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Advances in Trilobite Research

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ADVANCES IN TRILOBITE RESEARCH
ADVANCES IN TRILOBITE RESEARCH
ADVANCES IN TRILOBITE RESEARCH
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PUBLICACIONES DEL INSTITUTO GEOLÓGICO Y MINERO DE ESPAÑA
Serie: CUADERNOS DEL MUSEO GEOMINERO. Nº 9
planeta tierra
Ciencias de la Tierra para la Sociedad
Editors: I. Rábano, R. Gozalo and
D. García-Bellido
Serie: CUADERNOS DEL MUSEO GEOMINERO, Nº 9
All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means,
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References to this volume:
It is suggested that either of the following alternatives should be used for future bibliographic references to the whole
or part of this volume:
Rábano, I., Gozalo, R. and García-Bellido, D. (eds.) 2008.
Advances in trilobite research
. Cuadernos del Museo
Geominero, 9. Instituto Geológico y Minero de España, Madrid, 448 pp.
Adrain, J.M. 2008.A global species database of Trilobita: progress, results, and revision of the
Treatise
. In: Rábano, I.,
Gozalo, R. and García-Bellido, D. (eds.),
Advances in trilobite research
. Cuadernos del Museo Geominero, 9. Instituto
Geológico y Minero de España, Madrid, 27-28.
Cover:
Monotaxic cluster of complete specimens of
Asaphellus toledanus
, a species named after the Toledo province, Spain.
Lower Oretanian (mid Darriwilian) slates of the Valongo Formation, Canelas quarry,Arouca, Portugal.
© INSTITUTO GEOLÓGICO Y MINERO DE ESPAÑA
C/ Ríos Rosas, 23. 28003 Madrid
Tel.: +34 91 349 5700,Fax: +34 91 442 6216
www.igme.es
NIPO 657-08-018-1
ISBN 978-84-7840-759-0
Depósito Legal: 25280-2008
Fotocomposición: Inforama,S.A. Príncipe de Vergara, 210. 28002 MADRID
Imprime: Ibergraphi 2002, S.L.L. Mar Tirreno, 7 bis.28830 SAN FERNANDO DE HENARES (Madrid)
INTERNATIONAL TRILOBITE CONFERENCE (4. 2008.Toledo)
Advances in trilobite research: Fourth International Trilobite Conference,
Toledo, June,16-24, 2008 / I. Rábano, R. Gozalo and D. García-Bellido, eds.-
Madrid: Instituto Geológico y Minero de España, 2008.
448 pgs; ils; 24 cm .- (Cuadernos del Museo Geominero; 9)
ISBN 978-84-7840-759-0
1. Fauna trilobites. 2. Congreso. I. Instituto Geológico y Minero de España,
ed. II. Rábano,I., ed. III Gozalo, R., ed. IV. García-Bellido, D., ed.
562
Article
Full-text available
Queuing behaviour has been documented in marine arthropods from Cambrian to modern oceans. It was previously hypothesized that this behaviour provided energy savings through hydrodynamic drafting, with trilobites in following positions hypothesized to produce less drag than those leading. In this study, we evaluate the hydrodynamics of queuing behaviour in the Devonian trilobite Trimerocephalus chopini using computational fluid dynamics. The results show that the drag forces of the trilobites following in the queue were substantially lower than those produced by the leader (~65–79% lower at velocities of 0.5–2 cm s−1). Drag reduction was positively correlated with the movement speed of the trilobites, but decreased with increasing distance from the leader, and there was essentially no drag reduction at all for the first following trilobite when the following distance was greater than about six times its body length. This agrees with fossil evidence preserving trilobites in queues in close proximity to each other. The results also show that drag reduction was still significant (~86.8% at 2 cm s−1) even for the longest queues preserved in the fossil record. Our findings support the hypothesis that the queuing behaviour of trilobites was an adaptation for reducing hydrodynamic drag. This drag reduction effect compensated for the energy cost of movement, which would have been particularly advantageous during migration.
Article
Full-text available
Remains of the digestive system are described in the holotype of the rare harpidid trilobite Harpides grimmi Barrande, 1852 collected from the Lower Ordovician Mílina Formation of the Prague Basin. The intestine (post-stomach alimentary canal) starts just behind the glabellar posterior margin and extends through the narrow axial region in all nineteen thoracic segments of this exceptionally preserved specimen. The anterior-most part of the digestive system is masked by the in situ hypostome preserved under the missing glabella. Similarly, also the posterior-most part of the post-stomach alimentary canal is absent, as the pygidium is not preserved. This specimen constitutes the first example of preserved digestive structures in the family Harpididae. Earlier finds of digestive system in Ordovician trilobites are briefly assessed.
Article
Full-text available
Onset of maturity in trilobites is generally considered to occur when the last trunk segment is released into the thorax, marking the start of the holaspid stage. Here we describe striking morphological changes that occur within the holaspid ontogeny of Lonchopygella megaspina Zhou in Zhou et al., 1977, which include the effacement of dorsal furrows, the rapid and complete degeneration of pygidial lateral spines, and the increasing prominence of a pygidial axial spine. These notable changes, which are not coincident with the onset of the holaspid phase, emphasize that the onset of maturity in trilobites should be viewed on a character-by-character basis before assessing whether the exoskeleton as a whole can be described as mature. The holaspid pygidial condition in L. megaspina may represent an intermediate step in an evolutionary transition in the number, form, and allocation of segments in the tsinaniid trunk. Pygidial transition from a dynamically changing complement of segments in the meraspid phase to a static complement in the holaspid phase was accompanied by a marked change in the extent to which segment boundaries defined pygidial structure. Attaining this static complement allowed subsequent pygidial development to emphasize its structure as an integrated unit in which internal segmental boundaries became diffuse, a continuous margin to become prominent, and an elongated terminal spine, first evident at onset of epimorphic growth, to develop allometrically. Trilobite body development suggests that while the segmented construction placed constraints on how morphology varied, the influence of these constraints diminished following completion of thoracic segment construction. Selective premium for a distinct posterior tagma might favor the early ontogenetic acquisition of such a structure, and could have been a driver of the repeated trend toward caudalization witnessed among derived trilobite clades.
Article
Full-text available
A rich bivalve fauna from the Middle Ordovician (Sarka Formation, early and mid Darriwilian) of Bohemia shows close affinities to Middle Ordovician bivalves from Spain (Iberian Peninsula) and France (Armorican Massif). Twelve species and nine genera (one new) are described: Praenucula applanans (Barrande, 1881), Praenucula bohemica (Barrande, 1881), Praenucula dispar (Barrande, 1881), Concavodonta ponderata (Barrande, 1881), Pseudocyrtodonta ala (Barrande, 1881), Pseudocyrtodonta incola (Barrande, 1881), Tatula petula gen. et sp. nov., Redonia deshayesi Rouault, 1851, Babinka prima Barrande, 1881, Coxiconchia britannica (Rouault, 1851), and the oldest pteriomorphids in the Prague Basin Modiolopsis sp. and Cyrtodonta sp. Ctenodonta, widely used as cumulative name for all praenuculids, was not recorded in the Middle Ordovician of Bohemia. Remarks on the characters of the Protobranchia shell are discussed, the value of the orientation of the teeth to the umbo or out from the umbo for higher systematic has been overestimated in the past. Accessory muscle scars in the Protobranchia help to move with foot, not only by retraction and protraction but also by elevation; some of them hold a visceral sac. The Recent Protobranchia mostly show simpler type of taxodont teeth in comparison with the Ordovician Protobranchia. Palaeoecological aspects of all the species are shown, infaunal burrowers dominate in the lithofacies of the black shales of the Sarka Formation. The bivalve association is dominated numerically by heterodonts, subdominant are several species of protobranchs and two pteriomorphids. The palaeogeographic distribution of the Middle Ordovician bivalves is discussed. Some of the Middle Ordovician bivalves are widely distributed, they reach Baltica and also the Laurentian margins and probably had to have planktotrophic larvae. Clear preference of the heterodonts for high latitude is confirmed by the dominant heterodonts (six species) in the bivalve association of the Middle Ordovician Sarka Formation.
Article
Full-text available
En este trabajo se presenta una revisión histórica de todos los equinodermos cámbricos descubier tos en España, desde su primer hallazgo a finales del siglo XIX y las técnicas actuales que se utilizan para su estudio. El muestreo sistemático de nuevas localidades cámbricas del Norte de España y la revisión de otras ya conocidas, ha proporcionado más de 2.000 ejemplares de equinodermos. En total se han reconocido taxones pertenecientes a cinco clases: Cincta, Eocrinoidea, Edrioasteroidea, Stylophora y Ctenocystoidea, que muestran la mayor diversidad para este periodo en Gondwana. Estos hallazgos muestran que los equinodermos alcanzaron su primer pico de diversidad durante el Cámbrico medio. Esto, unido a la amplia distribución paleobiogeográfica de algunos clados, nos advierte de un origen para muchos grupos en el Cámbrico inferior, donde sólo unos pocos taxones han sido descritos a nivel mundial. Por último se dan algunas ideas de hacia dónde se podrían dirigir los esfuerzos en este campo de conocimiento.
Article
Eyes other than those of trilobites are rarely preserved in the fossil record. We describe here a set of six tiny, isolated, three‐dimensionally preserved compound eyes. These secondarily phosphatized eyes were etched from ‘Orsten’ limestone nodules dated to the Agnostus pisiformis Biozone from the Cambrian Alum Shale Formation of Sweden. The ovoid eyes arise from an elongated stalk, their surface being covered by a mosaic of regular and hexagonal‐shaped facets representing the surface of ommatidia. Facet size and pattern change within the same specimen from the posterior to the anterior end. With regard to some morphological criteria, we grouped the material in two different morphotypes, type A and B, the first being represented by specimens of two different developmental stages. From stage to stage, mostly growth in overall size and addition of new ommatidia was noticed. Among the meiobenthic ‘Orsten’ arthropods, only the crustacean Henningsmoenicaris scutula has been described as possessing stalked eyes, but the eyes of the largest specimen with preserved eyes of this species are much smaller than the new eyes and do not display any kind of ommatidia on their visual surface. However, fragments of larger specimens of H. scutula and the co‐occurrence of this species with the new isolated eyes in the sieving residues make it likely that the latter belong to this species but belong to more advanced stages than those described previously of H. scutula. Ontogenetically, the eye stalks of this fossil crustacean elongate progressively, while the regular hexagonal facets, lacking in early stages, appear later on.
Article
Full-text available
New collections of trilobites from the type section of the Parahio Formation in the Parahio Valley, Spiti, and from the Parahio, Karsha, and Kurgiakh formations in the Zanskar Valley, permit biozonation based on material precisely located within measured stratigraphic sections. Specimens preserved in limestone with mild tectonic deformation clarify the features of several Himalayan taxa known previously only from severely deformed specimens preserved in shale. A total of 75 trilobite taxa from the Cambrian of Spiti and Zanskar can be referred, questionably at least, at the generic level or below, and 61 of these are present in our new collections. This new material is assigned with confidence to 29 existing species, and to 12 new species. Three new genera, Haydenaspis, Bhargavia, and Himalisania, are established; new species include Haydenaspis parvatya, Prozacanthoides lahiri, Probowmania bhatti, Xingrenaspis parthiva, X. shyamalae, Bhargavia prakritika, Kaotaia prachina, Gunnia smithi, Sudanamonocarina sinindica, Proasaphiscus simoni, Koldinia odelli, and Torifera jelli. Ten additional Himalayan forms are assigned at the generic level only, and another 11 are questionably assigned to genera or species. The zonation proposed includes 6 zones and 3 levels, including the Haydenaspis parvatya level, the Oryctocephalus indicus level, the Kaotaia prachina Zone, the Paramecephalus defossus Zone, the Oryctocephalus salteri Zone, the Iranoleesia butes level, the Sudanomocarina sinindica Zone, the Lejopyge acantha Zone, and the Proagnostus bulbus Zone. The sections span from the upper part of the informal Stage 4, Series 2 of the Cambrian System, about 511 Ma old, to the Proagnostus bulbus zone of the Guzhangian Stage near the top of Series 3, dated at about 501 Ma. This time interval is represented by about 2000 m of section, which is thick compared to similar intervals elsewhere and is consistent with high rates of sedimentation along the Himalayan margin at the time. The fauna resembles others from equatorial peri-Gondwanaland, with closest similarity to that of South China. It also bears strong affinity to the North China fauna. Juvenile trilobites are described for the first time from India. A new Chinese species, Monanocephalus liquani, is also described.
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