Trilobiten.de

[Jens]

Ich möchte hier ein nicht ganz einfaches Thema aufgreifen.

Wer sich ein wenig mit dem ersten Auftreten der Trilobiten vertraut gemacht hat, wird feststellen, daß man im tiefen Unterkambrium auf mehreren Kontinenten etwa zeitgleich die ersten Trilobiten gefunden hat. Da es sich aber um verschiedene Gattungen handelt und somit schon bei den ältesten Trilobiten ein ausgeprägter Faunenprovinzialismus feststellbar ist, steht man vor einem Problem. Die ältesten bekannten Trilobiten müssen unbekannte Vorfahren gehabt haben. Einige Informationen über diese frühe Ära der Trilobiten-Evolution findet man im folgenden englischen online-Artikel von Robert B. MacNaughton, der auch viel weiterführende Literatur, aberleider keine Bilder, enthält:


http://www.swcp.com/~diamond/trilobites.html

wichtige Feststellungen sind:

das Vorkommen von Spurenfossilien im Vendium-Unterkambrium-Grenzbereich, für die als Verursacher Trilobiten oder die gesuchten Trilobiten-Vorfahren verantwortlich sein können.

die Spuren werden komplexer mit der Zeit, was auf eine zunehmende Spezialisation der Verursacher hindeutet.

Das Fehlen von Hartteilen kann durch noch nicht mineralisierte Exoskelette erklärt werden, wie sie ja auch bei der Trilobitenschwestergruppe der Naroiida bekannt sind.

Es gibt einen trilobitenverdächtigen Arthropoden in der Ediacara-Fauna.


Oki, lest den verlinkten Artikel und wir können die Geschichte dann noch näher im Anschluß besprechen.

Grüsse,

Jens

[Mike]

In Anlehnung an diesen Text habe ich meine Seite um folgende Unterseite erweitert:

http://www.kipping.org/origins.htm

Könnt ja mal schauen ob ich irgendwo Fehler gemacht habe oder etwas mißverständlich klingt!

Gruß

Mike

[Jens]

Hi Mike,

hast Du gut und verständlich rübergebracht, Du könnntest aber noch ein paar Referenzen und weiterführende Literatur angeben.

Schau doch mal diese Sachen durch:

The Precambrian to Cambrian Fossil Record and Transitional Forms

Keith B. Miller

http://www.asa3.org/ASA/topics/Evolution/PSCF12-97Miller.html

The Ediacaran Fauna
Chris Nedin explains Ediacara in three installments

http://www.antievolution.org/people/cnedin/ediacara.html

mit lustigen "Computer"-Strichzeichnungen

Es gibt auch PDF´s:

Paleoecology of the oldest known animal communities:
Ediacaran assemblages at Mistaken Point, Newfoundland
Matthew E. Clapham, Guy M. Narbonne, and James G. Gehling

http://geol.queensu.ca/people/narbonne/ClaphamNarbonneGehlingPaleobiology.pdf


The Ediacaran Biotas in Space and Time 1
BEN WAGGONER


http://www.geol.vt.edu/paleo/Xiao/GEOL5014/7_CambrianExplosion/WaggonerEdiacaranBiogeographyIntegrativeAndComparativeBiology2003.pdf


R.A. FORTEY, D.E.G. BRIGGS & M.A. WILLS: The Cambrian evolutionary ‘explosion’: decoupling cladogenesis from morphological
disparity.

http://www.geol.vt.edu/paleo/Xiao/GEOL5014/7_CambrianExplosion/ForteyCambrianExplosionBiologicalJournalLinneanSociety1996.pdf

SIMON CONWAY-MORRIS: The Cambrian “explosion” of metazoans and molecular biology: would Darwin be satisfied?

http://www.ijdb.ehu.es/fullaccess/fulltext.03078/ft505.pdf


oder was mit Trilos:

GABOR HORVATH, EUAN N K CLARKSON and WALTRAUD PIX : SURVEY OF MODERN COUNTERPARTS OF SCHIZOCHROAL TRILOBITE EYES: STRUCTURAL AND FUNCTIONAL SIMILARITIES AND DIFFERENCES.

http://www.tandf.co.uk/journals/pdf/ghbi_12_01_06.pdf


oder ein Abstract (PDF nicht frei erhältlich):


Xing-Liang Zhang, Jian Han, Zhi-Fei Zhang, Hu-Qin Liu and De-Gan Shu (2003): Reconsideration of the supposed naraoiid larva from the Early Cambrian Chengjiang Lagerstätte, South China. - Palaeontology
Volume 46 (3 ): Page 447.

Abstract

The Chengjiang Lagerstätte in the Lower Cambrian of South China yields a small, larva-like arthropod, which was considered to be a protaspis of naraoiids by many authors. The discovery of a large number of well-preserved specimens from many new localities has allowed the original study to be revised. The relatively large size, stable morphology and unusual structure of the appendages indicate that these specimens represent adults of a new arthropod, Primicaris larvaformis. The larva-like outline is considered to have arisen by the heterochronic process of progenesis. In addition, this animal displays primitive aspects of bodyplan and limb morphology that suggest a basal position within arachnomorphs, or perhaps even arthropods, and the similarities to the Vendian arthropod-like animal Parvancorina probably provide an evolutionary link between Vendian forms and Cambrian arthropods.


Denke, daß sollte fürs erste reichen,

Grüsse,

Jens

[Mike]

Dankööööö,

hab ich erstmal wieder einiges zu lesen!

Gruß

Mike

[Pavel]

Hi
Ein Link mit Bildern zu diesem Thema - Chengjiang Lagerstätte

http://www.fossilmall.com/EDCOPE_Enterprises/Chengjiang/Chengjiang1.htm

Grüsse Pavel

[Jens]

Habe hier noch einen interessanten Artikel zum Thema gefunden.



BRUCE S. LIEBERMAN (2002): PHYLOGENETIC ANALYSIS OF SOME BASAL EARLY CAMBRIAN TRILOBITES, THE BIOGEOGRAPHIC ORIGINS OF THE EUTRILOBITA, AND THE TIMING OF THE CAMBRIAN RADIATION. -Journal of Paleontology, 76 (4): 692-708.

Adress:

1 Departments of Geology and Ecology and Evolutionary Biology, University of Kansas, 120 Lindley Hall, Lawrence, 66045-7613, blieber@ku.edu

Abstract:

This paper presents a phylogenetic analysis of the "Fallotaspidoidea," a determination of the biogeographic origins of the eutrilobites, and an evaluation of the timing of the Cambrian radiation based on biogeographic evidence. Phylogenetic analysis incorporated 29 exoskeletal characters and 16 ingroup taxa. In the single most parsimonious tree the genus Fallotaspidella Repina, 1961, is the sister taxon of the sutured members of the Redlichiina Richter, 1932. Phylogenetic analysis is also used to determine the evolutionary relationships of two new species of "fallotaspidoids" distributed in the White-Inyo Range of California that have been previously illustrated but not described. These species had been referred to Fallotaspis Hupé, 1953, and used to define the occurrence of the eponymous Fallotaspis Zone in southwestern Laurentia. However, these two new species need to be reassigned to Archaeaspis Repina in Khomentovskii and Repina, 1965. They are described as Archaeaspis nelsoni and A. macropleuron. Their phylogenetic status suggests that the Fallotaspis Zone in southwestern Laurentia is not exactly analogous to the Fallotaspis Zone in Morocco, where that division was originally defined. Thus, changes to the biostratigraphy of the Early Cambrian of southwestern Laurentia may be in order. Furthermore, specimens of a new species referable to Nevadia Walcott, 1910, are recognized in strata traditionally treated as within the Fallotaspis Zone, which is held to underlie the Nevadella Zone, suggesting further biostratigraphic complexity within the basal Lower Cambrian of southwestern Laurentia.

Phylogenetic analyses of the Olenellina and Olenelloidea, along with the phylogenetic analysis presented here, are used to consider the biogeographic origins of the eutrilobites. The group appears to have originated in Siberia. Biogeographic patterns in trilobites, especially those relating to the split between the Olenellid and Redlichiid faunal provinces are important for determining the timing of the Cambrian radiation. Some authors have argued that there was a hidden radiation that significantly predated the Cambrian, whereas others have suggested that the radiation occurred right at the start of the Cambrian. The results from trilobite biogeography presented here support an early radiation. They are most compatible with the notion that there was a vicariance event relating to the origin of the redlichiinid trilobites, and thus the eponymous Redlichiid faunal province, from the "fallotaspidoids," whose representatives were part of the Olenellid faunal province. This vicariance event, based on biogeographic patterns, is likely related to the breakup of Pannotia which occurred sometime between 600–550 Ma, suggesting that the initial episodes of trilobite cladogenesis occurred within that interval. As trilobites are relatively derived arthropods, this suggests that numerous important episodes of metazoan cladogenesis precede both the earliest trilobitic part of the Early Cambrian, and indeed, even the Early Cambrian.

Bestätigt, daß man von einer präkambrischen "Vorphase" der Trilobitenevolution ausgehen kann, von der wir bisher aufgrund fehlender Funde nur noch nichts wissen.

Grüsse,

Jens

[Jens]

Hier etwas über höhere Systematik von Trilobiten und Verwandten (Arachnata). Weitere und jüngere Erkenntnisse findet man auch auf der berühmten Seite von Sam Gon III.

Edgecombe GD, Ramskold L (1999): Relationships of Cambrian Arachnata and the systematic position of Trilobita. - JOURNAL OF PALEONTOLOGY 73 (2): 263-287.


Abstract: Cladistic relationships of Trilobita, Naraoiidae (five ingroup taxa), Helmetiida (five ingroup taxa), Xandarellida, and the Cambrian arachnates Retifacies, Sinoburius, B, Emeraldella, and Sidneyia are investigated based on 29 characters. Documentation of appendage morphology and other ventral structures in Saperion from the Chengjiang fauna permits an appraisal of helmetiid relationships. A monophyletic Trilobita [= "Olenellida" (Emuellida + Eutrilobita)] is defined by numerous synapomorphies, including exoskeletal calcification and dorsal eyes with calcified lenses and circumocular sutures. Helmetiida is a robust clade, resolved as (Helmetiidae (Tegopeltidae (Saperiidae + Skioldiidae))). Naraoiid monophyly is well-supported, but neither a naraoiid-trilobite nor a naraoiid-Retifacies clade are parsimonious, the latter grouping ("Nectopleura") being explicitly paraphyletic. A sister group relationship between Xandarellida and Sinoburius is endorsed, although character support is novel compared to previous groupings of these taxa. The fourth postantennal limb pair in trilobites, naraoiids. and apparently helmetiids is based beneath the cephalothoracic articulation. Reweighted characters favor Trilobita and Helmetiida as closest relatives, with Petalopleura and then Naraoiidae as sister groups.
KeyWords Plus: BRITISH-COLUMBIA; BURGESS SHALE; OLDEST ARTHROPODS; CRUSTACEA; ORIGIN; FAUNA; GEN

[Jens]

Hier vielleicht ne Arbeit mit den jüngst entdeckten ältesten Trilobiten von Laurentia (in Nevada gefunden).

Hollingsworth JS (2005): The earliest occurrence of trilobites and brachiopods in the Cambrian of Laurentia. - PALAEOGEOGRAPHY PALAEOCLIMATOLOGY PALAEOECOLOGY 220 (1-2): 153-165


Abstract: The first trilobite to appear in Laurentia is a new form resembling the Siberian trilobite Repinaella. The lack of favorable lithologic environment for some distance below suggests that this occurrence is likely to be the oldest in western Nevada. The trilobites occur on siltstone surfaces and as rare molds in small leached carbonate nodules at parasequence flooding surfaces. Associated brachiopods are locally abundant. These parasequences occur in the lower part of a 50.5-m siliciclastic unit near the top of the Andrews Mountain Member of the Campito Formation that contains considerable light-colored quartzite. Trace fossils are common and diverse in this interval which is interpreted as a lowstand systems tract. Below this interval, the quartzite is dark gray to dark greenish-gray with limited bioturbation of siltstone interbeds suggesting deposition in a dysoxic environment. Above the trilobite-brachiopod-bearing interval, the siliciclastics are green ish-gray, also relatively dysoxic, and barren of body fossils. Trilobites reappear suddenly in relative abundance 57 m above, first as an Eofallotaspis-like form marking the base of the Montezuman Stage, then as several species of Fallotaspis. The occurrence of cf. Repinaella is approximately correlative with the earliest trilobites in Siberia and western Gondwana. © 2004 Elsevier B.V All rights reserved.
Author Keywords: trilobites; brachiopods; Cambrian; Begadean; Laurentia; lowstand systems tract

[Jens]

Hi Heiko,
zur Zeit nicht, Journal of Palaeontology haben wir aber in Greifswald.
Denke mal, daß der Ahlberg-Artikel über phosphatisierte Trilos (in der Rubrik: Kambrium von Baltoscandia) auch interessant sein sollte.

Grüsse,

Jens