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Explanations III::





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 Body planes:: Facial sutures:: Terminology::              


Some explanatory References III

- The next Step becoming a Trilophile -

Little Glossary of Trilobites Terminology

or simplified
Trilobites of A to Z


The Division of Arthropoda is integrated into Subdivision Eumetazoa, the associated Group of Articulate Protostomia into Animals Kingdom. The body is articulated into heterogeneous sections. They have limbs in paired, most articulated, with anterior limbs are developed as antennas or mouthparts. They have also a solid chitinous coat (cuticula), partially embedded with calcium carbonate- or phosphate.


Articulate Protostomia

Animal phylums with complete digestive tract are part of the Protostomia (plastopore). During the  process of embryogenesis, the protostoma is developing to mouth opening and the anus is rupturing secondarily. The Group of Protostomia with coelum is presented by Articulate Protostomia.


Benthic community

Basically it's a biocenosis of mixed ecobiotic species inhabiting a definite common area. Flora and fauna of the sea- flor are covered by the benthos.



Timebased reference system relative to fossils. Fossils don't occure inside a stratum in any randomized way, but there are certain fossils leading for defined periods of earth history (W. Smith, 1815 - Guiding value of fossils,key fossils).



By Biostratonomy one understands the science of organics body fate, from the beginning of death until it's final embedment.



The term Cambrian is based on the Cambrian mountains of Northern Wales (Cambria - roman name for Northern Wales). From geological view Cambrian is the earliest stratigraphic System (Period) of the Palaeozoic. It began about 542 million years before present day and continued about 54 million years. The Cambrian is diveded into the Series Upper-, Middle- and Lower Cambrian. The lower boundary of the Cambrian was set at the earliest appearance of early trilobites. During the Cambrian period, trilobites (about 60%) and brachiopods represented the major part of marine fauna.



This System is named for the extensive coal beds (Lat.- carbo- coal). It's divided into the Subdivisions Upper- and Lower Carboniferous. It extends from Devonians end 359 million years ago and ended to the beginning of the Permian System 299 million years ago.



Condition of a type of hypostome regarding it's structure and anatomical characteristics. At ventral view basically the hypostome can be attached to the anterior doublure by sutures, or unlike this condition, it can be free of the doublure. The conterminant condition discribes the attached condition. There's a wide diversity relating sizes and shapes at this type of hypostome. At dorsal view, hypostomes anterior edge is congruent to glabellas anterior edge (vitreous cephalon ;-)). Examining a trilobite with a conterminant type of hypostome mostly indicates watching a predator representative.


Chronology (relative)

Relative chronology associates biostratigraphical and lithostratigraphical units.



Chronostratigraphy globaly includes all  strata of the earth, formed within a definite period of time. From this strata, a geological time scale is created, subdivided into the chronostratical units Eonothem, Erathem, System, Series and Stage.



This Period (System) was named for the Devonshire of Englands Southwest. The Devonian is divided into Upper-, Middle- and Lower Series. It started before nearly about 410 Million years, lasting about 55 Million years. Plants, Insecta, fresh- water fishs ad first amphibians sucessfully colonized land and fresh- water habitats. By the end of Devonian Graptolites and Tentactulata extincted.



The diagenesis of fossils examines organic bodys further destiny after its embedding.



The diversity (Lat.- diversitas) generally discribes the variety. The variety of species are in this case discribed as quantity of different life forms (e.g. representatives of different families) within the marine environment, the biodiversity (Lat.- bios= life).



The division is a hierachical stage within the systematics (Classificating the organisms into groups, taxa) of biology. The division is directly upordinated the taxon kingdom, taxon class corresponding to this is subordinated.



The eumetazoa (tissue animals) envolving all kind of animals with real present cellular tissues. There are organs, muscles and nerves present.



External organ of protection- orthesis (cuticula) of arthropods.



The hypostome (Gr.- mouth) is the trilobites pre- oral located mouthpart, an ventral sided external part of the exoskeleton. There are three types of hypostomes to differentiate: the natant type, the conterminant type and finally the impendent type.



Another condition of a type of hypostome regarding it's structure and anatomical characteristics. In principle the impendent type has conterminant condition with differenced alignement to glabellas anterior edge (vitreous cephalon ;-)). That means the hypostome is attached to the anteriour dubloure, but it doesn't match (ventral sight) to the anterior glabellar border (dorsal view).



Animals without vertebral (spinal) column.



The Lithostratigraphy  evaluates the sequence of rock strata, the chonological seuence of development. The Lithostratigraphy is based on the Law of Storage (N. Steno, 1669), the oldest stratum is positioned below, so it was sedimented at earlier times than the upper layer of sediments. Therefore a timebased sequence of layers can be created.



Another condition of a type of hypostome regarding it's structure and anatomical characteristics. This kind of hypostome is free of the anterior dubloure. At ventral view there' a congruence of hypostomes and glabellas anterior border (vitreous cephalon ;-)). Compared to the conterminant type, a simple ovoid shape is a typicylally feature of the natant type, remained nearly unchanged over the complete period of trilobites evolutionary time. One assumes that this kind of hypostomes belongs to particle feeders.



The ontogenesis describes the developmental process (ontogenetic), starting with the fertilized egg, processing the larval stage until the end of the species specific complete development of the adult trilobite.



The naming of this system (period) based of the name of the celtic Welsh tribe of Ordovices of Northern Wales, Great Britain (C. Lapworth, 1879). The Ordovician is dividet into the Upper-, Middle- and Lower series. It started before nearly about 488 Million years, lasting about 45 Million years. Beside invertebrates, predominating in great diversity, the vertebrates with jawless fishes were also represented abundantly. At the end of this period, a great global mass extinction among the groups happened (probably caused by climatic changes), also the trilobites were affected.


Pelagic community

Basically  this is a biozoenosis of different ecobiotic specialized species in a defined common habitat. The pelagic habitat coveres the upper water layers down to great water depth. Pelagic animals are moving fromactive swimming up to passive adrifting.



Godparent of this last Palaeozoic period were the extensive exposures in the region around the russian town Perm at the Urals western hillsides. The Permian is divided into Upper- (Zechstein) and Lower (Rotliegendes) Permian. With the coalescence of all Earth's major landmasses (except. parts of East Asia) the supercontinent Pangea was developed. At Permian's end, the transition from Palaeozoic to Mesozoic, fauna is affected by the greatest mass extinction in earth history. The marine fauna decimated in a special amount. Additionally to trilobites more species like Foranimifera of class Rhizopoda, the representatives of predators of merostomatous the Eurypteridia a.l.m. extincted.



The naming of this system (period) is based on the rocks in the region of the 'Silurians' (Southern Wales), a celtic tribe. The Silurian, lasting from 443 until 416 Million years ago, is divided into Upper- and Lower Silurian. This period is characterized by the continent of Euramerica (Pre- Northern Europe+ Laurentian).



The stratigraphy (Lat.- Stratum = layer) describes the chronology of Earth history using studies of geological processes and events, formulating a periodic sequence of Earth history. Stratigraphy includes Lithostratigraphy, Biostratigraphy and relative Chronology.



In his publication 'Die Naturgeschichte der Versteinerung zur Erläuterung der Knorrischen Sammlung von Merkwürdigkeiten der Natur', the indication 'Trilobit' was introduced by Prof. Johann Ernst Immanuel Walch. The Class Trilobita actually including  nine Orders affirmed. This Orders again consisting of more than 150 Families including more than 15000 described Species on its part. Cause every year new Species are discovered, Class Trilobita is steadily increasing.








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