Pentadinium Alabamensis: a New, Unusual Dinoflagellate from The

Review of Palaeobotany and Palynology 175 (2012) 47–54

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Review of Palaeobotany and Palynology

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Research paper Pentadinium alabamensis: A new, unusual dinoﬂagellate from the early Oligocene of the Gulf Coast, Alabama, USA

Willemijn Quaijtaal a,b,⁎, Henk Brinkhuis a a Marine Palynology, Laboratory of Palaeobotany and Palynology, Department of Earth Sciences, Faculty Geosciences, Utrecht University, Budapestlaan 4, 3584 CD Utrecht, The Netherlands b Research Unit Palaeontology, Department Geology and Soil Science, Ghent University, Krijgslaan 281 S8/WE13, B-9000 Ghent, Belgium article info abstract

Article history: The Eocene–Oligocene Transition (EOT, ~34 Ma) marks the onset of major Antarctic ice sheets. The environmental Received 21 August 2011 consequences of the transition included major changes in e.g., sea level, temperature, and ocean circulation, com- Received in revised form 9 March 2012 plicating biostratigraphic correlations in this interval. Organic walled dinoﬂagellate cysts (dinocysts) however do Accepted 12 March 2012 show potential for EOT biostratigraphy, especially for ancient shallow marine settings. Available online 20 March 2012 At St. Stephens Quarry, Alabama, USA, we found a new, extremely suturocavate dinocyst, Pentadinium alabamensis sp. nov., described herein. The range of the new species spans the critical EOT magnetosubchron C13n, making Keywords: organic walled dinoﬂagellate cysts this taxon a useful biostratigraphic marker for this interval in the Gulf Coast region. The species appears to be as- Eocene/Oligocene transition sociated with shallow marine, euryhaline conditions. St. Stephens Quarry © 2012 Elsevier B.V. All rights reserved. Alabama USA

1. Introduction against magnetosubchron C13n (Wade et al., 2012). It appears morpho- logically related to representatives of the genus Pentadinium but differs The Eocene–Oligocene transition (EOT, ~34 Ma) reflects the tran- by displaying extraordinarily wide separation of the outer wall from the sition from the early Paleogene Greenhouse into the Icehouse world, inner wall. This taxon was reported earlier from multiple localities marking the onset of major Antarctic glaciation (e.g., Zachos et al., within the lower Oligocene of the Gulf Coast region (Fig. 1)by 1996, 2001; Coxall et al., 2005; Zachos et al., 2008). The EOT paleocli- Jaramillo and Oboh-Ikuenobe (1999) as ‘Pentadinium sp. A’. Our study matic and correlated paleoceanographic changes often complicate now confirms its consistent presence in the lower Oligocene in this straightforward biostratigraphic interpretations in this interval. region and the morphological stability of the species. The latter aspect Steepened latitudinal temperature gradients, surface water reorgani- warrants a separate taxonomic position. Here, we thus describe and zations, corrosive deep ocean currents and sea level changes caused document this biostratigraphically useful, new species, and propose diachronous range tops and first appearances, besides issues with placing it within the genus Pentadinium. preservation and reworking (see Coxall and Pearson, 2007 for an overview). Biostratigraphy based on the organic walled remains of 2. Material and methods dinoflagellates (dinocysts) has shown potential for the EOT interval in e.g., the Mediterranean, North Atlantic, and Tasman Sea regions 2.1. Material (e.g., Brinkhuis and Biffi, 1993; Brinkhuis, 1994; Bujak and Mudge, 1994; Sluijs et al., 2003; Eldrett et al., 2004). The St. Stephens Quarry borehole (SSQ, St. Stephens, Washington Because many organic-cyst-forming dinoflagellates are ecologically County, Alabama, USA; 31°33′ N lat., 88°02′ W long., see Fig. 1)was adapted to relatively marginal, shallow marine settings, this group is continuously cored by ARCO Oil and Gas Company in 1987 (Miller particularly useful when correlating ancient in- to offshore settings et al., 1993; Wade et al., 2012). The cored interval mainly consists of (see e.g., Pross and Brinkhuis, 2005). While analyzing the relatively silts, clays and sands with varying carbonate content. This succession shallow marine deposits of the Gulf Coast region at St. Stephens Quarry is interrupted by thin siliciclastic and glauconitic beds (Miller et al., (SSQ), Alabama, USA (see Fig. 1; see also Wade et al., 2012)werecorded 2008). Details of the lithology can be found in Miller et al. (2008). an unusual dinocyst within lower Oligocene sediments calibrated The studied interval of the SSQ bore hole contains the following typical Gulf Coast lithostratigraphic units: the Jackson Group and the Vicksburg Group. These units can be subdivided into several ⁎ Corresponding author at: Research Unit Palaeontology, Department Geology and Soil formations and their respective members (Fig. 2). The Jackson Science, Ghent University, Krijgslaan 281 S8/WE13, B-9000 Ghent, Belgium. Tel.: +32 9 264 46 10. Group is composed of the Moodys Branch Formation and the E-mail address: [email protected] (W. Quaijtaal). Yazoo Clay. The Yazoo Clay can furthermore be subdivided in the

0 50 km 90°W 89°W A total of 59 samples have generally been taken every ~1.5 m, 35°N 35°N and ~0.3–0.6 m for the EOT interval (see Fig. 2). MISSISSIPPI For the age model we follow Wade et al. (2012), which provides ALABAMA an update from the earlier data presented by e.g., Miller et al. (2008) (see Fig. 2). This update mainly regards the identiﬁcation of a ~200 kyr hiatus – associated with the Oligocene Isotope-1 Event t t (Oi-1) – near the base of magnetosubchron C13n, whereas Miller Atlantic Ocean 31°N 31°N et al. (2008) thought SSQ to be complete at this point. The age δ18 90°W 89°W model is based on magnetostratigraphy, O correlations and biostratigraphy (see Fig. 2).

Gulf of Mexico 2.2. Methods

Standard palynological techniques have been used to process the samples. Briefly: samples were cleaned and crushed before oven dry- ing at 60 °C. Dried samples were then weighed. Material was first rehydrated with the wetting agent Agepon® (1:200). Then, to re- #1 Wayne St. Stephens Quarry move carbonates, hydrochloric acid (HCl, 10%) was added. Next, to #1 Young dissolve silicates, 38% hydrofluoric acid (HF) has been used, followed Wayne County by shaking at ~250 rpm for 2 h and addition of a surplus of 30% HCl to 0 20 km Washington County remove fluoride gels. Samples were washed twice by decanting after a 24 h settling and filling up with water after each acid step. Samples Fig. 1. Locations of the localities where Pentadinium alabamensis has been recorded. t0: were first sieved with a 250-μm nylon mesh sieve; the filtrate was paleoshoreline during accumulation of Shubuta Clay and equivalents, t : paleoshoreline 1 again sieved with a 15-μm nylon mesh sieve. The sample was shortly during accumulation of Red Bluff Clay and equivalents (adapted from Jaramillo and Oboh-Ikuenobe, 1999, paleoshorelines after Tew and Mancini, 1995). placed in an ultrasonic bath to break up clumped residue. The sieved residue was transferred into a glass test tube. Test tubes were centri- fuged at 2000 rpm for 5 min without brake. Water surplus was re- following members: 1) the North Twistwood Creek Member, 2) the moved and the residue was transferred into a vial with addition of Cocoa Sand Member, 3) the Pachuta Marl Member and 4) the Shu- glycerin water. After homogenization, one drop of the residue was buta Member. The Vicksburg Group at SSQ contains the Bumpnose mounted on a microscopic slide together with some glycerin jelly Limestone, the Red Bluff Clay, the Marianna Limestone and the and stirred. Slides were covered with a cover slip and sealed with Byram Formation. The Glendon Limestone Member is the lowest nail polish. Per sample two slides have been prepared. A minimum member of the Byram Formation. number of 200 dinocysts was counted; afterwards the uncounted

Age (Ma, Berggren et al., 1995) 31 32 33 34 35 36 37 Magnetic inclination Oligocene Eocene Magnetosubchrons Samples -90 0 90 Lithostratographic units C12n 15 15

BFM Base C12n GL

20 20 HO Pseudohastigerina spp.

25 25

C12r HO R. umbilicus 30 30

HO E. formosa Depth (m) 35 35 Marianna Limestone Top C13n MSM Depth (m) 40 40

RB HO P. alabamensis C13n Base C13n 45 45 BLS HO P. micra LO P. alabamensis C13r HO T. cerroazulensis group 50 SM HO R. reticulata 50 HO Hantkeninidae C15r HO D. saipanensis FAD I. recurvus C 55 Top C16n.1n 55 Base C16n.2n

C16r Clay Yazoo NTC PM 60 GroupJackson Group Vicksburg 60

Fig. 2. Magnetic inclination, magnetostratigraphy, lithostratigraphic units, samples analyzed for palynology and age-depth plot for the St. Stephens Quarry core. Plusses indicate samples with erratic paleomagnetic behavior. Age model is based on magnetostratigraphy (black squares), δ13C correlations (gray circles) and biostratigraphy (white circles: calcareous nannoplankton, stars: planktonic foraminifera) (Miller et al., 2008). Tie points used for the age model are connected by a solid black line. Hiatuses are indicated by horizontal red dashed lines, the black dashed line in Yazoo Clay indicates a parasequence boundary. Highest and lowest occurrences of Pentadinium alabamensis have been indicated by black dotted lines. The Oi-1 event and corresponding hiatus are located at the base of C13n. HO: highest occurrence, LO: lowest occurrence, FAD: first appearance datum, BLS: Bumpnose Limestone, RB: Red Bluff Clay, BFM: Byram Formation, NTC: North Twistwood Creek Member, C: Cocoa Sand Member, PM: Pachuta Marl Member, SM: Shubuta Member, MSM: Mint Spring Marl Member, GL: Glendon Limestone Member. W. Quaijtaal, H. Brinkhuis / Review of Palaeobotany and Palynology 175 (2012) 47–54 49 50 W. Quaijtaal, H. Brinkhuis / Review of Palaeobotany and Palynology 175 (2012) 47–54 part of the slide was scanned for important biostratigraphic markers. plate interior and show separation at the plate margins. The endo- Taxonomy, unless indicated otherwise, follows that cited in Fensome phragm is thicker than the periphragm. Furthermore, it shows cava- et al. (2008). tion around the cingulum. Plates 1′ and 4′ are more or less fused Light microscopic images have been made with a Leica DFC320 and plate 6″ is poorly delimited (see Plate 2A,E). camera on a Leica DM LB2 microscope using Adobe Photoshop, addi- The endophragm is subsphaerical, scabrate or microgranulate. The tional scanning electron microscope (SEM) photography has been periphragm is thin, perforate and widely extends outwards. The tab- performed as well. For this purpose, splits of the palynological resi- ulation is expressed by these extreme outgrowths of the periphragm, dues were sieved with warm water over a 15 μm nylon mesh sieve considered to principally reflect extreme suturocavation. Outgrowths to remove glycerin and then transferred to a tray table. Each tray form septa at the apical plates and a fenestrate membrane on the rest table was coated with 12 nm platinum using a sputter coater (Cres- of the cyst. The sulcal plates are not reflected. sington 208 h). Samples have been examined using a Philips XL30S FEG device, located at Utrecht University. Material is stored in the col- Description: A medium sized (60–70 μm), subsphaerical to ellipti- lection of the Laboratory of Palaeobotany and Palynology, Utrecht cal species of Pentadinium, showing extreme suturocavation. The cyst University, The Netherlands. possesses two wall layers. The endophragm is thick and scabrate to The terminology for describing fossil dinocysts we use follows Evitt microgranulate (see Plate 2D). It does not show any tabulation, et al. (1977) and Evitt (1985). However, we refrain from using “para-” except for the precingular, 1P (3″) archeopyle, operculum free. The as a prefix of morphological features referring to the cyst (following periphragm is thin, perforate and closely appressed to the endo- Fensome et al., 1993), to avoid confusion with terminology solely phragm at the central areas of the plates. At these appressed areas used for exceptional situations, e.g. “parasutural ridges”.Furthermore, the periphragm is not perforate. At the plate boundaries the peri- we do not use the terms “autophragm” and “ectophragm” since in Pen- phragm is detached and extends outwards exceptionally (suturoca- tadinium there is no true, single layered autophragm, but an endo- vation). This aspect in Pentadinium alabamensis sp. nov. is so phragm and a periphragm that are appressed in the central plate area extreme that it appears to bear large distal crest-like structures, a and separated at the plate boundaries. fenestrate periphragm supported by slender processes (see Fig. 3; Plate 2B, F). We consider these to be exceptional outfolds of the suturocavate nature of the periphragm. Pentadinium alabamensis sp. 3. Systematic paleontology nov. displays a gonyaulacoid tabulation: 3–4′,6″, 6c, 6‴, 1p, 1⁗ with a 1P(3″) archeopyle, operculum free (see Fig. 3; Plate 2A, E). Division DINOFLAGELLATA (Bütschli, 1885) Fensome et al., 1993 The sulcal region is not reflected by the periphragm (see Fig. 3B). Subdivision DINOKARYOTA Fensome et al., 1993 The crest-like structures on the cyst are mostly found to represent Class DINOPHYCEAE Pascher, 1914 the apical plates series (plates 1–4′, see Plate 2A), while from the Subclass PERIDINIPHYCIDAE Fensome et al., 1993 precingular plates downward the periphragm is almost completely detached, reflecting the precingular, cingular, postcingular and Order GONYAULACALES Taylor, 1980 antapical plates. The cingular plates may be difficult to see under Suborder GONYAULACINAE Autonym the light microscope (see Fig. 3). Family GONYAULACACEAE Lindemann, 1928 Subfamily GONYAULACOIDEAE Autonym Dimensions: Average diameter of the endocyst was 55 μm, average Genus Pentadinium Gerlach, 1961, emend. Benedek et al., 1982 diameter of the pericyst 91 μm (n=15). Holotype: diameter of endocyst 53 μm, diameter of pericyst 95 μm; paratype 1: endocyst – Pentadinium alabamensis, sp. nov., Plate 1,A D 54 μm, pericyst 95 μm; paratype 2: endocyst 50 μm, pericyst fi 1999 Pentadinium sp. A, Jaramillo and Oboh-Ikuenobe, plate 2, g. 9 87 μm. Etymology: Named after the state of Alabama (USA), home of the type species. Comparison: Pentadinium alabamensis sp. nov. can be distinguished Holotype: Sample SSQ 17 (42.56 m core depth), slide 1, England from all species of Pentadinium in showing extreme separation of Finder (EF) coordinates N33/2, Plate 1,A–D the perforate periphragm from the endophragm. Although Pentadi- Paratype 1: Sample SSQ 17(42.56 m core depth), slide 2, EF G31/1, nium favatum also might show extreme separation of these layers, Plate 1,E–G this is not a consistent feature as in P. alabamensis.Moreimportantly, Paratype 2: Sample SSQ 17(42.56 m core depth), slide 2, EF H30/4, P. favatum has its characteristic honeycomb texture. Pentadinium? Plate 1,H–J circumsutum, P. corium Schiøler (2005), P. goniferum, P. granulatum Type locality: St. Stephens Quarry, Alabama, USA (Gocht, 1969) Fensome et al. (2009), P. imaginatum, P. membranaceum, Type stratum: Red Bluff Clay P. sabulum Fensome et al. (2009) and P. taenagrium can all be distinguished from the new species P. alabamensis in having a granular to ver- Repository: Laboratory of Palaeobotany and Palynology, Utrecht miculate endocyst surface structure, whereas P. lophophorum can be University, Budapestlaan 4, 3584CD Utrecht, The Netherlands. separated based on its typical surface ornamentation. P. alabamensis Diagnosis: A species of Pentadinium displaying a gonyaulacoid can be distinguished from P. netangei based on its size and having a per- tabulation (3–4′,6″, 6c, 6‴, 1p, 1⁗; Evitt, 1985) with a 1P (3″) arche- forate rather than a microgranulate periphragm. The camocavate P. opyle, operculum free. The species shows several characteristics typ- omasum has, unlike P. alabamensis, a pseudopunctate endocyst struc- ical for Pentadinium: two walls that appear as a single layer at the ture and cavation is restricted to the dorsal part of the cyst. P.

Plate 1. Light microscopy pictures of Pentadinium alabamensis sp. nov. The scale bar is 20 μm.

A–D: Holotype (sample “SSQ 17, slide 1”, EF Reference: N33/2). A: dorsal view, high focus. B: dorsal view, middle focus. C: same specimen with lower focus on ventral side. D: same specimen with lowest focus on the ventral side. E–G: Paratype 1 (sample “SSQ 17, slide 2”, EF Reference: G31/1). E: dorsal view, high focus. F: dorsal view, lower focus. G: same specimen, lowest focus on ventral side. H–J: Paratype 2 (sample “SSQ 17, slide 2”, EF Reference: H30/4). H: dorsal view, high focus. I: dorsal view, lower focus. J: same specimen, lowest focus on ventral view. K, L: “sample SSQ 17, slide 1”, EF Reference: K36/3, K: lowest focus on right lateral side. L: low focus on left lateral side. W. Quaijtaal, H. Brinkhuis / Review of Palaeobotany and Palynology 175 (2012) 47–54 51

Plate 2. Scanning electron microscope (SEM) pictures of Pentadinium alabamensis sp. nov.

A: Apical view (sample “SSQ 17”). Note the reduction of apical plates 1′ and 4′. B: Right lateral view (sample “SSQ 17”). This sample shows the restriction of the septa-like outfolds of the periphragm to the apical plates. C: Oblique antapical view (sample “SSQ 17”). D: Detail (sample “SSQ 17”) of the endophragm structure. Note the splitting of the base of the ‘process’, showing the suturocavate origin. E: Apical view (sample “SSQ 17”). Note the merged apical plates 1′ and 4′. F: Detail of Plate 2E (sample “SSQ 17”) showing the perforate, suturocavate nature of the periphragm. 52 W. Quaijtaal, H. Brinkhuis / Review of Palaeobotany and Palynology 175 (2012) 47–54

2’ 3’ 4’’ 2’’ 3’’ 1’’’ 6’’’

1P Cingular 4’’’ 2’’’ region 1’’’’

3’’’ AB

Fig. 3. Camera lucida images of the dorsal (A) and the ventral (B) sides of the holotype of Pentadinium alabamensis sp. nov. Visible plates have been marked with their respective plate numbers. Note that the periphragm is separated from the endophragm at the plate margins from the cingulum downwards, creating fenestrae. laticinctum s.s., P. polypodum, P. spinulum and P. galileoi Sancay et al. therefore not be confused with P. alabamensis. The periphragm of P. (2006) share the relatively smooth surface of the endocyst. However, laticinctum s.s. is not as extremely detached as in P. alabamensis the last three species possess processes of different sorts and can and is, where detached, not perforate.

(%)

h p

a s r spp. (%) re

g p. (%) i p

t s po a

r ium alabamensis

t blium rea s s d dex

e Biostratigraphically

s o

i n

r i

h fla len and s

e n

i entadin e important dinocyst

u L S Homotry P D Pol BIT-In species (% of total palynomorphs) 30

38 Marianna Limestone

40 Mint Spring Marl

OLIGOCENE HO Pentadinium alabamensis

42 RB

44 HO Wetzeliella articulata BLS 46 Depth (m) LO Pentadinium alabamensis 48 HO Hemiplacophora semilunifera SM HO Batiacasphaera compta 50 HO Schematophora speciosa LO Hemiplacophora semilunifera PM 52 LO Schematophora speciosa

CS HO Rhombodinium draco 54 EOCENE Yazoo Clay Yazoo 56 LO Reticulatosphaera actinocoronata NTC 58

60 02040600200200 204060800,0 0,2 0,4 0,6 0,8 1,0

Fig. 4. Abundances (%) of Pentadinium alabamensis and co-occurring species taxa Homotryblium spp. and Deﬂandrea spp., pollen and spore abundance (%), BIT-index and some biostratigraphically important dinocyst species plotted versus depth (m). BIT data from Wade et al., 2012, GSA Data Repository. BLS: Bumpnose Limestone, RB: Red Bluff Clay, NTC: North Twistwood Creek Member, CS: Cocoa Sand Member, PM: Pachuta Marl Member, SM: Shubuta Member, HO: highest occurrence, LO: lowest occurrence. W. Quaijtaal, H. Brinkhuis / Review of Palaeobotany and Palynology 175 (2012) 47–54 53

Geographic and stratigraphic distribution: Pentadinium alabamensis MINT SPRING sp. nov. has so far been reported from four localities; Jaramillo and Oboh-Ikuenobe (1999) recorded it in two cores in Mississippi State RED BLUFF (Mobil Exploration and Production Services #1 Young and #1 Wayne cores), as well as from the SSQ outcrop (see Fig. 1). We BUMPNOSE LOWER found P. alabamensis sp. nov. in the SSQ core, taken ca 1.6 km OLIGOCENE YAZOO from the SSQ outcrop analyzed by Jaramillo and Oboh-Ikuenobe (1999). The species has never been mentioned or shown in other YAZOO regions. Quantitatively, Pentadinium alabamensis sp. nov. may contribute MOODYS UPPER substantially to the dinocyst assemblages (up to 10% in the SSQ EOCENE BRANCH core). Furthermore, P. alabamensis sp. nov. co-occurs with taxa such ﬂ as Homotryblium spp. and De andrea spp. at all localities (see Fig. 4 GOSPORT and ﬁg. 9 of Jaramillo and Oboh-Ikuenobe, 1999). These taxa are typ- & ically found in relatively restricted, shallow marine environments, EQUIVALENTS characterized by a relatively large range in salinity (e.g., Brinkhuis, 1994; Pross and Schmiedl, 2002; Röhl et al., 2004; Pross and Brinkhuis, 2005). At the SSQ core, samples in which P. alabamensis sp. nov. occurs are characterized by high relative abundances of LISBON terrestrial palynomorphs (i.e., pollen and spores) and a high P. laticinctum P. granulatum P. P. alabamensis P.

Branched and Isoprenoid Tetraether (BIT)-index as well (Wade et polypodum P.

al., 2012, GSA Data repository; see Fig. 4). The BIT-index is a tracer membranaceum P. for terrestrially derived soil bacterial lipids and a high BIT may goniferum P. MIDDLE EOCENE therefore point toward a high influx of terrestrial organic matter favatum P. in sediments (e.g., Hopmans et al., 2004). In addition, Miller et al. (2008) characterized the Red Bluff Clay, where P. alabamensis has TALLAHATTA its highest occurrence (see Fig. 4), as a shelf environment with a depth of 75±15 m, based on the benthic foraminiferal Hanzawaia biofacies (Miller et al., 2008, and references therein). Altogether, Fig. 5. Ranges of Pentadinium species in western and central Alabama, including the new this suggests that P. alabamensis sp. nov. is associated with proxi- species Pentadinium alabamensis.DashedlinesonP. laticinctum laticinctum and P. laticinctum granulatum indicate the occurrences in the Piney Point Formation (middle Eocene) in mal environments. Virginia (adapted from Edwards, 1982). As can be seen in Fig. 4 and implied from table 8 and fig. 17 of Jaramillo and Oboh-Ikuenobe (1999) Pentadinium alabamensis sp. nov. typically has its highest relative abundance in the Oligocene 4. Concluding remarks Red Bluff Clay and upper Forest Hill Sand (not present at SSQ) (see Fig. 4). The lowest occurrence of P. alabamensis sp. nov. in all The distinctive new dinocyst species Pentadinium alabamensis sp. four locations may differ slightly (Fig. 4; Jaramillo and Oboh- nov. appears to be a useful regional biostratigraphic marker species – Ikuenobe, 1999), but it always occurs above the Eocene Oligocene for magnetosubchron C13n in the Gulf Coast region. In addition, boundary (not be confused with the younger Oi-1 isotope event). we surmise that the taxon reflects shallow marine, euryhaline set- fi The oldest rst occurrence out of all 4 locations is an occurrence tings. Future analysis at other locations in and outside the Gulf of of a single specimen within the SSQ core at 46.74 m, at a horizon Mexico will have to further confirm the age ranges given, as well calibrated to be against the very top of, but still within, magneto- as further elucidate the environmental preferences of P. alabamensis chron C13r. At all locations, P. alabamensis sp. nov. has its highest sp. nov. occurrence at the Red Bluff Clay/Forest Hill Sand–Mint Spring Marl contact, except for the location of the #1 Wayne core. However, in Acknowledgments that location it concerns only a single specimen, occurring 0.9 m above the Forest Hill Sand–Mint Spring Marl contact; it may repre- N.L.D. Welters, L.P.M. Bik and J. J. van Tongeren are thanked for tech- sent reworking. The boundary of the Red Bluff Clay–Mint Spring nical support. Prof. Ken Miller and co-workers (Rutgers University, NJ, Marl contact at SSQ is calibrated to be against the subchron USA) have kindly provided the samples. They, as well as dr. Bridget C13n–C12r boundary. Accordingly, we place the last occurrence Wade (University of Leeds, UK), are kindly thanked for cooperation. of P. alabamensis sp. nov. at this boundary, dated at ~33.058 Ma in Dr. C. Jaramillo (Smithsonian) is thanked for providing additional infor- Berggren et al. (1995). This implies that the range of P. alabamensis mation on Pentadinium sp. A. The two reviewers, dr. Lucy E. Edwards sp. nov. essentially straddles magnetosubchron C13n (see Fig. 2). and dr. Karin Zonneveld, as well as Sander Houben MSc are thanked In Fig. 4 the lowest and highest occurrences (LO; HO) of P. alaba- for carefully reading the manuscript and suggesting improvements. mensis can be compared to other biostratigraphically important species. The LO of P. alabamensis is ca. 1.3 m above the HO of References Hemiplacophora semilunifera, a species that can be associated fl with the Eocene–Oligocene boundary (Brinkhuis and Biffi, 1993). Benedek, P.N.v., Gocht, H., Sarjeant, W.A.S., 1982. The dino agellate cyst genus Pentadi- nium Gerlach: a re-examination. Neues Jahrbuch für Geologie und Paläontologie, This further confirms the early Oligocene age of the range of Abhandlungen 162, 265–295. P. alabamensis. Berggren, W.A., Kent, D.V., Swisher, C.C., Aubry, M.-P., 1995. A revised Cenozoic geochro- In 1982, Edwards already stated that Pentadinium species nology and chronostratigraphy. In: Berggren, W.A., Kent, D.V., Aubry, M.-P., Hardenbol, J. (Eds.), Geochronology, time scales and stratigraphic correlation: Society occur widely throughout the Eocene and the Oligocene and that of Economic Paleontologists and Mineralogists Special Publication, 54, pp. 129–212. they might provide good biostratigraphic markers. She introduced Brinkhuis, H., 1994. Late to Early Oligocene dinoflagellate cysts from the Priabionan a scheme of ranges of middle and upper Eocene Pentadinium type-area (Northeast Italy): biostratigraphy and paleoenvironmental interpretation. Palaeogeography, Palaeoclimatology, Palaeoecology 107, 121–163. species. We can now expand this scheme up into the Oligocene Brinkhuis, H., Biffi, U., 1993. Dinoflagellate cyst stratigraphy of the Eocene/Oligocene (see Fig. 5). transition in Central Italy. Marine Micropaleontology 22, 131–183. 54 W. Quaijtaal, H. Brinkhuis / Review of Palaeobotany and Palynology 175 (2012) 47–54

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