Treatise Online no. 114: Part V, Second Revision, Chapter 26: Family Retiolitidae: Introduction, morphology, and systematic descriptions (original) (raw)
Related papers
Silurian retiolitid graptolites: Morphology and evolution
2005. Silurian retiolitid graptolites: Morphology and evolution. Acta Palaeontologica Polonica 50 (4): 705–720. Developmental mode and proximal structures are commonly accepted as the best for the recognition of high−level taxo− nomic categories within the Graptoloidea. The petalolithids and retiolitids are unique in possessing a virgellar ancora and in the latter, distal ancora development. The ancora structures are considered homologous, and the ancorate petalolithids are considered to be the direct ancestors to the retiolitids. The Retiolitidae are unique among the diplograptoids in pos− sessing (1) outer, lateral, ancora sleeve walls (derived from distal extension of the ancora), and (2) a skeletal framework of bandaged lists between which are a succession of very thin and rarely preserved fusellar layers. Retiolitids possess differ− ent kinds of thecal profiles and two types of micro−ornamentation on the lists, and these have served to distinguish be− tween the subfamilies Reti...
A new Silurian graptolite, Reticuloplectograptus, and its bearing on retiolitid evolution
Palaeontology, 2010
The retiolitid graptolite Reticuloplectograptus serpaglii gen. et sp. nov. from the Gorstian, lower Ludlow, has been found in two localities: the Bartoszyce borehole of Poland (Baltica), and the Bykoš section, Barrandian, Czech Republic (PeriGondwanan Europe). The Polish material is isolated and was studied under the SEM. The main characters of Reticuloplectograptus are similar to those of Plectograptus: an asymmetrical ancora, simple ancora umbrella with an incompletely developed rim and parallel ventral walls with mid-ventral lists. The paired genicular processes of the new species are similar to but much wider than those of Plectograptus trijunctus and Plectograptus robustus. The main differences between the new genus and Plectograptus are the dense ancora sleeve wall and small proximal lateral orifices of the former. These primitive characters suggest that Reticuloplectograptus might be ancestral to genera with strong reduction in the proximal end, such as Plectograptus, Valentinagraptus and Kirkigraptus. However, Reticuloplectograptus appeared stratigraphically later than Plectograptus, indicating that this aspect of retiolitid evolution is more complicated, needing further study.
Comptes Rendus Palevol
The long ranging Silurian retiolitines belonging to the Paraplectograptus lineage (Spirograptus turriculatus to Cyrtograptus/lundgreni Biozone), represented by the genera Paraplectograptus Bouček & Münch, 1952 and Pseudoplectograptus Obut & Zaslavskaya, 1983 are described in detail based on well preserved, three-dimensional material from the Canadian Arctic and Poland. For the first time, reconstructions of their structure are attempted, and comparisons are made with the related genera, Stomatograptus Tullberg, 1883 and Retiolites Barrande, 1850. Ultrastructural details vary somewhat between the genera: the bandaging on the Paraplectograptus lineage and Pseudoplectograptus has a characteristic pustulose ornament, while that of Retiolites and Stomatograptus shows a surface of longitudinal striations. Prosicular preservation is generally incomplete, represented merely by the prosicular apex and prosicular rim. The thecal part of the Paraplectograptus and Pseudoplectograptus tubaria (r...
Treatise Online, 2018
Multiramous to two-stiped graptoloids with biradiate isograptid proximal development and maeandrograptid proximal symmetr y; colony shape scandent to reclined, horizontal, and pendent; prosicula small, with widening and much larger metasicula; thecae simple, widening tubes with or without rutellum; a sicular bitheca may be present in early taxa; branching dichotomous or cladial. Lower Ordovician (upper Tremadocian, Hunnegraptus copiosus Biozone)-Middle Ordovician (upper Darriwilian, Pterograptus elegans Biozone): worldwide.
Kirkigraptus, a New Retiolitid Graptolite from Poland
Acta Palaeontologica Polonica, 2008
The new retiolitid graptolite Kirkigraptus inexpectans gen. et sp. nov., from the Neodiversograptus nilssoni Biozone of the Bartoszyce borehole, Poland is described. It is unique among the retiolitids not having a preserved virgella or ancora. Instead the most proximal structures are two round proxi−lateral lists, joining the two genicular lists of the first thecae, connecting the two sides of the rhabdosome. The lists are interpreted as a possible homologue of the distal edge of the ancora umbrella in typical retiolitids. The size of rhabdosome with large proximal lateral orifices, and the ventral panels of thecae with mid−ventral lists, are similar to those of Plectograptus, whereas the two ancora sleeve panels consisting of spaced horizontal lists only, resemble those of Valentinagraptus. It is possible that the new retiolitid may represent a new pattern of development of the proximal end of the rhabdosome, different from that in all other retiolitids.