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New Calmoniid Trilobites (Phacopina: Acastoidea) from the Devonian of Bolivia

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New Calmoniid Trilobites (Phacopina: Acastoidea) from the Devonian of Bolivia PUBLISHED BY THE AMERICAN MUSEUM OF NATURAL HISTORY CENTRAL PARK WEST AT 79TH STREET, NEW YORK, NY 10024 Number 3407, 17 pp., 6 ®gures May 22, 2003 New Calmoniid Trilobites (Phacopina: Acastoidea) from the Devonian of Bolivia MARIA DA GLORIA PIRES DE CARVALHO,1 GREGORY D. EDGECOMBE,2 AND LEGRAND SMITH3 ABSTRACT Four new taxa of Lower Devonian Calmoniidae from Bolivia are described: Gemelloides delasernai, n. gen. and sp., Eldredgeia eocryphaeus, n. sp., Wolfartaspis liebermani,n. sp., and Granadocephalus hannibali, n. gen. and sp. The new genus Gemelloides is sister taxon to Vogesina Wolfart, 1968. Eldredgeia eocryphaeus, from the Scaphiocoelia Assem- blage Zone in La Paz and Tarija Departments, closes a stratigraphic gap/ghost lineage in the early history of the Metacryphaeus group. Wolfartasapis liebermani (Icla Formation, Kochis, central Bolivia) predates its only congener, W. cornutus. A novel combination of features within Calmoniidae characterizes Granadocephalus hannibali, from the Icla For- mation in Cochabamba Department. This monotypic genus may have its closest relatives in the Calmonia group. RESUMEN Se describen cuatro nuevos taxa de la familia Calmoniidae del DevoÂnico Boliviano: Gemelloides delasernai, n. gen. y sp., Eldredgeia eocryphaeus, n. sp., Wolfartaspis lie- bermani, n.sp., y Granadocephalus hannibali, n.gen. y sp. El nuevo geÂnero Gemelloides es el grupo hermano de Vogesina Wolfart 1968. Eldredgeia eocryphaeus, registrada para la fauna de la biozona Scaphiocoelia en los departamentos de La Paz y Tarija, cierra un 1 Research Associate, Division of Paleontology, American Museum of Natural History. e-mail: [email protected] 2 Principal Research Scientist, Australian Museum, 6 College Street, Sydney, NSW 2010, Australia. 3 266 Merrimon Avenue, Asheville, NC 28801-1218. Copyright q American Museum of Natural History 2003 ISSN 0003-0082 2 AMERICAN MUSEUM NOVITATES NO. 3407 gap estratigra®co/linaje duende en la historia temprana del grupo Metacryphaeus. TambieÂn parte de este grupo, la especie Wolfartaspis liebermani (FormacioÂn Icla, Kochis, Depar- tamento de Cochabamba) antecede a su uÂnico congeÂnere, W. cornutus. Entre los Calmon- iidae, Granadocephalus hannibali (FormacioÂn Icla del Departamento de Cochabamba) es caracterizada por una combinacioÂn de caracteres nueva para la familia. Este geÂnero mo- notõÂpico podrõÂa presentar como taxa maÂs cercanos miembros del grupo Calmonia. INTRODUCTION which contributes to the taxonomic and stratigraphic record of Bolivian calmoniids. Calmoniid trilobites from the Devonian of Morphological terminology follows that used Bolivia have a long history of study. Since in the Treatise on Invertebrate Paleontology, the initial descriptive work by d'Orbigny Part O (Whittington and Kelly, 1997) as well (1842), numerous papers have documented a as the terminology of Eldredge and BranisÏa rich diversity in the Lower and Middle De- (1980). The term Large Eye Index was intro- vonian (e.g., Kozlowski, 1923; BranisÏa, duced by Wolfart (1968), calculated as the 1965; Wolfart, 1968; Eldredge and Ormiston, ratio between the exsagittal length of the eye 1979; Eldredge and BranisÏa, 1980; Lieber- and the sagittal length of the glabella exclud- man et al., 1991; Lieberman, 1993). Most ing S0. The chronostratigraphic scheme for Bolivian calmoniids occur in three forma- the Devonian of Bolivia is as summarized by tions localized in distinct geographic areas Adrain and Edgecombe (1996: ®g. 2), after (®g. 1): the BeleÂn Formation (BeleÂn-La Paz- Blieck et al. (1996). Specimens studied and Sicasica region of the West Bolivian Altipla- ®gured here are deposited in the collections no); the Icla Formation (Icla-Padilla region, of American Museum of Natural History Sierras Subandinas of central Bolivia), and (AMNH), Division of Paleontology (Inver- the Gamoneda Formation (Tarija region, tebrates), and Museo de HistoÂria Natural de southern Bolivia). The basal portion of all Cochabamba (MHNC), Bolivia. three formations is considered to be time- equivalent, falling within the ``Scaphiocoe- SYSTEMATIC PALEONTOLOGY lia-bearing beds'' (Isaacson, 1977) recog- FAMILY CALMONIIDAE DELO, 1935 nized as the Scaphiocoelia Assemblage Zone by Eldredge and BranisÏa (1980). Trilobites GEMELLOIDES, NEW GENUS occur both within and above this level. The DERIVATION OF NAME: Literally, ``like Ge- total stratigraphic range of Calmoniidae in mellus'', in reference to the name Dalmanites Bolivia is Late Silurian (PrÏõÂdolõÂ) (Edgecombe gemellus Clarke, 1890; gemellus (Latin), a and Fortey, 2000) to Middle Devonian (Giv- twin. etian). TYPE SPECIES: Gemelloides delasernai,n. It is now well established that calmoniid gen. and sp. trilobites are endemic to a Southern-hemi- REFERRED SPECIES: Dalmanites gemellus sphere biogeographic region that Clarke Clarke, 1890 (5 ``Vogesina'' gemellus (1913) ®rst characterized as an ``austral fau- (Clarke) ®de Lieberman et al., 1991) is pro- na'', which he was able to distinguish from visionally assigned. a ``meridional fauna''. Richter and Richter DIAGNOSIS: Cephalon twice wider than (1942) observed the endemic character of long, gently convex (tr. and sag.). All lateral this fauna and coined the term ``Malvinokaf- glabellar furrows well incised; apodemal part fric Province'', which corresponds generally of S1 abruptly shallowing, S1 faintly con¯u- to the Malvinokaffric Realm of Eldredge and ent with axial furrow; S2 effaced abaxially; Ormiston (1979). S3 steeply inclined exsagittally. Pygidium Smith and Edgecombe (1996) informally triangular in outline, relatively wide, lacking reported two new genera and four new spe- marginal spines or lappets; pygidial axis cies of Calmoniidae from Bolivia, but did not comprises 11 rings (®rst 5 separated by name or describe them. In this paper we pre- groovelike impression of distal part of ring sent a systematic description of this material, furrows, posterior rings progressively weak- 2003 CARVALHO ET AL.: CALMONIID TRILOBITES FROM BOLIVIA 3 Fig. 1. A, map of Bolivia, showing location of inset (map B); B, locations of trilobite collection sites in this work (indicated by 3) relative to major cities and towns. er); pleural ®eld moderately convex (tr.), proximately 16 mm. Axial furrows are very with at least six ribs. distinct, narrow, weakly divergent, slightly curved externally at L2. The widest point of Gemelloides delasernai, new species the glabella (across L3) is approximately 7 Figure 2A, B mm, and its posterior width is 4.9 mm. The occipital furrow (S0) is deep, moderately DERIVATION OF NAME: After Salvador de la Serna, ®eld companion to L. Smith for many wide, curving anteriorly (sag.). S1 is a deep, years, who helped to collect the material. wedge-shaped groove, widest mesially, DIAGNOSIS: Lateral glabellar furrows S2 sharply narrowing and shallowing distally, and S3 sharply de®ned; apodemal part of S1 faintly con¯uent with the axial furrow, pos- wedge-shaped; sculpture consisting of small, teromedian part positioned close to S0; S2 is strong pits widely distributed on cephalon, longer and narrower than S1 (tr.), slightly thorax, and pygidium, without coarse gran- convex forward, with weak posteromedial ules or tubercles. orientation, effaced well inward of axial fur- TYPES: Holotype: MHNC 8130, external row; S3 is straight, narrow, widest distally, mold of almost complete specimen (®g. 2A, strongly divergent toward the anterior gla- B), from the lower part of the Upper Member bellar margin (this margin is not preserved, of the BeleÂn Formation, layer of Wolfartaspis and it is uncertain whether S3 reaches it); the cornutus (Wolfart, 1968), late Emsian, BeleÂn strongly divergent arrangement of S3 gives area, La Paz Department, Bolivia (latex cast rise to a pattern in which the glabellar fur- AMNH 48073). Paratype: AMNH 48074, in- rows appear to radiate away from the center ternal mold of part of thorax and external of the glabella. The glabellar furrows do not mold of frontal glabellar lobe, from type lo- cross the median region of the glabella, cality. which is not in¯ated. The glabellar lobes DESCRIPTION: The cephalon is wider than likewise lack independent in¯ation; L1 is long, with length (sag.) of cranidium 7.2 mm narrow mesially, becoming wider near the and width (tr.) across posterior border ap- axial furrow; L2 is wider than L1 and is trap- 4 AMERICAN MUSEUM NOVITATES NO. 3407 row is straight and moderately wide across most of its extent, gradually narrowing near the genal angle. The posterior border is very narrow adjacent to the axial furrow but is considerably wider (exsag.) abaxially, with an evenly convex posterior margin and a rounded genal angle. The palpebral lobe and surrounding area of the ®xigena are some- what swollen, sloping down laterally behind and around the eye. The palpebral lobe is narrow, bounded by a faint palpebral furrow. The cephalon (glabella, L0, ®xigenal ®eld, and posterior border) is ornamented with small, widely distributed pits, but lacks any granular or tuberculate sculpture. The thorax comprises 11 segments, all weakly convex (tr.) with the axial region somewhat higher than the pleurae. Maximum axial width is about one- third that of the thorax. The ®rst four axial rings are faintly convex forward sagittally; this convexity is gradually accentuated in more posterior rings. Axial furrows are shallow and narrow but well de®ned. Thoracic pleurae are trans- verse and horizontal proximally, becoming weakly ¯exed posteriorly in the distal por- tion; this ¯exure is also more accentuated posteriorly.
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