Discometra luberonensis, Eléaume & Roux & Philippe, 2020

Eléaume, Marc, Roux, Michel & Philippe, Michel, 2020, Discometra luberonensis sp. nov. (Crinoidea, Himerometridae), a new feather star from the Late Burdigalian, European Journal of Taxonomy 729, pp. 121-137 : 127-128

Discometra luberonensis sp. nov.

urn:lsid:zoobank.org:act:2C82EC72-FEDC-4BCB-9716-88EEFDB0146D

Fig. 2 A–F

Diagnosis

Robust species with arms up to 60 in number. Centrodorsal a rounded pentagonal, flattened, truncated cone; basal diameter up to 14.3 mm; aboral pole cirrus-free, flattened and slightly depressed, smooth or very slightly granular, reaching ¾ of centrodorsal diameter. Cirrus sockets in 2–3 irregular marginal rows. Cirri XXX–L of up to at least 30 never higher than wide cirrals, 27.5 mm long. Arm pattern with Ibr2ax, IIbr1-2 3+4ax; br1-2ax frequent up to fifth brachitaxis; ligamentary synarthry at br1-2; multiradiate syzygy at br3+4; very oblique muscular synarthries in proximal part of arms.

Etymology

The epithet refers to the Massif du Lubéron, a major mountain range in the Provence area where the specimens on which the description is based were collected. Lubéron is part of the greater administrative area (Région) called Provence-Alpes-Côte d’Azur in the southeast of France.

Material examined

Holotype

FRANCE • SE France, Vaucluse, Bassin d’Apt, Ménerbes-Lacoste Plateau ; MHNL 20.062682 .

Paratypes

FRANCE • same collection data as for holotype; MHNL 20.056148, 20.056151 .

Locus typicus

“Calcaire de Ménerbes” ( Demarcq 1970), facies with large pectinids ( Gigantopecten restitutensis ), quarries in Ménerbes-Lacoste Plateau (Bassin d’Apt, Vaucluse, southeastern France), Late Burdigalian.

Description

Holotype ( Fig. 2 A–B)

Specimen well exposed aborally, displaying centrodorsal, proximal part of three rays, about ten free arms visible in profile and recurved aborally, five cirri still attached to centrodorsal, and many fragments of arms and isolated cirri. Centrodorsal a flattened truncated cone; apex broad, almost flat and smooth, devoid of cirrus sockets; cirrus sockets arranged in 2 to 3 irregular rows. Maximum length of complete attached cirrus 27.50 mm with 30 cirrals; cirrals subcylindrical; c1–c5 wider than high; following cirrals as high as wide; maximum cirral diameter 1.0 mm, average width of proximal half of cirri 2.0 mm, most frequent height of cirrals about 1 mm; terminal claw slightly curved and about twice as long as preceding segment. Radial circlet hidden. Arms divided 4 or 5 times; Ibr2 always axillary; secundibrachitaxes IIbr1-2 3+4ax (4 cases), IIbr undivided (1); pattern observed in the following brachitaxes: IIIbr1-2ax (5), IVbr 1-2ax (4), IVbr 1-2 3+4ax (1), IVbr undivided (1), Vbr1-2ax (2), Vbr1-2 then broken (2), Vbr1 2+3 4... (1), VIbr1-2 3+4... (2), estimated total number of arms close to 60. Non-muscular (ligamentary) articulations: ligamentary synarthry at 1-2 and syzygy with multiradiate crenularium at 3+4 (most often ankylosed at IIbr3+4); syzygies or synostoses irregularly arranged along free arms, separated by 4 to 8 muscular synarthries; br1-9 more or less rectangular, following brachials wedge-shaped. Maximum primibrachial width 7.10 mm; maximum primibrachitaxis length 6.30 mm; Ibr2ax height 3.42 mm; secondibrachial width 4.90 mm; IIbr1-2 height 3.35 mm; IIbr1-2 3+4ax maximum length 6.25 mm; IIIbr1-2 width 3.50 mm, height 3.35 mm; maximum height of tertibrachial axillary 2.0 mm; average width of proximal half of distalmost free arm 2.65 mm; longest isolated fragment of free arm 38 mm with 26 brachials; maximum length of an attached free arm 50.0 mm. Preserved pinnules rare, proximal part of P II robust, composed of more or less squarish segments; more distal part of proximal pinnule getting thinner and flexible with relatively short pinnulars (less than twice as high as wide).

Paratypes

Specimen MHNL 20.056148 ( Fig. 2 C–D) with largest centrodorsal diameter, aboral cirrus-free depression flat and very slightly granular; about 30 cirri preserved around centrodorsal hiding proximal part of crown; complete cirrus with 25 cirrals, length 26 mm, longest cirrus fragment 27 mm with 28 cirrals. Specimen MHNL 20.056151 ( Fig. 2 E–F) with most flattened centrodorsal, aboral surface flat and smooth with two small pits; only ¾ of crown preserved, one brachitaxis visible, with same pattern as holotype; visible arms 38, allowing an estimated total number close to 60.

Figures

Fig. 2. Aboral view of the proximal crown and centrodorsal in three genera of Himerometridae A.H. Clark, 1908. A–F. Discometra luberonensis sp. nov., Late Burdigalian of Ménerbes-Lacoste Plateau. A–B. Holotype (MHNL 20.062682). C–D. Paratype (MHNL 20.056148). E–F. Paratype (MHNL 20-056151). G–H. Extant species of Himerometridae from western Pacific. G. Himerometra robustipinna (Carpenter, 1881) (MNHN-IE-2012-862). H. Heterometra savignii (Müller, 1841) (MNHN-IE-2016-1381). Scale bars: A–G = 10 mm; H = 5 mm.