# Taxonomic revision of the genus Carinolithus (Early - Middle Jurassic) based on morphometric analyses and diagenesis observations: Implications for biostratigraphy and evolutionary trends

Stefano Visentin, Giulia Faucher, Emanuela Mattioli, Elisabetta Erba

► To cite this version:

Stefano Visentin, Giulia Faucher, Emanuela Mattioli, Elisabetta Erba. Taxonomic revision of the genus Carinolithus (Early - Middle Jurassic) based on morphometric analyses and diagenesis observations: Implications for biostratigraphy and evolutionary trends. Marine Micropaleontology, 2021, 162, pp.101950. 10.1016/j.marmicro.2020.101950. hal-03860106

HAL Id: hal-03860106

https://hal.science/hal-03860106v1

Submitted on 2 Aug 2025

HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d'enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.

<figure><img src="image_1.png" /></figure>

Distributed under a Creative Commons Attribution 4.0 International License
1 Taxonomic revision of genus *Carinolithus* (Early - Middle Jurassic) based on morphometric
2 analyses and diagenesis observations: implications for biostratigraphy and evolutionary trends.

3 Stefano Visentinª, Giulia Faucherª, Emanuela Mattioliᵇ, c, Elisabetta Erbaª

4 ª Dipartimento di Scienze della Terra, Università degli Studi di Milano, Via Mangiagalli 34, 20133 Milano, Italy (stefano.visentin@unimi.it; giulia.faucher@unimi.it; elisabetta.erba@unimi.it).

6 b Univ Lyon, Univ Lyon 1, ENSL, CNRS, LGL-TPE, F-69622, Villeurbanne, France

7 c Institut Universitaire de France (IUF) (emanuela.mattioli@univ-lyon1.fr).

8 Corresponding author : Stefano Visentin, stefano.visentin@unimi.it. Dipartimento di Scienze della Terra, Università degli Studi di Milano, Via Mangiagalli 34, 20133 Milano, Italy.

10

11 **Abstract**

12 We applied morphometric analyses performed with a polarizing light microscope on a total of 100
13 specimens of *Carinolithus superbus* and *C. magharensis* to clarify the taxonomy based on
14 measurements of total height (TH), stem height (SH), stem width (SW), proximal shield width (PS),
15 distal shield width (DS) and thickness of the distal shield (TDS). Statistical analyses showed that
16 three of these parameters, namely the DS, TDS and SW, are diagnostic for taxa discrimination. New
17 taxa include *C. superbus* subsp. *crassus* subsp. nov. and *C. magarensis* subsp. *minor* subsp. nov.
18 Specimens of *C. cantaluppii* were qualitatively investigated to assess the potential role of secondary
19 modifications and our results revealed that, indeed, *C. cantaluppii* is a diagenetic artefact due to
20 different degrees of overgrowth on specimens of *C. poulnabronei*, *C. superbus* subsp. *crassus*, *C.
21 superbus* subsp. *superbus*, *C. magharensis* subsp. *minor* and *C. magarensis* subsp. *magharensis*.
22 This implies that *C. cantaluppii* is not a true taxon, and the overgrowth phase of *Carinolithus*
23 specimens is an effective proxy to assess the diagenetic degree. The morphometry-based revised
24 taxonomy of the genus *Carinolithus* was applied to improve the biostratigraphic resolution of the
25 Toarcian-Aalenian interval, with further implications for the reconstruction of evolutionary trends.
26

26
27 **Keywords**

28 Calcareous nannofossils; Early-Middle Jurassic; *Carinolithus*; Morphometry; Taxonomy; Diagenesis

29

30 **1. Introduction**

31 The genus *Carinolithus* was initially established as *Rhabdolithus* by Deflandre *in Deflandre & Fert*
32 (1954) and, in the same work, the new species *R. sceptrum*, *R. superbus* and *R. clavatus* (Fig. 1) were
33 introduced. Later, Prins *in Grün et al.* (1974) established the genus *Carinolithus* and emended *R.*
34 *superbus* as *C. superbus*. Similarly, Medd (1979) emended *R. sceptrum* and *R. clavatus* as *C.*
35 *sceptrum* and *C. clavatus*, respectively. Bown (1987a) interpreted *C. sceptrum* as a variant of *C.*
36 *superbus* and considered *C. clavatus* to group incomplete specimens of *C. superbus* without the distal
37 shield. Consequently, the species *C. clavatus* and *C. sceptrum* were abandoned by subsequent authors.

38 The species *C. magharensis* was initially established within the genus *Hexalithus* (Moshkovitz &
39 Ehrlich, 1976) and later Bown (1987a) moved it to genus *Carinolithus* based on scanning electron
40 microscope investigations since the hexaliths are distal shields of carinolithids. According to Bown
41 (1987a), *C. superbus* and *C. magharensis* are easily discriminated if detected in distal view (DV) as
42 the number of wedge-shaped elements forming their distal shields is ten to twelve in *C. superbus* and
43 six in *C. magharensis*. Moreover, Bown (1987a) observed that the distal shield of *C. magharensis*
44 flares sharply (roughly at right angles) from the stem and has a rectangular shape in a transverse
45 section whereas that of *C. superbus* flares more gradually. Taxonomic incongruity, however, emerges
46 when *Carinolithus* coccoliths are observed in side view (SV), because the shape is essentially the
47 same (T-shape structure). Two additional species were established: *C. cantaluppii* by Cobianchi
48 (1990) and *C. poulnabronei* by Mattioli (1996). The latter possesses a peculiar V-shape structure in
49 SV and is, thus, easily distinguishable from *C. superbus* and *C. magharensis*.

50 A solid taxonomy is fundamental since the different species of this genus are used as events in
51 standard zonations of higher (Bown, 1987a; Bown et al., 1988; Bown & Cooper, 1998; Fraguas et al.,
52 2015) and lower latitudes (Mattioli & Erba, 1999; Ferreira et al., 2019). In particular, the first
occurrence (FO) of *C. superbus* marks the inception of the NJT6 and NJ6 Zones in the Tethyan and Boreal Realms, respectively, and is calibrated with the positive carbon isotope rebound preceding the negative carbon isotope excursion which is correlative to the Toarcian Oceanic Anoxic event (T-OAE) on a supraregional scale (Mattioli et al., 2004; 2013; Casellato & Erba, 2015; Ferreira et al., 2019). The FO of *C. magharensis* is used to define the base of the NJT8f Subzone (Ferreira et al., 2019), which corresponds to the basal Aalenian Opalinum Zone. Moreover, although not considered zonal/subzonal events, the FOs of *C. cantaluppii* and *C. poulnabronei* are indicated as additional biohorizons in the standard biozonations.

In this work morphometric analyses, performed on smear slides under a polarizing light microscope, were applied to *C. superbus* and *C. magarensis* specimens in order to clarify the taxonomy. Moreover, a detailed study of *C. cantaluppii* was conducted to ascertain the potential role of overgrowth on its morphology.

Fig. 1, about here, one column and half.

66

## 2. Materials and Methods

A total of 100 specimens of the *C. superbus* and *C. magarensis* groups were investigated for morphometric analyses using photographs taken with polarizing light microscope. A total of 62 images were selected from published works (Appendix 1) complemented with 38 additional specimens from sections in the Lombardy Basin (Sogno Core in northern Italy and Breggia section in southern Switzerland). In Appendix 1, for each investigated specimen the following information (as reported in the original paper) is given: calcareous nannofossil Zones/Subzones, ammonite Zones/Subzones, stage/substage, core/section.

Smear slides were prepared with the random settling technique (Geisen et al., 1999) for the Sogno Core and the standard smear slide technique (Bown & Young, 1998) for the Breggia section. Photographs were acquired using a Leitz Laborlux optical polarizing light microscope at 1250X magnification and a Q imaging Micropublisher 5.0. RTV digital camera. Images were analyzed using
79

a PC with Q-capture Pro suite software adapted for nannofossil analyses. Measurements were taken using ImageJ software, with an error of measurements of ± 0.08 µm.

80

81

Six parameters were measured: the Total Height (TH); the Stem Height (SH); the Stem Width (SW); the Proximal Shield diameter (PS); the Distal Shield diameter (DS) and the Thickness of the Distal Shield (TDS) as illustrated in Fig. 2. In case of observations in side view or when specimens are broken or heavily overgrown, a few parameters could not be measured. A total of 341 measurements were obtained: 29 for the TH, 29 for the SH, 75 for the SW, 29 for the PS, 100 for the DS, 79 for the TDS.

82

83

84

85

86

87

Statistical parameters like mean, mode, median, standard deviation and 95% confidence level were calculated using the Matlab and PAST softwares and reported in Tab. 1. Moreover, a mixture analysis was run, using PAST software (Hammer et al., 2001), in order to find the overall mixing proportions of specimens belonging to different taxa. This probabilistic model is a maximum-likelihood method for estimating the parameters (mean, standard deviation and proportion) of two or more univariate normal distributions, based on a pooled univariate sample (Hammer & Harper, 2006).

88

89

90

91

92

93

As far as *C. cantaluppii* is concerned, 50 specimens were qualitatively investigated taking four pictures of each specimen, both with and without quartz lamina, both at 0° and 45° to the polarizers.

*Fig. 2, about here, two columns.*

94

95

96

97

### 3. Results

98

Figure 2 synthesizes the results obtained for TH, SH, SW, PS, DS and TDS for *C. superbus* (blue) and *C. magharensis* (red) specimens. Based on the DS and TDS two different-sized groups of coccoliths are distinguished. As far as the DS is concerned, one group shows values ranging from 2.8 to 6.8 µm whereas the other is from 7.8 to 10.9 µm. The bigger-sized group comprises only specimens of the *C. magharensis* group whereas the smaller-sized coccoliths belong to both groups. We also notice that no specimens have a DS in the range of 6.9 to 7.7 µm.

99

100

101

102

103
104 The TDS separates a first group varying between 0.4 and 1.5 µm from a second one in the range of
105 1.8 - 2.9 µm. This latter bigger-sized group entirely consists of specimens of the *C. magharensis*
106 group while the smaller-sized only comprises specimens of the *C. superbus* group.

107 The parameters TH, SH, SW and PS do not discriminate between the *C. superbus* and *C. magharensis*
108 groups. Nevertheless, *C. magharensis* specimens generally show higher values of TH and SH. Mode,
109 median, mean and standard deviation are provided in Tab. 1 for each parameter by considering a) all
110 the investigated specimens; b) specimens of the *C. magharensis* group; c) specimens of the *C.
111 superbus* group. Both DS and TDS have mode, median, mean and standard deviation much higher
112 (almost double) in the *C. magharensis* group, thus showing systematic differences.

113 *Tab. 1, about here, one column and half.*

114 The Pearson's correlation coefficient (Fig. 3) shows: a) positive values for TH/SH, TH/DS, TH/TDS,
115 SH/PS, SH/DS, SH/TDS, SW/PS, SW/DS, PS/DS, DS/TDS and b) negative coefficients for TH/SW,
116 TH/PS, SH/SW, SW/TDS, PS/TDS. In particular, a strong positive correlation exists for TH/SH (r =
117 0.97), DS/TH (r = 0.69), TDS/TH (r = 0.66), DS/SH (r = 0.62), TDS/SH (r = 0.51), TDS/DS (r =
118 0.64).

119 The Pearson's correlation coefficient was also calculated separately for the *C. magharensis* and *C.
120 superbus* specimens: a clear distinction between the two groups is indicated only for the TH/TDS,
121 SH/TDS, SW/TDS, PS/TDS, and DS/TDS ratios, as evidenced by the red and blue clouds in Fig. 3.
122 *Fig. 3, about here, two columns.*

123
124 **4. Discussion**

125 **4.1. Taxonomic revision of C. superbus and C. magharensis**

126 Morphometric analyses turned out to be an excellent tool to separate *C. magharensis* and *C. superbus*
127 specimens. In particular, the DS (Fig. 4a) discriminates 23 specimens with sizes of 7.8 - 10.9 µm
128 from a group of 77 specimens with a DS ranging between 2.8 and 6.8 µm. The former group
129 comprises exclusively large *C. magharensis* specimens, whereas the second group includes *C*.
superbus coccoliths and small specimens of *C. magharensis*. Within this latter group, the TDS separates two clusters (Fig. 4b): one cluster includes 56 specimens characterized by a TDS ranging from 0.4 to 1.5 µm and a second one, grouping 18 specimens, with a TDS varying from 1.8 to 2.9 µm. The latter group consists exclusively of *C. magharensis* with a thicker distal shield relative to *C. superbus* specimens.

A further subdivision was obtained using the SW of *C. superbus* specimens (Fig. 4c): a group includes 30 specimens characterized by a SW spanning from 0.5 to 1.0 µm and another cluster of 26 coccoliths with a SW varying from 1.3 to 2.5 µm. Therefore, within *C. superbus*, the SW separates thin from thick morphotypes.

Fig. 4, about here, two columns.

Our morphometric analyses allowed the identification of four separate groups: large *C. magharensis* (DS ≥ 7.8 µm), small *C. magharensis* (DS ≤ 6.8 µm and TDS ≥ 1.8 µm), thin *C. superbus* (SW ≤ 1 µm, TDS < 1.5 µm and DS < 6.8 µm) and thick *C. superbus* (SW ≥ 1.3 µm, TDS ≤ 1.5 µm and DS < 6.8 µm).

The large *C. magharensis* specimens (DS ≥ 7.8 µm) are characterized by DS fully consistent with the holotype of *H. magharensis* possessing a DS of 8 µm, whereas the small *C. magharensis* specimens (DS ≤ 6.8 µm) evidently do not fall within the original definition of this taxon. Therefore, the two morphogroups can be distinguished as *C. magharensis* subsp. *magharensis* (large specimens) and *C. magharensis* subsp. *minor* subsp. nov. (small specimens; see taxonomic remarks later on).

Within the *C. superbus* group, the thin specimens (SW ≤ 1.0 µm) are consistent with the original description of this species. In fact, the holotype of *R. superbus* (Deflandre in Deflandre & Fert, 1954; figs. 24, 25) has a SW of 0.7 µm. The specimens with SW ≥ 1.3 µm, instead, are distinctly thicker. Accordingly, the two morphogroups can be distinguished as *C. superbus* subsp. *superbus* (thin specimens) and *C. superbus* subsp. *crassus* subsp. nov. (thick specimens; see taxonomic remarks later on).
Recently, Ferreira et al. (2019) documented *C. superbus* specimens characterized by a thinner and longer stem which they named "*C. superbus* thin and long"; also, they made a distinction between *C. magharensis* and "*C. magharensis* large". The qualitative taxonomic subdivision of Ferreira et al. (2019) is consistent with our morphometric results and, specifically, their *C. superbus* corresponds to *C. superbus* subsp. *crassus*, *C. superbus* "thin and long" to *C. superbus* subsp. *superbus*, *C. magharensis* to *C. magharensis* subsp. *minor*, and *C. magharensis* "large" to *C. magharensis* subsp. *magharensis*. Figure 5 summarizes the morphometric data of the holotypes and specimens analyzed in this work for *C. superbus* subsp. *crassus*, *C. superbus* subsp. *superbus*, *C. magharensis* subsp. *minor* and *C. magharensis* subsp. *magharensis*. Polarizing light microscope photos are presented in Fig. 6. Based on morphometric investigations, we established size-dependent new taxa.

*Fig. 5, about here, one columns and half.*

In the following section, the systematics of *C. superbus* subsp. *crassus*, *C. superbus* subsp. *superbus*, *C. magharensis* subsp. *minor* and *C. magharensis* subsp. *magharensis* are detailed. Diagnosis, description, remarks and differentiation are provided for each taxon.

170 Genus *Carinolithus* Prins in Grün et al. (1974)

171 *Carinolithus superbus* subsp. *crassus* Visentin & Erba subsp. nov.

172 Fig. 6, a-f; Fig. 8, c1-c7, d1-d6.

173 **Etymology:** the name derives from the diagnostic thick stem.

174 **Diagnosis:** a subspecies of *Carinolithus superbus* with a thick stem (width > 1 µm).

175 **Description:** this new subspecies is characterized morphometrically by possessing a stem width > 1 µm and a relatively narrow but still open axial canal.

176 **Remarks:** on the basis of available data the total height varies between 6.3 – 12.1 µm; stem width: 1.3 – 2.5 µm; proximal shield diameter: 2.1 – 3.9 µm; distal shield diameter: 3.0 – 5.6 µm; thickness of distal shield: 0.4 – 1.5 µm.
Stratigraphic range: FO in the Lower Toarcian, Polymorphum or Tenuicostatum ammonite Zone, correlative with the positive carbon isotope rebound preceding the negative carbon isotope excursion which is correlative to the Toarcian Oceanic Anoxic event (T-OAE). The FO of this subspecies substitutes the FO of *C. superbus* as a marker for the base of the NJT6 and NJ6 Zones.

Differentiation: *Carinolithus superbus* subsp. *crassus* differs from *C. superbus* subsp. *superbus* by its thicker stem (width > 1 µm) and by its wider and well distinguishable axial canal, from *C. poulnabronei* by its T- shape, from *C. magharensis* subsp. *minor* by its thinner distal shield (≤ 1.5 µm) and from *C. magharensis* subsp. *magharensis* by its thinner (≤ 1.5 µm) and smaller (< 6 µm) distal shield. The T-shape of *C. superbus* subsp. *crassus* is unambiguously different for the V-shape of *C. poulnabronei*.

Holotype: Fig. 8, c1-c4. Holotype total height: 8.8 µm; stem width: 1.7 µm; proximal shield diameter 3.1 µm; distal shield diameter: 4.6 µm; thickness of the distal shield: 1.3 µm.

Type locality: Colle di Sogno (Italy).

Type level: Jurassic, Toarcian.

Depository: Department of Earth Sciences “Ardito Desio” of Milan (Reference MPUM 1870).

*Carinolithus superbus* (Deflandre *in* Deflandre & Fert, 1954) Prins *in* Grün et al. (1974)

subsp. *superbus* emend. Visentin & Erba

Fig. 6, g-l; Fig. 8, e1-e8, f1-f6.

Basionym:

1954 *Rhabdolithus superbus* Deflandre *in* Deflandre & Fert, p. 160; pl. 15; figs. 24-25; text-fig. 93.

Reference:

1974 *Carinolithus superbus* Deflandre; Prins *in* Grün et al., p. 313; pl. 15; figs. 1-3; text-fig. 13.

**Description:** the original description of *Carinolithus superbus* by Deflandre *in* Deflandre & Fert (1954) is maintained for *Carinolithus superbus* subsp. *superbus*. This subspecies is further characterized morphometrically by possessing a stem width ≤ 1 µm.
Remarks: on the basis of available data the total height varies between 5.8 – 15.9 µm; stem width: 0.5 – 1.0 µm; proximal shield diameter: 1.4 – 3.9 µm; distal shield diameter: 3.0 – 5.6 µm; thickness of distal shield: 0.4 – 1.5 µm.

Stratigraphic range: FO between the uppermost part of the Levisoni Zone and the base of the Bifrons Zone (Ferreira et al., 2019; Lower/Middle Toarcian boundary), in the lowermost part of the NJT7 and NJ7 Zones.

Differentiation: *Carinolithus superbus* subsp. *superbus* differs from *C. superbus* subsp. *crassus* by its thinner stem (≤ 1 µm), from *C. poulnabronei* by its T- shape, from *C. magharensis* subsp. *minor* by its thinner distal shield (≤ 1.5 µm) and from *C. magharensis* subsp. *magharensis* by its thinner (≤ 1.5 µm) and smaller (< 6 µm) distal shield.

Holotype: Deflandre *in Deflandre & Fert* (1954; figs. 24-25). Holotype total height: 10.3 µm; stem width: 0.7 µm; proximal shield diameter: 2.7 µm; distal shield diameter: 4.3 µm; thickness of the distal shield: 1.0 µm.

Type locality: Villers-sur-Mer, Calvados (Spain) (Deflandre & Fert, 1954).

Type level: Jurassic, Oxfordian (Deflandre & Fert, 1954).

Depository: Collection du Laboratoire de Micropaléontologie de l'Ecole pratique des Hautes Etudes, Paris (Deflandre & Fert, 1954).

Carinolithus magharensis subsp. minor Visentin & Erba subsp. nov.

Fig. 6, m-r; Fig. 8, g1-g7, h1-h4.

Etymology: the name derives from the diagnostic small diameter of the distal shield relative to *C. magharensis* subsp. *magharensis*.

Diagnosis: a subspecies of *C. magharensis* with a thick (> 1.5 µm) and small (< 7 µm) distal shield.
The distal shield is constituted by 6 elements.

Description: this new subspecies is characterized morphometrically by possessing a thickness of the distal shield > 1.5 µm and a distal shield diameter < 7 µm which is constituted by 6 elements.
Remarks: on the basis of available data the total height varies between 11.1 – 16.6 µm; stem width: 232 0.6 – 1.1 µm; proximal shield diameter: 1.7 – 3.0 µm; distal shield diameter: 4.1 – 6.8 µm; thickness 233 of distal shield: 1.8 – 2.9 µm. Morphometric analyses separate specimens with distal shield ≤ 6.8 µm 234 from specimens ≥ 7.8 µm (C. magharensis subsp. magharensis) and no intermediate sizes have been 235 found. According to the morphometric diagnosis of C. magharensis subsp. minor, specimens 236 attributed to C. magharensis by Bown (1987a; page 59) show features (distal shield diameter varying 237 between 4.5 and 5.9 µm) consistent with C. magharensis subsp. minor. 238

239 **Stratigraphic range:** *Hexalithus magharensis* was reported from the late Opalinum Zone (Early 240 Aalenian) in the Tethyan Realm occurring shortly after *Watznaueria contracta* (Mattioli & Erba, 241 1999). Recent data from the well-dated Cabo Mondego section (Portugal) show an earlier occurrence 242 of *C. magharensis*, close to the base of the Opalinum ammonite Zone still shortly following the FO 243 of *W. contracta* reported from the basal Aalensis ammonite Zone of latest Toarcian age (Ferreira et 244 al., 2019). Because of its distinctive morphological characters, the FO of *C. magharensis* was 245 proposed to define the base of the NJT8f Subzone (Ferreira et al., 2019). The separation of the two 246 subspecies *C. magharensis* subsp. *minor* and *C. magharensis* subsp. *magharensis* implies that future 247 investigations will clarify their FOs. 248

248 **Differentiation:** *Carinolithus magharensis* subsp. *minor* differs from *C. magharensis* subsp. *magharensis* for its smaller distal shield (< 7 µm), from *C. superbus* subsp. *crassus* and *C. superbus* subsp. *superbus* for its thicker distal shield (> 1.5 µm). 249 250

251 **Holotype:** Fig. 8, g1-g4. Holotype distal shield diameter: 5.6 µm; thickness of the distal shield: 2.3 252 µm. 253

253 **Type locality:** Breggia (Switzerland).

254 **Type level:** Jurassic, Aalenian.

255 **Depository:** Department of Earth Sciences “Ardito Desio” of Milan (Reference MPUM 1869).

256
257 *Carinolithus magharensis* (Moshkovitz & Ehrlich, 1976) Bown (1987a) subsp. *magharensis* emend.

258 Visentin & Erba

259 Fig. 6, s-x; Fig. 8, i1-i6.

260 Basionym:

261 1976 *Hexalithus magharensis* Moshkovitz & Ehrlich, p. 16, pl. 8; figs. 12-15.

262 Reference:

263 1987a *Carinolithus magarensis* Moshkovitz & Ehrlich; Bown, pp. 58-59; pl. 8; figs. 4-6; pl. 14; figs. 17-20.

265 **Description:** the original description of Moshkovitz & Ehrlich (1976) is maintained for specimens observed in top view. This subspecies is further characterized by a thick (> 1.5 µm) and large (≥ 8 µm) distal shield constituted by 6 elements. The original description of *Hexalithus magarensis* applies to hexaliths more or less hexagonal in shape composed of 6 distinct triangular elements; towards the margin, the corners of these triangles are obliquely truncated. In light microscope each element has its own optical orientation. *Hexalithus magarensis* comprises specimens of 8-9 µm in diameter. Bown (1987a) emended *H. magarensis* by transferring the species into the genus *Carinolithus*. However, the illustrated specimens possess a distal shield diameter varying between 4.5 and 5.9 µm, thus definitively smaller than the holotype and species variability of *H. magarensis*. Our morphometric analyses confirm the separation of two groups, and we attribute to *C. magarensis* subsp. *magarensis* only specimens with a distal shield larger than 8 µm.

276 **Remarks:** the original description of Moshkovitz & Ehrlich (1976) is confirmed for specimens observed in top views. On the basis of available data, the stem width varies between 1.2 – 1.7 µm; distal shield diameter: 7.8 – 10.9 µm; thickness of distal shield: 2.0 – 2.9 µm.

279 **Stratigraphic range:** Although *C. magarensis* subsp. *minor* and *C. magarensis* subsp. *magarensis* are very rare after their first occurrence (i.e., 1-2 specimens in 250 fields of view at 1250 X magnification), a re-analysis of the Cabo Mondego section shows the presence of both subspecies
282 from the Early Aalenian (base Opalinum Zone). However, *C. magharensis* subsp. *magharensis* 283 becomes more common from the Bajocian upwards.

284 **Differentiation:** *Carinolithus magharensis* subsp. *magharensis* differs from *C. magharensis* subsp. 285 *minor* for its larger distal shield (> 8 µm) and more sharply truncated triangular elements.

286 **Holotype:** Moshkovitz & Ehrlich (1976, figs. 14-15). Holotype distal shield diameter: 8 µm.

287 **Type locality:** Israel. This species occurs in the Gebel Maghara outcrop, in the Lower Sherif and 288 Upper Daya Formations (Moshkovitz & Ehrlich, 1976).

289 **Type level:** Jurassic, Bajocian-Bathonian (Moshkovitz & Ehrlich, 1976).

290 **Depository:** Geological Survey of Israel (Moshkovitz & Ehrlich, 1976).

291 *Fig. 6, about, here, two columns.*

292

293 **4.2. Effects of diagenesis on the genus *Carinolithus***

294 The taxon *C. cantaluppii* was established by Cobianchi (1990; fig. 4, h) as a species of *Carinolithus* 295 with a small proximal shield and a large distal spine that typically broadens at about 1/4 (from the base) 296 maintaining the size (width) up to the distal shield. Under crossed nicols *C. cantaluppii* shows high 297 birefringence colors (from white to orange) and a clear extinction line in the middle of the spine. The 298 proximal shield diameter is 2.3-2.8 µm, the distal shield diameter is 3.0-4.0 µm, and the height is 8.0- 299 10 µm. Cobianchi (1990) used the term “spine” as the equivalent of “stem” and, therefore, the 300 “broadening of the spine” corresponds to the broadening of the stem. Based on the original 301 description, *C. cantaluppii*, similarly to other *Carinolithus* species, should have a symmetric shape 302 including the broadening of the stem. However, the only specimen (presumably the holotype) 303 illustrated by Cobianchi (1990) is clearly asymmetric as the two sides of the stem broaden at different 304 points and with different widths. The right side of the stem (Fig. 1e) broadens at about 1/4 from the 305 base (as provided by the author’s description) whereas the left side of the stem slightly broadens (less 306 wide and with a different shape) at about 1/2 from the base. The drawing of *C. cantaluppii* in Mattioli 307 (1996; fig. 3) shows a symmetric stem broadening at about 3/4 from the base. In the literature, several
308 photos of *C. cantaluppii* specimens show an extremely asymmetric shape (e.g. Cobianchi 1990, fig. 4, h; Cobianchi 1992, fig. 20, g; Perilli & Duarte, 2006, pl. 1, fig. 5; Ferreira et al., 2015, pl. 1, fig. 12) whereas other specimens appear broadly symmetric (e.g. Gardin & Manivit, 1994, pl. 3, fig. 11; Perilli & Duarte, 2006, pl. 1, fig. 9; Sandoval et al. 2012, fig. 10, n. 8-10). In both cases, the stem broadens at a different height from the base.

313 We underline that *C. cantaluppii* is often not documented or is reported with a sparse occurrence and, consequently, its biostratigraphic value remains highly questionable. In order to clarify the diagnostic features of this taxon, a detailed characterization was conducted in smear slides using four different configurations under the polarizing light microscope: with and without quartz lamina, both at 0° and 45° to the polarizers (Fig. 7). Pictures at 0° to the polarizers show that specimens are rarely symmetric due to extremely variable broadening of the stem and the extremely high birefringence colors concur in suggesting that the stem broadening is due to overgrowth. Differences in asymmetry, height of stem broadening and its extension advocate variable degrees of diagenetic modifications. Indeed, pictures at 45° to the polarizers – both with and without the quartz lamina - document the overgrowth of the stem while showing the original distal shield and stem, thus allowing recognition of the original taxon.

324 Fig. 7, about here, one column

325 Figure 8 includes pictures of moderately and poorly (overgrown) preserved specimens of *C. poulnabronei*, *C. superbus* subsp. *crassus*, *C. superbus* subsp. *superbus*, *C. magharensis* subsp. *minor* and *C. magharensis* subsp. *magharensis*. The light blue bands (Fig. 8 specimens b, d, f, h) evidence overgrown specimens referable to *C. cantaluppii* of Cobianchi (1990). Specimens characterized by moderate preservation show an intermediate diagenetic phase (Fig. 8 specimens a, c, e, g, i). The use of the quartz lamina at 45° to the polarizer appears to be the best way to recognize those specimens which underwent the diagenetic modification, as in the case of photos a and b = *C. poulnabronei*, c and d = *C. superbus* subsp. *crassus*, e and f = *C. superbus* subsp. *superbus*, g and h = *C. magharensis* subsp. *minor* and i = *C. magharensis* subsp. *magharensis*.
334 *Fig. 8, about here, two columns*

335 Three diagenetic phases are separated based on the extent of overgrowth (O) starting from the base
336 of the distal shield downwards and eventually reaching the proximal shield (Fig. 9). Phase 1
337 characterizes specimens with negligible diagenetic modification (O = 0). In phase 2 diagenesis affects
338 the uppermost part of the stem without reaching the middle point of the stem (0 < O < SH/2) (Fig. 8
339 specimens a, c, e, g, i). In phase 3 overgrowth is more pervasive and exceeds the middle point of the
340 stem (O > SH/2) (Fig. 8 specimens b, d, f, h). Diagenetic modifications are generally prevalent on
341 one side of the stem as a result of differential overgrowth producing asymmetry as in the case of the
342 holotype of *C. cantaluppii* (Cobianchi, 1990; fig. 4, h). The species *C. cantaluppii* is, therefore, an
343 artefact due to advanced diagenesis and not a separate taxon. In addition to taxonomic clarification,
344 the recognition of the diagenetic phase in *Carinolithus* specimens is an effective proxy to assess the
345 impact of overgrowth and the diagenetic degree in the studied material. In Appendix 1 we present the
346 characterization of the diagenetic phase for all the investigated specimens illustrated in the literature.

347 *Fig. 9, about here, one column and half*

348

349 **4.3. Implications for the Lower and Middle Jurassic biostratigraphy**

350 The taxonomic revision of *Carinolithus* species has shown that the subsequent first occurrences (FOs)
351 of *C. superbus* subsp. *crassus* and *C. superbus* subsp. *superbus*, have the potential to significantly
352 increase the biostratigraphic resolution (Fig. 10).

353 The FO of *C. superbus* subsp. *crassus* has been recently identified just before the C isotopic negative
354 anomaly associated with the T-OAE in the Sogno Core (Visentin & Erba, unpublished data; Visentin,
355 2020). Pictures of *C. superbus* subsp. *crassus* are documented in several works (see Appendix 1) and
356 the oldest ones (Mattioli et al., 2013; Menini et al., 2018; Da Rocha et al., 2016) derive from samples
357 concomitant with the C isotopic positive rebound preceding the negative anomaly associated with the
358 T-OAE. Consistent results are reported by Ferreira et al. (2019).
The oldest photographic documentation of *C. superbus* subsp. *superbus* (see Appendix 1) indicates a FO in the Serpentinus ammonite Zone (Baldanza & Mattioli, 1992). Ferreira et al. (2019) placed the FO of *C. superbus* "thin and long" at the Lower/Middle Toarcian boundary, in the lowermost part of the NJT7 Zone. Ongoing investigations (Visentin, 2020) confirm the FO of *C. superbus* subsp. *superbus* in the lowermost part of the NT7 Zone in the Schandelah Core from the Boreal Realm (Visentin, 2020).

The FO of *C. superbus* subsp. *crassus* is, therefore, older than that of *C. superbus* subsp. *superbus* and corresponds to the FO of *C. superbus* in the biozonations of Mattioli & Erba (1999) and Bown & Cooper (1998) used to define the base of the NJT6 and NJ6 Zones, respectively. Based on our taxonomic revision, the FO of *C. superbus* subsp. *crassus* should be considered the marker for the base of the NJT6 and NJ6 Zones.

As far as the FOs of *C. magharensis* subsp. *minor* and *C. magharensis* subsp. *magharensis* are concerned, these two taxa have been grouped together until now, so future investigations are needed to discriminate their respective first appearance level. However, *C. magharensis* subsp. *minor* and *C. magharensis* subsp. *magharensis*, although very rare after their first occurrence, co-occur in samples from the Lower Aalenian (base Opalinum Zone) of the Cabo Mondego section. However, *C. magharensis* subsp. *magharensis* became more common from the Bajocian upwards in Portugal.

Fig. 10, about here, one column

377

4.4. Evolution of the genus *Carinolithus*

During the Late Pliensbachian – Early Toarcian time interval, calcareous nannoplankton underwent an intense phase of diversification evidenced by the appearance of several species and genera (Mattioli & Erba, 1999; Bown et al., 2004; Erba, 2004; 2006; Menini et al., 2018). As previously discussed by Crux (1987), Bown (1987b) and Mattioli (1996), the genus *Calyculus* gave rise to the genus *Carinolithus*. Mattioli (1996; fig. 3) illustrated the transition between *Calyculus* spp. and *C. poulnabronei* characterized by the gradual closing of the axial canal and the development of a vertical
stem showing progressive thinning along with thickening of the distal shield. The hypothesis that *C. cantaluppii* descended from *C. poulnabronei* is here rejected since the former species, as aforementioned, represents a diagenetic artefact due to overgrowth. Therefore, *C. poulnabronei* passes to *C. superbus* subsp. *crassus* through a decrease of both shield width and thinning of the stem.

Thus, in the Early Toarcian the V-shape of both the stem and the axial canal of *C. poulnabronei* coexisted with the typical T-shape of *C. superbus*. subsp. *crassus*. A further decrease of the stem width characterizes *C. superbus* subsp. *superbus*, that is generally represented by taller specimens (Fig. 5). The transition between the *C. superbus* group and the *C. magharensis* group seems related to variations in thickness and ultrastructure of the distal shield. In fact, morphometry evidenced a progressive thickening of the distal shield (TDS) correlated to TH and DS (r = 0.66 and 0.64, respectively) passing from *C. superbus* subsp. *superbus* to *C. magharensis* subsp. *minor*. A further increase of the DS diameter characterizes the transition from *C. magharensis* subsp. *minor* to *C. magharensis* subsp. *magharensis* directly correlated to an increase of PS and SW (r = 0.80 and 0.87, respectively).

399

## 5. Conclusions

Morphometric investigations of the genus *Carinolithus* resulted in a revision of its taxonomy.
Statistical treatment of the measurements validated the significance of the proposed coccolith parameters to separate taxa between and within the *C. superbus* and *C. magharensis* groups.
Specifically, based on the stem width, as well as thickness and width of the distal shield two new subspecies, *C. superbus* subsp. *crassus* and *C. magharensis* subsp. *minor*, were established.
The qualitative characterization of overgrowth affecting *Carinolithus* coccoliths revealed that *C. cantaluppii* represents a diagenetic artefact. The use of the lamina at 45° to the polarizers turned out to be an excellent tool to recognize the real species which underwent the diagenetic modification, and three diagenetic phases were distinguished. Overgrowth generally starts in the uppermost part of the
410 coccoliths at the base of the distal shield. Identification of the diagenetic phases can be used to
411 evaluate nannofossil/sediment preservation and degree of secondary modifications.

412 The application of the revised taxonomy implies a revised evolution of the genus *Carinolithus* and a
413 higher resolution of calcareous nannofossil biostratigraphy in the Toarcian and Lower Aalenian
414 interval. In particular, the FO of *C. superbus* subsp. *superbus*, which approximates the Lower/Middle
415 Toarcian boundary, has been recently used as an additional event in zonal schemes.

416

417 Acknowledgements

418 The authors are grateful to the Editor Richard Jordan and two anonymous Reviewers, whose
419 comments improved the quality of the manuscript. The research was conducted within the PRIN
420 2017RX9XXXY awarded to EE.

421

422 References

423 Aguado, R., O'Dogherty, L., Sandoval, J., 2008. Fertility changes in surface waters during the
424 Aalenian (mid-Jurassic) of the Western Tethys as revealed by calcareous nannofossils and
425 carbon-cycle perturbations. Marine Micropaleontology. 68, 268-285.

426 Aguado, R., O'Dogherty, L., Sandoval, J., 2017. Calcareous nannofossil assemblage turnover in
427 response to the Early Bajocian (Middle Jurassic) palaeoenviromental changes in the Subbetic
428 Basin. Palaeogeography, Palaeoclimatology, Palaeoecology. 472, 128-145.

429 Baldanza, A., Mattioli, E., 1992. Biostratigraphical synthesis of nannofossils in the Early Middle
430 Jurassic of southern Tethys. Knihovnička ZPN. 14a (1), 111-141.

431 Bodin, S., Mattioli, E., Fröhlich, S., Marshall, J.D., Boutib, L., Lahsini, S., Redfern, J., 2010. Toarcian
432 carbone isotope shifts and nutrient changes from the Northern margin of Gondwana (High
433 Atlas, Morocco, Jurassic): Palaeoenviromental implications. Palaeogeography,
434 Palaeoclimatology, Palaeoecology. 297, 377-390.
435 Bown, P. R., 1987a. Taxonomy, evolution, and biostratigraphy of Late Triassic-Early Jurassic
calcareous nannofossils. Palaeontological Association, Special papers in Palaeontology. 38,
436
1-118.
437

438 Bown, P.R., 1987b. The structural development of early Mesozoic coccoliths and its evolutionary
439
and taxonomic significance. Abhandlungen der Geologisches Bundesanstalt in Wien - A, 39,
440
33-49.
441

441 Bown, P.R., Cooper, M.K.E., Lord, A.R., 1988. A Calcareous Nannofossil Biozonation Scheme for
442
the early to mid-Mesozoic. Newsletter on Stratigraphy. 20, 91-114.
443

443 Bown, P.R., & Copper, M.K.E., 1998. Jurassic. In: Bown P.R. (Ed.), Calcareous nannofossil
444
biostratigraphy. British Micropaleontology Society Published Series: 34-85. Kluwer
445
Academic Publishers, London.
446

446 Bown, P.R., Young, J., 1998. Techniques. In: Bown P.R. (Ed.), Calcareous nannofossil
447
biostratigraphy. British Micropaleontological Society Published Series: 16-27. Kluwer
448
Academic Publishers, London.
449

449 Bown, P.R., Lees, J.A., Young, J.R., 2004. Calcareous nannoplankton evolution and diversity through
450
time. In: Thierstein H.R., Young J.R. (Eds), Coccolithophores: from molecular processes to
451
global impact: 481-508. Springer, Berlin, Heidelberg.
452

452 Casellato, C.E., Erba, E., 2015. Calcareous nannofossil biostratigraphy and paleoceanography of the
453
Toarcian Oceanic Anoxic event at Colle di Sogno (southern Alps, northern Italy). Rivista
454
Italiana di Paleontologia e Stratigrafia. 121, 297-327.
455

455 Cobianchi, M., 1990. Calcareous nannofossil biostratigraphy of the Domerian-Toarcian Boundary in
456
the Navezze Valley (Brescia). Atti Ticinensi di Scienze della Terra. 33, 127-142.
457

457 Cobianchi, M., 1992. Sinemurian-Early Bajocian calcareous nannofossil biostratigraphy of the
458
Lombardy Basin (Southern calcareous Alps; Northern Italy). Atti Ticinensi di Scienze della
459
Terra. 35, 61-106.
460
460 Crux, J.A., 1987. Concerning dimorphism in Early Jurassic coccoliths and the origin of the
genus *Discorhabdus* Noël 1965. Abhandlungen der Geologischen Bundesanstalt. 39, 51-55.

462 Da Rocha, R.B., Mattioli, E., Duarte, L., Pittet, B., Elmi, S., Mouterde, R., Cabral, M.C., Comas-Rengifo, M., Gomez, J., Goy, A., Hesselbo, S., Jenkyns, H., Littler, K., Mailliot, S., Veiga de Oliveira, L.C., Osete, M.L., Perilli, N., Pinto, S., Ruget, C., Suan, G., 2016. Base of the Toarcian Stage of the Lower Jurassic defined by the Global Boundary Stratotype Section and Point (GSSP) at the Peniche section (Portugal). Episodes Journal of International Geoscience, Seoul National University. 39 (3), 459-481.

468 Deflandre, G., Fert, C., 1954. Observations sur les coccolithophoridés actuels et fossiles en microscopie ordinaire et électronique. Annales de Paléontologie. 40, 115-176.

470 Erba, E., 2004. Calcareous nannofossils and Mesozoic oceanic anoxic events. Marine Micropaleontology. 52, 85-106.

472 Erba, E., 2006. The first 150 million years history of calcareous nannoplankton: Biosphere – Geosphere interaction. Palaeogeography, Palaeoclimatology, Palaeoecology. 232, 237-250.

474 Ferreira, J., Mattioli, E., Pittet, B., Cachao, M., Spangerberg, J.E., 2015. Palaeocological insights on Toarcian and Lower Aalenian calcareous nannofossils from the Lusitanian Basin (Portugal). Palaeogeography, Palaeoclimatology, Palaeoecology. 436, 245-262.

477 Ferreira, J., Mattioli, E., Suchéras-Marx, B., Giraud, F., Duarte, L. V., Pittet, B., Suan G., Hassler A., Spangenberg, J. E., 2019. Western Tethys Early and Middle Jurassic calcareous nannofossil biostratigraphy. Earth-Science Reviews. 197, 1-19.

480 Fraguas, A., Comas-Rengifo, M.J., Perilli, N., 2015. Calcareous nannofossil biostratigraphy of the Lower Jurassic in the Cantabrian Range (Northen Spain). Newsletter on Stratigraphy. 48, 179-199.

483 Gardin, S., Manivit, H., 1994. Biostratigraphie des nannofossiles calcaires du Toarcien du Quercy (Sud-Ouest de la France). Comparisione avec la coupe stratotypique de la cimenterie d'Airvault (Deux Sevrès, France). Geobios, M.S. 17, 229-244.
486 Geisen, M., Bollmann, J., Herrle, J.O., Mutterlose, J., Young, J. R., 1999. Calibration of the random
487 settling technique for calculation of absolute abundances of calcareous nannoplankton.
488 Micropaleontology. 45, 437-442.

489 Grün, W., Prins, P., Zweili, F., 1974. Coccolithophoriden aus dem Lias epsilon von Holzmaden
490 (Deutschland). Neues Jahrbuch für Geologie und Paläontologie Abhandlungen. 147, 294-328.

491 Hammer, Ø., Harper, D.A.T., 2006. Paleontological Data Analysis. Blackwell, London.

492 Hammer, Ø., Harper, D.A.T., Ryan, P.D., 2001. PAST: palaeontological statistics software package
493 for education and data analysis. Palaeontologia Electronica. 4 (1), 4-9.

494 Mattioli, E., 1996. New calcareous nannofossil species from the Early Jurassic of Tethys. Rivista
495 Italiana di Paleontologia e Stratigrafia. 102, 397-412.

496 Mattioli, E., Erba, E., 1999. Synthesis of calcareous nannofossil events in tethyan Lower and Middle
497 Jurassic successions. Rivista Italiana di Paleontologia e Stratigrafia. 105, 343-376.

498 Mattioli, E., Pittet, B., Bucefalo Palliani, R., Rohl, H.J., Schimd-Rohl, A., Morettini, E., 2004.
499 Phytoplankton evidence for the timing and correlation of paleoceanographical changes during
500 the early Toarcian oceanic anoxic event (Early Jurassic). Journal of Geological Society of
501 London. 161, 685-693.

502 Mattioli, E., Plancq, J., Boussaha, M., Duarte, L.V., Pittet, B., 2013. Calcareous nannofossil
503 biostratigraphy: new data from the Lower Jurassic of the Lusitanian Basin. Comunicações
504 Geológicas. Especial I, 69-76.

505 Medd, A.W., 1979. The Upper Jurassic coccoliths from the Haddenham and Gamlingay boreholes
506 (Cambridgeshire, England). Eclogae Geologicae Helvetiae, 72 (1), 19-109.

507 Menini, A., Mattioli, E., Spangenberg, J. E., Pittet, B., Guillaume, S., 2018. New calcareous
508 nannofossil and carbon isotope data for the Pliensbachian/Toarcian boundary (Early Jurassic)
509 in the western Tethys and their paleoenvironmental implications. Newsletter on Stratigraphy.
510 52 (2), 173-196.
511 Molina, J. M., Reolid, M., Mattioli, E., 2018. Thin shelled bivalve buildup of the lower Bajocian, South Iberian paleomargin: development of opportunists after oceanic perturbations. *Facies.* 64, 19-36.

514 Moshkovitz, S., Ehrlich, A., 1976. Distribution of Middle and Upper Jurassic calcareous nannofossils in the northeastern Negev, Israel and in Gebel Maghara, northern Sinai. *Bulletin of the Geological Survey of Israel.* 69, 1-47.

517 Perilli, N., Duarte, L.V., 2006. Toarcian nannobiohorizons from the Lusitanian Basin (Portugal) and their calibration against ammonite Zones. *Rivista Italiana di Paleontologia e Stratigrafia* 112, 417-434.

520 Reolid, M., Mattioli, E., Nieto, L.M., Rodriguez-Tovar, F.J., 2014. The Early Toarcian Oceanic Anoxic Event in the External Subbetic (Southiberian Paleomargin, Westernmost Tethys): geochemistry, nannofossils and ichnology. *Palaeogeography, Palaeoclimatology, Palaeoecology.* 411, 79-94.

524 Sandoval, J., Markus, B., Aguado, R., O' Dogherty, L., Rivas, P., Morard, A., Guex, J., 2012. The Toarcian in the Subbetic basin (southern Spain): Bio-events (ammonite and calcareous nannofossils) and carbonate-isotope stratigraphy. *Palaeogeography, Palaeoclimatology, Palaeoecology.* 342-343, 40-62.

528 Van de Schootbrugge, B., Richoz, S., Pross, J., Luppold, F.W., Hunze, S., Wonik, T., Blau, J., Meister, C., Van de Meijst, C. M. H., Suan, G., Fraguas, A., Fiebig, J., Herrle, J.O., Guex, J., Little, C.T.S., Wignall, P.B., Püttmann, W., Oschmann, W., 2018. The Schandelah Scientific Drilling Project: A 25-million-year record of Early Jurassic palaeoenvironmental change from northern Germany. *Newsletter on Stratigraphy.* 52 (3), 249-296.

533 Visentin, S., 2020. Calcareous nannofossil biostratigraphy and taxonomy across the Early Toarcian Oceanic Anoxic Event: a comparison between Tethyan and Boreal sections. *Ph.D. thesis*, Department of Earth Sciences "Ardito Desio". University of Milan, Italy.
CAPTIONS

537

538

539 **Fig. 1.** Holotypes of *R. superbus* (Deflandre *in* Deflandre & Fert, 1954) (a), *R. sceptrum* (Deflandre *in* Deflandre & Fert, 1954) (b), *R. clavatus* (Deflandre *in* Deflandre & Fert, 1954) (c), *H. magharensis* (Moshkovitz & Ehrlich, 1976) (d), *C. cantaluppii* (Cobianchi, 1990) (e) and *C. poulnabronei* (Mattioli, 1996) (f).

543

544 **Fig. 2.** Synthesis of the morphometric analyses performed on the *C. superbus* (in blue) and *C. magharensis* (in red) groups. Total height, stem height, stem width, proximal shield diameter, distal shield diameter and thickness of distal shield are indicated. The number of specimens measured (N) for each parameter is indicated.

548

549 **Fig. 3.** Correlation plots of the measured parameters. Every parameter is compared with each other. For each scatter plot, the Pearson's correlation coefficients (r), the linear regression line, the number of measured specimens (N) are given. Note that for TDS/SW, TDS/SH, TDS/PS, TDS/TH and TDS/DS the two groups are confined to clearly separated and distinct sets that do not overlap.

553

554 **Fig. 4.** Distribution histograms for a) the distal shield diameter (histogram class sizes 0.5 µm), b) thickness of the distal shield (histogram class sizes 0.2 µm) and c) stem width (histogram class sizes 0.2 µm). Histograms provide the number of data for each size bin, highlighting differences in morphology.

558

559 **Fig. 5.** Summary of sizes of investigated parameters in the holotypes and the variability quantified for the measured specimens for individual *Carinolithus* taxa. Number of specimens measured (N) are provided for each parameter.

562
Fig. 6. Photographs documenting the revised taxonomy. A = *C. superbus* subsp. *crassus* (a-f); B = *C. superbus* subsp. *superbus* (g-l), C = *C. magharensis* subsp. *minor* (m-r), D = *C. magarensis* subsp. *magharensis* (s-x). Specimens a, b, g, h, i, j, k, l, m, n, o, p, s, t are from this work: (a, b) Sogno Core; (g, h, i, j, k, l, m, n, o, p, s, t) Breggia section. Specimens c, d, e, f, q, r, u, v, w, x are from literature: (c) Bown & Cooper (1998; pl. 4.13, fig. 11); (d) Bown (1987a; pl. 14, fig. 15); (e) Menini et al. (2018; pl. 1, fig. 33); (f) Van de Schootbrugge et al. (2018; pl. 6, fig. 11); (q) Bown (1987a; pl. 14, fig. 17); (r) Bown & Cooper (1998; pl. 4.13, fig. 8); (u) Aguado et al. (2017; fig. 8, y); (v) Aguado et al. (2008; fig. 5, n. 19); (w) Bown & Cooper (1998; pl. 4.13, fig. 6); (x) Bown & Cooper (1998; pl. 4.13, fig. 7).

Fig. 7. Specimens of *C. cantaluppii* photographed in four different combinations both with and without quartz lamina, at 0° and 45° to the polarizers. Illustrated specimens are from the Breggia section.

Fig. 8. Photographs of *Carinolithus* specimens investigated in this study and taken from the literature. Specimens investigated in this study are illustrated with and without quartz lamina, at 0° and 45° relative to the polarizers. Based on the description proposed by Cobianchi (1990) specimens highlighted with light blue rectangles were assigned to *C. cantaluppii* before the current taxonomic revision. The new taxonomic identification of *Carinolithus* specimens allows to distinguish the true taxon which underwent diagenetic modifications. (a1-a4, b1-b4, c1-c4, d1-d4) Sogno Core; (e1-e4, f1-f4, g1-g4, h1-h4, i1-i4) Breggia section; (a5, a6) Sandoval et al. (2012; fig. 10, n. 16, 17); (b5, b6, b7) Mattioli (1996; pl. 2, figs. 9,11,12); (c5) Menini et al. (2018; pl. 1, fig. 33); (c6) Casellato & Erba (2015; pl. 1, fig. 16); (c7) Van de Schootbrugge et al. (2018; pl. 6, fig. 11); (d5) Reolid et al. (2014; fig. 6, CE30); (d6) Bodin et al. (2010; fig. 5, i); (e5) Sandoval et al. (2012; fig. 10, n. 20); (e6) Sandoval et al. (2012; fig. 10, n. 12); (e7) Aguado et al. (2008; fig. 5, n. 18); (e8) Molina et al. (2018; fig. 8, LL6); (f5) Ferreira et al. (2015; pl. 1, fig. 12); (f6) Cobianchi (1990; fig. 4, h); (g5) Sandoval et al.
589 (2012; fig. 10, n. 19); (g6) Bown & Cooper (1998; pl. 4.13, fig. 8); (g7) Bown (1987a; pl. 14, fig. 17); (i5) Aguado et al. (2008; fig. 5, n. 19); (i6) Bown & Cooper (1998; pl. 4.13, fig. 6).

591
592 **Fig. 9.** Schematic representation of increasing diagenetic phases of *Carinolithus* specimens: SH = stem height; SH/2 = half the stem height; O = overgrowth. **Phase 1:** no or negligible diagenetic overprint (O = 0); **Phase 2:** overgrowth affects the uppermost part of the stem, starting from the base of the distal shield downwards without reaching the stem middle point (0 < O < SH/2); **Phase 3:** diagenesis becomes more pervasive and exceeds the middle point of the stem (O > SH/2). Overgrowth may affect one or both sides of the stem and with different degrees.
593
594
595
596
597

598
599 **Fig. 10.** Stratigraphic distribution of *C. poulnabronei*, *C. superbus* subsp. *crassus* and *C. superbus* subsp. *superbus*.
600
601

602
603
604
605
**Tab. 1.** Number of specimens, mean, median, mode and standard deviation of measured taxonomic characters (TH, SH, SW, PS, DS, TDS): a) all specimens; b) *C. magharensis* group; c) *C. superbus* group.

606
607
608
609
610
611
612
**Appendix 1 – Data – set of *Carinolithus* specimens from literature used for morphometric analyses.**
Data are organized following the publication date and for each specimen the following information is given: investigated core/section; nomenclature adopted in the orginal paper; revised nomenclature following the revised taxonomy (this study); stage/substage; ammonite and calcareous nannofossil Zones and Subzones. Specimens selected for morphometric analyses are characterized with an X. The other specimens were used to characterize the diagenetic overprint. *Carinolithus* * is reported for specimens not attributable to a species due to high overgrowth.

613

614
FIGURES

<figure><img src="image_2.png" /><figcaption>FIG. 1.PDF (one column and half) NOT COLOURS</figcaption></figure>
<figure><img src="image_3.png" /><figcaption>FIG. 2.PDF (two columns) COLOURS</figcaption></figure>
<figure><img src="image_4.png" /><figcaption>FIG. 3.PDF (two columns) COLOURS</figcaption></figure>
<figure><img src="image_5.png" /></figure>

<figure><img src="image_6.png" /></figure>

<figure><img src="image_7.png" /><figcaption>FIG. 4.PDF (two columns) COLOURS</figcaption></figure>
<table><caption>FIG. 5.PDF (one column and half) NOT COLOURS</caption><thead><tr><th></th><th>TH</th><th>SH</th><th>SW</th><th>PS</th><th>DS</th><th>TDS</th></tr></thead><tbody><tr><td rowspan="2">C. superbus<br>subsp. crassus</td><td colspan="6">Holotype</td></tr><tr><td>8.8</td><td>6.1</td><td>1.7</td><td>3.1</td><td>4.6</td><td>1.3</td></tr><tr><td colspan="7">Variability among investigated specimens</td></tr><tr><td></td><td>N=10<br>6.3 - 12.1</td><td>N=10<br>5.1 - 10.9</td><td>N=26<br>1.3 - 2.5</td><td>N=10<br>2.1 - 3.9</td><td>N=26<br>3.0 - 5.6</td><td>N=26<br>0.4 - 1.5</td></tr><tr><td rowspan="2">C. superbus<br>subsp. superbus</td><td colspan="6">Holotype</td></tr><tr><td>10.3</td><td>8.5</td><td>0.7</td><td>2.7</td><td>4.3</td><td>1.0</td></tr><tr><td colspan="7">Variability among investigated specimens</td></tr><tr><td></td><td>N=11<br>5.8 - 15.9</td><td>N=11<br>4.9 - 14.1</td><td>N=30<br>0.5 - 1.0</td><td>N=11<br>1.4 - 3.9</td><td>N=30<br>2.8 - 5.8</td><td>N=30<br>0.5 - 1.3</td></tr><tr><td rowspan="2">C. magharensis<br>subsp. minor</td><td colspan="6">Holotype</td></tr><tr><td>/</td><td>/</td><td>/</td><td>/</td><td>5.6</td><td>2.3</td></tr><tr><td colspan="7">Variability among investigated specimens</td></tr><tr><td></td><td>N=7<br>11.1-16.6</td><td>N=7<br>8.7 - 13.1</td><td>N=16<br>0.6 - 1.1</td><td>N=7<br>1.7 - 3.0</td><td>N=21<br>4.1 - 6.8</td><td>N=18<br>1.8 - 2.9</td></tr><tr><td rowspan="2">C. magharensis<br>subsp. magharensis</td><td colspan="6">Holotype</td></tr><tr><td>/</td><td>/</td><td>/</td><td>/</td><td>8-9</td><td>/</td></tr><tr><td colspan="7">Variability among investigated specimens</td></tr><tr><td></td><td>N=1<br>/</td><td>N=1<br>/</td><td>N=3<br>1.2 - 1.7</td><td>N=1<br>/</td><td>N=23<br>7.8 - 10.9</td><td>N=5<br>2.0 - 2.9</td></tr></tbody></table>
<figure><img src="image_8.png" /><figcaption>FIG. 6.PDF (two columns) COLOURS</figcaption></figure>
<figure><img src="image_9.png" /><figcaption>FIG. 7.PDF (one column) COLOURS</figcaption></figure>
<table><caption>FIG. 8.PDF (two columns) COLOURS</caption><thead><tr><th></th><th>This study</th><th>Literature<br>Scale bar 2 µm</th></tr></thead><tbody><tr><td><strong>C. poulnabronei</strong></td><td><img src="poulnabronei_a1.png" alt="Image of C. poulnabronei subsp. crassus: a1"></td><td><img src="poulnabronei_a5.png" alt="Image of C. poulnabronei subsp. crassus: a5"></td></tr><tr><td><strong>C. superbus</strong><br>subsp. crassus</td><td><img src="superbus_c1.png" alt="Image of C. superbus subsp. crassus: c1"></td><td><img src="superbus_c5.png" alt="Image of C. superbus subsp. crassus: c5"></td></tr><tr><td><strong>C. magharensis</strong><br>subsp. minor</td><td><img src="magharensis_e1.png" alt="Image of C. magharensis subsp. minor: e1"></td><td><img src="magharensis_e5.png" alt="Image of C. magharensis subsp. minor: e5"></td></tr><tr><td><strong>C. magharensis</strong><br>subsp. magharensis</td><td><img src="magharensis_g1.png" alt="Image of C. magharensis subsp. magharensis: g1"></td><td><img src="magharensis_g5.png" alt="Image of C. magharensis subsp. magharensis: g5"></td></tr></tbody></table>
<figure><img src="image_10.png" /><figcaption>FIG. 9.PDF (one column and half) NOT COLOURS</figcaption></figure>

<figure><img src="image_11.png" /><figcaption>FIG10.PDF (one column) NOT COLOURS</figcaption></figure>
<table><caption>TABLE 1. (one column and half)</caption><thead><tr><th></th><th>TH</th><th>SH</th><th>SW</th><th>PS</th><th>DS</th><th>TDS</th></tr></thead><tbody><tr><td colspan="7" style="text-align: center; font-weight: bold;">a. Total specimens</td></tr><tr><td>Number of specimens</td><td>29</td><td>29</td><td>75</td><td>29</td><td>100</td><td>79</td></tr><tr><td>Mode</td><td>8.80</td><td>8.40</td><td>0.70</td><td>1.70</td><td>5.00</td><td>1.00</td></tr><tr><td>Median</td><td>10.20</td><td>8.40</td><td>0.90</td><td>2.87</td><td>5.40</td><td>1.00</td></tr><tr><td>Mean</td><td>10.59</td><td>8.82</td><td>1.17</td><td>2.73</td><td>5.71</td><td>1.32</td></tr><tr><td>Standard deviation</td><td>2.60</td><td>2.29</td><td>0.55</td><td>0.73</td><td>1.97</td><td>0.67</td></tr><tr><td colspan="7" style="text-align: center; font-weight: bold;">b. Carinolithus magharensis group</td></tr><tr><td>Number of specimens</td><td>8</td><td>8</td><td>19</td><td>8</td><td>44</td><td>23</td></tr><tr><td>Mode</td><td>11.40</td><td>/</td><td>0.90</td><td>/</td><td>8.10</td><td>2.00</td></tr><tr><td>Median</td><td>12.19</td><td>9.81</td><td>0.90</td><td>2.59</td><td>7.88</td><td>2.20</td></tr><tr><td>Mean</td><td>13.11</td><td>10.63</td><td>0.94</td><td>2.44</td><td>7.28</td><td>2.28</td></tr><tr><td>Standard deviation</td><td>2.16</td><td>1.97</td><td>0.26</td><td>0.51</td><td>1.81</td><td>0.34</td></tr><tr><td colspan="7" style="text-align: center; font-weight: bold;">c. Carinolithus superbus group</td></tr><tr><td>Number of specimens</td><td>21</td><td>21</td><td>56</td><td>21</td><td>56</td><td>56</td></tr><tr><td>Mode</td><td>8.80</td><td>8.40</td><td>0.70</td><td>2.40</td><td>5.00</td><td>1.00</td></tr><tr><td>Median</td><td>9.50</td><td>8.10</td><td>0.95</td><td>3.00</td><td>4.60</td><td>0.93</td></tr><tr><td>Mean</td><td>9.63</td><td>8.12</td><td>1.25</td><td>2.84</td><td>4.47</td><td>0.92</td></tr><tr><td>Standard deviation</td><td>2.08</td><td>2.04</td><td>0.59</td><td>0.78</td><td>0.95</td><td>0.23</td></tr></tbody></table>