Recent investigations based on bed-by-bed sampling of the Béni Kleb Formation (Fm) of Northern Tunisia (Kimmeridgian-Middle Berriasian) provide new data on Tithonian chitinoidellid associations. Fourteen species from seven genera (Daciella Pop, Borziella Pop, Longicollaria Pop, Dobeniella Pop, Cubanella Pop, Popiella Reháková and Chitinoidella Doben) are first documented in Tunisia. Their stratigraphic range fits the standards proposed for other Tethyan regions. In addition, three new species are described: Chitinoidellacarthagensis sp. nov., Ch. hegarati sp. nov. and Ch. popi sp. nov. They are compared to the recently revised taxa from the southern Carpathian ranges where the chitinoidellid populations were observed at various levels and revealed to be well diversified. The established biozonation is discussed and a phyletic pattern is proposed.
Sur la base d’un échantillonnage banc par banc, de récents travaux entrepris sur la formation (Fm) Béni Kleb du Nord tunisien (Kimméridgien-Berriasien moyen) ont fourni de nouvelles données sur les chitinoïdelles tithoniennes. Quatorze espèces appartenant à sept genres (Daciella Pop, Borziella Pop, Longicollaria Pop, Dobeniella Pop, Cubanella Pop, Popiella Reháková and Chitinoidella Doben) sont pour la première fois documentées de Tunisie. En outre, trois espèces nouvelles sont décrites : Chidinoidellacarthagensis sp. nov., Ch. hegarati sp. nov. et Ch. popi sp. nov. Elles sont comparées aux taxons récemment révisés dans les Carpathes méridionales où les chitinoïdelles ont été observées à différents niveaux et se sont avérées des plus diversifiées. Les biozonations établies sont discutées et un modèle phylétique est proposé.
Chitinoidellids, Taxinomy, Biozonation, Phylogeny, Tithonian, Northern TunisiaChitinoïdelles, Taxinomie, Biozonation, Phylogénie, Tithonien, Tunisie septentrionalepresentedPresented by Philippe TaquetIntroduction
The Tethyan pelagic sediments of the Upper Jurassic-Lower Cretaceous transition are mainly characterized by a small microfossil group of axially symmetrical planktonic protozoans included in three families based on the morphology of their lorica. These can be microgranular (Chitinoidellidae Trejo, 1975), combined microgranular and hyaline (Semichitinoidellidae Nowak, 1978) or only hyaline (Calpionellidae Bonet, 1956; Duben, 1963). Although the biological affinities of this widely distributed Tethyan group are still uncertain and a matter of debate, its high stratigraphic potential for the biozonation of Upper Jurassic-Lower Cretaceous series has been applied since the sixties of the last century. The biozonations currently in use for the Upper Tithonian-Lower Valanginian (e.g. Andreini et al., 2007, Grün and Blau, 1996 and Michalík et al., 2009 and references therein; Oloríz et al., 1995, Reháková and Michalík, 1997 and Remane et al., 1986 and references therein) consider that the lowermost Chitinoidella zone spans the Lower-Upper Tithonian transition levels. It was first defined in the West Carpathians by Borza (1969) and correlated to the ammonite zones by Enay and Geyssant (1975) and Cecca et al. (1989) after biostratigraphic analyses of successions from the Sub-betic range of SE Spain and Ardèche in SE France. Biostratigraphic investigations of Ammonitico Rosso successions from the Italian Venetia area allowed Grandesso (1977) to bring more precisions to the zonal content: small forms of the Ch. dobeni group occur in the lower part and specimens of Ch. boneti in the upper one. The formal subdivision of the Chitinoidella zone into the Dobeni and the Boneti Subzones was provided by Borza (1984) and Borza and Michalík (1986). Within these Subzones, all Chitinoidellid species had been assigned to the single genus ChitinoidellaDoben, 1963 until Pop, 1997 and Pop, 1998a revised its taxinomy on the basis of an abundant material from the south Carpathian range; five new genera (Dobeniella, Cubanella, Longicollaria, Borziella and Cylindrella) were then introduced by this author. In the central and West Carpathian Pieniny klippen Belt areas, Reháková (2002) recognized all the genera described by Pop, 1997 and Pop, 1998a and proposed another new genus (Popiella) limited to the single species P. oblongata.
From the South-Tethyan margin of the Maghreb, chitinoidellid faunas described from the Moroccoan Prérif (e.g. Bachnou, 1992, Benzaggagh, 2000 and Benzaggagh and Atrops, 1995) were all assigned to the genus Chitinoidella and were used mainly for biostratigraphic purposes. The Dobeni and Boneti Subzones of the Chitinoidella zone were recognised and correlated to the ammonite zones.
In Northern Tunisia, Chitinoidella boneti had been mentioned in the “Tunisian Dorsale” (“TD”) to identify its corresponding zone (Boughdiri et al., 2005 and Combémorel et al., 1981); however, its first illustration was provided by Boughdiri et al. (2006) in the “Tunisian Trough” (“TT”). Recent investigations of Tithonian successions from these areas led to the identification of rich chitinoidellid assemblages described here and first documented in Tunisia. New species are introduced and their stratigraphic distribution is detailed. A phyletic approach is proposed taking into account revised complementary data from the Moroccoan Prerif and the Carpathian Ranges.
Studied sections: location and stratigraphic context
Among six sections bearing chitinoidellids and calpionellids, only three were chosen (Fig. 1): the Jebel (J.) Oust section of the “TD” (Bir M’Cherga area, NE Tunisia) and the J. Jédidi and J. Chaabane sections of the “TT” (Mejez el Beb area, NW Tunisia). Their location and detailed palaeogeographic setting are described in previous papers (e.g. Boughdiri et al., 2007, Boughdiri et al., 2009, Cordey et al., 2005, Soussi, 2002 and Soussi, 2003).
In these areas, these sections are part of the Béni Kleb Fm (Peybernès, 1992emend. Boughdiri et al., 2006) composed by marls and pseudonodular limestones with Saccocoma and calpionellids, including four successive units: limestone beds with intercalated thin marly layers (unit A), marl/limestone alternations with relatively thicker marly levels (unit B). Follows another carbonate unit (C) and again a marl/limestone alternation (D) with chert nodules and rare turbidites. Chitinoidellid faunas studied in this paper are observed within the uppermost beds of Unit C and the lowermost part of unit D.
BiostratigraphyReference stratigraphic scale
The standard referred to in this work is that of Remane et al. (1986). Complementary updated data of Pop, 1994 and Pop, 1996, Boughdiri et al., 2006 and Boughdiri et al., 2009 and Michalík et al. (2009) were also considered. For the correlation of ammonite and praecalpionellid scales we used the standard proposed by the “Groupe français d’études du Jurassique” G.F.E.J (1997).
Faunal distribution and biozonation
Within bed “JD 60” of the Jédidi section, a rich assemblage of small chitinoidellids comprises: Longicollaria dobeni (Borza), Dobeniella colomi (Borza), D. cubensis (Furrazola-Bermúdez), D. bermudezi (Furrazola-Bermúdez), D. tithonica (Borza), Borziella slovenica (Borza) and Daciella svinitensis Pop.
A comparable assemblage was encountered within bed “CH 21” of the Chaabane section where, in addition, the genus Daciella Pop is represented by two species: D. aff. banatica Pop and D. gr. svinitensis Pop. The bed “OU 81.A” of the J. Oust section carries also very similar associations among which we also identified Popiella oblongata Reháková and Cubanella cristobalensis (Furrazola-Bermúdez). All these associations and co-occurrent taxa of the Dobeni Subzone were also identified in the Carpathian Range (e.g.: Pop, 1997, Pop, 1998a, Pop, 1998b and Reháková, 2002). This allows us to correlate the beds “JD. 60” (J. Jédidi), “CH 21” (J. Chaabane) and “OU 81.A” (J. Oust) as co-eval (Fig. 2). They are dated here to the upper Dobeni Subzone (Chitinoidella Zone) because the oldest association of the bed “OU 78.A” (J. Oust) includes only L. dobeni and Borziella slovenica in its lower part. Thus, the lower limit of the Dobeni Subzone can be traced below the bed “OU 78.A” of Jebel Oust which is older than the above-mentioned coeval beds “JD 60”, “CH 21” and “OU 81.A”.
Higher in the Jédidi section, the bed “JD 91” shows the first occurrence of Chitinoidella carthagensis sp. nov. and Ch. hegarati sp. nov. together with Dobeniella cubensis (Furrazola-Bermúdez) and L. dobeni. The bed “JD 95” has the same association to which corresponds also the first occurrence (F.O.) of Ch. boneti Doben and Ch. carthagensis sp. nov. and below which we place the boundary between the Dobeni and Boneti Subzones. In J. Oust, this limit can be traced on top of bed “OU 114” where Boughdiri et al. (2005) gathered an ammonite association of the uppermost Ponti Zone.
The bed “JD 107” (J. Jédidi) is mainly characterized by the FO of Ch. cf. elongata Pop, Ch. popi sp. nov. The same occurrence of Ch.elongata in the upper part of the Boneti Subzone was also documented within the Carpathian range by Pop, 1997, Pop, 1998a and Pop, 1998b and Reháková (2002). In J. Jédidi, the upper limit of the Boneti Subzone (= upper limit of the Chitinoidella Zone) is placed below the bed “JD 117” where Praetintinnopsella andrusovi (Borza) co-occurs with Ch. boneti for the first time. The first hyaline calpionellids appear within the bed “JD 127” (Boughdiri et al., 2006), which base indicates the boundary between the Praetintinnopsella and Crassicollaria zones and which is correlated with the bed “OU 126” of J. Oust where the same datum was detected by Boughdiri et al. (2005).
In conclusion, the Chitinoidellid distribution within the studied sections agrees with those obtained in the Carpathian Range where the succession is more complete and the assemblages are the most diversified. The biozonation established here easily fits their proposals for northern Tethys Margin regions. Nevertheless, some biozonation data are worth commenting. From top to base, as shown on Fig. 3, the index genus Chitinoidella does not span the whole Chitinoidella zone but only its upper part (= Boneti Subzone). Thus, an updated Chitinoidella zone should be restricted to the upper part of the classic Chitinodella zone (= Boneti Subzone). Furthermore, within this updated Chitinoidella zone, Ch. elongata and Ch. popi characterize its upper part; their FO can be considered to trace the base of a new Elongata/Popi Subzone (= the top of the classic Boneti Subzone or a Boneti/Carthagensis Subzone).
Lower, under the updated chitinoidella zone (Fig. 3), only the index species L. dobeni marks the lowermost part of the ex. Dobeni Subzone. Higher, Borziella svinitensis and many species of the genus Daciella appear and, in the upper part, all Dobeniella species appear among which D. bermudezi is the most diversified. Consequently, considering these bioevents, another updated biozonation is proposed here: a Longicollaria zone can be considered as a new equivalent of the ex. Dobeni zone. It includes henceforth a lower Dobeni Subzone, a medium Slovenica Subzone and an upper Bermudezi subzone (Fig. 3).
SystematicsNew chitinoidellid species from Northern Tunisia
Thin sections bearing the new species described below will be housed in the Geology museum of the Tunisia Geological Survey (Office National des Mines [ONM]).
Family:ChitinoidellidaeTrejo, 1975
Genus:ChitinoidellaDoben, 1963
Chitinoidella popisp. nov.
(Plate 1, Figs. 32 and 33)
Holotype
Specimen on Plate 1, Fig. 32 (ONM/HS 0409/JD 107.1).
Paratype
Specimen on Plate 1, Fig. 33 (ONM/HS 0409/JD 107.3).
Material and Depository reference
Five specimens from the Jédidi section: ONM/HS 0409/JD 107.1-4, ONM/HS 0409/JD 115.1.
Etymology
The specific name is chosen in memory of Grigore Pop, a former geologist from the Geological Institute of Romania (Bucharest) specialist of calpionellid palaeontology and biostratigraphy. He revised the genus Chitinoidella and described the majority of the chitinoidellid taxa currently in use.
Diagnosis
Elongated bell-shaped lorica with a conical aboral pole terminating in a well-marked caudal appendage. Large oral opening surrounded by a concave outwardly deflected collar, which is lense-like in section. The lorica is 70–85 μm long and 40–50 μm wide; the length/width (L/l) ratio is 1,7–1,8. Measurements of the holotype: L = 85 μm, l = 48 μm; L/l = 1,77.
Type locality
The Jédidi section (Mejez el Beb area, NW Tunisia)
Type beds
Beds JD 107 and JD 115 of the Jédidi section, upper Boneti Subzone
Remarks
Chitinoidella popi sp. nov. can be distinguished from Ch. elongata Pop by its concave collar, small preoral constriction, larger preoral opening and maximum width located at the middle part of the bowl. It is different from Ch. boneti in its elongated shape, the preoral constriction and the concave lense-like aspect of the collar. Ch. popi is a perfect homeomorph of the calpionellid Tintinnospsella carpathica (Murgeanu and Filipescu). It also displays the same bowl shape of Remaniella gr. catalanoi-colomi Pop.
Specimen on Plate 1, Fig. 28 (ONM/HS 0409/JD 107.7).
Paratype
Specimen on Plate 1, figs. 26, 27 and 29 (ONM/HS0409/JD115.02, (ONM/HS0409/JD107.18 ONM/HS 0409/JD 95.1)
Material and Depository reference
14 specimens from the Jédidi section; references: ONM/HS 0409/JD 95.1.
ONM/HS 0409/JD 107.5-10, ONM/HS0409/JD107.17-19, ONM/HS0409/JD91.03, ONM/HS0409/JD95.04-05, ONM/HS0409/JD103.03, and ONM/HS0409/JD115.02.
Etymology
The species name refers to the city of Carthage (814-146 B. C.), the capital of the Carthagenian Empire which included Tunisia. The Jédidi section is located 85 km to the southeast of former Carthage.
Diagnosis
Elongated bell-shaped lorica with a polygonal bowl. This latter is rather ellipsoid with a rounded aboral pole in oblique sections. Just below the large preoral opening, the bowl flanks converge towards the lower part where they are abruptly attached to a conical aboral pole at the end of which a small and smoothed caudal appendage is observed. A short angular “shoulder”-like feature characterizes the upper part of the bowl where the maximum width can be measured. The collar is outwardly deflected forming an angle of nearly 90° with the external edge of the oral opening. The lorica length is 55–65 μm and its width is 32–45 μm with a L/l = 1,4–1,6. Measurements of the holotype (L = 61 μm, l = 39 μm; L/l = 1,56).
Type locality
The Jedidi section (Mejez el Beb area, NW Tunisia).
Type level
Beds JD 91, JD 95, JD 103, JD 107 and JD 115 of the Jédidi section, lower Boneti Subzone (Chitinoidella Zone).
Remarks
Chitinoidella carthagensis can be easily differentiated from the co-occurrent species Ch. boneti, Ch. elongata and Ch. popi by its polygonal shape and maximal width that can be taken just below the collar. The oblique sections of Ch. carthagensis differ from the Daciella species in the following traits: a larger size, a smaller and smoothed caudal appendage and the absence of a thickened wall on the “shoulder”-like feature below the preoral opening. They can be easily distinguished from axial and oblique sections of Ch. hegarati by their elongated ellipsoid shape.
Age
Lowermost Upper Tithonian, lower Boneti Subzone of the Chitinoidella Zone.
Chitinoidella hegaratisp. nov.
(Plate 1, Figs. 25, 30–31)
1995 Chitinoidella bermudezi- Benzaggagh et Atrops, fig. 4:7
1997? Chitinoidella sp1- Grün and Blau, pl. 1, fig. 7
2000 Chitinoidella bermudezi- Benzaggagh, pl. 5, fig. 7
2007 Chitinoidella boneti - Andreini et al., pl. I, fig. 1, 3 and 4).
Holotype
Specimen on Pl. 1, Fig. 30 (ONM/HS 0409/JD 91.01).
Paratypes
Specimen on Pl. 1, Fig. 25, 31 (ONM/HS 0409/JD 107.12, ONM/HS 0409/JD 103.02).
Material and Depository reference
12 specimens from the Jédidi section; thin sections and references: ONM/HS0409/JD91.01-02, ONM/HS0409/JD 95.02-03, ONM/HS0409/JD103.01-02 and ONM/HS0409/JD107.11-16.
Etymology
The species name is chosen in memory of Gérard Le Hégarat, a former palaeontologist and stratigrapher from the Claude Bernard University of Lyon (France), specialist of ammonites and calpionellids of the Jurassic-Cretaceous boundary and particularly Berriasian markers.
Diagnosis
Fairly isometric bell shaped to polygonal lorica with parallel lateral edges. The oblique section of Ch. hegarati is spheroid to slightly elongated (L = 40–60 μm, l = 30–40 μm; L/l = 1,3–1,5). Conical aboral pole terminating in a caudal appendage (rounded in oblique sections). Large oral opening surrounded by a collar outwardly deflected in its distal extremity, its lower part being small and cylindroid with a small preoral constriction. Parallel to fairly rounded lateral flanks converge to the oral part through a “shoulder”-like structure. For axial sections, L = 50–65 μm, l = 38–43 μm; L/l = 1,2–1,5 and the maximum width can be measured by the middle of the lorica. Measurements of the holotype: L = 57 μm, l = 39 μm; L/l = 1,46.
Type locality
The Jedidi section (Mejez el Beb area, NW Tunisia).
Type level
Beds JD 91, JD95, JD 103 and JD 107 of the Jédidi section, lower Boneti Subzone (Chitinoidella Zone).
Differentiation
Ch. hegarati is different from Ch. carthagensis in the following traits: isometric bowl, subparallel lorica flanks and characteristic preoral constriction. The maximum width of Ch. hegarati can be measured at the middle of the bowl, whereas that of Ch. carthagensis can be taken just below the collar. Compared to Ch. hegarati, Ch. boneti has rather rounded bowl flanks devoid of the preoral constriction. Daciella banatica has a smaller size and a narrower aboral pole terminating in a longer caudal appendage.
Specimens of Ch. hegarati sp. nov. are morphologically close to some published forms referred to as Ch. boneti (see synonymy list). We consider that Chitinoidella boneti includes specimens with rounded edges of the bowl and a conical aboral pole and a suddenly outward deflected collar without a constriction (see Plate 1, Fig. 34 of this work). These new forms are perfect homeomorphs of a microgranular nature for “Tintinopsella” remanei Borza which appears just above, in the lower part of the calpionellid Crassicollaria zone.
The species first documented in Tunisia are briefly described below with a particular focus on their synthetic range considering other published data from the Carpathians.
GenusChitinoidellaDoben, 1963
Chitinoidella cf. elongataPop, 1997
(Plate 1, Fig. 34)
1969 Chitinoidella boneti Doben–Borza, pl. LXVIII, fig. 8
2002 Chitinoidella elongata–Reháková, p. 2, fig. 5–8
Description
Cylindridoid lorica showing a conical aboral pole marked by a caudal appendage. Large oral pole bounded by an outwardly deflected collar directly attached to the preoral opening. Measured at the lower third of the lorica, the maximum width is l = 39 μm with a length of L = 82 μm; L/l = 2,1.
Age
Upper Tithonian, upper Boneti Subzone (Chitinoidella Zone) to lower Remanei Subzone (Crassicollaria Zone of calpionellids).
Chitinoidella bonetiDoben Trejo, 1963
(Plate 1, Fig. 24)
This species was already mentioned from Tunisia, its first figuration is due to Boughdiri et al. (2006). Its synonymy listed below includes only important references where one can find more exhaustive data.
1963 Chitinoidella boneti n.sp.- Doben, p. 42, pl. 6, figs. 1–5
1965 Tintinnopsella carpathica (Murgeanu et Filipescu) - Furrazola-Bermúdez, pl. 4, fig. 2
1969 Chitinoidella boneti Doben - Borza, p. 78, pl. 67, figs. 3–16; pl. 68, figs. 1–13
1975 Tintinnopsella carpathica (Murgeanu et Filipescu) - Trejo, pl. XII, fig. 34
1985 Chitinoidella boneti Doben - Remane, p. 564, fig. 13.
1989 Chitinoidella boneti Doben - Cecca et al., p. 114, pl. 6, fig. 1, 2, 4, 6, 7
1993 Chitinoidella boneti Doben -Lakova, pl. I, figs. 7–8
1995 Chitinoidella boneti Doben -Reháková, pl. I, figs. 6–7
1995 Chitinoidella boneti Doben - Oloriz et al., pl. I, fig. 3
1997 Chitinoidella boneti Doben - Grün et Blau, p. 208, pl. I, fig. 7
1998 Chitinoidella boneti Doben - Pop, pl. I, fig. 3
2007 Chitinoidella boneti Doben - Gloria et al., pl. I, figs. 3–5.
Diagnosis
Chitinoidella boneti shows a bell-shaped test, with a large oral opening crowned by a deflected collar and a pointed aboral pole. The rounded lorica converges on the oral opening via a well-marked preoral constriction. Commonly, dimensions are 55–83 μm in length and 40–50 μm in width with a L/l ratio smaller than 1,5.
The Jedidi and Chaabane sections (Mejez el Beb area, NW Tunisia).
Chitinoidellasp. 1
(Plate 1, Fig. 35)
Cylindroid to spindle-shaped lorica with a conical aboral extremity ending with a sharp caudal appendage. Preoral opening narrow to moderately large surrounded by an outwardly deflected arched collar. The bowl of this species is morphologically close to that of the Berriasian calpionellid genera Calpionellopsis and some specimens of Tintinnopsella oblonga. Measurements of the figured specimen: L= 68 μm, l = 38 μm; L/l= 1,79.
Spheroidal to slightly elongated lorica with a rounded aboral pole. Medium-sized oral opening with an arched and outwardly deflected collar. This is directly attached to the lorica without any intermediate cylindrical lower part. Measurements of the figured specimen: L = 50 μm, l = 40 μm; L/l = 1,25.
Differentiation
This form can be distinguished from Ch. elongata by its narrower oral opening its arched collar and the maximum of its width that can be measured in the middle part of the bowl.
2007 Borziella slovenica (Borza)–Andreini et al., pl. I, fig. 1
Description
Spheroidal to ovoidal lorica with a rounded aboral pole. The preoral part is bounded by an outwardly deflected collar close to a slight constriction L = 43 μm, l = 28 μm; L/l = 1,5.
2002 Popiella oblongata–Reháková, p. 372, fig. 4: 10–12
Description
Two specimens of elongated cylindrical lorica with a rounded aboral pole. The oral part, as wide as the lorica bowl (l = 36 μm), does not display a collar. The total height is L = 64 μm with a L/l ratio = 1,8.
1998b Dobeniella cubensis (Furrazola-Bermúdez)–Pop, pl. I, fig. 27–29.
2002 Dobeniella cubensis (Furrazola-Bermúdez)–Reháková, p. 372, fig. 3: 4–6
2007 Dobeniella cubensis (Furrazola-Bermúdez)–Andreini et al., pl. I, fig. 8.
Remark
Two specimen groups of different sizes are observed within Dobeniella species described below. Smaller representatives are interpreted here as juvenile forms.
Description
Ovoid to elongated lorica with a conical aboral extremity terminating in a long caudal appendage in axial sections. Large preoral opening surrounded by a composite collar formed by an inner annular part (circular in section) and a straight and outwardly deflected one.
Measurements: small specimens: L = 42 μm, l = 29 μm; L/l = 1,45; big specimens: L = 57 μm, l = 39 μm; L/l = 1,47.
2007 Dobeniella bermudezi (Furrazola-Bermúdez)–Andreini et al., pl. I, fig. 6–7
Description
Bell-shaped to elongated lorica with a conical aboral pole terminating in a short caudal appendage. The large preoral part is followed by an elongated composite collar. The external part is short and cylindrical at the base and outwardly deflected near the oral aperture. The annular internal piece is lenticular and sharp.
Measurements: small specimens: L = 42 μm, l = 29 μm; L/l = 1,45; big specimens: L = 57 μm, l = 39 μm; L/l = 1,47.
Bell shaped lorica with a conical aboral pole terminating in a long caudal appendage (new character). The walls of the bowl are subparallel with fairly straight edges that converge on the preoral part through a “shoulder”-like feature. The preoral opening is attached to a cylindrical lower part of the collar of which the upper part is composite and made of two pieces: an inner annular one lodging on the end of the cylindrical structure and an external piece outwardly deflected, arched and lens-like in section. Measurements: small specimens: L = 37 μm, l = 29 μm; L/l = 1,28; big specimens: L = 57 μm, l = 43 μm; L/l = 1,32.
Bell-shaped lorica with a conical aboral pole terminating in a long caudal appendage (new character). Large preoral part followed part by a subcylindrical collar, the wall of which is notably thickened at the distal extremity marking an annular piece (circular in section) surrounding the wide oral aperture. Measurements: L = 45 μm, l = 29 μm; L/l = 1,7.
2007 Longicollaria dobeni (Borza)–Andreini et al., pl. I, fig. 2
Description
Elongated ovoid lorica with a conical aboral pole terminating in a sharp and comparatively long caudal appendage in axial sections. A slight constriction in the preoral segment is followed by a subcylindrical collar thickened at the distal end. The length of the collar and that of the bowl are comparable.
Measurements: small specimens: L = 37 μm, l = 29 μm; L/l = 1,28; big specimens: L = 57 μm, l = 43 μm; L/l = 1,32.
Cylindrical elongated lorica of a single specimen with a conical aboral pole terminating in a caudal appendage. Large oral pole surrounded by a cylindrical short collar at the distal part of which a thickening of the wall is characteristic. Measurements: L = 43 μm, l = 22 μm; L/l = 1,9.
Age
Upper-to-Lower Tithonian transition, Chitinoidella Zone-lowermost Praetintinnopsella Zone
Conical to ovoid lorica with an aboral pole ended with a caudal appendage. Large preoral opening characterized by a wall thickening and a shoulder-like feature where a cylindrical collar is attached. Measurements: L = 39 μm, l = 27 μm; L/l = 1,44
Elongated lorica with an ovoid to conical bowl. This is made of an ovoid upper part and a conical aboral extremity terminating in a long caudal appendage. Moderate to large preoral opening surrounded by a subcylindrical simple collar.
Pop (1998a) discussed the details of the chitinoidellid evolution during the Lower-Upper Tithonian transition and proposed several phyletic lineages relating chitinoidellids and calpionellids. Reháková (2002, fig. 5) presented the stratigraphic distribution and possible lineages in the evolution of chitinoidellids where evolutionary trends were discussed at the species level. In continuation of these works, published biostratigraphic and palaeontological data from the Carpathians complemented by those presented here allow us to rethink the potential phyletic relationships among these microbiomarkers (Fig. 3).
The phylogenetic history of chitinoidellids starts from their high diversity as old as the uppermost lower Tithonian (upper Fallauxi Zone of ammonites); their ancestors are still uncertain.
Within this interval, two main groups characterize the lower part of the Dobeni Subzone: the genus Daciella and the assemblage composed of Carpathella rumanica, Borziella slovenica and Longicollaria insueta (= group II). Both groups display common characters with L. dobeni, the oldest species of the Chitinoidella Zone. These characters consist of the conical aboral pole for Daciella and the simple collar surrounding the lorica bowl for group II. This leads us to consider, as already stated by Reháková (2002), L. dobeni as a possible common ancestor. In addition, this same pioneer species could have given rise to Daciella svinitensis and D. danubica, a first phyletic datum marking the lowermost part of the Dobeni Subzone.
Higher within this subzone, Daciella banatica and D. almajica Pop could have derived from D. danubica, which shows the same general morphology but differs in size as well as the outwardly deflected distal part of the collar. D. danubica could have given rise to Cubanellacristobalensis, which displays the same cylindrical collar and conical aboral pole terminating in a comparatively long caudal appendage. In contrast to the hypothesis of Reháková (2002), all the Dobeniella species, which appear at the same stratigraphic level (upper part of the Dobeni Subzone), could have been derived from L. dobeni, which is characterized by the thickened distal end of the collar also observed among the Dobeniella colomi representatives. This thickening characteristic feature can be considered a primitive character that would have been detached to evolve into the inner annular part of the composite collar of Dobeniella bermudezi, D. cubensis and D. tithonica. These lineages do not fit the phyletic scheme proposed by Benzaggagh and Atrops (1995, fig. 1–3), who admitted that “Chitinoidella” slovenica is a common ancestor for “Ch.” dobeni, “Ch.” colomi and “Ch.” tithonioca and also stated that “Ch.” slovenica gave rise to “Ch.” bermudezi, “Ch.” boneti, “Ch.” cubensis and “Ch.” cristobalensis. In fact, our different interpretation is supported by the different Chitinoidellid range charts. For example, as observed in the Carpathians and confirmed in Northern Tunisia, the FO of Dobeniella bermudezi, D. cubensis and Cubanella cristobalensis marks the upper part of the Dobeni Subzone and not the Boneti Subzone as obtained by Benzaggagh and Atrops (1995) in the Moroccoan Prerif.
We also agree with Reháková (2002) that Longicollaria insueta of our group II exhibits many common characters with Popiellaoblongata, which is interpreted as its direct descendant.
At the base of the Boneti Subzone, a phyletic lineage could have linked Borziellaslovenica to the Chitinoidella boneti group as well as the new species Chitinoidellahegarati and Chitinoidella carthagensis. In fact, these forms share many characters such as the isometric to slightly elongated bowl, some dimensional characters and the outwardly deflected collar with a more or less marked swelling at its base.
In the upper part of the Boneti Zone, Ch. boneti representatives display tight affinities with Ch. elongata and Ch. popi sp. nov. which differ in their elongated bowl and the aspect of the collar deflection. These species would have been derived from Ch. boneti by a cladogenetic process.
As far as the relationships between Chitinoidellids and Calpionellids are concerned, we retain the same idea formulated by Reháková and Michalik (1997), Pop (1998a) and Reháková (2002), who stated that many chitinoidellid species are perfect homeomorphs of calpionellid ones and differ only in the features of the lorica. Across the Lower-Upper Tithonian boundary, the same evolutionary pattern may have concerned Ch. popi sp. nov. as a direct ancestor of Preatintinnopsellaandusovi and Tintinnopsellacarpathica. In fact, apart from their lorica, the degree of similarity between these species is particularly high. Similarly, only the lorica distinguishes oblique sections of Chitinoidella hegarati sp. nov (see Plate 1, fig. 25) from “Tintinnopsella” remanei, the index species of the lowermost calpionellid Subzone. Furthermore, the tight affinities between the same Ch. popi and Ch. carthagensis, on one hand, and Remaniella species of the Lower Berriasian, on the other, is also worth underlining.
Conclusion
Previous studies of Chitinoidellid faunas from the South-Tethyan regions of Maghreb dealt only with scarce and unrevised taxa from the Prerif (Morocco) or sporadic representatives from disparate sections of Tunisia. The Chitinoidellid faunas studied here include the most diversified assemblages of Maghreb, including a great majority of taxa described in the North-Tethyan areas. In view of the important number of new species recently introduced from the Carpathians, we present here three new Chitinoidella species and fifteen other morphotypes included in five genera. Their range is very comparable to that obtained in the Carpathian Range and the established biozonation fits the standards currently in use for the whole Tethyan Realm. Although the proposed phyletic approach needs to be completed, it nevertheless offers potential lineages at the species level where evolutionary data are well placed within the Chitinoidella Zone and can serve as biostratigraphic markers. Future works may be focused on the taxinomy of the Preatintinnopsella group so far restricted to the unique P. andrusovi species. Its stratigraphic range is around the LO of Chitinoidellids and the FO of Calpionellids, which leads us to consider the detailed analysis of its phyletic relationships with these groups of great relevance. In fact, the evolution of chitinoidellids, semichitinoidellids and calpionellids across the Jurassic-Cretaceous boundary shows phylogenetic characteristics which are of great interest for solid long distance correlations.
Acknowledgments
We sincerely thank an anonymous reviewer, Prof. Daniela Reháková from the University of Bratislava (Slovakia) and the editorial board of the C. R. Palevol. who greatly improved a first draft of this paper. Particular thanks can be addressed to M. Benzaggagh of the University of Meknès, the third referee with whom we did not share his opinion, but respect special aspects of calpionellid palaeontology and stratigraphy.
AndreiniG.CaracuelJ.E.ParisiG.Calpionellid biostratigraphy of the Upper Tithonian–Upper Valanginian interval in western Sicily (Italy)Suiss J. Geosci.1002007179–198Bachnou, A., 1992. Stratigraphie et faunes d’ammonites du Malm-Berriasien basal dans la région de Moyen Ouerrha (Prérif interne, Maroc). Thèse, Univ. Claude-Bernard Lyon I, 196 p.BenzaggaghM.Le Malm supérieur et le Berriasien dans le Prérif interne et le Mésorif (Rif, Maroc); biostratigraphie, lithostratigraphie, paléogéographie et évolution tectono-sédimentaireDoc. Lab. Geol. Lyon15220001–347BenzaggaghM.AtropsF.Les Zones à Chitinoidella et à Crassicollaria (Tithonien) dans la partie interne du Prérif (Maroc). Données nouvelles et corrélation avec des zones d’ammonitesC. R. Acad. Sci. Paris, Ser. IIa3201995227–234BonetF.Neue Daten aus dem Rosso Ammonitico Superiore und dem Biancone (Oberjura/Unter Kreide: Tith. -Valangin) von Ra Stua (Prov. Belluno, Italien)Rev. Paleobiol. Genève1521956571–595BorzaK.Neue Arten der Gattung Chitionodella Doben, 1962 in den WestkarpatenGeologicky Sbornik Slovenkej Akademie Vied171966259–265BorzaK.Die Mikrofacies und Mikrofossilien des Oberjuras und der Unterkreide der Klippen Zone der Westkarpaten1969Slovak Academy of Sciences Publishing HouseBratislava302 pBorzaK.The Upper Jurassic-Lower Cretaceous parabiostratigraphic scale on the basis of Tintinninae, Cadosinidae, Stomiosphaeridae, Calcisphaerulidae and other microfossils from the West CarpathiansGeol. Zbor. Geol. Carpath.3551984539–550BorzaK.MichalíkJ.Problems with the delimitation of Jurassic/Cretaceous boundary in the West CarpathiansActa Geol. Hung.291–21986133–149BoughdiriM.OlorizF.Lopez MarquesB.LayebM.De MatosE.SallouhiH.Upper Kimmeridgian and Tithonian Ammonites from the Tunisian “Dorsale” (NE Tunisia): updated biostratigraphy from J. Oust. Riv. Ital. Stratig.Paleont.1112005305–316BoughdiriM.SallouhiH.MaalaouiK.SoussiM.CordeyF.Calpionellid zonation of the Jurassic-Cretaceous transition in North-Atlasic Tunisia. Updated stratigraphy of the ‘Tunisian Trough’ and Upper Jurassic regional correlationsC. R. Geoscience33820061250–1259BoughdiriM.CordeyF.SallouhiH.MaalaouiK.MasrouhiA.SoussiM.Jurassic radiolarian-bearing series of Tunisia: biostratigraphy and significance to western Tethys correlationsSuiss J. Geosci.1002007431–441BoughdiriM.SallouhiH.HaddadS.CordeyF.SoussiM.Integrated biostratigraphy and regional correlations of Upper Jurassic-Lowermost Cretaceous series in northern TunisiaGFF131200971–81CeccaF.EnayR.Le HégaratG.L’Ardescien (Tithonique supérieur) de la région stratotypique : série de référence et faunes (ammonites, calpionelles) de la bordure ardéchoiseDoc. Lab. Geol. Lyon10719891–115CombémorelR.DonzeP.Le HégaratG.MemmiL.Les dépôts du Jurassique terminal et du Crétacé basal en Tunisie nord-orientaleAnn. Min. Geol. Tunisie361981151–158CordeyF.BoughdiriM.SallouhiH.First direct age determination from the Jurassic radiolarian-bearing siliceous series (Jédidi Formation) of northwestern TunisiaC. R. Geoscience3372005777–785DobenK.Ueber Calpionelliden an der Jura/Kreide-GrenzeMitt. Bayer. Staatsam Paläontol. Hit. Geol.3196335–50EnayR.GeyssantJ.R.Faunes tithoniques des Chaînes bétiques (Espagne méridionale)Mem. BRGM86197539–55Furrazola-BermúdezG.New species of tintinnids from Upper Jurassic of Cuba. Instituto Cubano de Recursos MineralesPubl. Espec.219651–29(in Spanish)GrandessoP.Tithonian parccalpionellids derived from Ammonitico Rosso faciesMem. Sci. Geol.32119771–14(in Italian)« Groupe français d’étude du Jurassique »Biostratigraphie du Jurassique ouest-européen et méditerranéen. Zonations parallèles et distribution des invertébrés et microfossilesCariouE.HantzpergueP.Bull. Centres Rech. Elf Explor. Prod.17199787–96GrünB.BlauJ.Phylogenie, systematic und Biostratigraphie der Calpionellidae BONET, 1956: Neue Daten aus dem Rosso Ammonitico Superiore und dem Biancone (Oberjura/Unterkreide: Tithon-Valangin) von Ra Stua (Prov. Belluno, Italien)Rev. Paleobiol., Genève151996571–595GrünB.BlauJ.New aspects of calpionellid biochronology: proposal for a revised calpionellid zonal and subzonal divisionRev. Paleobiol., Genève161997197–214LakovaI.Middle Tithonian to Berriasian praccalpionellid and calpionellid zonation of the Western Balkanides, BulgariaGeol. Balcanica2319933–24MichalíkJ.RehákováD.HalásováE.Stratigraphy of the Jurassic- Cretceous boundary beds in the Hlboč Valley (Vysoká Unit of the Krížna Nappe, Malé Karpaty Mts)Knih. ZPN9a1990183–204MichalíkJ.RehákováD.HalásováE.LintnerováO.The Brodno section- a potential regional stratotype of the Jurassic/Cretaceous boundary (western Carpathians)Geol. Carpathica6032009213–232NowakW.A.Semichitinoidella n. gen (Tintinnina) of the Upper Jurassic of the Czorsz-tyn succession. Pieniny Klippen Belt (Carpathians, Poland)Rocz. Pol. Tow. Geol. Krakow48119783–25OlorízF.CaracuelJ.E.Lopez MarquesB.Rodriguez- TovarF.J.Asociaciones de Tintinnoides en facies Ammonitico Rosso de la Sierra Norte (Mallorca)Rev. Esp. Paleontol. (Sp. N°. Hom. G. Colom)199577–93PeybernèsB.The Jurassic of Tunisia: an attempt at reconstitution of the South-Neotethyan margin during and after the rifting phaseGeol. Libya, Elsevier19921679–1766PopG.Calpionellid evolutive events and their use in biostratigraphyRom. J. Stratigraphy7619947–24PopG.Trois nouvelles espèces du genre Remaniella (Calpionellidae Bonet, 1956)C. R. Acad. Sci. Paris, Ser. IIa3221996317–323PopG.Révision systématique des chitinoïdelles tithoniennes des Carpathes méridionales (Roumanie)C. R. Acad. Sci. Paris, Ser. IIa3241997931–938PopG.Nouvelles chitinoïdelles tithoniennes des Carpathes méridionales (Roumanie)C. R. Acad. Sci. Paris, Ser. IIa3261998817–822PopG.Stratigraphic distribution and biozonation of Tithonian Praecalpionellids and calpionellids from the South CarpathiansRom. J. Stratigraphy77419983–25RehákováD.Calpionellid distribution in Upper Jurassic and Lower Cretaceous sequences of the Western CarpathiansMiner. Slovaca271995107–110RehákováD.Chitinoidella Trejo, 1975 in Middle Tithonian carbonate pelagic sequences of the West Carpathian Tethyan areaGeol. Carpath.5362002369–379RehákováD.MichalíkJ.Evolution and distribution of calpionellids–the most characteristic constituent of Lower Cretaceous Tethyan microplanktonCretaceous Res.181997493–504RemaneJ.Bakalova-IvanovaD.BorzaK.KnauerJ.NagyI.PopG.Tárdi-FiláczE.Agreement on the subdivision of the standard calpionellid Zones defined at the IInd Planktonic Conference, Roma 1970Acta Geol. Hung.2919865–14SoussiM.Le Jurassique de la Tunisie atlasique. Stratigraphie, dynamique sédimentaire, paléogéographie et intérêt pétrolierDocum. Lab. Geol. Lyon15720021–363SoussiM.Nouvelle nomenclature lithostratigraphique « événementielle » pour le Jurassique de la Tunisie atlasiqueGeobios362003761–773TrejoM.Los Tintinidos mesozoicos de MexicoMem. BRGM86197595–104
Location of the studied sections. A: Northern Tunisia. 1: Thrust fault; 2: Main fault; 3: Trough; 4: Jurassic outcrops; 5: Triassic exposure; 6: Study area. B, C: Location of sections (B: Jebels Jédidi and Chaabane; C: J. Oust). 1: Highway; 2: Gravel road; 3: Elevation; 4: Creek; 5: Railway tracks; 6: Position of successions.
Localisation des coupes étudiées. A : Tunisie du Nord. 1 : Chevauchement ; 2 : Faille majeure ; 3 : Fossé ; 4 : Affleurement jurassique ; 5 : Affleurement triasique ; 6 : Zone d’étude. B, C : Localisation des coupes (B : Jebels Jédidi et Chaabane, C : J. Oust). 1 : Route principale ; 2 : Piste ; 3 : Courbe de niveau ; 4 : Ravin, oued ; 5 : Chemin de fer ; 6 : Position des coupes.
Lithological succession, chitinoidellid distribution and biostratigraphy of the studied sections. 1: limestone; 2: marly limestone; 3: nodular limestone; 4: limestone with silex; 5: marls; 6: olistolithes; 7: slumps; 8: covered level; 9: correlation line.
Succession lithologique, répartition des chitinoïdellidés et stratigraphie des coupes étudiées. 1 : calcaire ; 2 : calcaire marneux ; 3 : calcaire noduleux ; 4 : calcaire à silex ; 5 : marnes ; 6 : olistolithes ; 7 : niveaux glissés ; 8 : niveau tendre couvert ; 9 : trait de corrélation.
Synthetic phyletic approach: Chitinoidellid evolution during Lower-to-Upper Tithonian transition. (*): Species known in the Carpathian Ranges and their stratigraphic range (after Pop (1998)); mentioned here for their close affinities with Tunisian taxa expressing potential phyletic relationships.
Approche phylétique synthétique : évolution des chitinoïdellidés au cours de la transition Tithonien inférieur–Tithonien supérieur. (*) : Espèces connues dans les Carpathes méridonales avec leur répartition stratigraphique (d’après Pop, 1998) ; elles sont mentionnées ici pour leurs affinités étroites avec des taxons tunisiens exprimant des liens phylétiques potentiels.