbour; 3= Stars Valley outcrop; C. Geological map of Minab region (after Peterson and Rudzinskas, 1982), 4= Bemani outcrop.
The stratigraphic units of the Qeshm Island include the Hormoz series, Mishan Formation, Agha Jari Formation, and Quaternary deposits (Rezaee and Zarezadeh, 2014). Additional to the Late Proterozoic/Early Paleozoic salt complex of the Namakdan Group, the main prominent geological formations of the Qeshm Island are the extended outcrops of the Miocene-Pliocene-Early Pleistocene marly and sandy to silty deposits of the Mishan-Agha Jari and younger equivalent formations, with Quaternary calcareous marine terraces. The surface geology of Qeshm Island comprises gentle folds of Lower Miocene Mishan marls, Upper Miocene to Pliocene Agha Jari sandstones, and Lahbari marls, as well as Plio-Pleistocene Kharg limestones. This manuscript is the first report of Pectinid bivalves from Guri Member of Mishan Formation, near Direstan village, and ostracods of Guri Member and Gushi marls (Makran Basin), southern Iran. All recorded biota of the Mishan Formation and Gushi marls in the studied areas remain unpublished. The Makran Basin extends from the Oman Sea coasts in the south to the Jazmurian depression in the north. Its western limit is the Minab fault that separates the Makran and Zagros basins. There are no formal lithostratigraphic divisions in the Makran Basin; thus, the Makran successions are informally divided into 14 different units (Ghaedi et al., 2016). Gushi marl is the third unit composed of gypsiferous and calcareous marls, with interbedded siltstone and sandstone (Peterson and Rudzinskas, 1982; Ghaedi et al., 2016).
2. Geological settings
The pectinid specimens were collected from calcareous marls of the Mishan Formation, including patches of scleractinian corals, located south of Direstan Village (26°44’14” N; 55°56’07” E), Qeshm Island in the Persian Gulf. Ostracod specimens were collected from four sections: Direstan (south of Direstan village); Kendaloo (26°41’45.84” N; 55°55’25.67” E), near Kendaloo harbor, Star Valley section (26°52’9.99” N; 56°7’20.42” E); and Bemani (26°55’42” N; 57°07’25” E). The first three sections are the Mishan Formation (Zagros Basin), in Qeshm Island, and the fourth is part of the Makran units in the Minab region, Hormozgan Province, southern Iran (Figures 1 and 2). In Qeshm Island, the Mishan Formation contains about 943 m of green to grey marl and clay-limestone with a rich fossil content (Yazdi et al., 2013). The Mishan Formation is overlaid by the Agha Jari Formation (Figure 3A).
Qeshm Island is part of the Hormozgan province, and like other parts of this province, Mishan Formation is composed of two members; a thick to massive, rock-forming, hard limestone that is called Guri Member, and a very thick unnamed green or grey marl with intercalated of thin to medium bedded limestone reported by Rashidi et al. (2023), as the Marly Member, an informal member at the north end of the Island. In Direstan, the boundary of Guri Member and Marly Member is distinctly recognizable (Figure 3E).
Figure 2 Stratigraphic column and profiles of studied areas; A. Stars Valley section (Qeshm Island, Zagros Basin), B. Kendaloo outcrop (Qeshm Island, Zagros Basin), C. and Bemani section (Makran Basin).
Figure 3 More details of Direstan outcrops; A. Layers from top, Stormy bed (Agha Jari Formation), Guri Member and Marly Member (Mishan Formation); B. Close-up of Figure A (see green line boxes), showing a colony of Scleractinian coral; C. Ostreid bivalve; D. Stormy bed and Guri Member Boundary; E. Guri Member and Marly Member boundary; F. Close-up of Stormy bed; G. Close-up of Guri Member, shows a colony of Scleractinian coral exactly under the Stormy bed.
The Mishan Formation is the middle unit of the Fars Group that begins with the Gachsaran Formation sediments or its clastic equivalents (i.e., Razak Formation) and continues with Mishan Formation sediments, finally forming Aghajari with red clastic sediments (Haghipour and Aghanabati, 2005; Motiei, 1993). The Mishan Formation is exposed and present in most parts of the Zagros basin (Motiei 1993) but is well developed in Hormozgan Province (Rashidi et al., 2023) and Qeshm Island. In Qeshm Island, Guri Member organisms include bryozoans, echinoids, corals, gastropods, pectinid and oyster bivalves, crustaceans such as crabs and balanoids, and their shell fragments, while Gushi marls only bear ostreids (oyster bars) and balanoids (Figure 2C).
3. Materials and methods
Three well-exposed outcrops of the uppermost part of the Mishan Formation in the east (Star Valley, 26°52’9.99” N; 56°7’20.42” E) and central part (south Direstan, 26°44’19.06” N; 55°56’21.86” E and Kendaloo 26°41’45.84” N; 55°55’25.67” E) of the Qeshm Island and one profile (Bemani, 26°55’42”N; 57°07’25”E) in the Minab province (alongside the eastern margin of the Persian Gulf) were sampled to reveal the ostracod assemblages.
In Direstan only the Pectinidae assemblages were exposed. Forty-nine specimens of pectinids were collected from the studied area, all display extreme taphonomic features like breakage, bioerosion, encrustation, disarticulation, and abrasion. Most important taphonomic features, like bioerosion (ichnospecies) and activities of encrusting organisms like colonies of bryozoans or polychaetae tubes, are listed in Table 1. Overall, 34 ostracod carapaces and valves were studied, 5 specimens from Direstan; 8 specimens from Kendaloo; 9 specimens from Star Valley, and 12 specimens from the Minab province (Bemani section) were selected and are described herein. The material includes plentiful, well-preserved specimens that were cleaned using a mild detergent, and whenever necessary, an ultrasonic vibrator bath and a preparation needle. Finally, a light binocular microscope was used when necessary. Pectinid bivalves were washed in water and cleaned ultrasonically before taking pictures. To measure samples a pair of callipers were applied. All studied materials are housed within the Department of Geology, Faculty of Science, University of Isfahan, Iran, under the acronym of IUMC.
Table 1 Measurements and taphonomic features (like encrusting organisms, ichnogenera or ichnospecies, etc) of identified species of family Pectinidae, collected from Direstan Outcrop, Qeshm Island, southern Iran. Note: Ex=external of the valve, In=internal of the valve, AL= Auricular Length.
| Specimen number | AL (mm) | Height (mm) | Length (mm) | Ex/In of the Valve | Genus/specie | Figures | Taphonomic features | Figures | |
| 0-CLD | 45 | 67 | 67 | Ex | - | Pecten aff. rotundatus | 7A | bryozoan colony | 7B |
| 1-CLD | 36 | 69 | 70 | - | left | Chlamys varia | - | abrased balanoid cluster | - |
| 3-CLD | broken | broken | 35 | - | “ | Chlamys aff. multistriata | - | ventral margin breakage | - |
| 4-CLD | 17 | 41 | 36 | - | left | Ch. multistriata | 6A-B | Encrusting organisms | - |
| 5-CLD | broken | 44 | 35 | Ex | “ | Talochlamys articulata | 8D-E | Gastrochaenolites isp. | 8F |
| 6-CLD | 33 | 62 | 53 | - | Chlamys varia | - | - | - | |
| 7-CLD | 35 | 66 | 67 | - | right | 6G-H | Polycheate worms | 6H | |
| 8-CLD | 37 | 58 | broken | both | left | Ch. varia | 6D-E | Entobia cf. ovula | 6F |
| 9-CLD | 31 | 54 | 48 | Ex | right | Ch. varia | - | - | - |
| 10-CLD | 29 | 53 | 45 | “ | right | Ch. varia | 7G | calcareous tubes of polycheate worms | 7G |
| 3-PCD | 26 | 35 | 40 | - | “ | Flabellipecten piramidesensis | 7D-E | Microporella berningi | 7F |
| 4-PCD | 26 | 35 | 40 | - | “ | Flabel. piramidesensis | 8A-B | Encrusting bryozoan | 8C |
| 5-PCD | 28 | 41 | 47 | - | “ | Pecten cf. subarcuatus | 6C | Encrusting bryozoans | - |
| D1-PC4 | 33 | 65 | 56 | both | right | Argopecten gratus | 9A-B | Rogerella isp. | 9C-D |
| Gastrochaenolites isp. | |||||||||
| Ex | Trypanites weisei | 9E | |||||||
| “ | Maeandropolydora sulcans | 9F | |||||||
| D1-PC8 | 30 | 72 | 60 | Ex | “ | 10A-B | Maeandropolydora isp. | 9C | |
| both | Entobia cateniformis | 9D | |||||||
| Rogerella isp. | 9E-F | ||||||||
| D1-PC14 | 42 | 79 | 70 | Ex | “ | 11A-B | G. cluniformis | 11D | |
| Trypanites weisei | |||||||||
| Renichnus aff. arcuatus | |||||||||
| In | M. sulcans | 11C | |||||||
| “ | Encrusting bryozoans | 11E-F | |||||||
| D1-CL16 | 37 | 69 | 59 | both | left | Chalamys actinodes | 4A-B | Rogerella isp. | 4D |
| Ex | Gastrochaenolites isp. | ||||||||
| D1-CL17 | 38 | 66 | 57 | both | left | 5A-B | Maeandropolydora isp. | 5E-G | |
| Rogerella isp. | |||||||||
| Gastrochaenolites isp. | |||||||||
| D1-CL18 | 26 | 57 | 49 | “ | right | 4E | Oichnus simplex | 4F | |
4. Systematic descriptions
Scallops represent a large and diverse group of molluscs living mostly as vagile epifauna in marine environments, except for some species which are attached or cemented to the bottom. Species living free on the bottom are capable of swimming. Pectinids are common in the fossil record due to their calcite shell with high preservation potential. They are also important as a biostratigraphic tool, and a paleoecological and paleomigrational indicator of the possible open marine corridors.
4.1. PECTINIDAE BIVALVES
The systematic arrangement of the described Pectinidae follows Del Río (1992) and Bieler et al., 2010. Additionally, it takes into consideration the papers of Jimenez et al. (2009) and Fontannes (1880), Mandic (2004), Dijkstra and Maestrati (2008), Kroh et al. (2011), and Moore (1971).
Phylum Mollusca Linnaeus, 1758
Class Bivalvia Linnaeus, 1758
Subclass Autobranchia Grobben, 1894
Superorder Pteriomorphia Beurlen, 1944
Suborder Pteriina Newell, 1965
Superfamily Pectinacea Rafinesque, 1815
Family Pectinidae Rafinesque, 1815
Subfamily Chlamydinae Von Teppner, 1922
Genus Chlamys Roding, 1798
Chlamys actinodesSowerby, 1846
1846 Pecten actinodes -Sowerby in Darwin, p. 376, Pl. 3, fig. 33.
1921 Chlamys theresinae -Roveretto, p. 27, fig 27, fig. 12a.
1992 Chlamys actinodes -Del Río, p. 58, pl. 5, figs. 1-4.
2016 Chlamys actinodes -Del Río et al., p. 650, fig. 3.
Figure 4 Chalamys actinodes (Sowerby, 1846); A. external view of the left valve, showing exterior of the shell that is perforated, and also bearing a marginal breakage; B. internal view of the left valve, bearing a colony of encrusting Cheilostomata bryozoan; C. Close-up view of Figure B, showing a colony of encrusting Cheilostomata bryozoan; D. Close-up view of Figure A, exhibiting ichnogenus Rogerella (Saint-Seine, 1951), and ichnogenus Gastrochaenolites (D1-CL16). E-F. Chalamys actinodes (Sowerby, 1846); E. external view of the right valve, bearing one eroded and two well-preserved shells of genus Balanus, welded to the surface of the valve; F. Close-up view of Figure E, represented by Oichnus simplex (Bromley, 1981) and apical view of two specimens of genus Balanus (D1-CL18).
Figure 5 Chalamys actinodes (Sowerby, 1846); A. internal view of the left valve, showing interior of the shell is perforated, and bearing calcareous tubes of polychaete worms; B. external view of the left valve, bearing a colony of encrusting Cheilostomata Bryozoan, and also the shell is perforated; C. Close-up view of Figure B, showing a colony of encrusting Cheilostomata Bryozoan; D. Close-up view of Figure A, exhibiting a calcareous tube of polychaete worm; E. Close-up view of Figure B, ichnogenus Gastrochaenolites, two colonies of encrusting Cheilostomata Bryozoans, and Maeandropolydora sulcans (Bromley, 1981); F-G. Close-up view of Figure B, showing colonies of encrusting Cheilostomata Bryozoans perforated by activity of bioeroders produce ichnogenus Gastrochaenolites, Rogerella and Maeandropolydora (D1-CL17).
Studied material. 20 valves, all disarticulated, all affected by taphonomic features.
Description. Shell large, thick, and left-convex. The auricular dorsal margin is straight and short. Anterior auricle longer than posterior. Resilial insertions are deep, triangular, and higher than long. A pair of short and moderately impressed cardinal crura with a prominent denticle. Right valve with anterior auricle ornamented with 5 to 10 fine riblets and with a rounded free margin. The byssal notch is deep, and wide, with the apex commonly rounded, exceptionally acute, and byssal fasciole broad. Posterior auricles sculptured with 15 to 20 riblets; free margin straight and forming a right-angle at junctures with the outer ligament. Ornamentation of disk is highly variable consisting of 40 to 50 low rounded plicae and shallow interspaces, both longitudinally sculptured with flat, narrow, and closely set secondary riblets. Other specimens are characterized by the presence of 60 to 70 very fine, low, sharp, or flattopped primary ribs separated by wider and shallow interspaces with 5 to 7 riblets narrower than the primary ones (Del Río, 1992)
Remarks. Although the samples are affected by taphonomic features specially bioerosion, and valves are full of boreholes or fused to balanoid barnacles (see Figures 4F and 5E-G), they still show the most characteristic features of the species. Some specimens were perforated by bioeroders. Some specimens bear polychaeta worms indwelling deep in the byssal notch (see Figure 5D).
Distribution. Del Río et al. (2016) mentioned this species as widely distributed along lower shoreface to mid-shelf facies and for recent species, they inhabit gravel-substrate or firm-sandy bottoms of depths ranging between 70 and 185 m in open sea.
Chlamys multistriataPoli, 1795
1887 Pecten multistriatus -Bucquoy et al., p. 104. Gives extensive synonymy.
1939 Chlamys multistriata -Roger, p. 165. Gives extensive synonymy.
1972 Chlamys multistriata -Comaschi Caria, p. 69, pl. XXV, figs. 12-17.
1982 Chlamys (Chlamys) multistriata -Andres, p. 137, pl. 3, figs. 4-5.
1989 Chlamys (Chlamys) pusio -Lauriat Rage et al., p. 125, pl. II, figs. 6-7.
1994 Chlamys (Chlamys) multistriata -Ben Moussa, p. 76, pl. 3, fig. 3.
2009 Chlamys multistriata -Jimenez et al., p. 9, figs. 4c-d.
Figure 6 A-B. Chlamys multistriata (Poli, 1795); disarticulated, left valve; A. internal view; B. external view (4-CLD); C. Pecten cf. subarcuatus (Hilber, 1879), disarticulated, broken Auricular, right valve, external view (5-PCD); D-E. Chlamys varia (Linnaeus, 1758); disarticulated, left valve; D. internal view; E. internal view (8-CLD); F. Close-up view of Figure E, represent by ichnospecie Entobia cf. ovula (Bromley and D’Alessandro, 1984); G-H. Chlamys varia (Linnaeus, 1758); disarticulated, left valve; G. internal view, not affected by post-mortem processes; H. internal view, shows a calcareous tube of polychaetae worm (7-CLD).
Studied material. One disarticulated left valve, a little fragmented.
Description. Shell of small size, oval in shape, larger in height than in length. The anterior lateral margin is a bit shorter than the posterior one, which is slightly concave. On the outer surface of the valve, there are 22 thin and rounded radial ribs close to the umbo. The ribs split as the individual grows, thus doubling the number of ribs in the ventral margin. Ribs and interspaces are similar in width (less than 1 mm). Secondary ornamentation consists of thin growth striae that intersect the radial ribs, giving way to imbricate scales with an arrangement similar to tiles on a roof. The cardinal margin is not straight, being higher in the anterior part of the shell. Auricles have 5 to 12 small costae diverging to the margins. (Jimenez et al., 2009).
Remarks. Chlamys multistriata is similar to C. varia, but the latter is larger. Additionally, C. multistriata contains more radial ribs and they are irregularly divided to the ventral margin. Finally, C. varia has spines, which do not occur in C. multistriata (Jimenez et al., 2009).
Distribution. Lower Miocene to present. Jimenez et al. (2009) mentioned that Chlamys varia and C. multistriata are quite common in fine- to medium-grained sands and silts of Pliocene strata of SE Spain.
Chlamys variaLinnaeus, 1758
1758 Ostrea varia Linnaeus, p. 698.
1907 Chlamys varia -Cerulli Irelli, p. 89, pl. IV, figs. 46-48.
1939 Chlamys varia -Roger, p. 157, pl. XXII, figs. 21-23.
1974 Chlamys (Chlamys) varia -Malatesta, p. 44, pl. III, fig. 11.
1981 Chlamys (Chlamys) varia -Lauriat Rage, p. 42, pl. IV, fig. 8.
1990 Chlamys varia -Demarq and Schoepfer, p. 23, pl. II, fig. 3.
1994 Chlamys (Chlamys) varia -Ben Moussa, p. 77, pl. 3, figs. 4, 5, 10, 11.
Studied material. Six disarticulated specimens, four left and two right valves, two bear encruster organisms, and two affected by bioerosion.
Description. All three individuals are small. Not equilateral. Both the anterior and posterior margins are almost straight; the anterior one is slightly curved close to the end of the margin. The external surfaces of the valve have 26 radial ribs rounded in section and with the same width as the interspaces. One of the three valves shows growth striae parallel to the ventral margin as secondary ornamentation. Two specimens show tile-like scales at the intersection of striae and ribs. For more descriptions see Jimenez et al. (2009).
Distribution. Jimenez et al. (2009) mention that the species is one of the most abundant pectinids in Pliocene deposits. It mostly occurs in medium- to coarse-grained sands, calcarenites-calcirudites, and occasionally in conglomerates.
Remarks. From six specimens, four valves are affected by taphonomic features. One of them is full of boreholes produced by boring Entobia sponges (Figure 6F), still showing the most characteristic features of the species. Overall, the two valves are well-preserved and show all characteristic features.
Genus PectenMuller, 1776
Pecten cf. subarcuatusHilber, 1879
1879 Pecten styriacus Hilber, p. 455, pl. 6, figs. 13-15.
1928 Pecten subarcuatus Tournouer. var. styriaca Kautsky, pl. 7, figs. 9-10.
1947 Pecten subarcuatus Tourn. var. styriaca -Sieber, p. 158
2001 Pecten subarcuatus styriacus -Schultz, p. 271, pl. 42, figs. 2-3.
Studied material. A disarticulated right valve, moderately preserved, with a broken right auricle.
Description. Small size, equilateral shell, very short hinge line, both the anterior and posterior margins are slightly curved; the external surfaces of the valve have 33 radial ribs. Growth striae parallel to the ventral margin as secondary ornamentation (Mandic, 2004).
Remark. Mandic (2004) reports this species from the late Burdigalian of the Suez region in NE Egypt, and Reuter et al. (2009) report it from the Oligo-Miocene, Qum formation, Iran.
Pecten aff. rotundatus, Lamarck, 1819
1918 Pecten rotundatus -Favre, pl. 5, fig. 14a-b, non fig. 15a-b.
1819 Pecten rotundatus- Natural history of animals without vertebrae, p. 179, pl. VI.
1880 Pecten rotundatus -Fontannes, p. 161, pl. V, fig. 1.
1897 Pecten rotundatus -Nicolas, p. 45.
1938 Pecten rotundatus -de Lapparent, p. 123, 125, 126, 128, 136.
2015 Pecten rotundatus var. dromica -Bongrain, pl. V, figs. 2 et 3
Figure 7 A-C. Pecten aff. rotundatus (Lamark, 1819); A. external view of undefined valve with broken auricular, B. Close-up view of Figure C, showing a colony of encrusting bryozoan (0-CLD); C. Close-up view of Figure A, showing anterior auricular is broken; D-E. Flabellipecten piramidesensis (Ihering, 1907); disarticulated, left valve; D. internal view; E. external view (3-PCD); F. Close-up of Figure E, represent by an encrusting colony of Cheilostomata bryozoan, Microporella berningi (Zágoršek, 2010); G. Chlamys varia (Linnaeus, 1758); disarticulated; external view of the right valve (10-CLD).
Studied material. An articulated specimen, moderately preserved, with a broken auricle.
Diagnosis. see (Fontannes, 1880).
Description. Equilateral, moderately large size shell, short hinge line, rib width almost 2 mm, interspace almost less than 1 mm, sinusoidal commissure, auricles broken.
Remark. Fontannes (1880) reported this species only once in his thesis from Burdigalin of Qum formation, Siyah kuh, Central Iran as Pecten rotundatus var. dromica and we never see it again in any reports from Iran or other parts of the world. He suggested that the species could have derived from any previous species, by having a more complete equilateral valve, the slightly wider apical angle, the less curved hinge near the ventral margin, and also the anterior auricle of the right valve less indented.
Genus FlabellipectenSacco, 1897
Flabellipecten piramidesensisIhering, 1907
(Figures 7D-E, 8A-B)
1907 Pecten oblongus pyramidesius Ihering, 375
1992 Flabellipecten piramidesensis Ihering-Del Río, p. 22, pl. 3, fig. 3, pl. 4, figs. 1- 4.
Figure 8 A-B. Flabellipecten piramidesensis (Ihering, 1907); disarticulated, left valve; A. external view; B. internal view (4-PCD); C. Close-up view of Figure A, represent by a colony of encrusting Cheilostomata bryozoan; D-F. Talochlamys articulata (Sowerby, 1840); disarticulated, broken Auricular, left valve; D. internal view; E. external view showing a fixed valve of an undefined bivalve from early ontogenetic stages, perforated by ichnospecies Oichnus cf. simplex (Bromley, 1981); F. Close-up view of Figure E, represent by Oichnus cf. simplex (5-CLD).
Studied material. Two left valves, both individually moderately well preserved, both specimens are disarticulated, external surfaces of both valves bear one or more colonies of Cheilostomata bryozoans as encrusting organisms.
Description. Shell small, attaining heights of 35 mm, thick, equilateral in outline and slightly shorter than high, left valve flat. The dorsal margin was straight. Anterior auricle covered with fine growth lines. Free margin sigmoidal in the plane of commissure. Byssal notch moderately deep. The posterior auricle sculptured with only fine growth lines and with free margin straight. The triangular resilial pit was very small and almost flattened. Left valve flat, concave near the umbonal area. Auricular margin straight. Disk sculptured with 23 to 26 equidistant, low, slightly rounded, wide plicae. Interspaces wider than plicae (Del Río, 1992).
Remarks. Del Río (1992) reported Flabellipecten piramidesensis from Miocene deposits of the Puerto Madryn Formation, Spain; and also, from Tertiary marine deposits of eastern Patagonia, Argentina (Del Río, 2004).
Genus TalochlamysIredale, 1929
Talochlamys articulataSowerby, 1840
*1840 Pecten articulatus Sowerby, pl. 25, fig. 15.
*1853 Pecten articulatus Sowerby -D’Archiac and Haime, p. 269-270, pl. 24, fig. 1.
*1901 Pecten kokenianus spec. nov., -Noetling, p. 117-121, pl. 4, figs. 2-6.
1916 Pecten (Chlamys) senatorius -Martin, p. 263.
1928 Pecten (Chlamys) articulatus -Vredenburg, p. 434.
1928 Chlamys Senatoria -Douglas, p. 2-4, pl. 8, figs.3-5.
1950 Chlamys senatoria -Eames, p. 145.
2011 Talochlamys articulata Sowerby -Kroh et al., p. 433-435, figs 11, 12.1-13.
Figure 6 A-B. Chlamys multistriata (Poli, 1795); disarticulated, left valve; A. internal view; B. external view (4-CLD); C. Pecten cf. subarcuatus (Hilber, 1879), disarticulated, broken Auricular, right valve, external view (5-PCD); D-E. Chlamys varia (Linnaeus, 1758); disarticulated, left valve; D. internal view; E. internal view (8-CLD); F. Close-up view of Figure E, represent by ichnospecie Entobia cf. ovula (Bromley and D’Alessandro, 1984); G-H. Chlamys varia (Linnaeus, 1758); disarticulated, left valve; G. internal view, not affected by post-mortem processes; H. internal view, shows a calcareous tube of polychaetae worm (7-CLD).
Studied material. One specimen, disarticulated, left valve, with broken auricular.
Description. Shell of medium size, moderately thick-walled, rounded in outline, somewhat higher than long, with about 26 prominent ribs fixed. The commissural line is wavy, triangular resilium, disc outline is equilateral to slightly inequilateral. The beak does not project over the hinge line. The anterior auricle is broken. Rib width and interspace width reflect the internal of the valve (Kroh et al., 2011).
Remark. This specimen is a sclerobiont of taphonomic features, like a borehole represented by Oichnus simplex (Bromley, 1981), see (Figure 8F), an undefined early-stage bivalve, fused on the external surface of the valve and an encrusting colony of bryozoans, indwelling internal side of the valve.
Genus ArgopectenMonterosato, 1889
Argopecten gratusDel Río, 1992
1989 Argopecten gratus Del Río, p. 246, pl. 1, fig. 7.
1992 Argopecten gratus Del Río- Del Río; p. 60, pl. 2, fig. 5; p. 61, pl. 3, fig. 7.
Figure 9 Argopecten gratus (Del Río, 1992); A. external view of the right valve, showing exterior of the shell is perforated by different type of bioerosion activities and a breakage around umbo. B. internal view of the right valve, bearing continued parts of bores, which are performed external of the valve or the whole thickness of the shell; C-D. Close-up view of Figures A and B, respectively, bearing a remain part of a Pholadid bivalve, producer of ichnogenus Gastrochaenolites, and Pouch-shaped bores refers to ichnogenus Rogerella (Saint-Seine, 1951), E-F. Close-up view of Figure A, exhibiting calcareous tubes of Polychaetae worm, Glomerula? sp. (Brünnich Nielsen, 1931), which are producers of ichnospecies Trypanites weisei and Maeandropolydora sulcans, respectively (D1-PC4).
Figure 10 Argopecten gratus (Del Río, 1992); A. external view of the right valve, bearing fixed valve of an Ostreid from early ontogenetic stages and a breakage near it; B. internal view of the right valve, showing the breakage and other parts of boreholes through the entire thickness of the studied shell C. Close-up view of Figure A, showing ichnogenus Maeandropolydora; D. Close-up view of Figure A, exhibiting ichnogenus Entobia cateniformis (Bromley and D’Alessandro, 1984); E. Close-up view of Figure F, exhibiting ichnogenus Trypanites weisei (Magdefrau, 1932), and Rogerella isp., F. Close-up view of Figure A, showing the fixed valve of a juvenile Ostreid, which is attached to the shell of Argopecten gratus (D1-PC8).
Figure 11 Argopecten gratus (Del Río, 1992); A. internal view of the right valve, showing the shell is broken, perforated, and also bears a fused undefined valve from early ontogenetic stages of bivalves; B. external view of the right valve, showing the studied valve is almost a heavily used shell; C. Close-up view of Figure A, showing a remain of calcareous tubes of worms produced by the ichnogenus Maeandropolydora; D. Close-up view of Figure B, exhibiting different ichnogenera such as Gastrochaenolites cluniformis (Kelly and Bromley, 1984), Trypanites weisei, Renichnus aff. arcuatus (Mayoral, 1987), and Maeandropolydora sulcans; E-F: Close-up views of Figure A, present by a Cheilostomata Bryozoan as an encruster fauna, with a rhomboidal colony (D1-PC14).
Studied material. Altogether 13 specimens were studied, all are disarticulated right or left valves, moderately well to weakly preserved. Internal and external surface of the valves affected by taphonomic features.
Description. Shell of medium size, longer than high, lightly inflated right valves. Apical angle obtuse. The auricular margin and dorsal margin of the disk are straight. The margin and dorsal margin of the disk are straight. All three right valves show anterior auricle longer than posterior, covered with 7 wide and distinct riblets and growth. Byssal notch triangular. All three valves show sculptured posterior auricle with 11 or 12 fine riblets. The resilial pit is shallow, higher than long (Del Río, 1992).
Remarks. Almost all samples affected by taphonomic features, and valves are perforated by trace fossils like Entobia cateniformis (Bromley and D’Alessandro, 1984), Trypanites weisei (Magdefrau, 1932), Rogerella isp (Saint-Seine, 1951), Renichnus aff. arcuatus (Mayoral, 1987), Gastrochaenolites cluniformis (Kelly and Bromley, 1984), Maeandropolydora sulcans (Bromley, 1981), and overlayed by Cheilostomata bryozoans, undefined bivalves from early ontogenetic stages or polychaetae worms (Figures 9-11).
4.2. THE CRUSTACEANS OSTRACODA
The systematic arrangement of described Ostracoda follows Khalaf (1984; 1988) and the papers of Hawramy and Khalaf (2013), Gammudi and Keen (1993), Sciuto (2014), and Forel (2021).
Class Ostracoda Latreille, 1806
Order Podocopida Sars, 1866
Suborder Cytherocopina Grundel, 1967
Superfamily Cytheroidea Baird, 1850
Family Trachyleberididae Sylvester-Bradley, 1948
Subfamily Trachyleberidinae Sylvester-Bradley, 1948
Genus AlocopocythereSiddiqui, 1971
Alocopocythere kendengensisKingma, 1948
2021 Alocopocythere kendengensis Kingma - Forel, p. 4, figs. 4 T, U, 5A.
Figure 12 A-E. Alocopocythere kendengensis (Kingma, 1948); A-B. Dorsal views of two complete carapaces, from Star Valley section (S.Ost.Cc.Msh.Fm.1) and Kendaloo section (K.Ost.Cc.Msh.Fm.2), respectively; C. Internal view of a left valve (K.Ost.LV.Msh.Fm.3); D. Lateral view of a left valve (D.LV.Ost.Msh.Fm.4); E. Right lateral view of a complete carapace (B.Ost.Cc.Gsh.M.5); F-J. Actinocythereis iraqensis (Khalaf, 1982a); F. Dorsal view of the complete carapace (B.Ost.Cc.Gsh.M.6); G. Internal view of a right valve (S.Ost.RV.Msh.Fm .7); H. Lateral view of a left valve (S.Ost.LV.Msh.Fm.8); I. Lateral view of a left valve (K.Ost.LV.Msh.Fm.9); J. Internal view of a left valve (K.Ost. LV.Msh.Fm.10); K-M. Loxoconcha (Loxoconcha) hamrinensis (Khalaf, 1998); K. Dorsal view of a complete carapace (S.Ost.Cc.Msh.Fm.11); L. Left lateral view of a complete carapace (D.Cc.Ost.Msh.Fm.12); M. Right lateral view of a complete carapace (B.Ost.Cc.Gsh.M.13).
Studied material. Five specimens were studied, 4 carapaces, and one valve. One carapace and one valve are from Kendaloo, and others are from Direstan, Star Valley, Bemani sections.
Diagnosis. see (Forel, 2021).
Distribution and Occurrence. Recent (Forel, 2021; Kingma, 1948; Dewi, 1993; Fauzielly et al., 2013). Pliocene of China (Guan et al., 1978), for more see (Forel, 2021). In the present study, Mid-late Miocene of Mishan Formation, Qeshm Island, Zagros Basin, and also, Mio-Pliocene of Minab region, Makran Basin, southern Iran.
Genus Actinocythereis Puri, 1953
Actinocythereis iraqensis Khalaf, 1982a
(Figures 12F-J) 1982a Actinocythereis iraqensis Khalaf, Stero-Atlas 9(9) 51-54.
2013 Actinocythereis iraqensis Khalaf- Hawramy and Khalaf, p. 71, pl. 2, figs. 1,2.
Studied material. Seven specimens were studied, one carapace and one valve from Star Valley; one carapace and one valve from Kendaloo, and also three carapaces were studied from the Bemani section.
Diagnosis. see (Khalaf, 1982a; Hawramy and Khalaf, 2013).
Distribution and Occurrence. According to Hawramy and Khalaf (2013), the species was found only in Mid-Late Miocene of Iraq, and now we found and collected this species from Mid-Late Miocene strata of Mishan formation in Qeshm Island, Zagros Basin, and also, from Mio-Pliocene strata of Minab region, Makran Basin, southern Iran.
Genus Hermanites Puri, 1955
Hermanites transversicostataKhalaf, 1982b
1982b Hermanites transversicostata Khalaf- Stero-Atlas of Ostracoda Shells, 9(11), 59-62. 2013 Hermanites transversicostata Khalaf- Hawramy and Khalaf p. 71, pl. 2, figs. 15-18.
Figure 13 A-C. Neomonoceratina iniqua (Brady, 1868); A. Left lateral view of a complete carapace (B.Ost.Cc.Gsh.M.14); B. Right lateral view of a complete carapace (D.Ost.Cc.Msh.F. 15); C. Ventral view of a complete carapace (K.Ost.Cc.Msh.F.16); D-F. Bairdoppilata triangulate (Edwards, 1944); D. Dorsal view of a complete carapace (S.Ost.Cc.Msh.Fm.17); E. Right lateral view of a complete carapace (S.Ost.Cc.Msh. Fm.18); F. Right lateral view of a complete carapace (S.Ost.Cc.Msh.Fm.19); G-J. Hermanites transversicoststs (Khalaf, 1982a); G. Left lateral view of a complete carapace (K.Ost.Cc.Msh.Fm.20); H. Dorsal view of a complete carapace (B.Ost.Cc.Gsh.M.21); I. Right lateral view of a complete carapace (S.Ost.Cc.Msh.Fm.22); J. Internal view of a left valve (D.Ost.LV.Msh.F.23); K. Costa (Cuneocosta) cf. tricostata pliocenica (Ruggieri, 1992); Right lateral view of a complete carapace (B.Ost.Cc.Gsh.M.24); L-N. Cytherelloidea hamrinensis (Khalaf, 1993); L. Dorsal view of a complete carapace (B.Ost.Cc.Gsh.M.25); M. Right lateral view of a complete carapace (D.Ost.LV.Msh.F.26); N. Left lateral view of a complete carapace (S.Ost.Cc.Msh.Fm. 27).
Studied material. Four specimens were studied, three are carapaces and one valve. The valve is from Kendaloo, one carapace Star Valley, one from Bemani and also, one from Direstan section. Diagnosis: see (Khalaf, 1982b; Hawramy and Khalaf, 2013).
Distribution and Occurrence. Mid-late Miocene of Qeshm Island and Mio-Pliocene of Minab region, southern Iran (present study). Midlate Miocene of Iraq.
Genus CostaNeviani, 1928
Subgenus CuneocostaRuggieri, 1992
Costa (Cuneocosta) cf. tricostata pliocenicaRuggieri, 1992
1992 Costa (Cuneocosta) tricostata pliocenica Ruggieri, p. 177-178, fig. 6;
2000 Costa (Cuneocosta) tricostata pliocenica Ruggieri- Aiello et al., p. 102, pl. 5, fig. 2;
2003 Costa tricostata pliocenica Ruggieri-Sciuto, p. 181, pl. 1, fig. 2f.
Studied material. four carapaces, from the Bemani section.
Diagnosis. see (Sciuto, 2014).
Distribution and occurrence. According to Ruggieri (1992), Costa (Cuneocosta) tricostata pliocenica is referred to bathyal environments. The species is known from Early Pliocene (Ruggieri, 1992) to Early Pleistocene (Aiello et al., 2000). Also, Sciuto (2014) reported the species from Upper Pliocene layers of Punta Mazza, Italy. From southern Iran, the species was found and recorded from Mio-Pliocene marly strata of Bemani section, Minab region, Makran Basin.
Family Loxoconchidae Sars, 1925
Subfamily Loxoconchinae Sars, 1825
Genus LoxoconchaSars, 1866
Loxoconcha (Loxoconcha) hamrinensisKhalaf, 1998
(Figures 12K-M) 1998 Loxoconcha (Loxoconcha) hamrinensis Khalaf- p. 2, pl. 1, figs. 1,2,4,5.
2013 Loxoconcha (Loxoconcha) hamrinensis Khalaf- Hawramy and Khalaf, p. 71, pl. 2, figs. 22-24.
Studied material. Four specimens were studied, all carapaces, one from Kendaloo, one Star Valley, one Bemani, and one from Direstan section.
Diagnosis. see (Khalaf, 1998; Hawramy and Khalaf, 2013).
Distribution and Occurrence. According to Hawramy and Khalaf (2013), the species was reported only in Mid-Late Miocene of Iraq, and in this study, they were collected from Mid-Late Miocene strata of Mishan formation, Qeshm Island, Zagros Basin.
Family Schizocytheridae Howe in Moore, 1961
Subfamily Schizocytherinae Mandelstam, 1960
Genus NeomonoceratinaKingma, 1948
Neomonoceratina iniquaBrady, 1868a
2021 Neomonoceratina iniqua Brady- Forel, p. 4, figs. 4D, E
Studied material. Four specimens were studied, all are carapaces, one from Kendaloo, one Star Valley, one Bemani, and one from Direstan section.
Diagnosis. see (Forel, 2021).
Distribution and Occurrence. Mid-late Miocene of Qeshm Island, southern Iran (present study); Recent (Forel, 2021); Holocene of Iraq (Al-Jumaily and Al-Sheikhly, 1999); Pliocene-Pleistocene of India (Guha, 1968); Persian Gulf (e.g., Mostafawi et al., 2010); Middle Miocene, Late Pliocene-Pleistocene of Japan (Nohara, 1987); for more see (Forel, 2021; Al-Jumaily and Al-Sheikhly, 1999).
Superfamily Bairdiacea Sars, 1888
Family Bairdiidae Sars, 1888
Genus BairdoppilataCoryell, Sample and Jennings, 1935
Bairdoppilata triangulataEdwards, 1944
1944 Bairdoppilata triangulata Edwards, p. 507, pl. 85, figs. 5, 6.
1954, Bairdoppilata triangulata Edwards - Puri, p. 223, pl. 1, figs. 3, 4; text figs. 1a, b.
1974 Bairdoppilata triangulata Edwards- Swain, p. 53, pl.1, figs. 2a, b; text figs 2, 3.
1993 Bairdoppilata triangulata Edwards- Gammudi and Keen, p. 123, pl. 1, fig. 1.
2011 Bairdoppilata triangulata Edwards - Ceolin et al., p. 115, figs. 3q-p.
Studied material. Three specimens were studied, one carapace and one valve from Star Valley section and one carapace from Kendaloo section.
Diagnosis. see (Swain, 1974; Gammudi and Keen, 1993).
Distribution and Occurrence. Mid-Late Miocene of Qeshm Island, south of Iran (present study), Late Miocene of Atlantic Coast region (Pliocene, Swain, 1968; Hazel, 1971), mid-Late Miocene of Florida (Puri, 1954); Recent (Benson and Coleman, 1963; Swain, 1974).
Family Cytherellidae Sars, 1866
Genus CytherelloideaAlexander, 1929
Cytherelloidea hamrinensisKhalaf, 1993
1993a Cytherelloidea hamrinensis Khalaf, Iraq. Geol. Jour. 26(3), pp. 184-186, pl. 3, figs. 1-4.
2013 Cytherelloidea hamrinensis Khalaf- Hawramy and Khalaf, p. 70, pl. 1, figs. 5,6.
Studied material. Three specimens, all are carapaces, one carapace from Star Valley, one from Bemani and one from Direstan section.
Diagnosis. see (Khalaf, 1993; Hawramy and Khalaf, 2013).
Distribution and Occurrence. Mid-Late Miocene of Qeshm Island and Mio-Pliocene of Minab region, southern Iran (present study). Mid- late Miocene of Iraq.
4.3. ENCRUSTER ORGANISMS
The systematics of described Cheilostomat bryozoans takes into consideration the books of Bassler (1953) and Zágoršek (2010).
Phylum Bryozoa Ehrenberg, 1831
Class Gymnolaemata Allman, 1896
Order Cheilostomata Busk, 1852
Suborder Ascophora Levinsen, 1909
Infraorder Acanthostega Levinden, 1902
Family Microporellidae Hincks, 1879
Genus Microporella Hincks, 1877
Description. Encrusting colony. Aperture semilunar, ascopore very distinct at the top of a short umbo. Frontal wall porous. Oral spines present. Avicularia adventitious, with a pivotal bar. Ovicell prominent, slightly immersed, or recumbent.
Microporella berningiZágoršek, 2010
Non 1999 Microporella appendiculata Heller - Hayward and Ryland, p. 294, figs. 134,135.
2006 Microporella aff. appendiculata Heller - Berning, p. 103, fig. 13.
2010 Microporella berningi Zágoršek -Zágoršek Pl. 116, figs. 1-5.
Studied material. One encrusting colony, indwelling on the external side of the left valve of a pectinid specie, Flabellipecten piramidesensis (Ihering, 1907), collected from Direstan outcrop, Mishan Formation, Qeshm Island, Persian Gulf, Southern Iran.
Diagnosis. See Zágoršek (2010).
Remarks. The preserved colony is well-preserved and shows all characteristic features of the species.
Distribution and Occurrence. Mid-Late strata of Mishan Formation, Zagros Basin (present study); Langhian, Miocene of Czech Republic (Zágoršek, 2010).
5. Conclusions
This study identified and described nine Ostracods species belonging to nine genera and five families from thirty-four Ostracoda specimens. Also, this study identified and described eight bivalve species belonging to the five genera of one family Pectinidae (overall forty-nine bivalve specimens). Only one encrusting bryozoan was identified and described, Microporella berningi (Zagorsek, 2010), from the Langian stage of Middle Miocene for carbonate strata of Mishan Formation, near Direstan village, Qeshm Island, southern Iran. Several ostracod species collected from four outcrops were studied in this paper, reported as Mediterranean-Indopacific-Tethyan realm fauna of the Middle Miocene of the region.
Rögl (1997), suggested that in southern Iran including Qeshm Island and Minab region a Tethyan seaway basin existed during the Oligo-Miocene. Overall, some of the native ostracod species in this study were reported from the Fat’ha Formation of Iraq as Middle Miocene Ostracoda from Northern Iraq (Khalaf, 1984, 1988, 1993, 1998; Hawramy and Khalaf, 2013), before, which Hawramy and Khalaf (2013) believed they represented intermediate bioprovences zone between Mediterranean and Indopacific. They concluded that the region paleoenvironmentally was a shallow basin similar to a Lagoonal environment with salinity fluctuations.
Hawramy and Khalaf (2013), reported the presence of the genus Cytherelloidea indicating that the Middle Miocene Sea of Iraq was a warm temperature environment. Additionally, Al-Shareefi et al. (2022), reported some ostracod species like Actinocythereis iraqensis (Khalaf, 1982a) and Hermanites transversicostata (Khalaf, 1982b) from the Fat’ha Formation of Iraq, vary from normal salinity to brackish and saline environments, with the shallow lagoonal environment and sometimes deep lagoonal environment that do not exceed the margin of shelf zone. Moreover, Mohammadi and Hassani (2021), reported Bairdia rafidainensis (Khalaf, 1984) from Rupelian of Qom Formation (Central Iran) and mentioned that this genus is adaptable to diverse environments with finegrained sandstones, rich in nutrients, and maximum flourish usually occurs in medium depth.
