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'Orsten' Fossils in a Phylogenetic Framework

It is remarkable that the 'Orsten' has yielded, so far, only material two bilaterian (gastroneuralian) taxa, cycloneuralian nemathelminths and arthropods. Notabably, both have an epidermis that produces a cuticle. This is not unique among bilaterins, but in these two taxa the cuticle is layered and consists of an outer layer (epicuticle) and a proximal, chitin-bearing layer (procuticle). And even more, in both the cuticle is shedded/moulted no matter how thin or flexible. This co-occurrence of characters has led authors to consider these taxa as closely allied and to propose the taxon Cycloneuralia to bracket them. This problems can't be discussed in detail at present here, but we need to remark that our 'Orsten' preservation clearly is not based on chitin preservation. It is, in most cases, the non-chitinous outermost layer that is preserved and that it is this layer that shows the beautiful details such as wrinklings, fine hairs or pores! Therefore it cannot hold as another indicator of relationships between these two taxa!

There are also other problems in terms of external and in particuar with the anatomical features of arthropods and/or cycloneuralians that are completely ignored by proponents of the Ecdysozoa theory – and it is likewise difficult to make the annelids into the sister group of arthropods! Neither the segmentation nor the coelom or nervous system would work well – and the gonad system is also extremely different.

It may just be added that there is still good reason to regard the Gastrotricha (Ax 1995) as the sister taxon of Cycloneuralia, and if so it causes a further problem ...

1. Nemathelminthes (Gastrotricha + Cycloneuralia)

Representatives of this taxon have been found until recently only in material from the outback of Australia (Georgina Basin) dated to the Middle Cambrian. Yet, this refers not just to single record, but we collected numerous Palaeoscolecida with cuticle preservation, specimens belonging to a form named Markuelia and representing a larva within an egg membrane (see new paper by Donoghue et al. 2006) – and with this Not an embryo at all –, a tiny supposedly cycloneuralian larva named Shergoldana australiensis and several loricae of a possibly priapulid larva (ms currently under construction). Some pictures of these creatures are shown in the taxon list (see also under current projects).

More details will be added soon.

2. Arthropoda s. l. ((stemlineage derivatives + Arthropoda s. str. (stemlineage derivatives + Erarthropoda))

The taxonomic range of fossils preserved in an 'Orsten'-type of preservation spans now from stem arthropods – a lobopodian named Orstenotubulus ewamuellerae (uppermost Middle Cambrian; close to publication, see current projects), a tardigrade (Middle Cambrian, under construction, see also Müller et al. 1995) and pentastomids (several papers out, latest in TRSE vol. 96(4) 2006) to chelicerates – to three of the euarthropod taxa – a chelicerate larva belonging to the Pycnogonida named Cambropcnogon (see e.g. Waloszek & Dunlop 2002, slightly re-interpreted with regard to the anterior head part by Vilpoux & Waloszek 2003), Agnostus pisiformis as a representative of a larger group of tiny forms living in a "nut-shell" (e.g., Müller & Waloszek 1987; see also Walossek & Müller 1990 and Stein et al. 2005 for a possible systematic position of agnostids) and various Crustacea.

Remarkably we have not a single fragment at hand so far that we could assign to the trilobites, which are widespread and abundant in the Cambrian. And until now Malacostraca als also completely lacking, but which must have been around in the Cambrian too..

In fact, the majority of animals we described so far, belong to the stem lineage of the Crustacea (6 species so far), a taxon called Phosphatocopina (>10 species), which are bivalved forms and the most aboundant animals in the phosphatic remains (>50,000 specimens), and entomostracan eucrustaceans (6).

A seventh has been added recently from the Lower Cambrian of China, named Yicaris dianensis. All these forms are tiny and all seem to be representatives of the benthic bottom fauna, more specifically a meiofauna that lived above, at or below the sediment-water interface. Meiofauna is defined by size, and these animals below two millimetres mainly, were adapted to this dysoxic regime. Yet, all have their special neeche, and some were surely better swimmers than others, some may have lived only temporarily there, i. e. during a spcific part of the life span, and few might have lived with al stages there, such as Bredocaris admirabilis.

Equally variable as the locomotion were the different feeding strategies, and we even found clear evidence of parasitic forms: the pentastomids. More soon.

Now to the animals: For more theoretical stuff and the different species and groups described from 'Orsten' sites see:
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