AMNH NOVITATES Tuesday Dec 11 2001 10:21 AM 2000 novi 00147 Mp_1 Allen Press x DTPro System File # 01cc CORE Metadata, citation and similar papers at core.ac.uk Provided by American Museum of Natural History Scientific Publications PUBLISHED BY THE AMERICAN MUSEUM OF NATURAL HISTORY CENTRAL PARK WEST AT 79TH STREET, NEW YORK, NY 10024 Number 3292, 15 pp., 5 ®gures March 16, 2000 A Middle Devonian Trilobite Assemblage from Venezuela MARIA DA GLORIA PIRES DE CARVALHO1 AND JOHN MOODY2 ABSTRACT Three new species of trilobites are described from the upper level of the CanÄo del Oeste Formation (Middle Devonian) of Venezuela. These taxa include a phacopinine, Viaphacops venezuelensis, n. sp., and two asteropyginines, Rhenops odremani, n. sp., and Greenops per- ijaensis, n. sp. The biogeographic implications of these records are discussed. Viaphacops is somewhat cosmopolitan in its distribution. The presence of Rhenops in Venezuela represents a profound range extension beyond the Rhenish-Bohemia region of the Old World Realm. The Venezuelan occurrence of Greenops represents a southerly range extension within the Eastern Americas Realm, reinforcing faunal similarities previously recognized among Devonian bra- chiopods and trilobites of Venezuela and North America. RESUMEN Se describen tres especies nuevas de trilobites provenientes del nivel maÂs alto de la For- matioÂn CanÄo del Oeste (DevoÂnico medio) de Venezuela. Estos taxones incluyen un facopinino, Viaphacops venezuelensis, n. sp., y dos asteropigininos, Rhenops odremani, n. sp. y Greenops perijaensis, n. sp. Se discuten las implicancias biogeogra®cas de estos registros. Viaphacops tiene una distribucioÂn amplia. La presencia de Rhenops en Venezuela representa una extensioÂn signi®cativa de su distribucioÂn maÂs alla de la regioÂn Rheno-Bohemia del Viejo Mundo. El registro de Greenops en Venezuela extiende su distribucioÂn hacia el sur dentro del Dominio del Este de las AmeÂricas, apoyando las similtudes reconocidas previamente, entre los bra- quioÂpodos y los trilobites devoÂnicos de Venezuela y AmeÂrica del Norte. 1Research Associate, Division of Paleontology, American Museum of Natural History. 2Professor, SeccioÂn de PaleontologõÂa, Museo de BiologõÂa, Universidade del Zulia, Facultad de Ciencias, Apartado 526, Maracaibo 4011, Zulia, Venezuela. Copyright q American Museum of Natural History 2000 ISSN 0003-0082 / Price $1.90 AMNH NOVITATES Tuesday Dec 11 2001 10:21 AM 2000 novi 00147 Mp_2 Allen Press x DTPro System File # 01cc 2 AMERICAN MUSEUM NOVITATES NO. 3292 INTRODUCTION either destroyed in a ®re at MeÂrida or was lost during its relocation to Caracas, accord- The Devonian marine invertebrate fauna ing to Venezuelan ministry of®cials. from Venezuela has been known since the In the present work, new species of Via- beginning of the 20th century (Yeakel, 1924; phacops, Greenops, and Rhenops are de- Weisbord, 1926; Liddle et al., 1943), follow- scribed. This material was collected by one ing early expeditions to collect fossils from of us (J. M.) and is housed in the Museo de the type locality of the CanÄo del Oeste For- BiologõÂa, Universidad de Zulia (MBLUZ), mation (Middle Devonian; Eifelian±Give- Maracaibo, Venezuela. Casts of this material tian), which extends along the Cachirõ river are also deposited in the fossil invertebrate in the Perija Mountains. Benedetto (1979, collection of the American Museum of Nat- 1984) subsequently described assemblages of ural History. pelecypods, trilobites, and brachiopods that The presence of Greenops in the Devonian were collected from several exposures of the of Venezuela supports the proposed biogeo- CanÄo del Oeste Formation in the area of graphic connection with the Eastern Ameri- CanÄo Colorado (®g. 1). The trilobites de- cas Realm, and the presence of Rhenops in scribed in the present work were also col- the Venezuelan assemblage suggests a link lected from this region. with the Rhenish-Bohemian subprovince of The ®rst Devonian trilobite described from Europe and Morocco (part of the Old World Venezuela (a fragmentary specimen lacking Realm; Boucot, 1988). Viaphacops is more the cephalon, deposited in the Cornell Uni- widespread and occurs in three different bio- versity Paleontological Laboratory) was re- geographic realms. The biogeographic sig- ferred to Phacops argentinus Thomas (Weis- ni®cance of these trilobites is discussed fur- bord, 1926). Eldredge and Ormiston (1979: ther below. 148) suggested that it may belong to Via- phacops, and according to Benedetto (1979: LOCALITIES AND STRATIGRAPHY 85) Weisbord's material was probably col- lected from the CanÄo Grande Formation, The CanÄo del Oeste Formation has long which underlies the CanÄo del Oeste Forma- been considered to be of Middle Devonian tion and is probably of Lower Devonian age. age (Barret and Isaacson, 1988; Benedetto, Additional trilobites from CanÄo del Oeste 1979, 1984; Weisbord, 1926). This forma- Formation were described by Benedetto tion, ®rst described by Liddle et al. (1943), (1979), who identi®ed a phacopinine (Pha- represents the middle beds of the Rio Cachirõ cops sp. cf. P. rana; ibid., 96±97, pl. 4, ®gs. Group (Sutton, 1936), and consists princi- 1±7) and two asteropyginines (Greenops sp., pally of ®ne-grained, micaceous, quartzitic plus gen. and sp. indet.; ibid., 97±98, pl. 4, sandstones, siltstones, and shales. In the type ®gs. 8, 9). As discussed below, Benedetto's section, the formation may be up to 1000 m (1979) phacopinine apparently differs in sev- in thickness, but in the area from which the eral respects from the material described here present material was collected (a few kilo- as Viaphacops. Thus, the assemblage prob- meters south of the type section), it is less ably contains at least two different phacopi- than 400 m thick. The contact with the un- nines, although only Viaphacops is repre- derlying CanÄo Grande Formation (Early De- sented in the new sample (the identity of vonian) is faulted (Liddle et al., 1943; Hea Weisbord's original specimen is left an open and Whitman, 1960; Benedetto, 1984). The question). Two asteropyginine taxa are also Campo Chico Formation (Upper Devonian) described here, but it is not possible to com- appears to be transitional from a near-shore pare these with Benedetto's examples be- marine environment to one that is dominated cause critical characters cannot be deter- by terrestrial deposits (Benedetto, 1984; Ber- mined from his descriptions or illustrations. ry et al., 1993). Unfortunately, no direct comparison with any All of the specimens were collected from of his original material (which was deposited three localities along old and new parts of in the Ministerio de EnergõÂa y Minas collec- the Rio Socuy Road, between 1.2 and 2.5 km tion) is possible because that material was north of Hacienda El Reposo, and along the AMNH NOVITATES Tuesday Dec 11 2001 10:21 AM 2000 novi 00147 Mp_3 Allen Press x DTPro System File # 01cc 2000 DE CARVALHO AND MOODY: MIDDLE-DEVONIAN TRILOBITES 3 Fig. 1. Locality map of the CanÄo Colorado Area, Perija Mountains, Zulia State, Venezuela, with insert map of northern South America. Approximate limit of Perija Mountains indicated by stronger dashed line. high, eastern ¯ank of the upper valley from along the old road correspond to Level formed by CanÄo Colorado, a northern tribu- Co7 of Benedetto (1984), whereas the new tary of Rio Palmar in the Perija Mountains, road collecting locality, which was exposed Zulia, Venezuela (®g. 1). The collections after Benedetto made his collections, proba- AMNH NOVITATES Tuesday Dec 11 2001 10:21 AM 2000 novi 00147 Mp_4 Allen Press x DTPro System File # 01cc 4 AMERICAN MUSEUM NOVITATES NO. 3292 bly represent beds of his Level Co4, and pos- sibly slightly higher (®g. 2). Fragmentary tri- lobites have also been collected from addi- tional beds of the CanÄo del Oeste Formation between Levels Co4 and Co7, so trilobites are probably present throughout the upper section. Morphological terminology follows that used in the Treatise on Invertebrate Pale- ontology, Part O (Struve, 1959), Eldredge (1972, 1973), and Lieberman and Kloc (1997). SYSTEMATIC PALEONTOLOGY CLASS TRILOBITA WALCH, 1771 ORDER PHACOPIDA SALTER, 1864 SUBORDER PHACOPINA STRUVE, 1959 SUPERFAMILY PHACOPOIDEA HAWLE AND CORDA, 1847 FAMILY PHACOPIDAE HAWLE AND CORDA, 1847 SUBFAMILY PHACOPINAE HAWLE AND CORDA, 1847 Genus Viaphacops Maximova, 1972 TYPE SPECIES: Phacops pipa Hall and Clarke, 1888; early Middle Devonian of North America (New York State, Michigan and Southern Ontario). GENERIC DIAGNOSIS (Maximova, 1972): Preoccipital lobe entirely reduced; preoccip- ital furrow merged with occipital furrow to form a deep broad furrow on site of preoc- cipital lobe. Occipital ring usually narrow. Vincular furrow deep, with prominent inner border. Eyes of moderate size, less frequently large. Pygidium usually wide, weakly seg- mented. Surface of glabella with fairly large nodes. SYSTEMATIC NOTE: Those phacopids that were originally placed in the genus Phacops from Central Kazakhstan and the Far Eastern part of the former Soviet Union were reex- amined by Maximova (1972), who erected a new genus, Paciphacops, with two subgen- era, P. (Paciphacops) and P. (Viaphacops), each containing several species. Elsewhere Fig. 2. Geological column for the CanÄo del Viaphacops has been elevated to generic Oeste Formation, CanÄo Colorado Area, Perija Mountains, Zulia, Venezuela (after Benedetto, rank (e.g., RamskoÈld and Werdelin, 1991; 1984), showing the approximate stratigraphic lev- Linsley, 1994) and that practice is also fol- els of the trilobites described in this study. lowed here. AMNH NOVITATES Tuesday Dec 11 2001 10:21 AM 2000 novi 00147 Mp_5 Allen Press x DTPro System File # 01cc 2000 DE CARVALHO AND MOODY: MIDDLE-DEVONIAN TRILOBITES 5 Fig. 3. Viaphacops venezuelensis, n. sp., holotype, MBLUZ P-33, internal mold of cephalon. (A) Dorsal view; (B) frontal view; (C) lateral view; (D) oblique dorsolateral view of right side. Viaphacops venezuelensis, new species AGE: Middle Devonian (Eifelian/Give- Figure 3, A±D tian). DESCRIPTION: The cephalon is approxi- DIAGNOSIS: Cephalon broader than long, mately twice as broad as long, with a maxi- with posterior border slightly concave.