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The ontogeny and systematics of the otarionine trilobite Otarionella from the Devonian of the Montagne Noire, France and the Maider, Morocco

RUDY LEROSEY-AUBRIL^*, RAIMUND FEIST^, and BRIAN D. E. CHATTERTON

^* Laboratoire Magmas et Volcans, Université Blaise Pascal, 5 rue Kessler, 63038 Clermont-Ferrand Cedex, France
Laboratoire de Paléontologie, Institut des Sciences de l’Evolution, Université Montpellier II, Cc 062, Place E. Bataillon, 34095 Montpellier Cedex 05, France
Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta T6G 2E3, Canada

View larger version (28K): [in this window] [in a new window]   Figure 1. Location of silicified and calcareous trilobite beds. (a) Location of Cabrières area in the southeastern Montagne Noire, southern France (vertical hatch lines indicate pre-Mesozoic massifs). (b) Location of sites in the Devonian Pic de Bissous mountain range north of Cabrières village, 8 km SW of Clermont-l’Hérault township. Site 1, western slope of Bissounel peak. Site 2, southwestern vicinity of hill 340 at Col de Mourèze, WNW of Bissous peak. (c) Vertical section through the Bissounel and Mont Peyroux formations showing silicified faunas (site 1) and calcareous faunas (site 2).

View larger version (75K): [in this window] [in a new window]   Figure 2. Otarionella rastrum sp. nov. (a–m, t–v) Scanning electron micrographs of silicified specimens from the middle member of the Bissounel Formation (early to late Emsian), Bissounel Peak, Montagne Noire, France. (n–s, w–y) Digital photographs of calcareous specimens from the Mont Peyroux Formation (late Emsian), Montagne Noire, France. Scale bars 0.25 mm (a–e) and 0.5 mm (f–y). (a–e) Metaprotaspides; (a) dorsal view, UMC-IP490; (b) dorsal view, UMC-IP491; (c–e) specimen with anterior border broken, UMC-IP492; (c) dorsal view; (d) left lateral view; (e) postero-lateral view. (f–r) Cranidia, dorsal views; (f) smallest meraspid specimen, UMC-IP493; (g) meraspis, UMC-IP494; (h) meraspis, UMC-IP495; (i) meraspis, UMC-IP496; (j) meraspis, UMC-IP497; (k) meraspis (?), UMC-IP498; (l) meraspis (?), UMC-IP499; (m) meraspis (?), UMC-IP500; (n) holaspis (?), UMC-IP501; (o) holaspis, UMC-IP502; (p) holaspis, UMC-IP503; (q) holotype, holaspis, UMC-IP504; (r) holaspis, UMC-IP505; (s) holaspis, anterior view, UMC-IP506. (t, u) Fragments of the anterior region, anterior views; (t) small specimen, UMC-IP507; (u) large specimen, UMC-IP508. (v–x) Right lateral views; (v) meraspis, UMC-IP496; (w) holaspis (?), UMC-501; (x) holaspis, UMC-IP502; (y) mirrored left lateral view, holaspis, UMC-IP505.

View larger version (70K): [in this window] [in a new window]   Figure 3. Otarionella rastrum sp. nov. (a–g, j–y, aa, bb) Scanning electron micrographs of silicified specimens from the middle member of the Bissounel Formation (early to late Emsian), Bissounel Peak, Montagne Noire, France. (h, i, z, cc) Digital photographs of calcareous specimens from the Mont Peyroux Formation (late Emsian), Montagne Noire, France. Scale bars 0.5 mm (a–s) and 0.25 mm (t–cc). (a–g) Librigenae, dorsal views; (a) smallest meraspid specimen, UMC-IP509; (b) meraspis, UMC-IP510; (c) meraspis (mirrored), UMC-IP511; (d) meraspis, UMC-IP512; (e) meraspis (?), UMC-IP513; (f) meraspis (?) (mirrored), UMC-IP514; (g) holaspis (?) (mirrored), UMC-IP515. (h, i) Librigenae, dorso-lateral views; (h) holaspis with genal spine broken, UMC-IP516; (i) holaspis with lateral border broken (mirrored), UMC-IP517. (j) Right librigena, ventral view (mirrored), UMC-IP518. (k) Left librigena (note the three rows of lateral border spines), lateral view, UMC-IP519. (l–n) Hypostomes, ventral views; (l) UMC-IP520; (m) UMC-IP521; (n) UMC-IP522. (o–s) Thoracic segments with (o, q, s) or without (p, r) an axial spine; (o) right lateral view, UMC-IP523; (p) posterior view, UMC-IP524; (q) anterior view, UMC-IP525; (r) dorsal view (front to the top), UMC-IP526; (s) dorsal view (front to the top), UMC-IP527. (t–z) Transitory pygidia and pygidia, dorsal views; (t) meraspid degree 2, UMC-IP528; (u) meraspid degree 3, UMC-IP529; (v) large meraspid degree 3, UMC-IP530; (w) meraspid degree 4, UMC-IP531; (x) meraspis, UMC-IP532; (y) small holaspis (?), UMC-IP533; (z) large holaspis, UMC-IP534. (aa) Small meraspis, ventral view, UMC-IP535; (bb) meraspid degree 2, lateral view (mirrored), UMC-IP528; (cc) large holaspis, lateral view, UMC-IP534.

View larger version (98K): [in this window] [in a new window]   Figure 4. Otarionella chamaeleo (Basse, 1997), middle Eifelian, Ohle Formation, Sauerland, Germany. All figures are digital photographs. Scale bars 1 mm. (a, b) Holotype; (a) latex cast of the external moult, right lateral view, UMC-IP536; (b) latex reproduction of the internal moult, dorsal view, UMC-IP537; (c) latex reproduction of an external moult, dorsal view, UMC-IP538.

View larger version (14K): [in this window] [in a new window]   Figure 5. Spine distribution in early meraspid cranidium of Cyphaspis (a), and in early meraspid cranidium (b) and librigena (c) of Otarionella. Bd – dorsal spine of the librigenal lateral border; Blm – long marginal spine of the librigenal lateral border; Bsm – short marginal spine of the librigenal lateral border; Fx – fixigenal spine; G – glabellar spine; Gd – dorsal spine on the genal spine; Gm –marginal spine on the genal spine; P – palpebral spine.

View larger version (144K): [in this window] [in a new window]   Figure 6. Otarionella lkomalii sp. nov., early Eifelian, El Otfal Formation, Jbel Zireg region, south side of Ma’der basin, Anti-Atlas, Morocco. All figures are digital photographs. Scale bars 2.5 mm. (a–f) holotype, UA11821; (a) dorsal view; (b) left lateral view; (c) right lateral view; (d) posterior view; (e) antero-dorsal view; (f) anterior view.

View larger version (33K): [in this window] [in a new window]   Figure 7. Cyphaspis sp., early to late Emsian, middle member of the Bissounel Formation, Bissounel Peak, Montagne Noire, France. All figures are scanning electron micrographs of silicified specimens in dorsal views. Scale bars 0.25 mm. (a) Metaprotaspis (note the four fixigenal tubercles), UMC-IP539. (b–d) Meraspid cranidia; (b) small specimen with six major border spines, strong Fx4, and grouped G2/G3, UMC-IP540; (c) small specimen with seven major border spines, UMC-IP541; (d) large specimen with Fx2 and Fx3 lost and numerous glabellar tubercles, UMC-IP542.