The Miocene (Burdigalian) lepidocyclinids and

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Palaeontographica, Abt. A: Palaeozoology – Stratigraphy Vol. 312, Issues 1–4: 1–15 Stuttgart, August 2018

Article

The Miocene (Burdigalian) lepidocyclinids and miogypsinids of Channa Kodi, Padappakkara, Kerala, Southern India by

Antonino Briguglio with 2 text-figures and 3 plates Abstract A well preserved miogypsinids and lepidocyclinids assemblage collected from the fossiliferous Quilon Beds in SW India (Padappakkara locality) is here illustrated and discussed. This assemblage is composed by two species of miogypsinids (Miogypsina globulina and Lepidosemicyclina thecideaeformis) and two species of lepidocyclinids (Nephrolepidina chavarana and Nephrolepidina sumatrensis). Forty-one specimens of miogypsinids have been investigated by computed tomography: this allowed the measurements of a number of biometric parameters obtained on equatorial and axial sections of the specimens as well as abundant information on the ontogenetic changes of the chamber morphology which is of pivotal importance to differentiate the genera Miogypsina from Lepidosemicyclina. Especially for primitive stages of Lepidosemicyclina, the differentiation between these two genera can be rather difficult but the CT scans here obtained help in making a clear separation. Additionally, the complete test geometry in both equatorial and axial sections is displayed for agamonts of both miogypsinids, which are very rare for the Indian taxa. The results from this work point to a clear Burdigalian assemblage with some biometric characteristics such as the reduction of the proloculus size which is relatively common evidence in all Indo-Pacific miogypsinids fauna so far investigated. Keywords: Larger Foraminifera, biometry, computed tomography, Miocene, India

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1. Biometry on miogypsinids and lepidocyclinids . . . 1.2. Previous studies on indian miogypsinids . . . . . . . . . 2. Materials and methods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3. Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Contents 1 4. Systematic palaeontology . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 5. Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 6. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Acknowledgements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1. Introduction The first published research on the palaeontological composition of the Quilon Beds with focus on its larger foraminifera content is by Jacob & Sastri (1950). In this study, they investigated a sample collected at Chavara near Quilon situated in the extreme southwest coast of India forming part of the Kerala State. The fauna investigated is mainly composed by Larger Benthic Foraminifera (LBF) including operculinids, gypsinids and lepidocyclinids. Rasheed &

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Ramachandran (1978) also investigated the foraminifera from the Quilon beds and described more taxa including miogypsinids and planktonic foraminifera. The most recent description of the Quilon beds is compiled by Reuter et al. (2010), where solid biostratigraphic and palaeoecological data are presented and discussed, the samples used have been further investigated and Rögl & Briguglio (2018) listed all small benthic foraminifera recovered from it, Bri-

Author’s address: Antonio Briguglio, DI.S.T.A.V. – Dipartimento di Scienze della Terra, dell’Ambiente e della Vita, Università degli Studi di Genova, Corso Europa 26, 16132 Genova, Italy, e-mail: [email protected] © 2018 E. Schweizerbart’sche Verlagsbuchhandlung, Stuttgart, Germany

www.schweizerbart.de

DOI: 10.1127/pala/2018/0078

0375-0442/2018/0078

$ 6.75

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guglio & Rögl (2018) investigated all the operculinids, and Briguglio et al. (2018) collated all available information revealing new aspects concerning the palaeoenvironment and the biostratigraphy of the investigated deposit. In this work, only the miogypsinids and lepidocyclinids are illustrated and discussed. 1.1 Biometry in miogypsinids and lepidocyclinids

The most important biometric parameters to be measured in a miogypsinid population have been firstly introduced by Drooger (1952) who applied the population concept to his analysis, which is currently used in most recent papers. Such an approach consists in measuring 5 parameters on the axial sections of the tests, such parameters are: the medium cross diameter of both the embryonic chambers proloculus (P) and deuteroloculus (D), the total number of post embryonic spiral chambers (X) to be counted on the longest spiral, the orientation of the nepiont (angle γ) and the symmetry index of the two protochonchal spirals (V) which is measured as the result of the calculation 200 x (α/β) (Text-fig. 1). For lepidocylcinids, the most used biometric parameters are those proposed by Drogger (1993) based on population level. The same approach is here used to classify the specimens investigated. 1.2 Previous studies on Indian miogypsinids and lepidocyclinids

While there is relatively recent abundant literature and biometric data on Mediterranean and Tethyan miogypsinids (e.g., Cahuzac & Poignant 1997, Özcan et al. 2009a, b), taxonomic lists for the American (e.g., Boudagher-Fadel & Price 2010a) and indo-pacific provinces (e.g., Renema 2007) are relatively scarce. The most complete work on Indian miogypsinids is definitely the one by Raju (1974) and later updated by Raju & Mishra (1991) and Mishra (1996), but there are several other more specific papers which provide a quite complete overview even if in most cases their taxonomic and stratigraphic interpretation diverge. The best example is by Mohan (1958), who described several species of both Miogypsina and Lepidosemicyclina but he provides very little information on the stratigraphic position of his samples, furthermore, he managed to measure only few parameters on each specimens and in most cases of relatively low importance such as shell diameter and thickness instead of parameters measured on the internal structure as it

was common practise since the beginning of the 1950. However, he abundantly discussed the details of the ontogenetic variation of the chamberlets as a taxonomic valid character as proposed by Tan (1936). He recognized that for Indian miogypsinids there is a variation which can be easily used to differentiate different species within the genus Miogypsina and Lepidosemicyclina. Specifically, he recognized that different species of Miogypsina can develop from arcuate to ogival chambers in equatorial view, while other species develop from arcuate to isodiametric-rhombic chambers. For Lepidosemicyclina he recognized that in the most advanced growth stage, the species develop either isodiametric-hexagonal chambers (L. thecideaeformis) or elongated hexagonal ones (L. droogeri). He further observed that for Indian miogypsinids, the best parameters to discriminate the species are the V value and the γ angle beside the ontogenetic variation of the equatorial chambers morphology. Furthermore, he recognized that test size does not change among species and cannot be considered diagnostic not even when correlated with nepiont size, and the external ornamentation, which he also considered as a gerontic feature, does not serve in differentiating the species. In agreement with Tan (1936), he recognized that in Indian miogypsinids, the nepionic acceleration serves well to delimit the different species along a stratigraphic continuum within the Oligocene to Miocene successions. Little more information is added by Drooger & Raju (1973) when comparing the Tethyan evolution of the forms and the Indo-Pacific one. While the generic trends are very similar and an eastward trend is visible, high latitude assemblages tend to have greater mean proloculus diameters than assemblages of the same species closer to the equator (Drooger & Raju 1973). Amount of illumination and photosynthesis was considered as a possible explanation for this evidence but since these taxa live in the photic zone and sediment can be a shelter from light and energy, this explanation does not seem to be sufficient. However, the most complete summary on Indo-Pacific miogypsinids remains the book by Drooger (1993) in which the evolutionary lineages are reported and the proposed biometric boundaries are here used for species identifications. Concerning the lepidocyclinids, there is comparatively much less literature available and the most important works published so far are those by Drooger

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The Miocene (Burdigalian) lepidocyclinids and miogypsinids

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Text-fig. 1. 1: schematic drawing with the most important biometric parameters measured on equatorial section of the investigated miogypsinids (P: proloculus diameter, D: deuteroloculus diameter, X: number of single stolon chambers of the longest spire including the Principal Auxiliary Chamber here all signed by the symbol *, γ: embryonic angle, α and β: length of the angles to be measured to get the symmetric index of the two protoconchal spirals V, 2: clear differentiation between the two investigated miogypsinids based on the P vs. V diagram, 2: clear differentiation between the two investigated miogypsinids based on the P vs. D diagram, 4: all measured parameters for both population of miogypsinids here investigated.

(1993), Özcan & Less (2009), Van Vessem (1978) and Boudagher-Fadel & Price (2010). It seems that there is a consensus in identifying clear lineages spreading from the Caribbean to the Tethyan and the Indo-Pacific provinces, for the realm here investigated the lepidocyclinids increase trough time the number of their adauxiliary chamberlets and the embryonic embracement ratio (sensu Özcan & Less 2009).

2. Materials and Methods The material used in this study has been selected from the sands of bed number 1 in Reuter et al. (2010, fig. 2) below the famous Quilon Limestone of India (Padappakkara locality). For this study, 41 specimens of miogypsinids have been selected from the entire sample based on their external appearance and preservation state: only the most complete and best preserved have been chosen. Additionally, few specimens belonging to the lepidocyclinids have also been

scanned but from only in three of them the embryo was completely visible and the biometric parameters have been measured. All of them have been scanned by micro Computed Tomography (CT) at the Institute of Palaeontology, University of Vienna. The possibility to investigate foraminifera by means of CT enables the observation of internal and external structures, their quantification and their 3-dimentional rendering avoiding specimen destruction by sectioning or polishing procedures. There are a number of studies which describe how to obtain high-quality CT scans from fossil (Speijer et al. 2008, Görög et al. 2012, Benedetti & Briguglio 2012, KĘdzierski et al. 2015) and how to use them for biometric purposes (Briguglio et al. 2011, 2013, 2016, Ferrandez Canadell et al. 2014, Briguglio & Hohenegger 2014, Hohenegger & Briguglio 2012, Eder et al. 2016). Concerning the material studied here, for each specimen perfectly centered equatorial and axial sec-

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tions have been obtained by letting them run through the coiling axis and by following the equatorial plane as precise as possible. This procedure allows the visualization of the entire ontogenetic development of the test by showing the morphology of all chambers from the nepiont to the last calcified chamber. This information is very important to discriminate among some miogypsinids at genus and species level. All parameters measured in the investigated specimens have been taken using CT sections.

3. Results Two species of miogypsinids and two lepidocyclinids have been identified, respectively Miogypsina globulina, Lepidosemicyclina thecideaeformis and Nephrolepidina chavarana and N. sumatrensis. The biometric measurements made on the miogypsinids are reported in Text-fig. 1 where the most important taxonomy-related parameters are given for the investigated population. For the two specimens of N. chavarana and the one specimen of N. sumatrensis, the values are directly reported in their respective species description.

4. Systematic palaeontology Family Miogypsinidae Vaughan, 1928 Genus Miogypsina Sacco, 1893 Type species: Nummulina globulina Michelotti 1841 Morphology: The embryo is eccentric, near the apex, no canal system is present. Test is subcircular to triangular in outline, no equatorial chambers between the nepiont and the marginal fringe but it is followed by two unequal sets of coiling chambers, the larger set is equal in size to the secondary spirals and the other somewhat smaller, equatorial chambers spatulate, ogival, or rhombic and arranged in concentric circles, hexagonal ones if present are confined to the frontal margins of large specimens only. Stratigraphic distribution: Early Oligocene (late P20) to Early Miocene (Burdigalian, early N8) in the Americas (see Boudagher-Fadel & Price 2010a), late Oligocene (Chattian, P22) in the Mediterranean, and Early Miocene (Aquitanian, N4) in the Indo-Pacific, to Middle Miocene (Langhian, N8) in the Mediterranean and (Middle Serravallian, N13) in the Indo-Pacific province (Boudagher, Fadel & Price 2013) . In the circum Mediterranean region, long-spiralled primitive Miogypsina species such as M. septentrionalis and M. basraensis are typically from the latest Chattian, whereas M. gunteri and M. tani are common successive Aquitanian species, and M. globulina, M. intermedia, M. cushmani and

M. mediterranea cover the evolution of the lineage during the Burdigalian (Drooger 1993).

Species Miogypsina globulina (Michelotti) (Plate 1, Figs 1–12) 1841 Nummulites globulina Michelotti, 1841 – Michelotti, p. 297, pl. 3, fig. 6 1841 Nummulites irregularis Michelotti, 1841 – Michelotti, p. 297, pl. 3, fig. 5 1952 Miogypsina irregularis (Michelotti) – Drooger, pp. 54 – 55, pl .2, figs. 25 – 29 1973 Miogypsina japonica (Ujie), p. 116, pl. 2, figs 1– 5 2008 Miogypsina globulina (Michelotti, 1841) – Boudagher-Fadel, p. 485, fig. 20 Morphology: Miogypsina with a biometric factor V between 17 and 56 with an average of 33. In the diagnosis by Drooger (1993), the factor V for this species is limited to 0 – 45. The protoconch is globular and relatively small of 72 –127 μm in diameter (93 μm in average) followed by a similar sized deuteroconch and two principal auxiliary chambers of unequal size. The main protoconchal spiral is composed of four to six spiral nepionic chambers and it is always easily distinguishable. The equatorial chambers are ogival and rhombic in shape with curved edges. The orientation of the nepiont is always positive. In axial section it is characterized by a centrally inflated structure where pillars are always present in number of 2 to 4 per side. Such pillars can have different thickness and depending on their position can or cannot be present on the true axial section. Some specimens are characterized by gently thinner test and thinner but evenly distributed pillars. From the external shape they could be identified as M. nipponica (Matsumaru, 1980), which is considered to be a younger synonym of M. antillea (Cushman) but on their equatorial layer they still display the well known M. globulina V value and therefore have been here grouped within this taxon. However, similar values are also common for the much rarer M. borneensis (Tan Sin Hok, 1936), which, according to the description by Cole (1954) and Matsumaru et al. (2010) can have larger proloculus and slightly higher X values (up to 8) and therefore might be considered as a senior synonym for M. tani (Drooger, 1952). Among the specimens here observed, there is none that fulfils all these requirements and the available illustrated material comes from poorly preserved specimens and further analogies cannot be done.

Genus Lepidosemicyclina Rutten 1911 Type species: Orbitoides (Lepidosemicyclina) thecideaeformis Rutten, 1911. A roughly circular test, with an embryonic apparatus made of a spherical protoconch and a relatively large reniform deuteroconch, which has a tendency to become more enlarged in most advanced forms. Two sets of planispiral periembryonic chambers surround the embryo: a larger primary spiral and a small unequal secondary spiral. The equatorial chamberlets are at first ogival, then rhombic and finally distinctly hexagonal. Early Miocene (Burdigalian, N4 –N8) in the Indo-Pacific.

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Lepidosemicyclina thecideaeformis (Rutten, 1911)

Family Lepidocyclinidae Scheffen, 1932

(Plate 2, Figs 1–17, Text-fig. 2)

Genus Nephrolepidina Douville, 1911 Type species: Nummulites marginata Michelotti, 1941 Morphology: Megalospheric generation with complex embryonic apparatus made by proloculus surrounded (partially or completely) by the reniform deuteroloculus. Principal auxiliary chambers and accessory auxiliary chambers are diagnostic for the species and they increase their number from older to younger sediments. The embryonic apparatus is located at the centre of the equatorial layer and the successive chambers are arcuate and connected with a complex system of stolones. Lateral chamberlets are displaced on both sides of the equatorial layer.

1911 Orbitoides (Lepidosemicyclina) thecideaeformis Rutten – Rutten, pp. 1157–1158 1974 Miogypsina (Lepidosemicyclina) thecideaeformis (Rutten) – Raju, pp. 84 – 85, pl. 6, figs. 2 – 4 2008 Lepidosemicyclina thecideaeformis (Rutten), BouDagher – Fadel, p. 445, pl. 7.12, fig. 8 Morphology: Embryonic chambers consist of protoconch and deuteroconch and are followed by two principal auxiliary chambers of unequal size with biometric factors V ranging from 45 –70. Equatorial chambers are ogival, rhombic and short hexagonal in shape, lateral chambers are well developed and occur in regular tiers between thin pillars. Test large, somewhat irregularly flabelliform and fan shaped in outline and mostly parallel in axial view. The proloculus is relatively large with an average of almost 140 μm in diameter and a much larger reniform deuteroloculus that can read 240 μm in maximum length. The V value is in this population comprehended between 38 and 77 which is slightly higher than the standard recorded for the species and plots between it and the consequent taxon L. droogeri (Raju, 1974). However, this population is much closer to L. thecideaeformis than to L. droogeri. The last row of chambers in the majority of the specimens shows the characteristic hexagonal shape which is typical of the species but some specimens still show only what could be described as an elongated hexagonal shape which, according to Mohan (1958) can be diagnostic for the species L. polymorpha and L. droogeri. However, the embryonic apparatus is rather diagnostic for the species and therefore we consider it as L. thecideaeformis.

Text-Fig. 2. Equatorial and axial CT sections of an agamont of Lepidosemicylcina thecideaeformis with typical isodiametric hexagonal chambers at the adult stage, specimens LTpop16, scale bar 500 μm.

Nephrolepidina chavarana ( Jacob & Sastri, 1950) (Plate 3, Figs 1– 5) 1950 Lepidocyclina (Nephrolepidina) chavarana, Jacob & Sastri, p. 354, fig. 9a, b, 12a, b

Test thick and somehow cube shaped. The equatorial layer is saddle shape thus creating the characteristic 4 thin rays if seen trough the equatorial section. Such layer is very gentle curved and rounded at the periphery which creates symmetric depressions which are filled symmetrically with the lateral chamberlets, thus creating the cubic geometry. The embryo is nephrolepidinid with a tendency to isolepidinid. Pillars are not present along the lateral chamberlets. In the two investigated specimens the proloculus diameter measures 176 and 207 μm and the deuteroloculus measures 239 and 332 μm. The degree of embracement of the proloculus by the deuteroloculs measures 40 and 47 in our two specimens respectively and their number of adauxiliary chamberlets is 3. According to the description made by the Authors describing the holotype, the measurements here obtained are very similar to the reported values (P: 0.25 mm and D: 0.40 mm) of the holotype but they did not provide the embracement value which is also very difficult to obtain looking at the section they provided, similar problems occur considering the number of adauxiliary chambers. However, the biometric values measured on the investigated specimens closely resemble those proposed for N. sumatrensis which is characterized by embracement value comprised between 40 and 52.5 and number of adauxiliary chamberlets lower than 3.75 (Van Vessem 1978). The very typical geometric construction of the equatorial layer is here considered as a specific character and therefore the specimens here reported are assigned to the species N. chavarana and not N. sumatrensis. Additionally, it is very diffi-

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cult to assign the values of so few indiduals to a specfic taxon because the biometric approach here used (as suggested by Drogger 1952) only considers averages of population studies, which are here not available at this stage. Nephrolepidina sumatrensis Brady, 1875 (Plate 3, Figs 6 – 8) 1875 Orbitoides sumatrensis, Brady, p. 536, pl. 14, figs. 3a–b 1978 Lepidocyclina sumatrensis (Brady), Van Vessem, pp. 126 –127, pl. 1, fig. 3 2009 Nephrolepidina sumatrensis (Brady) Özcan & Less, pl. 1, Figs. 1– 23

Nephrolepidina with embracement value comprised between 40 and 52.5, less than 3.75 adauxiliary chamberlets and lenticular in shape. Equatorial layer mostly flat or very gently curved. The specimen here displayed has a proloculus diameter of 203 μm and a deuteroloculus diameter of 353 μm. The biometric parameters are identical with those of N. chavarana but the general shape and geometry of this specimen is very different. N. sumatrensis has been intensively discussed by Van Vessem (1978) and it is consider belonging into the well established lineage of the Indo-Pacific lepidocyclinds (L. isolepidinoides – L. sumatrensis – L. angulosa – L. martini – L. rutteni) and it marks the Burdigalian.

5. Discussion The fauna here presented belongs to the Middle Burdigalian as indicated by nannofossil association (Briguglio et al. 2018). This information is further supported by a number of studies on larger benthic foraminifera in the eastern part of the Tethyan ocean where the lineages of both Miogypsina and Lepidosemicyclina have been observed and their stratigraphic distribution recorded. However, most of such biostratigraphic studies deal with central Tethyan or European material and they provide extensive and precise information, they can hardly be directly correlated with eastern Tethyan and western Indo-Pacific faunal provinces. Nonetheless, there have been a number of studies which are trying to create large correlations trough time and space especially in the shallow benthic zonation and some results are available especially concerning the miogypsinids (Özcan & Less 2009, Boudagher-Fadel & Price 2010a, 2013) and the lepidocylcinids (Boudagher-Fadel & Price 2010b). A comprehensive

summary of the latest studies on this concern has been published by Renema (2007). Biostratigraphic correlations in shallow waters are very important as they can reveal migrations, evolutionary tendencies and separated extinctions. Especially for the Neogene, lineages have been used to correlate different bioprovinces and to establish circum-tropical relation. The occurrence of a wellknown Tethyan miogypsinid in this Indian assemblage (M. globulina) testify the fact that such species had the possibility to migrate and occupy a large variety of niches trough time as it is has been already observed for other member of the same taxonomic groups and for other LBF, e.g., the modern world-wide spread species Operculina ammonoides (Hohenegger, 2014). In fact, it has also been recently proven from a molecular genetics point of view that exactly the same species can migrate to different bioprovinces without changing its genetic specific signal and only sporadically very minor morphological differences can be observed, which are apparently not enough to discriminate at a species level (Holzman et al. 2003, Weber & Pawlowski 2014). Therefore the presence of Tethyan taxa in an Indian assemblage shall not create major concerns at this stage. The presence of the genus Lepidosemicyclina has been so far only recorded in the Indo-Pacific provinces and it seems to have been evolved from the Miogypsina lineage (Boudagher-Fadel & Price 2013) as well as other genera which are characteristics of different bioprovinces. These forms were previously considered to be distinctly different in each of the provinces: the subgenera Helicosteginoides and Miogypsinita in Central America, Miolepidocyclina in Central America and the Mediterranean, and Lepidosemicyclina in the Indo-Pacific (Boudagher-Fadel & Price 2010a, b). Miogypsinids have firstly developed in the American provinces by advanced forms of Neorotalia already during the early Oligocene time and before the earliest Miocene they entered into the Mediterranean and North African realm (Boudagher-Fadel & Price 2010a). Subsequently, the miogypsinids reached the Indo-Pacific realm during the early Miocene, from where the samples here presented are coming from, and there developed their diversity due to the climatic convenient conditions. All those migrations and parallel developments of forms and shapes lead to some minor but important modifications of some important biometric parame-

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ters here presented. It is worth to mention the variation of the size of the proloculus which seems to be the most effective parameter differentiating the studied population with those typical of the European assemblages. The postulated theories indicate a reduction in proloculus size for specimens close to the equator line due to high light irradiance and larger proloculi in less illuminated regions. However, this explanation still needs to be further confirmed and according to studies on modern foraminifera, proloculus variation is mainly related to either depth distribution or sexual di- or tri-morphisms (Eder et al. 2016, 2017, in press) A further parameter which has drawn the attention of the scientists working on the miogypsinids of the Indo-Pacific bioprovince is the geometric development of the equatorial chambers, as suggested firstly by Tan (1936). The geometry of the equatorial chambers changes from the juvenile into the adult stage and apparently such variation is species dependent. While most of the juvenile chambers excluding the nepionts look the same, their development shows up to 6 different sets: arcuate, ogival, isodiametric rhombic and elongate rhombic for more Miogypsina related species and isodiametric hexagonal to elongated hexagonal for those species belonging to the genus Lepidosemicyclina. In the studied assemblage illustrated in Plates 1– 2, such geometries are nicely visible. In the assemblage here presented, we have scanned two specimens which revealed to be agamonts of L. thecideaeformis and they also present isometric to slightly elongated hexagonal shaped equatorial chambers in their adult stage (Text-fig. 2 and Plate 2, Fig. 6).

6. Conclusion The assemblage presented shows a population of very nicely preserved Miogypsina globulina and Lepidosemicyclina thecidaeformis specimens that indicate a middle Burdigalian age (due to the presence of M. globulina) with very distinctive Indo-Pacific bioprovince characteristics (i.e., the presence L. thecideaeformis and minor variations in proloculus sizes in the miogypsinids). Their co-occurrence with Nephrolepidina chavarana and a number of other taxa reported in the literature mentioned points to a shallow water assemblage located between 50 to 70 meters water depths. The morphological variation of some biometric parameters matches with the geographical distribution of the presented fauna and indicates a slightly higher variability in terms of shape of equatorial chamberlets in the adult stage of the miogypsinids.

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Acknowledgements This work was performed at the micro-CT Facility, which is part of the Department of Palaeontology at the University of Vienna and has been sponsored by the Austrian Science Foundation project P 23459-B17. The assistance for scanning electron microscopy at the Austrian Geological Survey is gratefully acknowledged. The author would also like to thank Fred Rögl (Natural History Museum Vienna) for his magnificent effort toward the preparation of this manuscript and his extraordinary identification skill, Ercan Özcan (Istanbul), György Less (Miskolc) and Wolfgang Eder (Vienna) for valuable discussions during the preparation of an early draft of this paper. References Benedetti, A. & Briguglio, A. (2012): Risananeiza crassaparies n. sp. from the Late Chattian of Porto Badisco (southern Apulia). – Bolletino della Societa Paleontologica Italiana 51: 167–176. Boudagher-Fadel, M. K. (2008): Evolution and geological significance of larger benthic foraminifera. – Developments in Palaeontology and Stratigraphy 21: 544 pp., Elsevier, Amsterdam. Boudagher-Fadel, M. & Price, G. D. (2010a): American miogypsinidae: an analysis of their phylogeny and biostratigraphy. – Micropaleontology 56: 576 – 586. Boudagher-Fadel, M. & Price, G. D. (2010b): Evolution and paleogeographic distribution of the lepidocyclinids. – Journal of Foraminiferal Research 40: 79 –108. Boudagher-Fadel, M. & Price, G. D. (2013): The phylogenetic and palaeogepgraphic evolution of the miogypsinid larger benthic foraminifer. – Journal of the Geological Society 170: 185 – 208. Briguglio, A., Metscher, B. & Hohenegger, J. (2011): Growth Rate Biometric Quantification by X-ray Microtomography on Larger Benthic Foraminifera: Threedimensional Measurements push Nummulitids into the Fourth Dimension. – Turkish Journal of Earth Sciences 20: 683 – 699. Briguglio, A., Hohenegger, J. & Less, G. (2013): Paleobiological applications of three-dimensional biometry on larger benthic foraminifera, a new route of discoveries. – Journal of Foraminiferal Research 43 (1): 67– 82. Briguglio, A. & Hohenegger, J. (2014): Growth oscillation in larger Benthic Foraminifera. – Paleobiology 40 (3): 494 – 509, doi: 10.1666/13051. Briguglio, A., Kinoshita, S., Wolfgring, E. & Hohenegger, J. (2016): Morphological variations in Cycloclypeus carpenteri: multilple embryos and multiple equatorial layers. – Palaeontologia Electronica 19.1.4A: 1– 22. Briguglio, A. & Rögl, F. (2018): The Miocene (Burdigalian) Operculinids of Channa Kodi, Padappakkara, Southern India. – Palaeontographica A 312 (1–4): 17–39.

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Briguglio, A., Coric, S. & Rögl, F. (2018): Micropalaeontological investigations of the Quilon Formation at the Channa Kodi section of Padappakara, Kerala, India. – Palaeontographica A 312 (1– 4): 41– 46. Cahuzac, B. & Poignant, A. (1997): Essai de biozonation de l‘Oligo-Miocène dans les bassins européens à l’aide des grands foraminifères néritiques. – Bulletin de la Société géologique de France 168: 155 –169. Cole, W. S. (1954): Larger foraminifera and smaller diagnostic foraminifera from Bikini Drill Holes. – U.S. Geological Survey Professional Paper 260: 569 – 608. Douville, H. (1911): Les Foraminiferes dans le Tertiarie des Philippines. – Philippine Journal of Science 6: 53 – 80. Drooger, C. W. (1952): Study of American Miogypsinidae. – University of Utrecht, 80 pp. Drooger, C. W. (1993): Radial Foraminifera, morphometrics and evolution – Proceedings of the Koninklijke Nederlandse Akademie van Wetenschappen Series afd. Physics, eerste reeks 41: 242 pp. Drooger, C. W. & Raju, D. S. N. (1973): Protoconch diameter in the Miogypsinidae. – Proceedings Koninklijke Nederlandse Akadamie Wetenschappen, Ser. B 76: 206 – 216. Eder, W., Briguglio, A. & Hohenegger, J. (2016): Growth of Heterostegina depressa under natural and laboratory conditions. – Marine Micropalaeontology 122: 27– 43. Eder, W., Hohenegger, J. & Briguglio, A. (2017): Depth-Related Morphoclines Of Megalospheric Tests Of Heterostegina depressa D’orbigny: Biostratigraphic And Paleobiological Implications. – Palaios 32: 110 –117. Eder, W., Hohenegger, J., Konoshita, S., Wöger, J. & Briguglio, A. (2016): Test flattening in the larger foraminifer Heterostegina depressa: predicting bathymetry from axial sections. – EGU General Assembly Conference Abstracts 18: 2859. Ferràndez-Cañadell, C., Briguglio, A., Hohenegger, J. & Wöger, J. (2014): Test fusion in adult foraminifera: A review with new observations of an early Eocene Nummulites specimen. – Journal of Foraminiferal Research 44 (3): 316 – 324. Görög, A., Szinger, B., Toth, E. & Viszkok, J. (2012): Methodology of the micro-computer tomography on foraminifera. – Palaeontologia Electronica 15 (1): 3T. Hohenegger, J. (2014): Species as the basic units in evolution and biodiversity: Recognition of species in the recent and geological past as exemplified by larger foraminifera. – Gondwana Research 25 (2): 707–728. Hohenegger, J. & Briguglio, A. (2012): Axially oriented sections of nummulitids: a tool to interpret larger benthic foraminiferal deposits. – Journal of Foraminiferal Research 42 (2): 145 –153. Holzmann, M., Hohenegger, J., Pawlowski, J. (2003): Molecular data reveal parallel evolution in nummulitid foraminifera. – Journal of Foraminiferal Research 33: 277– 284.

Kędzierski, M., Uchman, A., Sawlowicz, Z. & Briguglio, A. (2015): Fossilized bioelectric wire – the trace fossil Trichichnus. – Biogeosciences 12: 1– 9, doi: 10.5194/ bg-12-1-2015. Jacob, K. & Sastri, V. V. (1950): Miocene foraminifera from Chavara, near Quilon, Travancore. – Records of the Geological Survey of India 82: 342 – 353. Matsumaru, K. (1980): Note on a new species of Miogypsina from Japan. – In: Professor Saburo Kanno Memorial Volume, 213 – 219, Sasaki Publication Co., Sendai. Matsumaru, K., Sari, B. & Özer, S. (2010): Larger foraminiferal biostratigraphy of the middle Tertiary of Bey Dağlari Autochton, Menderes-Taurus Platform, Turkey. – Micropalaeontology 56: 439 – 463. Michelotti, G. (1841): Saggio historico die Rizopodi caratteristici die terreni Sopracretacei. – Memoria di Matematica e di Fisica della Società Italiana del Scienze Residente in Modena 22: 253 – 302. Mishra, P. K. (1996): Study of Miogypsinidae and associated planktonics from Cauvery, Krishna–Godavari and Andaman Basins of India. – Geosciences Journal 17: 123 –130. Mohan, K. (1958): Miogypsinidae from western India. – Micropalaeontology 4: 373 – 390. Özcan, E. & Less, G. (2009): First record of the co-occurrence of western Tethyan and indo-pacific larger foraminifera in the burdigalian of the Mediterranean province. – Journal of Foraminiferal Research 39: 23 – 39. Özcan, E., Less, G., Báldi-Beke, M., Kollányi, K. & Acar, F. (2009a): Oligo-Miocene foraminiferal record (Miogypsinidae, Lepidocyclinidae and Nummulitidae) from the Western Taurides (SW Turkey): Biometry and implications for the regional geology. – Journal of Asian Earth Sciences 34: 740 –760. Özcan, E., Less, G. & Baydogan, E. (2009b): Regional implications of biometric analysis of Lower Miocene larger foraminifera from central Turkey. – Micropalaeontology 55: 559 – 588. Raju, D. S. N. (1974): Study of India Miogypsinidae. – Micropaleontological Bullettins 9, Utrecht. Raju, D. S. N. & Mishra, P. K. (1991): Miogypsinidae from the Andaman Basin, India. – Journal of the Palaeontological Society of India 36: 15 – 30. Rasheed, D. A. & Ramachandran, K. K. (1978): Foraminiferal bio-stratigraphy of the Quilon Beds of Kerala State, India. – In: Rasheed, D. A. (ed.): Proceedings of the VII Indian Colloquium on micropalaeontology and stratigraphy: 301– 320, Department of Geology, University of Madras. Renema, W. (2007): Fauna development of Larger Benthic Foraminifera in the Cenozoic of Southeast Asia. – In: Renema, W. (ed.): Biogeography, Time and Place: Distributions, Barriers and Islands. – pp. 179 – 215, Springer, Dordrecht. Reuter, M., Piller, W. E., Harzhauser, M., Kroh, A., Rögl, F. & Ćorić, S. (2010): The Quilon Limestone, Kerala Basin, India: an archive for Miocene Indo-Pacific seagrass beds. – Lethaia 44: 76 – 86.

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Rögl, F. & Briguglio, A. (2018): The Foraminiferal Fauna of the Channa Kodi Section at Padappakkara, Kerala, India. – Palaeontographica A 312 (1– 4): 47–101. Rutten, L. (1911): Studien über Foraminifeen aus OstAsien. – Sammlungen des geologischen Reichs-Museums in Leiden, 1. Serie, Beiträge zur Geologie Ost-Asiens und Australiens 9: 201– 217. Sacco, F. (1893): Sur quelques tinoporinae de Miocene de Turin. – Bullettin de la Societe Belge de geologie, de Paleontologie et d’Hydrologie 7: 204 – 207. Scheffen, W. (1932): Zur Morphologie und morphogenese der „Lepidocyclinen“ Palaeontologischen Zeitschrift 14: 233 – 256. Speijer, R. P., Van Loo, D., Masschaele, B., Vlassenbroeck, J., Cnudde, V.& Jacobs, P. (2008): Quantifying foraminiferal growth with high-resolution X-ray

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computed tomography: new opportunities in foraminiferal ontogeny, phylogeny, and paleoceanography applications. – Geosphere 4: 760 –763. Tan, S. H. (1936): Zur Kenntnis der Miogypsiniden, I–II. – Ingenieur Nederlaendischen Indie 3: 45 – 61, 84 – 98, 109 –123. Vaughan, T. W. (1928): Notes on the types of Lepidocyclina mantelli (Morton) Gümbel and on topotypes of Nummulites floridanus Conrad. – Proceedings of the Academy of Natural Sciences of Philadelphia 79: 299 – 303. Weber, A. A. & Pawlowski, J. (2014): Wide Occurrence of SSU rDNA Intragenomic Polymorphism in Foraminifera and its Implications for Molecular Species Identification. – Protisten 165: 645 – 661, doi: 10.1016/j.protis.2014.07.006

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Explanation of the plates Plate 1 Figs. 1–10: Equatorial and axial CT sections of Miogypsina globulina. 1: specimen MG1 2: specimen MG2 3: specimen MGpop2 4: specimen MG3 5: specimen MG4 6: specimen MGpop3 7: specimen MGpop8 8: specimen MGpop10 9: specimen MGpop11 10: specimen MGpop6 11: SEM image of the equatorial section with visible stolones 12: SEM image of the external ornamentation of the shell Scale bar is always 500 μm.

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Plate 2 Figs. 1– 9: Equatorial and axial CT sections of Lepidosemicyclina thecideaeformis. 1: specimen LTpop1 2: specimen LTpop2 3: specimen LTpop3 4: specimen LTpop4 5: specimen LTpop5 6: Agamont specimen LTpop6 7: specimen LTpop7 8: specimen LTpop8 9: specimen LTpop9 10: thin section though the equatorial layer with visible stolon system 11: SEM image with visible fan shape very common among most specimens 12: SEM image with exposed nepiont, lateral chamberlets surrounding the nepiont are visible 13: close up of 12 14: SEM image of the nepiont through the equatorial layer 15 –17: classic exagonal shape of the equatorial chambers at the adult stage Scale bar is always 500 μm if not other specified.

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Plate 3 Figs. 1– 5: Nephrolepidina chavarana 1– 3: external and enlarged surface views and equatorial sections of the tests, note the classic cube shape of the test and the 4 rays of the equatorial layer resulted from its saddle shape 4 – 5: different views of the 3D models of the nepiont and the equatorial layer as reconstructed from CT scans where the saddle shape is visible, the lateral chambers are not visualized in this model Figs. 6 – 8: Nephrolepidina sumatrensis 6 equatorial view with gently curved equatorial shape 7 axial section 8 3D virtual rendering of the test with equatorial and axial cuts revealing both the equatorial and axial chamber arrangement Scale bar: 500 μm if not other specified.

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