Producción CyT
Glossary of Hemichordata
Capítulo de Libro
Autoría:
Maletz, J. ; Bates, D.E.B. ; Brussa, E.D. ; Cooper, R.A. ; Lenz, A.C. ; Riva, J.F. ; TORO, BLANCA AZUCENA ; Zhang YuandongFecha:
2013Editorial y Lugar de Edición:
The University of KansasLibro:
Treatise Online (pp. 1-23)The University of Kansas
ISBN:
978-2-153401-00-2Resumen *
The terminology of the Hemichordata used herein differs considerably from the terminology used in the previous versions of the ?Graptolite Treatise? (Bulman, 1955, 1970), which were focused entirely on the fossil members of the Graptolithina and the few known tube-bearing extant and extinct Pterobranchia. Both classes were regarded as independent groups of the Hemichordata, but are now included as a single taxon, the Pterobranchia, with the Graptolithina and the Cephalodiscida as two subclades (Mitchell & others, 2013). A number of terms had to be changed due to a better understanding of the construction of the graptolite tubarium and the phylogenetic relationships within the Pterobranchia, the main group of fossilized hemichordates, in an attempt to homogenize the terminology of these previously separated groups. The term tubarium, for example, is reintroduced to the pterobranch terminology to describe the organic housing or domicile of all Pterobranchia, instead of using the term rhabdosome for the fossil Pterobranchia (Graptolithina in Bulman, 1955, 1970) and the coenecium for the extant members (Pterobranchia sensu Bulman, 1955, 1970). Lankester (1884) initially introduced the term tubarium to describe the housing of the extant Pterobranchia, as he considered the term coenecium or zooecium as inappropriate since they described the housing construction of bryozoans, to which the Pterobranchia were referred initially. Tubarium describes the housing construction of extant and extinct Pterobranchia more independently; it also describes it more precisely as being formed by glandular secretions and can easily be used for all members. It is therefore extended here to include the homologous glandular constructions of the domiciles of fossil graptolite taxa. Other terms such as the periderm, have been eliminated due to constructional considerations. The term periderm, introduced by Wiman (1895), suggests a dermal construction of the tubarium, which is now known to be incorrect. The tubarium is formed from glands on the head shield of the zooids and is not a dermal construction as is the coenecium of a bryozoan. The tubarium can perhaps be compared with the formation of a hornet?s nest, though a hornet?s nest is largely constructed with foreign material. A comparison with hydrozoan colonies also falls short, as these are often covered by an organic exoskeleton, the perisarc (also identified as the periderm in Hyman, 1940, p. 400), which is secreted by the epidermis of the advancing stolon (e.g., Berking, 2006). Early graptolite literature is written in a number of languages, including Chinese, Czech, English, French, German, Latin, Norwegian, Spanish and Swedish. Thus, paleontological terms describing graptolite features were created in a variety of languages and terms have been suggested for graptolite terminology in a number of languages. Many terms originally proposed in other languages were translated into English before they became the standard, though a few are kept in their original form. Reference is given here to the various terms translated from other languages to indicate the historical origin and evolution of the hemichordate terminology. A number of papers were entirely dedicated to terminoloy (e.g., Törnquist, 1894, Wiman, 1893, 1896) or included chapters on terminology (e.g. Ruedemann, 1904, Jaanusson, 1960, Cooper & Fortey, 1982). However, I am not aware of any glossary for graptolite or pterobranch terminology, except for a German one (Kraatz, 1978), providing a compilation of graptolite terms in other languages than the English in the former versions of the Graptolite Treatise (Bulman, 1955, 1970). The German glossary (Kraatz, 1978) provides some translations of terms of the English terminology, but no additional original terminology useful has been proposed and the terms are in general not included here. References are provided for all morphological terms listed in this chapter, in case the terms were originally created for graptolites. The most recent revision is quoted and discussed in case of changes in use. General paleontological or biological terms not restricted to graptolites are not referenced. As modern taxa of the Enteropneusta are not included in the volume and the anatomy of the soft-bodied organisms is not discussed, many terms related to the anatomy of these are not included here, unless they are used in the text of the various chapters dealing with taxonomy. The precise terminology has considerable effect on the taxonomic and evolutionary understanding of graptolite phylogenies and evolution. A good example is the use of the term virgella, long considered to be important for graptolite taxonomy and identified as a homologous character in all later graptoloids (Cooper & Fortey, 1982: Virgellina). However, as Bulman (1963b, p. 404) stated, ?it is likely that the virgella spine has evolved more than once?, a statement that was supported by the analysis of the dorsal and ventral virgellar spines by Maletz (2010). A differentiation of types of virgellar spines, therefore, is necessary for the understanding of graptolite taxonomy and evolution and should be reflected in the terminology. General descriptive terms that have been used in the past to describe thecal form (dichograptid, glyptograptid, climacograptid) are not included herein and should not be used any more. These terms should be replaced by a more precise constructional terminology. The climacograptid thecal style, for example, is based on a geniculate theca, but many apertural features in these thecae are not considered in this terminology (e.g. genicular additions, thecal apertural features, thecal overlap, local thickenings). Climacograptid thecae in a very generalized sense have been found in Archiclimacograptus, Climacograptus, Amplexograptus, Monoclimacis, Pseudomonoclimacis and other taxa and do not indicate a precisely defined term. These features are clearly developed independently in the listed genera. Terms describing proximal development types (e.g. dichograptid, isograptid, diplograptid and monograptid development types) are not included here as they are generallizations, initially used to describe the precise development of certain genera. They are now known to consist of numerous independently changing characters and are quite variable. Proximal development types, as long as they are used in graptolite taxonomy, are described in the individual chapters dealing with taxonomy. Terms in bold type are recommended for use. Terms combining italic with nonbold type are not recommended for use. Información suministrada por el agente en SIGEVAPalabras Clave
TERMINOLOGYGRAPTOLITHINAPTEROBRANCHIAHEMICHORDATA