The rich and well-preserved Maastrichtian-Paleogene benthic foraminiferal species of the agglutinated genus Gaudryina in the Tethys shows an increasing phylogenetic plasticity through the modifications of morphologic features first appearing in the ancestors. Two phylogenetic lineages are observed in some agglutinated benthic foraminiferal species throughout Maastrichtian to Lutetian in some localities in the Tethys: in the Gaudryina pyramidata and Gaudryina arabica groups. These lineages help, not only to define the major faunal changes throughout the Cretaceous-Tertiary (K-T) and the Paleocene-Eocene (P-E) boundaries, but also to emphasize the stratigraphic importance of them in different localities in the Tethys. In this study, the first lineage in Gaudryina pyramidata group is observed in four species throughout the time, from Maastrichtian (G. pyramidata) to Danian (G. limbata) to Ypresian (G. speijeri) to Lutetian (G. ennakhali). Another lineage in Gaudryina arabica group is also observed in four species, from Maastrichtian (G. arabica) to Paleocene (G. salimi) to Early Eocene (G. ameeri) to Middle Eocene (G. osmani). Four out of the identified species from the two groups are treated here to be new: Gaudryina arabica, G. osmani, G. salimi and G. ennakhali. The identified Maastrichtian-Lutetian species in this study are recognized in different localities in the Tethys: Atlantic Ocean, USA, Trinidad, Barbados, France, Spain, Italy, Tunisia, Egypt, UAE, Qatar and Iran.

Keywords: phylogeny, agglutinated benthic foraminifera, Gaudryina, Maastrichtian, Paleogene, atlantic ocean, Tethys

The evolutionary patterns depend mainly on the concept of taxonomy and stratigraphy. The relatively rapid or slow observable morphological changes in the foraminiferal tests, number, size, shape and arrangement of the chambers, ornamentation, position of aperture, periphery throughout the Maastrichtian-Lutetian species over a time of some 30 m. y. (70-40 Ma) from the ancestors to the descendants, offer an opportunity to observe many evolutionary changes in two groups in this study: the Gaudryina pyramidata group: G. pyramidata, G. limbata, G. speijeri and G. ennakhali, and Gaudryina arabica group: G. arabica, G. salimi, G. ameeri and G. osmani Tjalsma & Lohmann¹ and Bolli et al.² noted that there is a remarkable difference in size among the specimens of Gaudryina pyramidata in Trinidad and other parts in the Atlantic Ocean, and the larger and smaller ones have relatively triserial or biserial chambers are often better developed. The evolutionary lineages may be produced by one of the two evolutionary models: Phyletic gradualism or Punctuated equilibrium. Most probably the first model causes the present lineages due to the open marine conditions between the different oceans throughout the Maastrichtian and Paleogene times.

Many attempts have been made to interpret the phylogeny of some benthic foraminiferal species, which could have evolved from another earlier stratigraphic species. Nakkady³ presented five evolutionary trends (by his own identification) of accelerated benthic foraminiferal evolution in the Maastrichtian-Paleogene transition of Egypt: (1) Cibicides abudurbensis Nakkady⁴ evolved to Anomalina pseudoacuta Nakkady⁴, (2) Siphogenerina esnehensis Nakkady⁴ to Siphogenerinoides eleganta Plummer,⁵ (3) Siphogenerina esnehensis Nakkady⁴ to S. higazyi Nakkady³, (4) Verneuilina cretacea Karrer⁶ to Gaudryina pyramidata Cushman⁷, (5) Eouvigerina aegyptiaca Nakkady⁴ to Gümbelina globulosa Ehrenberg.⁸

The last attempt was followed later by thirty one evolutionary trends of Anan^9-14: (1) Orthokarstenia oveyi (Nakkady)⁴ to O. applinae (Plummer)⁵, (2) Discorbis p. pseudoscopos Nakkady⁴ to D. p. duwi Nakkady⁴, (3) Verneuilina aegyptiaca Said & Kenawy¹⁵ to V. luxorensis Nakkady⁴, (4) Coryphostoma incrassata (Reuss)¹⁶ to C. midwayensis (Cushman)¹⁷, (5) Anomalinoides rubiginosus (Cushman)¹⁸ to A. midwayensis (Plummer)⁵, (6) Gyroidinoides girardanus (Reuss)¹⁶ to G. luterbacheri Anan¹⁰, (7) Angulogavelinella nekhliana Said & Kenawy¹⁵ to A. avnimelechi (Reiss)¹⁹, (8) Cibicidoides pharaonis (LeRoy)²⁰ to C. farafraensis (LeRoy)²⁰, (9) Bathysiphon californicus (Martin)²¹ to B. paleocenicus El Dawy²² to B. saidi (Anan)²³, (10) Spiroplectinella knebeli (LeRoy)²⁰ to S. paracarinata (Said & Kenawy)¹⁵, (11) Gaudryina pyramidata Cushman¹⁸ to G. ameeri Anan¹² (12) Gaudryina pyramidata Cushman¹⁸ to G. speijeri Anan¹² (13) Bolivinoides draco aegyptiaca Anan¹³ to B. d. draco (Marsson)²⁴, to B. d. dorreeni Finlay²⁵, (14) Clavulina parisiensis d'Orbigny²⁶ to C. pseudoparisensis Anan²⁷, (15) Laevidentalina granti (Plummer)⁵ to L. salimi Anan²⁸, (16) Lenticulina carinata (Plummer)⁵ to L. turbinata (Plummer)⁵ to L. chitanii (Yabe & Asano)²⁹, (17) Percultazonaria ameeri Anan³⁰ to P. allami Anan³⁰, (18) Percultazonaria alii Anan³⁰ to P. longiscata (Nakkady)⁴, (19) Percultalina wadiarabensis (Futyan)³¹ to Percultazonaria tuberculata (Plummer)⁵, (20) Palmula woodi undulata Nakkady⁴ to P. w. woodi Nakkady⁴, (21) Gavelinella b. brotzeni Said & Kenawy¹⁵ to Gavelinella brotzeni paleocenica Said & Kenawy¹⁵, (23) Siphogaudryina tellburmaensis (Futyan)³¹ to S. africana (LeRoy)²⁰, (24) Textularia haquei Anan³² to T. farafraensis LeRoy²⁰, (25) Pseudoclavulina barnardi Futyan³¹ to P. maqfiensis LeRoy²⁰, (26) Pyramidulina robinsoni (Futyan)³¹ to P. leroyi Anan³², (27) Frondicularia bignoti Anan³³ to F. nakkadyi Futyan^31, (28) Frondicularia pickeringi Futyan³¹ to F. gahannamensis Ansary³⁴, (29) Hopkinsina arabina Futyan³¹to H. haquei Anan³², (30) Gyroidinoides tellburmaensis (Futyan)³¹ to G. subangulata (Plummer)⁵, (31) Angulogavelinella convexa (LeRoy)²⁰ to A. bandata Futyan³¹ (1976).

Benthic foraminiferal evolutionary trends

Minor differences in the morphology of the test, wall structure, arrangement of the chambers, position and type of aperture, stratigraphic level, size of the test and chambers are also recognized as being of the decisive specific or subspecific value. This study represents another new attempt is made here to present two evolutionary trends marked by changes in the test morphological members of the diagnostic benthic foraminiferal genus Gaudryina in the Maastrichtian-Lutetian time: Gaudryina pyramidata group and Gaudryina arabica group (Figure 1). These lineages help not only to defined the major faunal changes at the K/T and through the different stages of the Paleogene, but also to emphasis the stratigraphic importance of them in different localities in the Tethys.

Figure 1 The two phylogenetic lineages from the Maastrichtian-Paleogene of the Tethys. (1) Gaudryina pyramidata group (figs. 1-3: Gaudryina pyramidata, 4-6: Gaudryina limbata, 7: Gaudryina speijeri,  8: Gaudryina ennakhali) and (2) Gaudryina arabica group (fig. A: Gaudryina arabica, B: Gaudryina salimi, C: Gaudryina ameeri, D: Gaudryina osmani).

Gaudryina pyramidata lineage

The triangular test has transverse section, early acute triserial chambers, later semi-circular final chamber in the biserial, chambers distinct and slightly inflated, truncate to subrounded periphery, sutures slightly depressed, wall agglutinated arenaceous with a smooth surface, aperture a low opening in a semicircular re-entrant of the inner margin of the last formed semi-circular chamber. The Maastrichtian Gaudryina pyramidata was probably ancestral of three subsequent Paleocene to Middle Eocene lineages, these are:

1. The Maastrichtian Gaudryina pyramidata Cushman⁷ to the Paleocene limbata Said & Kenawy¹⁵ lineage.
2. The Paleocene Gaudryina limbata Said & to the Early Eocene speijeri Anan¹² lineage.
3. The Early Eocene Gaudryina speijeri Anan¹² to the Middle Eocene ennakhali Anan (n. sp.) lineage

Gaudryina arabica lineage

The triangular test has transverse section, acute triserial early chambers, later elongate tapering final chamber in the biserial stage, chambers distinct and slightly inflated, truncate to subrounded periphery, sutures slightly depressed, wall agglutinated arenaceous with a smooth surface, a large opening semicircular aperture of the inner margin of the last formed tapering chamber. The Maastrichtian Gaudryina arabica was probably ancestral to three subsequent Paleocene to Middle Eocene lineages, these are:

2.1 The Maastrichtian Gaudryina arabica Anan (n. sp.) to the Paleocene G. salimi Anan (n. sp.) lineage.

2.2 The Paleocene Gaudryina salimi Anan (n. sp.) to the Early Eocene G. ameeri Anan¹² lineage.

2.3 The Early Eocene Gaudryina ameeri Anan¹² to the Middle Eocene G. osmani Anan (n. sp.) lineage.

Taxonomy

The taxonomy of Kaminski³⁴ is followed here for the recorded fauna. The Gaudryina pyramidata group includes four species throughout Maastrichtian to Lutetian (G. pyramidata, G. limbata, G. speijeri and G. ennakhali), but the Gaudryina arabica group includes another four species (G. arabica, G. salimi, G. ameeri and G. osmani), which illustrated in Plate 1. Some modern references are added to complete descriptions, synonymies, stratigraphy and new taxonomic considerations.   

Plate 1 The Gaudryina pyramidata group: Fig.1-3: The Maastrichtian Gaudryina pyramidata Cushman (1926): 1. after Cushman (1926) x 40, 2. after Bolli et al. (1994) x 65, 3. after Anan (2005) x 100; 4-8: The Paleocene Gaudryina limbata Said and Kenawy (1956): 4. after Said and Kenawy (1956) x 70, 5. after Anan (1993) x 160, 6. after Bolli et al. (1994) x 50, 7. after Bolli et al. (1994) x 95, 8. after Abdelghany and Abu Saima (2013) x 70; 9. The Early Eocene Gaudryina speijeri Anan (2012) x 100; 10. The Middle Eocene Gaudryina ennakhali Anan, n. sp. x 85, The Gaudryina arabica group: Fig. 11. The Maastrichtian Gaudryina arabica n. sp. x 45; 12. The Paleocene Gaudryina salimi Anan, n. sp. x 90; 13. The Early Eocene Gaudryina ameeri Anan (2012) x 85; 14. The Middle Eocene Gaudryina osmani Anan, n. sp. x 45.

Order Foraminiferida Eichwald, 1830

Suborder Verneuilinina Mikhalevich and Kaminski, 2004

Superfamily Verneuilinoidea Cushman, 1911

Family Reophacellidae Mikhalevich and Kaminski, 2004

Subfamily Verneuilininae Cushman, 1911

Genus Gaudryina d'Orbigny, 1839

Type species Gaudryina rugosa d'Orbigny, 1839

1. The Gaudryina pyramidata group:

Gaudryina pyramidata Cushman¹⁸ - (Pl. 1, figs. 1-3)

1926 Gaudryina laevigata Franke var. pyramidata Cushman¹⁸, p. 587, pl. 16. fig. 8.

1946 Gaudryina (Pseudogaudryina) pyramidata Cushman³⁶, p. 36, pl. 8, fig. 14.

1953 Gaudryina pyramidata Cushman - LeRoy²⁰, p. 31, pl. 1, figs. 17, 18.

1956 Gaudryina pyramidata Cushman - Said & Kenawy¹⁵, 124, pl. 1, fig. 26.

1978 Gaudryina pyramidata Cushman - Proto Decima & Bolli³⁷, p. 793, pl. 1, fig. 6.

1983 Gaudryina pyramidata Cushman - Tjalsma & Lohmann¹, p.12, pl. 2, fig. 4; pl. 8, fig. 1.

1988 Gaudryina pyramidata Cushman - Kaminski et al.³⁸, p. 194, pl. 8, fig. 7.

1993 Gaudryina pyramidata Cushman - Hewaidy & Al-Hitmi³⁹, p. 478, pl. 4, fig. 8.

1993 Gaudryina pyramidata Cushman - Kuhnt & Kaminski⁴⁰, p. 73, pl. 6, fig. 9.

1994 Gaudryina pyramidata Cushman - Bolli et al.², p. 90, fig. 24. 4 (non 5, 6).

2001 Gaudryina pyramidata Cushman - El-Dawy²², p. 42, pl. 1, fig. 4.

2003 Gaudryina pyramidata Cushman - Abdelghany⁴¹, p. 398, fig. 7. 1.

2005 Gaudryina pyramidata Cushman - Anan⁴², p. 81, pl. 1, fig. 4.

2005 Gaudryina pyramidata Cushman - Sztrakos⁴³, p. 184, pl. 2, fig. 5.

2012 Gaudryina pyramidata Cushman - Ismail⁴⁴, p. 29, pl. 1, fig. 15.

2014 Gaudryina pyramidata Cushman - Hewaidy et al.⁴⁵, p. 22, pl. 4, fig. 6.

2016 Gaudryina pyramidata Cushman - VahdatiRad et al.⁴⁶, p. 6, fig. 2. 17.

Remarks: According to Cushman³⁶, the test of this species somewhat longer (1.25 mm) than broad (0.09 mm), triangular in transverse section, the early chamber triserial, later biserial, angles acute, chambers distinct and slightly inflated, truncate periphery, sutures slightly depressed, wall agglutinated arenaceous with a smooth surface, aperture a low opening in a semicircular re-entrant of the inner margin of the last formed chamber. It is indicated by many authors as an index fossil for the Maastrichtian, and may ranges to Danian. The cosmopolitan species Gaudryina pyramidata was originally recorded from the Maastrichtian Velasco Shale in Mexico and occur also in USA, Trinidad, Atlantic Ocean, but later on from the Paleocene strata in many parts of the Northern Tethys (Spain, France, Italy), and Southern Tethys (Tunisia, Egypt, Qatar, Iran). It is related to Velasco-Type Fauna (VTF). 

Figure 2 The paleogeographic map of the K/T boundary showing some Tethyan localities, which including the recognized Maastrichtian members of the genus Gaudryina in the Tethys: Atlantic Ocean (USA, Trinidad, Barbados), Europe (Spain, France, Italy), North Africa (Tunisia, Egypt), southwest Asia (Jordan, Qatar, UAE). 

Figure 3 The paleogeographic map of the Middle Eocene showing the connections between the Pacific, Atlantic, Tethys and Indian Oceans which including the recognized Lutetian members of the genus Gaudryina: the Middle Eocene Gaudryina ennakhali Anan, n. sp. and the Middle Eocene Gaudryina osmani Anan, n. sp.

Gaudryina limbata Said & Kenawy¹⁵ - (Pl. 1, fig. 4-8)

1956 Gaudryina limbata Said & Kenawy¹⁵, p. 123, pl. 1, fig. 23.

1975 Tritaxia midwayensis (Cushman) - Berggren & Aubert⁴⁷, p. 158, pl.1, fig. 1e (non 1a-d).

1993 Gaudryina limbata Said & Kenawy - Anan⁴⁸, p. 314, pl. 1, fig. 6.

1993 Gaudryina limbata Said & Kenawy - Hewaidy & Al-Hitmi³⁹, p. 478, pl. 4, figs. 6, 7.

1994 Gaudryina pyramidata Cushman - Bolli et al.², p. 90, fig. 24. 4.5, 6 (non 4).

2013 Gaudryina limbata Said & Kenawy - Abdelghany & Abu Saima⁴⁹, pl. 1, fig. 10.

2014 Gaudryina limbata Said & Kenawy - Hewaidy et al.⁴⁵, p. 21, pl. 4, fig. 5.

2016 Gaudryina limbata Said & Kenawy - Anan⁵⁰, p. 357, fig. 3m.

2017 Gaudryina pyramidata Cushman - Hewaidy et al.⁵¹ p. 83, pl. 2, fig. 16.

2021 Gaudryina limbata Said & Kenawy - Anan⁵², p. 271, pl. 1, fig. 3.

Figure 4 The three locations which the holotype species of the genus Gaudryina were used in this study: USA and Atlantic Ocean (G. pyramidata, G. salimi, G. ennakhali, G. osmani), Egypt=E (G. ameeri, G. limbata, G. speijeri) and UAE (G. arabica).

Remarks: This species has triangular transverse section, triserial early stage and later biserial, angled acute with truncated periphery and limbate sutures. Tjalsma & Lohmann¹ considered the Gaudryina limbata Said & Kenawy¹⁵ is conspecific with G. tumeyensis Israelski⁵³ which treated by them as a synonym of Cushman. In this study, the two species are separated. The Danian G. limbata differs from the Maastrichtian G. pyramidata in being less elongated test, having sharper edges, more limbate sutures and younger stratigraphic level. In this study, the G. pyramidata is considered here as the ancestor of the descendent G. limbata. The latter species was originally recorded from the Danian of Sinai of Egypt, and later the figured forms of Anan⁴⁸ and Abdelghany & Abu Saima⁴⁹ of UAE, Bolli et al.² of Trinidad. 

Gaudryina speijeri Anan¹² - (Pl. 1, fig. 9)

1994 Gaudryina cf. ellisorae Cushman - Speijer⁵⁴, p. 147, pl. 5, fig. 1. 

2012 Gaudryina speijeri Anan¹², p. 66, pl. 1, fig. 10.

2016 Gaudryina speijeri Anan - Anan⁵⁰, p. 357, fig. 3n.

2019 Gaudryina pyramidata - Bejaoui et al.⁵⁵, p. 523, pl. 11, fig. 2.

2021 Gaudryina speijeri Anan - Anan⁵², p. 271, pl. 1, fig. 5.

Remarks: The carinate rib is very distinct in this Early Eocene species G. speijeri, which exists in the triserial stage and extends to the final chamber of the biserial stage. This species differs from the Late Cretaceous Gaudryina (Pseudogaudryina) ellisorae Cushman in its semiglobular last chamber with more circular aperture than the triangular last chamber, and more elongate aperture than in Cushman'­s specimen. It seems that the illustrated side view of G. pyramidata in Bejaoui et al⁵⁵ is closely related to G. speijeri due to its semi-rounded final chamber, which characterized this species. In this study, the G. speijeri more accurately was evolved from the Paleocene G. limbata, not directly from the Maastrichtian G. pyramidata as previously noted by Anan¹², that the G. speijeri was evolved directly from the Maastrichtian G. pyramidata. This species was recorded from the Early Eocene in many sections in Egypt. 

Gaudryina ennakhali Anan, n. sp. - (Pl. 1, fig. 10)

1983 Gaudryina pyramidata Cushman - Tjalsma & Lohmann¹, p. 12, pl. 8, fig. 1.

Holotype: Illustrated specimen in Pl. 1, fig. 10.

Dimension: Length 0.40 mm. width at top part 0.30 mm.

Etymology: After the late micropaleontologist Prof. H. El-Nakhal, Islamic University-Gaza.

Age: Middle Eocene.

Diagnosis: Test triangular in transverse section, the early chamber triserial, later biserial with more or less rounded angles, chambers slightly inflated, subrounded periphery, sutures slightly depressed, wall agglutinated arenaceous with a smooth surface, aperture a large semi-circular opening in the inner margin of the last formed chamber.

Remarks: This Middle Eocene species loose the carinate rib along the test and more or less rounded periphery. In this study, the Early Eocene G. speijeri is considered here as the ancestor of the descendent Middle Eocene G. ennakhali.

2. Gaudryina arabica group:

Gaudryina arabica Anan, n. sp. - (Pl. 1, fig. 11)

2003 Gaudryina pyramidata Cushman - Abdelghany⁴¹, p. 398, fig. 7.1.

Holotype: Illustrated specimen in Pl. 1, fig. 11.

Dimension: Length 0.40 mm. width at top part 0.40 mm.

Etymology: After the United Arab Emirates (UAE).

Age: Late Maastrichtian.

Diagnosis: The early triserial stage is triangular in transverse section, the later biserial angled acute, chambers distinct and slightly inflated, truncate periphery, sutures slightly depressed, wall agglutinated arenaceous with a smooth surface, aperture a low opening in a semicircular of the inner margin of the last formed chamber.

Remarks: The front acute periphery of the test is very distinct in this Maastrichtian species, which exists along the chamber of the triserial stage, without extending to biserial stage. The elongation and tapering final chamber with semi-circular aperture at the apertural face is distinguished this species and all other species of this group.

Gaudryina salimi Anan, n. sp. - (Pl. 1, fig. 12)

1983 Gaudryina pyramidata Cushman - Tjalsma & Lohmann¹, p. 12, pl. 2, fig. 4.

Holotype: Illustrated specimen in Pl. 1, fig. 12.

Dimension: Length 0.75 mm. width at top part 0.70 mm.

Etymology: After my late son Salim Anan.

Age: Late Paleocene.

Diagnosis: Test large, triangular in transverse section, the early chamber triserial, later biserial, angles acute, chambers distinct and slightly inflated, truncate periphery, sutures slightly depressed, wall agglutinated arenaceous with a smooth surface, aperture a large opening in a semicircular of the inner margin of the last formed chamber. It is indicated as an index fossil for the Paleocene.

Remarks: The front edge grow to produce a semi-carinate rib extends on the hole triserial portion, and extends to the pre-final chamber of the biserial stage. In this study, the Maastrichtian G. arabica represents the ancestor of the descendent Paleocene G. salimi. 

Gaudryina ameeri Anan¹² - (Pl. 1, fig. 13)

2012 Gaudryina ameeri Anan¹², p. 63, pl. 1,fig. 7.

2021 Gaudryina ameeri Anan - Anan⁵², p. 86, pl. 1, fig. 9.

Remarks: The front carinate rib is very distinct in this Early Eocene species, which exists along the pre-final chamber of the biserial stage as well as the whole triserial portion. The elongate and tapering final chamber with semi-circular aperture at the apertural face in Gaudryina ameeri Anan differs from the semiglobular final chamber with circular aperture in the other G. speijeri Anan, and G. ameeri is shorter test than G. speijeri. The author believes that the Early Eocene G. ameeri was derived from the Paleocene G. salimi due to the growing of front edge to produce a carinate rib extends on the hole triserial portion and extends to the pre-final chamber of the biserial stage, but in another edge of the test. The second changes exist in the final chamber of G. salimi, which tending to be tapered through the younger time. In this study, the Paleocene G. salimi is considered here as the ancestor of the descendent Early Eocene G. ameeri.

Gaudryina osmani Anan, n. sp. - (Pl. 1, fig. 14)

2003 Gaudryina cf. pyramidata Cushman - Tjalsma & Lohmann¹, p. 31, fig. 8.2.

Holotype: Illustrated specimen in Pl. 1, fig. 14.

Dimension: Length 0.45 mm. width at top part 0.40 mm.

Etymology: After the micropaleontologist Prof. Osman Abdelghany, UAE University.

Age: Early-Middle Eocene.

Diagnosis: This species differs from G. pyramidata by its more strongly tapering initial triserial end part without carinate rib, more or less quadrate biserial part, elongate and tapering final chamber with elongate aperture at the apertural face.

Remarks: In this study, the Ypresian G. ameeri is considered here as the ancestor of the descendent the Lutetian G. osmani. 

Paleogeography

In this study, the identified Maastrichtian-Lutetian species of the two Gaudryina groups are recognized in different localities in the Tethys: Atlantic Ocean, USA, Trinidad, France, Spain, Italy, Tunisia, Egypt, UAE and Qatar. Haq & Aubry⁵⁶ noted that the North Africa and Middle East formed important parts of the Tethyan link between the Atlantic and Pacific Oceans during the K/T boundary (Fig. 2) and the Middle Eocene (Fig. 3). Abdelghany⁴¹ noted that the Maastrichtian benthic foraminiferal species of Qarn El Barr section, UAE (including Gaudryina arabica n. sp.) and some other sections in Iraq, Jordan and Egypt are closest to the Maastrichtian fauna of Nekhl section, Sinai, Egypt (including Gaudryina pyramidata and G. limbata) (Fig. 4). The closest morphology of any recorded species from different localities in the Tethys (specimens of G. pyramidata from USA, Trinidad and Egypt, Pl. 1, figs. 1-3; specimens of G. limbata from Egypt, UAE and Trinidad, Pl. 1, figs. 4-8) prove the open marine conditions between the different localities in different oceans throughout the Maastrichtian and Paleogene times. 

Paleoenvironment

The following is an account on the relevant paleoenvironment and interpretation in this study:

Said & Kenawy¹⁵ described and recorded more than two hundred and fifty benthic foraminiferal species (including Gaudryina limbata) from the Maastrichtian-Paleogene strata of Sinai, Egypt. These taxa shown an affinity with Midway Type Fauna (MTF) of American Gulf Coastal Plain which documented also by Berggren & Aubert⁴⁷, while Anan⁵⁷ (2011) noted that the probable environment for Sinai in the northern Egypt (the type locality of Gaudryina limbata) is outer neritic-upper bathyal (200-400 m).

 Murray⁵⁸ noted that arenaceous foraminifera (including the genus Gaudryina and its members) tend to increase in cooler (usually deeper) environments. Anan⁵⁹ noted that the cosmopolitan cooling of the top Maastrichtian (including Gaudryina pyramidata) was prevailed also in Jiran El Ful section, Abu Rawash area, northern Egypt.

Tjalsma & Lohmann¹ recorded and described the DSDP which includes bathyal and abyssal fauna (including the Middle Eocene Gaudryina ennakhali and G. osmani) from Atlantic Legs 3,10, 14, 15, 36, 39, 40 and 44, and compared these material from the uplifted surface sections of the Paleocene (in Mexico, Trinidad) and Eocene (in Barbados). 

Anan⁴⁸ noted that the Paleocene assemblage of benthic foraminiferal species (including Gaudryina limbata) in the Malaqet section (UAE) belongs to the MFT, middle to outer neritic environment (50-200 m), while the Maastrichtian species in the UAE (including Gaudryina pyramidata, G. limbata, and also G. arabica in this study) representing  shallow to deep water environment, which may prevailed in the Arabian Gulf area in that time (Anan⁴²).

Speijer⁵⁴ noted that the carinate ribs are very distinct in his Early Eocene Gaudryina cf. ellisorae (= G. speijeri in this study) from Wadi Nukhul (west Sinai, Egypt), and represents the deeper localities which have smooth tests, while the shallow water specimens are more coarse grained.

Gawenda et al.⁶⁰ noted that the turbidite sedimentation is the product of a complex interplay of tectonics, climate, production of biogenic material, and sea-level changes, and these factors control the availability and volume of detrital material transported by the gravity flows from the neritic shelf environment to adjacent basins.

Meulenkamp & Sissingh⁶¹ noted that the Arabian Platform still largely covered by the sea in the Early to Middle Eocene, while it subjected to a major regression in the Middle to Late Eocene.    

Bejaoui et al.⁵⁵ considered some agglutinated genera in Wadi Necham section, (northwest Tunisia) yields agglutinated species, such as G. pyramidata, of typical bathyal to upper abyssal assemblage with high terrigenous sedimentation rate and associated moderate organic flux.

Anan⁵² considered the genus Gaudryina with the other genera of the family Verneuilinidae (Plectina, Siphogaudryina, Verneuilina) presented deep marine environments.

The rich and well-preserved Maastrichtian-Paleogene benthic foraminiferal species of the agglutinated genus Gaudryina in the Tethys shows an increasing phylogenetic plasticity through the modifications of morphologic features first appearing in the ancestors, which made it possible to present two lineages: (1) Gaudryina pyramidata lineage (Maastrichtian Gaudryina pyramidata to Paleocene G. limbata to Early Eocene G. speijeri to the Middle Eocene G. ennakhali), and (2) Gaudryina arabica lineage (Maastrichtian Gaudryina arabica to the Paleocene G. salimi to the Early Eocene G. ameeri to the Middle Eocene G. osmani). The evolutionary lineages may be produced by one of the two evolutionary models: Phyletic gradualism or Punctuated equilibrium. Most probably the first model causes the present lineages. Four out of the recorded species from the two lineage groups are believed here to be new: Gaudryina arabica, G. salimi, G. osmani and G. ennakhali. The identified species of the two groups are recorded from wide localities in the Tethys: Atlantic Ocean, USA, Trinidad, France, Spain, Italy, Tunisia, Egypt, UAE, Qatar and Pakistan. The recorded species ranges from the middle-outer neritic, Midway Type Fauna (MTF) to bathyal environment Velasco-Type Fauna (VTF ) (100-400 m depth), which also indicated an open marine conditions between the different oceans throughout the Maastrichtian and Paleogene times.

None.

Authors declare that there is no conflict of interest.

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