# Taxonomic revision of Cidaris echinoids
(Echinodermata) with "fan-shaped" radioles from the
Serravallian (Miocene) of Motta San Giovanni
Formation (Calabria, Italy)

Philippe Nicolleau, Alain Vadet, Pascal Barrier, Julien Bailleul, Sandra
Brocheray, Francis Kezirian, Sébastien Rohais, Foulques Guillet de Chatellus,
Adrien Marchiel, Alice Prosperi, et al.

► To cite this version:

Philippe Nicolleau, Alain Vadet, Pascal Barrier, Julien Bailleul, Sandra Brocheray, et al. Taxonomic revision of Cidaris echinoids (Echinodermata) with "fan-shaped" radioles from the Serravallian (Miocene) of Motta San Giovanni Formation (Calabria, Italy). Revue de Paléobiologie, 2025, 44 (6), pp.1-14. 10.5281/zenodo.14802581. hal-05163233

HAL Id: hal-05163233

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# Taxonomic revision of *Cidaris* echinoids (Echinodermata) with “fan-shaped” radioles from the Serravallian (Miocene) of Motta San Giovanni Formation (Calabria, Italy)

Philippe Nicolleau<fnref n="1" />, Alain Vadet<fnref n="2" />, Pascal Barrier<fnref n="3" />, Julien Bailleul<fnref n="3" />, Sandra Brocheray<fnref n="3" />, Francis Kezirian<fnref n="3" />, Sébastien Rohais<fnref n="4" />, Foulques Guillet de Chatellus<fnref n="3" />, Adrien Marchiel<fnref n="3" />, Alice Prosperi<fnref n="3" /> & Nathan Rispal<fnref n="3" />

**Abstract:** Fossil remains of fan-shaped spines *Cidaris* have been largely described in the literature since the 19th century. However, it is the first time that they have been found in serravalian outcrops in the vicinity of Motta San Giovanni and Musuponiti (Calabria, Southern Italy). Modern description of numerous test fragments and spines collected in the field allows classifying these remains of *Cidaris* in their taxonomic context. The graphic analysis of biometric measurements carried in this study made it possible to name *Cidaris remiger* (Ponzi, 1876) as representative of the calabrian fossils as well as the other fossils studied or known. This taxonomy facilitates the comparisons with the present-day known examples, namely *Cidaris blakei* (Agassiz, 1878) and helps clarify the paleo-depth of the Motta San Giovanni formation deposits at these localities.

**Keywords:** *Cidaris remiger*, Miocene, echinoids, taxonomy, Italy, Calabria.

**Résumé:** Révision taxonomique de l'échinoïde *Cidaris* avec des radioles en forme d'éventail du Serravallien (Miocène) de la Formation Motta San Giovanni (Calabre, Italie).- Depuis le XIXe siècle, de nombreux auteurs ont décrit et figuré des restes fossiles de *Cidaris* dotés de radioles en « éventail ». Nous rapportons ici pour la première fois la présence de tels radioles dans le Serravallien de Calabre, en particulier à Motta San Giovanni et à Musuponiti, au sud de Reggio di Calabre. La récolte de nombreux fragments de tests et radioles nous permet donc de réviser la description en replaçant ces restes de *Cidaris* dans leur contexte taxonomique. L'analyse statistique des données biométriques nous permet d'envisager *Cidaris remiger* (Ponzi, 1876) comme producteur des fossiles calabrais, mais également de faire le point sur les autres fossiles étudiés ou connus, facilitant alors les comparaisons avec les exemplaires actuels connus attribués à *Cidaris blakei* (Agassiz, 1878). Cette démarche actualiste contribue à préciser la paléo-profondeur de dépôt de la base de la formation de Motta San Giovanni dans ces localités.

**Mots-clés:** *Cidaris remiger*, Miocène, échinoïdes, taxonomie, Italie, Calabre.

## 1. INTRODUCTION

Fossil remains of fan-shaped spines *Cidaris* from the Tertiary of Italy and North Africa have been the subject of past studies (Ponzi, 1858; Meneghini, 1862; Ponzi, 1876; Agassiz, 1878, Pomel, 1887, Airaghi, 1901; Stephanini, 1908; Checchia-Rispoli, 1918; Borghi & Magnani, 2020). The material of the Motta San Giovanni

Formation belongs to the species *Cidaris remiger* (Ponzi, 1876). Echinodermal remains are particularly abundant in this Formation, associated with a diversified bathyal fauna (Barrier *et al.*, 1987) (see list below) (Fig. 1). Among these remains, a species of the family Cidaridae is predominant. The collected material was compared to the extant species in order to evaluate the morphological characters and taxonomic attribution of these cidarid

<footnote n="1">¹ 147 rue de la Massatrie, F-79230 Aiffres. SHNB (Société d'Histoire Naturelle du Boulonnais); philippe.nicolleau@gmail.com</footnote>

<footnote n="2">² Rue du Dr Brousse, F-62360 Pont-de-Briques, France. SHNB</footnote>

<footnote n="3">³ UniLaSalle - Collège géosciences, 19 rue Pierre Waguet, BP 30313, F-60026 Beauvais cedex, France and B2R (Bassins, Réservoirs, Ressources) - EA 7511</footnote>

<footnote n="4">⁴ IFP Energies nouvelles, 1 et 4 avenue de Bois-Préau, F-92852 Rueil-Malmaison, France</footnote>
remains. These broad, fan-shaped radioles appear to refer to those of a modern species, *Cidaris blakei* (Agassiz, 1878).

The province of Reggio Calabria has been known for its palaeontological richness since the works of Scilla (1670), Melograni (1823), Seguenza (1880) and Cortese (1895), even if subsequent works focused mainly on the stratigraphy (Ogniben, 1973; Barrier, 1984) or on the tectonics of the Plio-Quaternary and its Miocene substratum (Bousquet *et al.*, 1980; Sauret, 1980; Barrier, 1984; Chabellard, 1984; Barrier, 1982; Barrier *et al.*, 1986).

Our study consisted in listing and examining the Tertiary and extant worldwide *Cidaris* species with fan-shaped radioles. Their past and modern geographical location is confined to the Mediterranean and Caribbean regions. The species still living in the deep seas off the Caribbean, *Cidaris blakei*, is indistinguishable from Tertiary species and the species collected in Calabria. The valid name

retained, after taxonomic revision, is *Cidaris remiger*
(Ponzi, 1876).

## 2. GEOLOGICAL SETTINGS

A synthesis of the early work of Barrier *et al.* (1987), accompanied by a geological description of the province of Reggio Calabria (Raber, 2003) are at the origin of our work. They make it possible to lay the stratigraphic and cartographic bases of the two outcrops studied in the Motta San Giovanni Formation.

2.1. The Miocene of the Motta San Giovanni
Formation

After an exploratory phase based on cartography, the
geological work focused on specific questions. In

<figure><img src="image_2.png" /><figcaption>Fig. 1. Location of the Serravallian fossil deposits (star) found in southern Calabria. The first one is located in the coves of the locality called Vigne della costa (38°0′27.28″N, 15°41′37.41″E) a few hundred meters west of the type section of the Motta San Giovanni Formation, in the cliff of Monte Gonia (Figs 2, 3) studied by Barrier *et al.* (1987).</figcaption></figure>

The Miocene outcrops of the typical section of the Motta San Giovanni Formation (Fig. 2) show both units, Motta 1 claystone (A) and Motta 2 sandstone (B).
particular, we studied the Miocene stratigraphy of coarse turbidite deposits whose emplacement is situated at the transition between an extensive back-arc context and the internal zone of the present Calabrian prism (Bonardi *et al.*, 2001). These terrigenous deposits are preserved in confined sub-basins organised in tilted blocks (Guillois & Polard-Taine, 2016; Colas & Ripoll, 2017; Pichancourt & Terrier, 2016). The sedimentary system (facies, depositional profile, architectural elements, drone models of outcrops, survey of the sections with a portable gamma ray reader), its stratigraphic architecture and its structural context, were characterised using serial sections (Chirol & Kubiak, 2019; Marchiel & Rispal, 2019). These sections make it possible to establish a correlation between the different Miocene layers whose lateral facies passages are controlled by active tectonics (Bourel & Degrave, 2020). Thanks to this work, it was possible to show the synchronous nature of the clayey basement of the Motta Formation. The detail of the section, from which the fossils presented here come, are given in the works cited above and in Rohais *et al.* (2021). It is along these sections that we collected fragments of cidarids, associated with a rich fauna of molluscs and corals collected for study. Sampling consisted of a surface collection over the entire height of the two clay outcrops of badlands without precise distinction.

## 2.2. Location of outcrops

The Miocene Motta San Giovanni Formation (Barrier, 1984) is subdivided into two members: a basal part, mainly clayey (Motta 1) and a top part, mainly sandy (Motta 2). The two fossiliferous outcrops are located south of Reggio Calabria (Fig. 1) in the clayey part of the Motta San Giovanni Formation (Motta 1). (star)

In the *badlands* of the locality called “Vigne della costa” at Motta San Giovanni (38°0′27.28″N, 15°41′37.41″E)

(Fig. 3) we observe three units, the Floresta calcarenites Formation (A), the fossiliferous deposit of Motta 1 (B) and the sandstone of Motta 2 (C).

The second unit is located about ten kilometres east of the first one in the Musuponiti coves (37°58′6.30″N, 15°48′14.71″E), along the road from Melito di Porto Salvo to Bagaladi. The Miocene outcrops of Musuponiti (Fig. 4) consists of two distinct units: the fossiliferous deposit of the Motta 1 claystone (A), the Motta 2 sandstone (B). The fossiliferous deposit of the Musuponiti badlands (Fig. 5) is about 5 m (height of the outcrop).

## 2.3. The creeks of Vigne della costa

The fossils are found at the base of the silty clays of Motta 1, which form the coves of the locality called “Vigne della costa”, near the road that leads to the cemetery of Motta San Giovanni (Fig. 3). Details sections of Vigne della costa are given in Rohais *et al.*, 2021. At this locality, the Motta San Giovanni Formation is over 400 m thick. It includes at the base, in transgressive contact on the “Calcarenites of Floresta” Formation of Langhian age, clayey siltstones with small banks of fossiliferous decimetric sandstones. They are overlain by fossiliferous silty micaceous clays, at the origin of the deposit, less and less silty while going up in the series and poor in macro-fossils with the exception of some sharks’ teeth. The distribution of fossils at the base does not correspond to a continuous level but rather to concentrations in lenses, over a few tens of metres long, which disappear and then reappear a few hundred metres further on (Guillet de Chatellus & Prosperi, 2020). The thickness of these clays varies from 60 m to 270 m through a system of syn-sedimentary horsts and grabens (Guillet de Chatellus & Prosperi, 2020). The series continues with turbiditic silt-sandstone deposits including conglomerates and boulder sandstones of

<figure><img src="image_3.png" /><figcaption>Fig. 2. Miocene cliff outcrops of the typical section of the Motta-San-Giovanni Formation. A-the Motta 1 claystone; B-the Motta 2 sandstone.</figcaption></figure>
<figure><img src="image_4.png" /><figcaption>Fig. 3. Fossiliferous deposit of the badlands in the locality called "Vigne della costa" in Motta-San-Giovanni (38°0′27.28″N, 15°41′37.41″E). A: Formation of the Floresta calcarenites; B: the fossiliferous deposit of the Motta 1 clay; C: the Motta 2 sandstone.</figcaption></figure>

plutonic and metamorphic rocks. At the top, on Monte Gonia, the Miocene series is truncated by Quaternary deposits (Barrier, 1984).

## 2.4. The creeks of Musuponiti

The outcrop corresponds to coves developed on the clayey base of the Motta San Giovanni Formation (Motta 1). Details sections of Musuponiti are given in Rohais *et al.*, 2021.

It is located below the village of Musuponiti (Figs 4, 5). The clays outcrop near the road, for about 100 m, going up towards the village. At the base, the contact with the Langhian is siltstone without macrofauna. The clays then develop, they are initially silty and fossiliferous and then become impoverished in macrofauna. Then less silty, they contain a few flattened ferruginous nodules whose sulphurous core systematically contains a crushed nautiloid. Some decimetric sandstone banks with carbonised wood fragments are present in the clay mass. The Motta San Giovanni Formation continues to the south of the deposit with sandstones (Motta 2). These contain coarse, conglomeratic and chaotic facies of the submarine canyon fill type. The sandstones contain numerous reworked macrofossils. The most abundant are rhodolithes (algae), which vary in size from praline to pellet. They are locally associated with molluscs and colonial corals from infralittoral reefs, which have also been displaced from their original environment. These canyon infill facies alternate with sandstone facies of channels, levees and lobes. *Paleodictyon* (Meneghini, 1850) burrows on the surface of the lobe facies sandstones.

<figure><img src="image_5.png" /><figcaption>Fig. 4. The Miocene outcrops of Musuponiti (37°58′6.30″N, 15°48′14.71″E). A: the fossiliferous deposit of the Motta 1 clay; B: the Motta 2 sandstone.</figcaption></figure>

<figure><img src="image_6.png" /><figcaption>Fig. 5. View of a Miocene outcrop of Musuponiti, basal part (height of the outcrop is about 5 m). All fossils collected come from surface sampling carried out across the entire badlands visible in Figures 4 and 5.</figcaption></figure>

## 3. PALEONTOLOGICAL CONTENT

The associated fauna was determined by the authors, with the exception of the anthozoans identified by Helmut Zibrowius, marine biologist from the Endoume Marine station. All the fauna was collected in lenticular deposit in the first meters of the Motta 1 clay. It includes (A: abundant; F: frequent; R: rare): **Cepholopoda**, **Nautiloidea**: *Aturia aturi* (Basterot, 1825) (A) **Scaphopoda**: *Dentalium badense* (Partsch, 1856) (A), *Dentalium lamarckii* (Chenu, 1843) (R); **Bivalvia**: *Nucula aegeensis* (Forbes, 1844) (A), *Pholadomya candida* Sowerby, 1823 (R), *Pycnodonta* sp. (Fischer von Waldheim, 1835) (R); **Gastropoda**: *Lophocochlias* sp. (Pilsbry, 1921) (A),
*Natica* sp. (Scopoli, 1777), shells and opercules (F), other undetermined gastropod species; *Bryozoa: Lunulites* sp. (Lamarck, 1816), (R) *Brachiopoda: Crania* sp. (Retzius, 1781), (R) *Actinopterygii: Otoliths of Moronidae* (Jordan & Evermann, 1896) (A), various other undetermined of otoliths (R), *Chondrichthyes: Otodus* sp. (Agassiz, 1838) (F), *Isurus* sp. (Rafinesque, 1810), (E) *Echinoidea: Cidaris reminger* (Ponzi, 1876) (F), *Histocidaris* sp. (Mortensen, 1903), (R), *Toxopatagus italicus* (Manzoni & Mazzetti, 1877) (A), *Crinoidea: Pentacrinitidae* (Gray, 1842) (R); *Anthozoa: forms close to Heterocyathus* sp. (Milne-Edwards & Haime, 1848), (A), *Caryophyllia* sp. (Lamarck, 1801) (A), *Flabellum* sp. (Lesson, 1831), (A), *Isideae* (Lamouroux, 1812) (R). Both deposits show differences in the relative abundance of the fauna. The Vigne della costa coves contain abundant and diverse solitary corals, whereas they are much rarer at Musuponiti. Echinoids are rare in the Vigne della costa coves, whereas they are very abundant in Musuponiti. The same is true of the nautiloid *Aturia aturii*, (Basterot, 1825) which are very rare in the creeks of Vigne della costa whereas they are very abundant in Musuponiti. The rest of the fauna is distributed in much the same way in both sections. Both sites show an abundance of wood fragments probably charred.

## 4. MATERIAL AND METHOD

The fragments of tests and radioles studied here were collected in the Serravallian clay at the base of the Motta San Giovanni Formation in Calabria. They were discovered in the type locality of this Formation (Vigne della costa sector, GPS coordinates: 38°0′27.28″N, 15°41′37.41″E), during the systematic survey of sedimentological sections in order to elaborate a depositional model of these turbidite sediments (Rohais *et al.*, 2021). They were later searched in other Calabrian outcrops and found at Musuponiti (GPS coordinates: 37°58′6.30″N, 15°48′14.71″E).

<figure><img src="image_7.png" /><figcaption>Fig. 6. Biometric measurements on an isolated plate of test.</figcaption></figure>

About 100 fragments of radioles (12 with the button) and 9 isolated plates of test (fragments) were collected in situ in the Serravallian of Motta-San-Giovanni at Vigne della costa and Musuponiti, Calabria (Italy) by one of us (P.B.). We took biometric measurements (Figs 6, 7) using a calliper and a binocular magnifier fitted with a graduated lens accurate to a tenth of a millimetre. The results were compiled in a spreadsheet and analysed using the software Datadesk 7, which can produce scatter plots or boxplots.

<figure><img src="image_8.png" /><figcaption>Fig. 7. Biometric measurements on a radiole.</figcaption></figure>

## 5. TAXONOMY

We follow Smith's taxonomy in Echinoid Directory access in 2020, except for the definition of the genus *Cidaris*.

Order Cidaroida (Claus, 1880)
Family Cidaridae (Gray, 1825)
Genus Cidaris (Leske, 1778)

**Type species:** *Echinus cidaris* Linné, 1758, by subsequent designation of Mortensen, 1928

**Diagnose:** Cidaridae with no ambital miliary zone, with radiole equipped with fine spines arranged in line.
*Cidaris remiger* (Ponzi, 1876)

Fig. 8

1858. *Cidaris remiger* Ponzi, p. 558, without figuration or description, from a place and collection not indicated: *nomen nudum*.

1862. *Rabdocidaris oxyrine* Meneghini, p. 13, pl. 2, fig. 3a-a', from the Miocene of the Turin Hill or the Mio-Pliocene of Imola (Italy): *nomen dubium*.

1876. *Cidaris remiger* Ponzi, p. 947, pl. 3, fig. 2a-e, from the Tortonian marls of Monte Vaticano (Italy) and from the Ponzi collection (?).

1878. *Dorocidaris blakei* Agassiz, p. 185, pl. 4, figs 1-3, from the present seas, fished off Havana (Cuba), at "175 to 450 fathoms depth".

1887. *Dorocidaris saheliensis* Pomel, p. 324, pl. 1, figs 1-20, from the "Sahelian" (Upper Miocene of the Oran ravine in Algeria).

1901. *Cidaris oxyrine* Airaghi (*non sensu* Meneghini, 1862), p. 167, pl. 1, figs 26-33, from the Helvetian of the Turin hill and the Rovasenda collection.

1901. *Rhabdocidaris rovasendai* Airaghi, p. 171, pl. 19, figs 34-40, from the Bartonian of Piedmont and the Rovasenda collection.

1918. *Rhabdocidaris remiger* Checchia-Rispoli, p. 74, p. 4, figs 1-21, from the Pliocene of Monte Vaticano, and from the Checchia-Rispoli collection (?)

1980. *Cidaris cubensis* Cutress (*non sensu* Lambert in Lambert & Thiery, 1925, p. 53, pl. 2, fig. 1, from the Eocene of Cuba and from the collection of the California Academy of Sciences.

1928. *Cidaris blakei* Mortensen, p. 86, pl. 32, figs 1-6, present-day caught in the West Indies off Havana and Barbados.

1970. *Cidaris blakei* Phelan, p. 10, pl. 6, figs 1, 3, 5, pl. 7, figs 1, 6-8, pl. 8, figs 1-9, and pl. 9, figs 1-2, caught between 315 and 420 m, off Barbados and Cuba.

2020. *Cidaris saheliensis* Borghi & Magnani, p. 26, figs 1-4 in text, from the Langhian of Pescale, Modena (Italy).

**Diagnosis:** Interambulacral plaques bear a single perforated, non-crenulate tubercle and are surrounded by a scrobicle of fine granules. The button of the radioles is not crenulate and their diameter corresponds to the diameter of the mamelon of the interambulacral tubercle. Their stem has numerous slightly spiny ridges. This species have fan-shaped radioles on upper side of the test.

**Referred specimens:** All the figured samples (Fig. 8) were found in the Serravalian of Vigne della costa and Musuponiti. They are housed in the collection of the institute UniLaSalle, Collège géosciences, 19 rue Pierre Waguet, BP 30313, F-60026 Beauvais. The fan-shaped radioles are carried by the ambital and adapical part of the test (Fig. 8A, B, D, E, G, H, J, K, O). The narrowest radioles are on the adoral part of the test (Fig. 8M, N). Some radioles have been digitally reconstructed (Fig. 8C, F, I, L). Only interambulacral plates of the test were harvested (Fig. 8P, Q, R, S).

**Description:** Only nine isolated interambulacral plates

were collected. The interambulacrum at the ambitus measures between 18 and 20 mm (Fig. 7), the height of the interambulacral plate is between 8 and 9 mm, the scrobicle is ovoid, slightly flattened antero posteriorly. The interambulacral tubercle is perforated and smooth or slightly in the adapical area. The platform of the interambulacral tubercle is 2.1 mm in diameter and the mamelon 1.5 mm. Secondary granulation is present in the median miliary zone (4 granules) and in the adradial miliary zone (1 granule). The test lacks an ambital miliary zone. The number of ambulacral plates in front of the ambital interambulacral plate is 12 and the ambulacral plates are devoid of a median miliary zone.

The tests have fan-shaped radioles from the ambitus to the subapical surface. They become narrower on the adoral side. The fan-shaped radioles (reconstructed) are about 30 mm long and 20 mm wide. There are 60 to 70 rows of spines distally, varying in density from 6 to 20 per cm. The articular surface of the button is generally smooth, the collar is 1.4 mm long, the ring about 3.5 mm in diameter, the button 1.4 to 1.7 mm long.

All the biometric measurements are specified in Table 1 and Table 2.

# 6. ANALYSIS OF CALABRIAN FOSSILS

The biometric measurements of the figured elements are grouped in Table 1 for the tests and in Table 2 for the radioles.

## 6.1. Isolated interambulacral plates of test

These plates correspond to the genus *Cidaris*. In the two deposits of Musuponiti and Vigne della costa only nine isolated plates of tests were collected, no complete test was found (Fig. 8P, Q, R, S). These are isolated interambulacral plates from different parts of the test. They are very eroded. On one ambital plate the mamelon is smooth and perforate. The median miliary zone shows four granules and none in the ambital miliary zone. All the biometric measurements of figured plates of test from the Calabrian deposits of Musuponiti and Vigne della costa are grouped in Table 1.

In order to specify the position of the isolated interambulacral plates, adapical plate (Fig. 8Q) have a little tubercle and great miliary zone, plate above the ambitus have granule in the upper zone (Fig. 8P) and ambital plates (Fig. 8R-S) have no granule in the ambital miliary zone.
<figure><img src="image_9.png" /><figcaption>Fig. 8. *Cidaris remiger* Serravallian from Musuponiti, A, B, D, E, G, H, J, K, M, N, O radioles; C, F, I, L digital reconstructions of radioles (scale bar 1 = 10 mm); P to S: test fragments (scale bar 2 = 10 mm) (plates and mounting P. Nicolleau). The dimensions are specified in Tables 1 and 2.</figcaption></figure>
<table><caption>Table 1. Biometric measurements of the figured tests from the two Calabrian deposits of Musuponiti and Vigne della costa.

Captions: int (width of interambulacrum), lScro (width of scrobicle), hScro (height of scrobicle), hPi amb (height of interambulacral plate), dPIFo (diameter of platform), dMam (diameter of mamelon), zm med (number of granules in the median miliary zone), zm amb (ambital miliary zone), zm adr (adradial miliary zone), npa/pia (number of ambulacral plates abutting the interambulacral plate).</caption><thead><tr><th>Fig. 8</th><th>int</th><th>lScro</th><th>hScro</th><th>hPi amb</th><th>dPIFo</th><th>dMam</th><th>Zm med</th><th>zm amb</th><th>Zm adr</th><th>npa/pia</th></tr></thead><tbody><tr><td>P</td><td>19</td><td>6.0</td><td>5.5</td><td>8.2</td><td>2.1</td><td>1.5</td><td>4</td><td>0</td><td>----</td><td>12</td></tr><tr><td>Q</td><td>------</td><td>------</td><td>------</td><td>------</td><td>2.1</td><td>1.5</td><td>------</td><td>------</td><td>------</td><td>------</td></tr><tr><td>R</td><td>20</td><td>6.2</td><td>5.8</td><td>9.0</td><td>2.2</td><td>1.5</td><td>4</td><td>0</td><td>1</td><td>12</td></tr><tr><td>S</td><td>18.5</td><td>5.5</td><td>------</td><td>------</td><td>2.1</td><td>1.5</td><td>4</td><td>0</td><td>1</td><td>------</td></tr></tbody></table>

<table><caption>Table 2. Biometric measurements of the radioles figured in the two deposits of Musuponiti and Vigne della costa. The * means that the measurements were made on the reconstruction.</caption><thead><tr><th>Fig. 8</th><th>length overall (Lo)</th><th>largest width (lw)</th><th>Nb rows spines</th><th>Nb spines per cm</th><th>Lenght Collar (Lc)</th><th>crenulation</th><th>Ø ring (Dr)</th><th>Ø articular surface (Das)</th><th>lenght button (Lb)</th></tr></thead><tbody><tr><td>B</td><td>10.8</td><td>8.2</td><td>32</td><td>20</td><td>1.4</td><td>0</td><td>3.5</td><td>1.6</td><td>1.7</td></tr><tr><td>A</td><td>&gt;19</td><td>17.5</td><td>58</td><td>12</td><td>------</td><td>------</td><td>------</td><td>------</td><td>------</td></tr><tr><td>C*</td><td>26.3</td><td>17.5</td><td>------</td><td>------</td><td>------</td><td>------</td><td>------</td><td>------</td><td>------</td></tr><tr><td>E</td><td>&gt;14</td><td>9.8</td><td>36</td><td>12</td><td>1.4</td><td>0</td><td>3.8</td><td>1.7</td><td>1.7</td></tr><tr><td>D</td><td>&gt;27.5</td><td>23.2</td><td>70</td><td>12</td><td>------</td><td>------</td><td>------</td><td>------</td><td>------</td></tr><tr><td>F*</td><td>36.5</td><td>23.2</td><td>------</td><td>------</td><td>------</td><td>------</td><td>------</td><td>------</td><td>------</td></tr><tr><td>H</td><td>&gt;19.7</td><td>9.5</td><td>36</td><td>12</td><td>1.4</td><td>0</td><td>3.8</td><td>1.8</td><td>1.4</td></tr><tr><td>G</td><td>&gt;22.3</td><td>19.2</td><td>70</td><td>12</td><td>------</td><td>------</td><td>------</td><td>------</td><td>------</td></tr><tr><td>I*</td><td>29.5</td><td>19.2</td><td>------</td><td>------</td><td>------</td><td>------</td><td>------</td><td>------</td><td>------</td></tr><tr><td>O</td><td>&gt;16.4</td><td>12.8</td><td>90</td><td>18</td><td>1</td><td>1</td><td>3.4</td><td>1.7</td><td>1.4</td></tr><tr><td>K</td><td>&gt;11.8</td><td>6.2</td><td>30</td><td>22</td><td>1.2</td><td>0</td><td>2.9</td><td>1.4</td><td>1.5</td></tr><tr><td>J</td><td>&gt;18.2</td><td>18.0</td><td>112</td><td>12</td><td>------</td><td>------</td><td>------</td><td>------</td><td>------</td></tr><tr><td>L*</td><td>28</td><td>18</td><td>------</td><td>------</td><td>------</td><td>------</td><td>------</td><td>------</td><td>------</td></tr><tr><td>M</td><td>&gt;18.5</td><td>5.4</td><td>23</td><td>6</td><td>------</td><td>------</td><td>------</td><td>------</td><td>------</td></tr><tr><td>N</td><td>&gt;17.5</td><td>4.1</td><td>11</td><td>8</td><td>------</td><td>------</td><td>------</td><td>------</td><td>------</td></tr></tbody></table>
## 6.2. Radioles

These radioles can be linked to the isolated *Cidaris* plates collected; their button is smooth, and their articular surface is compatible with the diameter of the mamelon of the interambulacral tubercles. All the radioles collected from the two deposits of Musuponiti and Vigne della costa have a more or less enlarged fan shape, which gives them a subapical position. Smaller or finer radiole fragments were not collected due to lack of identification. Some of them are narrower and rectilinear, and were in a subambital position on the test. We show several radioles reconstructed based on proximal and distal parts of two separate specimens (Fig. 8C, F, I, L). The subambital radioles do not widen in their distal part and become almost cylindrical. We compared the radioles with those of recent *Cidaris blakei* (Figs 13, 14, 15): only those which are in the sub-apical region are fan-shaped, the others have a cylindrical or ovoid section.

They are between 30 to 110 lines of fine spines, evenly distributed over the entire surface and along the edge. The articular surface is mostly smooth, and sometimes very slightly crenulate (indicating their adapical position on the test). The collar is short. All the biometric measurements of the radioles figured in the two deposits of Vigne della costa and Musuponiti are grouped in Table 2.

## 6.3. Graphic analysis

The aim of this work is not only to study the taxonomy of the different genera of Cidaroida, but above all to compare Miocene Calabrian fossils with the available fossil and modern material. To carry out this study, we measured more than 820 tests and 1400 radioles (Vadet & Nicolleau, 2021) of the extant species assigned to the genus "Cidaris", as well as 140 tests and 180 radioles from various Tertiary localities. The measurements were carried out on specimens from various private and public collections, and on figures found in the literature or on websites.

In particular, we took measurements on the following material:

- The test (isolated interambulacral plates) and radioles studied here;

- Radioles of *Cidaris cubensis* from the Upper Eocene of Cuba, shown in Cutress, 1980, pl. 2, fig. 1;

- The radioles of *Rabdocidaris rovasendai* from the Bartonian of Piedmont, figured in Airaghi, 1901, pl. 19 (1), figs 34-40;

- The holotype (radioles) of *Rabdocidaris oxyrine*, from the Miocene, figured in Meneghini, 1862, pl. 2, fig. 3a' and fig. 3a"-c;

- The radioles of *Cidaris oxyrine*, figured in Airaghi, 1901, pl. 19, figs 26-33, and the original of fig. 33 (provided by Enrico Borghi);

- Figures of *Cidaris saheliensis*, Sahelian, figured in Pomel, 1887, p. 324, pl. 1, figs 10-20, from Oran (Algeria);

- The figures of *Cidaris remiger* figured in Ponzi, 1876, pl. 3, figs 2a-d, from the Upper Tortonian of Monte Vaticano (Italy);

- The syntypes of *Cidaris mazzettii*, figured in Stephanini, 1908, pl. 13, figs 3-4, from the Miocene of Pavullo, Emilia-Romagna (Italy);

- The tests and radioles of "*Cidaris*" *mazzettii*, figured in Borghi & Stara, 2016, pl. 5, fig. E, from the Upper Burdigalian-Lower Langhian of Pescale, Modena, pl. 5, figs E-F, pl. 6, fig. C1-4, fig. E;

- Tests and radioles of *Cidaris saheliensis* from the Langhian of Modena, shown in Borghi & Magnani, 2020, on original photographs provided by Enrico Borghi;

- One of the syntypes of *Cidaris hystrix*, present-day Mediterranean from the Muséum national d'histoire naturelle in Paris (MNHN-IE-2013-10419);

- Figures of the holotype (test with radioles) of *Cidaris blakei*, figured in A. Agassiz, 1878, caught in the West Indies;

- The tests and radioles of *C. blakei*, figured in A. Agassiz, 1883, fished at depth of 300 and 500 m in the West Indies, pl. 4, figs 1-3;

- The tests and radioles of *C. blakei*, shown in Mortensen, 1928, pl. 32, fig. 1-6, fished in the West Indies, off Havana and Barbados;

- Tests and radioles of *C. blakei*, figured in Phelan, 1970, pl. 6, fig. 3, and pl. 7, fig. 1, presently fished between 315 and 420 m, off Barbados and Cuba;

- The specimens (tests and radioles) of *Cidaris cidaris*, shown in Mortensen, 1928, pl. 31, fig. 7 and pl. 31, fig. 10, from the Mediterranean;

- Several specimens (tests and radioles) of *C. cidaris*, Mediterranean, Perpignan, Les Embiez, Toulon and Tarragona, from the collections Schultz 54, Vadet V36, V152, V153, V154 and Nicolleau.

Only the adapical radioles are fan-shaped, which is an apomorphy of this species in the genus *Cidaris*. These radioles therefore belongs to the group of *Cidaris* with fan-shaped radioles called the "*blakei*" group. According to our results (Figs 9, 10, 11, 12), the test fragments and radioles collected from the Motta Formation belong to the genus *Cidaris* (Leske, 1778), based on Smith's diagnosis from the Echinoid Directory, and more specifically belongs to the "*blakei*" group. The subambital radioles correspond perfectly to the characters of the genus. Within the genus *Cidaris*, we focus the specific identification on species with large or fan-shaped radioles.

Of the 10 characters measured or observed, only four were discriminating and independent of radioles size:
radioles diameter in mm (Fig. 9), collar length in mm (Fig. 10), number of rows of spines (Fig. 11) and linear density of spines (Fig. 12). In the size range studied, these characters are independent of size, and all the examples studied have an average size; small and large samples are missing.

The other characters studied are not discriminating and have not been presented here.

The box plots (Figs 9-12) illustrate the results of the graphic studies on different material: - *cubensis*, Eocene of Cuba (1); - *rovasendai*, Bartonian of Piedmont (2); - *oxyrine*, Bartonian of Piedmont (3); - "saheliensis", Langhian of Modena (4); - Miocene of Calabria studied in this paper (5); - *remiger*, Tortonian of Monte Vaticano (6); - *saheliensis*, Pliocene of the Ravine of Oran (7); - present-day *blakei* of the Antilles (8). Stars and circles correspond to outliers.

<figure><img src="image_10.png" /><figcaption>Fig. 9. Radioles diameter (mm).</figcaption></figure>

<figure><img src="image_11.png" /><figcaption>Fig. 10. The length of the collar (mm).</figcaption></figure>

<figure><img src="image_12.png" /><figcaption>Fig. 11. The number of rows of spines.</figcaption></figure>

<figure><img src="image_13.png" /><figcaption>Fig. 12. The number of spines per linear cm.</figcaption></figure>

## 6.4. Comparison with recent *Cidaris blakei*

See Figs 13-15

<figure><img src="image_14.png" /><figcaption>Fig. 13. *Cidaris blakei in situ*, showing the adapical position of fan-shape radioles; Bahamas; 22°41.05' N 74°20.75' W; 1988 (photo Smithsonian Institution JSLI-2269).</figcaption></figure>
<figure><img src="image_15.png" /><figcaption>Fig. 14. *Cidaris blakei*, radiole figured in Phelan, 1970, pl. 8, figs1-2; L1=41.5 mm, L2=46.5 mm.</figcaption></figure>

<figure><img src="image_16.png" /><figcaption>Fig. 15. *Cidaris blakei*, test figured in Phelan, 1970, pl. 7, fig. 1; D=27,5 mm.</figcaption></figure>

# 7. DISCUSSION

## 7.1. Background

Meneghini (1862) described and figured radioles which he called *Rabdocidarischyrine*. The tubercle is described as crenulated. Furthermore Meneghini (1862) called it *Rabdocidarisch* (without “h”), a choice based on the presence of strong crenulations. This description is insufficient to diagnose the species, because it does not precise the nature of the crenulations, which is an important character. It is considered as a *nomen dubium*. Ponzi (1858) cited a *Cidaris remiger* but gave no figure or description. Consequently, it is considered as a *nomen nudum*.

Van den Hecke (1858) in a letter addressed to the Geological Society of France and read by P. Deshayes

cited a list of fossils among which is included *Cidaris remiger*. However the description is insufficient. It is a *nomen dubium*.

Ponzi (1876) described *Cidaris remiger* (giving biometric measurements) and figured a fanshaped radioles with a smooth articular surface and a test in adoral view. He described the mamelons of the interambulacral tubercle as smooth and perforate. This description with figures is sufficient.

Pomel (1887) described and figured the test and radioles of *Dorocidarischaheliensis*, from the Sahelian (Pliocene?) of the Oran ravine in Algeria, which have smooth and perforate tubercles.

Airaghi (1901) described and figured a series of radioles that he attributed to *Cidaris oxyrine*, from the Serravalian of the Turin hill, and placed it in synonymy with *Cidaris sahaliensis*. Pomel. He also created a new species, *Rabdocidarischrovasendai*, from the Bartonian of various localities in Piedmont, Italy.

It shows broadly fanned radioles with smooth knobs that do not differ from the radioles of the *blakei* group.

Stefanini (1908) described *Dorocidarischazzetti*, p. 70, pl. 13, figs 3-4. It is a single test, impossible to classify without its radioles.

Checchia-Rispoli (1918) studied material from Monte Vaticano and the Van den Hecke, Ponzi and Rayneval collections. He examined numerous remains of *Cidaris remiger* and validated the *remiger* species of Ponzi (1876).

Mortensen (1928) p. 307, pl. 32, figs 1-6, pl. 71, fig. 6, described tests and radioles of *Cidaris blakei* and gave a complete synonymy.

Phelan (1970) described several specimens (tests, radioles, test with radioles) of *Cidaris blakei*, p. 10, pl. 6, figs 1, 3, 5, pl. 7, figs 1, 6-8, pl. 8, figs 1-5, 8, pl. 9, figs 1, 2. The subapical radioles slightly crenulate and the subambits smooth. Borghi & Magnani (2020) included (fig. 2c) one of the radioles figured in Airaghi (1901), pl. 1, fig. 33. These authors did not retain Ponzi's (1876) description, considered incomplete, and choosed to call the fan-shaped radioles *Cidaris sahaliensis* (Pomel, 1887). Vadet & Nicolleau (2021) clarified the characters of the genus *Cidaris*. They showed in particular the differences with *Stylocidarisch* and *Stereocidarisch*.

The description, figuration and biometric measurements of *Cidaris remiger* Ponzi, 1876 sufficiently characterize this species to affirm that the Miocene fossils from the Motta Formation can be attributed to this species.

The determination of the genera and species of the family *Cidaridae* cannot be done without their radioles (Vadet & Nicolleau, 2021) which become essential elements of the taxonomy. Moreover, radioles alone can be used to define new species (Hostettler *et al.*, 2023). In fact, tests of "Cidaris" alone often show no morphological difference between the different species.
The four discriminating characters studied on the fan-shaped radioles of both Tertiary here studied fossils and present-day forms show no difference and consequently we refer this material to *Cidaris remiger* (Ponzi, 1876).

## 7.2. Living environment

The radioles and test fragments of the Calabrian fossils have been attributed to *Cidaris remiger*. They are identical to those of the present species, formerly described as *Cidaris blakei* (Agassiz, 1878). The known ecological data for this extant species are applicable to the fossils (principle of actualism). *Cidaris blakei* lives exclusively in the Caribbean, in the Gulf of Mexico where it has been caught between 320 and 825 m depth (175 and 450 fathoms depth) (Agassiz, 1878), off Cuba, between 450 and 685 m depth, off the Bahamas (Bennett, 2009), between 577 and 902 m depth, off the Bahamas (Pawson & Pawson, 2013), between 408 and 569 m depth, off the Bahamas, Grenadines and Barbados (Rice & Miller, 1991). *In situ* temperature surveys have shown this species to live at 13°C (Bennett, 2009). No data on the nature of the substrate is provided. However, photos taken by the Okeanos Explorer in 2015 and 2018 show that the nature of the substrate can be a more or less fine mud or a harder bottom. The fact that *Cidaris blakei* has never been associated with *Cidaris cidaris* (Linnaeus, 1758), neither in the fossil record nor in the present-day database, unfortunately does not allow to use the numerous data on *Cidaris cidaris* to specify the living environment of *Cidaris blakei*.

## 7.3. Geographical distribution

The fossils described in Italy, Algeria and Cuba under different names and collected here under the name *Cidaris remiger* show both a Mediterranean and Caribbean distribution. They are present from the Bartonian to the Upper Miocene in the Mediterranean and in the Eocene in Cuba.

Nowadays it is found, under the name *Cidaris blakei*, only in the Caribbean.

In the Mediterranean, *Cidaris remiger* persisted until the Upper Miocene (Checchia-Rispoli, 1918) and probably disappeared after the Messinian crisis, suffering from the lowering of the sea level, and no fossil traces are reported in Western European sediments. When deep sea conditions are again available in the Mediterranean, only two closely related species, *Cidaris cidaris* (Linnaeus, 1758) and *Stylocidaris affinis* (Philippi, 1845) are present in the bathyal environment (Terribile & Scembri, 2013). No records of *Cidaris remiger* have yet been made in the Pliocene around the Mediterranean or in the present

Mediterranean Sea. A few questions remain unanswered. Why is *Cidaris remiger* not present on the Atlantic coast, like its closest counterpart *Cidaris cidaris*, while the same *Cidaris remiger* survives in the Caribbean? Similarly, why is the *Cidaris cidaris* not present in the Caribbean?

## 8. CONCLUSION

This study allowed us to clarify the taxonomic position of *Cidaris remiger* Ponzi, 1876 by compiling known and new Calabrian fossils from the Motta Formation (Miocene). They were all measured and treated graphically. Thus, the Calabrian fossils studied are attributed to *Cidaris remiger*. The stratigraphic distribution of this species extends in the Mediterranean from the Upper Eocene to the Messinian. It then disappeared from the Mediterranean basin, where it currently survives exclusively in the Caribbean, where it occupies a silted-up bottom between 300 and 900 m in depth. This is a valuable piece of information that can be transposed to the depositional depth of the clays at the base of the Motta San Giovanni Formation in Calabria.

## ACKNOWLEDGEMENTS

We thank Enrico Borghi, who provided us with photographs, enlightened comments and bibliography. The same goes for the students of UniLaSalle who, as part of their fieldwork, made it possible to collect fossils in sufficient quantity to perform graphic analyses. Thanks to Andrea Barrier who finalized the figures.

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