Thuy B et al. (2021), New fossils of Jurassic ophiurid brittle stars ...

ECB-ART-48996

R Soc Open Sci 2021 Aug 18;88:210643. doi: 10.1098/rsos.210643.

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New fossils of Jurassic ophiurid brittle stars (Ophiuroidea; Ophiurida) provide evidence for early clade evolution in the deep sea.

Thuy B , Numberger-Thuy LD , Pineda-Enríquez T .

Abstract
Understanding of the evolutionary history of the ophiuroids, or brittle stars, is hampered by a patchy knowledge of the fossil record. Especially, the stem members of the living clades are poorly known, resulting in blurry concepts of the early clade evolution and imprecise estimates of divergence ages. Here, we describe new ophiuroid fossil from the Lower Jurassic of France, Luxembourg and Austria and introduce the new taxa Ophiogojira labadiei gen. et sp. nov. from lower Pliensbachian shallow sublittoral deposits, Ophiogojira andreui gen. et sp. nov. from lower Toarcian shallow sublittoral deposits and Ophioduplantiera noctiluca gen. et sp. nov. from late Sinemurian to lower Pliensbachian bathyal deposits. A Bayesian morphological phylogenetic analysis shows that Ophiogojira holds a basal position within the order Ophiurida, whereas Ophioduplantiera has a more crownward position within the ophiurid family Ophiuridae. The position of Ophioduplantiera in the evolutionary tree suggests that family-level divergences within the Ophiurida must have occurred before the late Sinemurian, and that ancient slope environments played an important role in fostering early clade evolution.

PubMed ID: 34457344
PMC ID: PMC8371378
Article link: R Soc Open Sci

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	Figure 1. . Map showing the position of the localities that yielded the fossil described herein, each indicated by a star.
	Figure 2. . Palaeogeographic map of Europe during the Early Jurassic showing the position of the Sedan and Sanem localities (star no. 1) and the Glasenbach Gorge locality (star no. 2).
	Figure 3. . Bayesian phylogenetic tree of the matrix of Thuy & Stöhr [9] including the extinct species described herein (Ophiogojira labadiei gen. et sp. nov. and Ophioduplantiera noctiluca gen. et sp. nov.) marked in bold. Numbers at nodes indicate posterior probabilities. Extinct species are marked by a cross.
	Figure 4. . ML phylogenetic tree of the matrix of Thuy & Stöhr [9] including the extinct species described herein (Ophiogojira labadiei gen. et sp. nov. and Ophioduplantiera noctiluca gen. et sp. nov.) marked in bold. Numbers at nodes indicate bootstraps values. Extinct species are marked by a cross.
	Figure 5. . Consensus tree derived from the parsimony analysis in PAUP of the matrix of Thuy & Stöhr [9] including the extinct species described herein (Ophiogojira labadiei gen. et sp. nov. and Ophioduplantiera noctiluca gen. et sp. nov.) marked in bold. Numbers at nodes indicate decay indices and bootstrap values, respectively. Extinct species are marked by a cross.
	Figure 6. . Ophiogojira labadiei gen. et sp. nov. from the late Early Pliensbachian (Davoei chronozone, Early Jurassic) of Sedan, Ardennes, France. (a–f) Holotype (MnhnL OPH159), disc fragment in ventral (a) and dorsal (b) views, and with details of the genital papillae (c), the proximal arm segments (d), the arm spine articulations (e) and the arm spines (f). AOS, adoral shield; AOSs, adoral shield spine; AS, arm spine; DAP, dorsal arm plate; di, distal; do, dorsal; GP, genital plate (abradial); GS, genital scale; LAP, lateral arm plate; MO, muscle opening; NO, nerve opening; RS, radial shield; TS, tentacle scale; VAP, ventral arm plate; VAP1, first ventral arm plate; ve, ventral. Scale bars equal 1 mm in (a,b), 0.5 mm in (c,d) and 0.1 mm in (e,f).
	Figure 7. . Ophiogojira labadiei gen. et sp. nov. from the late Early Pliensbachian (Davoei chronozone, Early Jurassic) of Sedan, Ardennes, France. (a) Holotype (MnhnL OPH159), arm fragment in ventral view. (b–e) Paratype (MnhnL OPH160), disc in dorsal (b) and ventral (c) views and with details of ventral arm base (d) and oral skeleton (e). (f) Paratype (MnhnL OPH161), oral plate in adradial view. (g) Paratype (MnhnL OPH162), proximal vertebra in distal view. (h–i) Paratype (MnhnL OPH163), proximalmost lateral arm plate in external (h) and internal (i) views. (j–k) Paratype (MnhnL OPH164), proximal lateral arm plate in external (j) and internal (k) views. (l–m) paratype (MnhnL OPH165), median lateral arm plate in external (l) and internal (m) views. (n–o) Paratype (MnhnL OPH166), distal lateral arm plate in external (n) and internal (o) views. adMA, adradial muscole attachment area; AOSs, adoral shield spine; AS, arm spine; CPP, central primary plate; di, distal; do, dorsal; GP, genital plate (abradial); GS, genital scale; OPa, oral papillae sensu lato; pr, proximal; R, vertebral articular ridge; RS, radial shield; RTo, ridge bordering the tentacle opening; SA, spine articulation; SP, spur; TO, tentacle opening; TS, tentacle scale; VAP, ventral arm plate; ZC, zygocondyle; ZS, zygosphene. Scale bars equal 1 mm in (a–c), and 0.5 mm in (d–o).
	Figure 8. . (a–g) Ophiogojira andreui gen. et sp. nov., from the earliest Toarcian (Tenuicostatum chronozone, Early Jurassic) of Uerschterhaff near Sanem, Luxembourg. (a,b) Holotype (MnhnL OPH167) proximal lateral arm plate in external (a) and internal (b) views. (c–e) Paratype (MnhnL OPH168), median lateral arm plate in external (c) and internal (d) views and with detail of spine articulations (e). (f–g) Paratype (MnhnL OPH169), distal lateral arm plate in external (f) and internal (g) views. (h–n) Ophioduplantiera noctiluca gen. et sp. nov., from the late Sinemurian to late Pliensbachian (Raricostatum to Margaritatus chronozones, Early Jurassic), Glasenbach Gorge near Salzburg, Austria. (h,i,l) Holotype (MnhnL OPH170) proximal lateral arm plate in external (h) and internal (i) views and with detail of spine articulations (l). (j,k) Paratype (MnhnL OPH171), median lateral arm plate in external (j) and internal (k) views. (m–n) paratype (MnhnL OPH172), distal lateral arm plate in external (m) and internal (n) views. di, distal; do, dorsal; MO, muscle opening; NO, nerve opening; pr, proximal; SP, spur; TO, tentacle opening. Scale bars equal 0.2 mm.
	Figure 9. . Evolutionary tree of the subclass Euryophiurida based on the Bayesian inference tree of figure 3, calibrated against the stratigraphic ranges of the fossil taxa, with key synapomorphies marked by stars and colour-mapped on the tree. Taxa shaded in grey predominantly occur below shelf depths (greater than 200 m). (a) Genital papillae in Ophiogojira labadiei gen. et sp. nov. in lateral view. (b) Genital papillae of Ophiura ophiura in lateral view. (c–f) Proximal lateral arm plates with dorsal side up and distal side to the left, of the ophiopyrgids Amphiophiura radiata (c) and Aspidophiura forbesi (d), and the ophiurids Ophiura ophiura (e) and Ophiura ooplax (f). Arrows show the orientation of tentacle openings.