Preliminary remark Pragmatically, we use the distinction between Bourgueticrinidae and Phrynocrinidae sensu Hess (2011). As the classification of extant crinoids with a xenomorphic stalk is not clearly established at the order and family levels (see discussion in Messing 2016), the taxonomic attributions of the fossil columnals here described are inevitably provisional, waiting more material, especially well preserved aboral cups and brachials. Synonymies are restricted to main references that include illustration.
Family Rhizocrinidae Jaekel, 1894
Genus Paraconocrinus Roux, Eléaume and Améziane, 2018
Paraconocrinus romanensis (Roux and Plaziat 1978)
Figures 3a–c, 4a, 5b, f–g, 6a, b, 8, 9, 10
Synonymy Bourgueticrinus thorenti sensu Rouault, 1850 [non d’Archiac, 1846]: 437, pl. A, figs. 13–14; Conocrinus romanensis Roux and Plaziat 1978: 304, fig. 4.
Material examined Syntypes A (MNHN.F.A69327, Roux and Plaziat 1978, Fig. 4), two aboral cups and two columnals from San Roman (Santander Province, Spain); Syntypes B (MNHN.F.A69328, not figured), three aboral cups and 56 columnals from same location; MNHN.F.A69329, two aboral cups from Bosdarros near Gan; Specimen A (MNHN.F.A69330, Fig. 4a), one distal stalk with its proximal roots from Gan bed 6; Specimen B (MNHN.F.A69331, Fig. 3a, b), 1 isolated columnal from the same bed and location; Specimens C (MNHN.F.A69332, not figured), 2 isolated columnals from the same bed and location; Specimen D (MNHN.F.A69333, Fig. 3c), one isolated columnal from bed 4, same location; Specimen E (MNHN.F.A69334, Fig. 5a, f, g), 3 rhizoid ossicles detached from Specimen A; Specimen F (MNHN.F.A69335, not figured), 3 isolated columnals from bed 2–4, same location.
Description Usually, each distal columnal with a single conspicuous root socket prolonging the greatest diameter of one articular facet, a few cases with two sockets of the same size (one adjacent to each facet). Maximum size: H 3.5 mm, D 3.75 mm, d 2.75 mm, d′ 3.5 mm. H/D 0.72–0.95 and D/d 1.36–1.66 in dististele. H/D up to 1.22 and D/d about 1.50 in two mesistele columnals. Distal columnals variously inflated at mid-height. Articular facet with eight-shaped ligament fossae larger than in the two other species from Gan, width 1/2 d (Fig. 3a). Fulcral ridge forming a conspicuous relief between the two adjacent slightly depressed areas with conspicuous parallel borders, its axis filled in with massive calcite and bordered on each side by 20–25 small regularly arranged crenulae (Fig. 3b). Dististele from bed 6 consisting of eight columnals articulated over a length of 20 mm (Fig. 3a), columnal shape very variable (Fig. 10). Two roots branched on one side and a third on the other side. Main root beginning with a short ossicle (H = 0.7 mm, D = 1.0 mm) followed by a long axillary (2.5 mm) with an isometric branching. On one branch, a second highly anisometric division occurring at 2.3 mm, the other branch remaining undivided over 7.9 mm with three observable ossicles. Root ossicles articulated by synostoses. Largest root ossicles having articular facet with a slight depression around the axial canal (Fig. 5a, f, g).
Remarks No significant correlation between shape (H/D and D/d) and size (d′) could be documented because the shape of successive columnals in the distal segment varied substantially, and the sample size was too small (Figs. 8, 9). Mesistele and dististele columnals in the type-series of P. romanensis from Upper Ypresian of Spain (Roux and Plaziat 1978) are very similar of those from Gan. They share the same fulcral ridge characters with mesistele columnals of P. handiaensis Roux, 1978a, from the Bartonian at the base of the Biarritz Eocene section (Roux 1978b, pl. 2 fig. 5). However, distal columnals of P. handiaensis differ in having a hollowed fulcral ridge axis as observed in the extant species C. cabiochi Roux, 1976, from the Bay of Biscay (Roux 1977a, pl. 4 fig. 3). The type-series of P. romanensis includes five aboral cups. The two cups (MNHN.F.A69329), unfortunately in poor preservation, and those figured with associated columnals by Rouault (1850, pl. A, figs. 13, 14), both from Bosdarros near Gan, could belong to the same species.
Occurrence Upper Ypresian of Bosdarros and Gan (SW France) and San Roman (Santander, Spain), Ypresian/Lutetian boundary of Sierra de Cadi (Lerida, Spain).
Genus Democrinus Perrier, 1883
Democrinus londinensis (Forbes, 1852)
Figures 3d–i, 4b, c, 8, 9, 10
Synonymy Bourgueticrinus londinensis Forbes, 1852: 36, fig. 4; Democrinus londinensis Rasmussen, 1972: 31–33, pl. 1 fig. 9; Roux, 1978b: 226–227, fig. 13, pl. 2 figs. 6–11.
Material from Gan, bed 6 Specimen A (MNHN.F.A69336, Fig. 4c), one distal stalk with a few proximal root ossicles, including one columnal detached for SEM study (Fig. 3h, i); specimen B (MNHN.F.A69337, Fig. 3d–g), one isolated distal columnal; specimen C (MNHN.F.A69338, Fig. 4b), one isolated root fragment. Root ossicles collected by sediment washing and attributable to either C. romanensis or D. londinensis (see Remarks): (MNHN.F.A69339, Fig. 5b–e), six ossicles; (MNHN.F.A69340, not figured), 29 ossicles.
Description Each distal columnal with one or several root sockets, sometimes of various size, developed from the outer ends of fulcral ridge, inflation at mid-height variable. Isolated columnal with an ankylosed facet (Fig. 3d): H 4.2 mm, D 4.15 mm, d 2.3 mm, d′ 3.4 mm, H/D 1.01, D/d 1.43. Columnals in the distal stalk segment (Fig. 3c): H 2.9–3.05 mm, D 4.1–4.25 mm, d 2.6–2.7 mm, d′ 3.0–3.15 mm, H/D 0.68–0.74 and D/d 1.56–1.62. Articular facet with 8-shaped ligament fossae of width usually 1/3 d, other parts of ligament area significantly more depressed than in C. romanensis (Fig. 3h). Fulcral ridge axis without massive calcite and lateral crenulae, filled in with irregular stereom except for a conspicuous hollowed area near the ligament fossae, lateral ridge borders progressively depressed and marked by stereom of larger meshes (Fig. 3f–i). Isolated columnal (probably from proximal dististele of another specimen) displaying articulation anchylosis with development of a thin layer of synostosial stereom on outer facet (Fig. 3d, e), previous functional synarthry (well-preserved under this layer) with ligament fossea width about 1/2 d (Fig. 3e–g). Dististele from bed 6 with 11 articulated columnals together 44 mm long. Several articulations partly slipped or slightly dislocated, and two columnals tilted (Fig. 4c). Proximal root ossicles sub-parallel to the stalk and dislocated. A single root segment 12 mm long, of seven articulated ossicles of variable length (Fig. 4b), found 30 mm away from the columnals. The proximal-most ossicle the longest (4.3 mm) with maximum diameter of 1.1 mm. Distal end of the four distal ossicles bearing one socket of 0.5 mm in diameter indicating highly anisometric branching. One small branch ossicle still connected to the sixth main root ossicle.
Remarks The Natural History Museum and Geological Survey in London house numerous columnals of D. londinensis from the London Clay (Early Ypresian, NP11–12) (Aldiss 2014). Their maximum size is lower than in those from Gan: H < 3.5 mm and D < 3 mm (Roux 1978b, fig. 13). Articular facets in distal mesistele and dististele (Roux 1978b, pl. 2 figs. 6–8) and anchylosed articulations in distal mesistele (M.R. unpublished SEM views) share exactly the same characters with those from Gan. In both sites, the stereom is exceptionally preserved. All root ossicles collected by sediment washing (Fig. 5b–e, h, i) and the root fragment found near the stalk segment (Fig. 4b) suggest that both D. londinensis and P. romanensis share the same dendritic root pattern. The longest root ossicle is 4.7 mm long, 1.2 mm across its greatest diameter, and has three branch sockets at its distal end (Fig. 5e). One isolated distal-most root ossicle displays a small incrusting disk which was probably attached on a shell fragment (Fig. 5i). In contrast, columnal shape in the dististele of D. londinensis preserved at Gan is less variable than in P. romanensis (Fig. 10).
Occurrence Early Ypresian (London Clay, G.B.), Late Ypresian of Tuilerie de Gan (SW France).
Family Phrynocrinidae A.H. Clark, 1907
Genus Eocenocrinus n. gen.
Type species of the genus Eocenocrinus hessi n. gen. n. sp.
Diagnosis Crinoid with its distal xenomorphic stalk (distal mesistele and dististele) having frequent successive articulations anchylosed (cryptosynarthries). Anchyloses developed at various ontogenic stages with flat outer ring on columnal facets (secondary synostoses). Fulcral ridge in distal columnals with hollow axis bordered by small rudimentary crenulae. Usually, columnals without root socket or with rudimentary ones. Possibly stalked attachment to hard substrate by encrusting disk or roots.
Included species Eocenocrinus hessi n. gen. n. sp., E. bayani n. gen. n. sp., E. didymus (Schauroth, 1855).
Remarks In extant crinoids with a xenomorphic stalk, rigidity or low flexibility of the distal stalk is associated with attachment to a hard substrate. Frequent cryptosynarthries, sometimes with several successive anchylosed articulations, are especially known in the genus Porphyrocrinus (Phrynocrinidae). In this genus, the outer ring of a cryptosynarthrial facet is a secondary syzygy with a conspicuous crenularium (A.M. Clark 1973; Roux 1977a; Messing 2016). Moreover, phrynocrinid stalk synarthries have the fulcral ridge completely surrounded by a deep ligamentary area, which is a highly derived character (Donovan and Pawson 1994; Messing 2016). Eocenocrinus differs in combining several plesiomorphies in its mesistele: a flat synarthrial facet, fulcral ridge with rudimentary crenularium, and deep areola restricted to an 8-shaped ligament pit. It could represent the Eocene ancestor of extant Phrynocrinidae, preceding development of derived characters in the stalk such as large deep synarthrial ligament fossae, which first appear in the Late Eocene species E. didymus. The single previously known fossil phrynocrinid, Porphyrocrinus fossilis Roux and Montenat, 1977, from Late Miocene of Spain, bears distal columnals with the ligament depression as deep and as large as in extant representatives of the genus.
Occurrence Late Ypresian (SW France), Middle Lutetian to Priabonian (northeastern Italy).
Eocenocrinus hessi n. gen., n. sp.
Figures 6a–f, 8, 9, 10
Etymology Dedicated to Hans Hess who published numerous fine and significant studies on post-Paleozoic crinoids.
Type material Syntype A (MNHN.F.A69341, Fig. 6a–d), 1 isolated columnal; syntype B (MNHN.F.A69342, Figs. 6e–f, 11e–f), 1 isolated columnal; syntypes C (MNHN.F.A69343, not figured), 29 columnals, all from beds 2 and 4 of Tuilerie de Gan.
Diagnosis As in description
Description Each columnal with fulcral ridges at opposite ends oriented 90° from each other, no conspicuous root socket (Fig. 6a). Small spines or rudimentary root sockets prolonging the greatest facet diameter. A single columnal, unfortunately poorly preserved, with distal half resembling an attachment disk, including a conspicuous root socket. Maximum size: H 5.75 mm, D 9.5 mm, d 5.1 mm; d′ 7.25 mm. Usually H/D 0.60–0.91 and D/d 1.50–1.92. Smallest columnal (proximal mesistele): H 2.6 mm, D 2.1 mm, d 1.7 mm, d′ 1.85 mm, H/D 1.24, D/d 1.21. Figures 8 and 9 document change in columnal shape (decrease in H/D and increase in D/d) related to size and growth from proximal to distal stalk, with the smallest, most proximal at left in both figures. Articular facet relatively flat (Fig. 6b, c) with eight-shaped ligament fossae width usually < 1/2 d, sometimes as little as 1/3 d. Hollow fulcral ridge axis bordered on each side by rudimentary small crenulae (Fig. 6d). A single columnal without spine or root socket (probably from distal mesistele) and with both facets exhibiting the ankylosed articulation characteristic of late ontogeny (Fig. 6e, f): flat outer ring surrounding the previous functional synarthry with partly altered or resorbed stereom at center.
Remarks The characters visible in the well-preserved synarthries of E. hessi n. gen, n. sp. were previously unknown in either fossil or extant xenomorphic stalks. The columnal with its two facets indicating anchylosed articulations documents a series of three successive columnals fused during late ontogeny within the distal mesistele. Such relatively flat synarthries suggest low flexibility in the distal stalk (at least in distal mesistele). However, a differentiated dististele could be formed by a few distal-most columnals, which were absent in our material from Gan (see Discussion below). Rudimentary root sockets or small spiny expansions cannot contribute to permanent stalk attachment to the substrate. The single columnal, presumably from a distal-most stalk, displays both an attachment disk and a conspicuous socket, possibly corresponding to encrusting roots.
Occurrence Late Ypresian of Tuilerie de Gan (SW France)
Eocenocrinus bayani n. gen., n. sp.
Figures 6g, h, 7, 8, 9, 10
Etymology Dedicated to Ferdinand Bayan (1845–1874) who first mentioned this “grand Bourgueticrinus” in his description of the Eocene section in Val della Guichelina.
Synonymy Bourgueticrinus sp. Bayan, 1870: 459 and 461; Conocrinus didymus Pasotti, 1929, pl. 1, figs. 4, 18 and 21.
Type material Syntype A (MNHN.F.A69344, collection d’Orbigny no. 9017, Fig. 7e), one large columnal from Vicentin; syntypes B (MNHN.F.A69345, MNHN collection d’Orbigny no. 9017 not figured), four isolated columnals from Val della Gichelina; syntypes C (MNHN.F.A69346, Fig. 6g, h), one columnal from Val della Gichelina near Malo, NE Italy; syntype D (MNHN.F.A69347, Fig. 7f–i), four columnals from the same location; syntype E (MNHN.F.A69348, not figured), one columnal from the same location; syntype F (MNHN.F.A69349, Fig. 7a–c), three connected columnal pairs from Val di Ciuppio; syntype G (MNHN.F.A69350, Fig. 7d), one isolated columnals from the same location; syntype H (MNHN.F.A69351, not figured), seven isolated columnals from the same location. All from northeastern Italy.
Diagnosis As in description.
Description Large columnals without root sockets, most with articular facets poorly preserved. Distal mesistele columnals from Ciuppio with moderate inflation at mid-height: H 6.5–8.4 mm, D 8.4–12.0 mm, d 5.2–6.7 mm, d′ 6.9–10.05 mm, H/D 0.63–0.86, D/d 1.61–1.89. Main characters of articular facets as in E. hessi. Most other dististele columnals strongly inflated and joined by cryptosynarthries: H 5.45–8.6 mm, D 10.1–12.6 mm, d 5.8–7.8 mm, d′ 7.75–10.0 mm, H/D 0.49–0.75, D/d 1.13–1.87. Several cryptosynarthries are anchylosed articulations characterized by an interior, early ontogenetic stage synarthry with conspicuous 8-shaped ligament pit (“Conocrinus stage” sensu Roux 1977) surrounded by a flat outer ring (Figs. 6g, h, 7e, g, h).
Remarks Columnal biometry shows the same ontogenetic trends in E. hessi and in E. bayani, the later having larger distal columnals with frequent cryptosynarthries (Figs. 8, 9). The graph of H/D versus D/d (Fig. 10) illustrates the main variations in columnal shape independent of growth. The substantial overlap in values, confirms that the two species are closely related. Of the three columnals figured by Pasotti (1929: pl. 1) and attributed to Conocrinus didymus (Schauroth, 1855), two from San Giovanni Ilarione are articulated (Pasotti 1929: pl. 1, fig. 4) and strongly resemble MNHN columnals from Ciuppio. In the third columnal from Val della Gichelina, one facet is a functional synarthry with a markedly depressed areola (Pasotti 1929: pl. 1, fig. 18), and the other is an early anchylosed articulation (Pasotti 1929: pl. 1, fig. 21). Undoubtedly, these three columnals belong to E. bayani n. sp. Columnals belonging to different stalk segments were found in different localities: from dististeles at Val della Gichelina and from mesisteles at Val di Ciuppio and San Giovanni Ilarione.
Occurrence Middle Lutetian of northeastern Italy (Val di Ciuppio, Croce grande, Val della Gichelina, San Giovanni Ilarione, Pozza).
Eocenocrinus didymus (Schauroth, 1855)
Synonymy ?Bourgueticrinus ellipticus Schauroth, 1855: 546–547, pl. 3 fig. 10; Schauroth, 1865: 188, pl. 8 fig. 4; ?Bourgueticrinus didymus Schauroth, 1855: 547; Bourgueticrinus ?didymus Oppenheim, 1900–1901; 97–98, pl. 18 fig. 4.
Remarks Schauroth (1855, 1865) figured two columnals from the Late Eocene of Priabona with a maximum diameter of 11 mm, no inflation at mid-height, H/D of about 0.5, well developed fulcral ridges, and the whole ligament area markedly depressed. They strongly resemble proximal mesistele columnals of the large extant species Phrynocrinus nudus or Porphyrocrinus thalassae. Oppenheim (1900–1901) figured another columnal from the Late Eocene of Costalunga near Possagno resembling Ciuppio columnals but displaying a more conspicuous fulcral ridge, 8-shaped ligamentary pit small or lacking, and no inflation at mid-height. Schauroth’s columnals could belong to the flexible proximal mesistele and Oppenheim‘s columnal to the more rigid distal mesistele of the same species. However, it cannot be excluded that they belong to two distinct species. Additional material is required for a robust diagnosis of E. didymus and to clarify its relationships with the other species of the genus Eocenocrinus. E. bayani n. gen., n. sp. differs in having columnals more inflated, H/D > 0.6, and articular facets usually with 8-shaped ligament fossae. The presence of stalk synarthries with the whole areola completely depressed places E. didymus closer to extant phrynocrinids than to E. hessi n. sp. However, in E. didymus, this character could represent an adaptation to deeper environment.
Occurrence Late Eocene (Priabonian) of northeastern Italy.
