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Rhabdopleura compacta Hincks, 1888, Recent. SEM micrographs of complete coenecia. A. Young coenecium composed of a sicula and two zooids (ZPAL Pb.5/1). B. Adult coenecium consisting of a sicula and a dozen or so zooids (ZPAL Pb.5/2). C. Young coenecium built of a sicula and three zooids (ZPAL Pb.5/3). Abbreviations: c, creeping tube; e, erect tube; m, metasicula; mm, marginal membrane; p, prosicula; x, boundary between prosicula and metasicula.
Source publication
C. 2003. Cortical fibrils and secondary deposits in periderm of the hemichordate Rhabdopleura (Graptolithoidea). Acta Palaeontologica Polonica 48 (1): 99–111. Coenecia of extant hemichordates Rhabdopleura compacta and Rh. normani were investigated using SEM techniques. Cortical fibrils were detected in their fusellar tissue for the first time. The...
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Citations
... The earliest taxon referable to the extant genus Rhabdopleura may be Rhabdopleura hollandi rickArDs, chApmAn, & temple, 1984 from the Silurian Spirograptus turriculatus Biozone of Wales (rickArDs, chApmAn, & temple, 1984), while older rhabdopleurids can be referred to the genus Kystodendron kozłowski 1959 (see mierzejewski & kUlicki, 2001mierzejewski & kUlicki, , 2002mierzejewski & kUlicki, , 2003 Poland, andkUlicki (1969, 1971) recorded the species Rhabdopleura kozlowskii kUlicki, 1969 from the Callovian (Jurassic) of Poland. A single record of Rhabdopleura exists from the Eocene of England (thomAs & DAvies, 1949a, 1949b, 1950 10).-- ...
Subclass GRAPTOLITHINA Bronn, 1849
[Graptolithina Bronn, 1849, p. 149] [=Rhabdophora Allman, 1872, p. 380] [incl. order Rhabdopleurida Fowler, 1892, p. 297; order Rhabdopleuroidea Beklemishev, 1951, p. 414; order Graptovermida Kozłowski, 1949, p. 204, herein]
Pterobranchs with a colonial habit, building a tubarium from individual fusellar rings and half rings or, in some instances, featureless membranes; rigid stolon system (black stolon) connects the individual, clonally produced zooids attached to stolon by highly flexible and extendable zooidal stalk. Cambrian (Terreneuvian, Fortunian)–Holocene (extant): worldwide.
... Extant pterobranchs are benthic and classified into two major orders: the Cephalodiscida and the Rhabdopleurida. A close relationship between rhabdopleurid pterobranchs and graptolites was suggested by some previous studies (Urbanek, 1986(Urbanek, , 1994Urbanek and Dilly, 2000;Mierzejewski and Kulicki, 2003) and confirmed by a cladistic investigation (Mitchell et al., 2013), which indicated that the extinct Graptolithina should be included in the Pterobranchia. On the basis of scanning electron microscope back-scatter electron (SEM-BSE) analyses (Maletz et al., 2005), some fossils previously presumed to represent Cambrian algae have been reinterpreted as pterobranchs (Maletz et al., 2005;Maletz, 2014;LoDuca et al., 2015aLoDuca et al., , 2015bMaletz and Steiner, 2015), greatly improving our knowledge of the early fossil record of the Pterobranchia. ...
Malongitubus kuangshanensis Hu, 2005 from the early Cambrian Chengjiang Lagerstätte of China is redescribed as a pterobranch and provides the best evidence to demonstrate that hemichordates were present as early as Cambrian Stage 3. Interpretation of this taxon as a hemichordate is based on the morphology of the branched colony and the presence of resistant inner threads consistent with the remains of an internal stolon system. The presence of fusellar rings in the colonial tubes cannot be unambiguously proven for Malongitubus , probably due to early decay and later diagenetic replacement of the thin organic material of the tubarium, although weak annulations are still discernible in parts of the tubes. The description of M. kuangshanensis is revised according to new observations of previously reported specimens and recently collected additional new material. Malongitubus appears similar in most features to Dalyia racemata Walcott, 1919 from the Cambrian Stage 5 Burgess Shale, but can be distinguished by the existence of disc-like thickenings at the bases of tubarium branching points in the latter species. Both species occur in rare mass-occurrence layers with preserved fragmentary individuals of different decay stages, with stolon remains preserved as the most durable structures. Benthic pterobranchs may have occurred in some early Cambrian shallow marine communities in dense accumulations and provided firm substrates and shelter for other benthic metazoans as secondary tierers.
... There is no information on mucus production in modern pterobranchs. Interestingly, non-fusellar tissue occurs in some rhabdopleurids (e.g., kuLicki, 1971;Mierzejewski, 1986;Mierzejewski & kuLicki, 2003) and may be indicative of early development of tubarium secretion. ...
The Pterobranchia can be differentiated into two main groups: the pseudocolonial Cephalodiscida and the entirely colonial Graptolithina. The Cephalodiscida include organisms with separate individuals, but clonal, asexually produced zooids are connected to their mother individuals when immature. After reaching maturity, they may separate from their mother zooid and lead an independent life in their communal housing constructions. There is no apparent difference between sexually and clonally produced mature zooids in the Cephalodiscida.
... The position of Spartobranchus tenuis is based on a taphonomic study of extant and fossil enteropneusts [11]. Character states: 1) pharyngeal gill bars, suspension feeding; 2) notochord; 3) tubicolous; 4) miniaturization, coloniality; 5) fuselli; 6) loss of tubicolous lifestyle, deposit feeding; 7) indirect development via tornaria larva; 8) stereom, water vascular system Mastigograptus [29], as well as the comparable periderm of rhabdopleurid [30] and cephalodiscid pterobranchs [31]. An important inference is that Oesia (and Spartobranchus) possessed secretory glandular cells, presumably homologous with those located on the cephalic shield of the pterobranchs. ...
Background:
The combination of a meager fossil record of vermiform enteropneusts and their disparity with the tubicolous pterobranchs renders early hemichordate evolution conjectural. The middle Cambrian Oesia disjuncta from the Burgess Shale has been compared to annelids, tunicates and chaetognaths, but on the basis of abundant new material is now identified as a primitive hemichordate.
Results:
Notable features include a facultative tubicolous habit, a posterior grasping structure and an extensive pharynx. These characters, along with the spirally arranged openings in the associated organic tube (previously assigned to the green alga Margaretia), confirm Oesia as a tiered suspension feeder.
Conclusions:
Increasing predation pressure was probably one of the main causes of a transition to the infauna. In crown group enteropneusts this was accompanied by a loss of the tube and reduction in gill bars, with a corresponding shift to deposit feeding. The posterior grasping structure may represent an ancestral precursor to the pterobranch stolon, so facilitating their colonial lifestyle. The focus on suspension feeding as a primary mode of life amongst the basal hemichordates adds further evidence to the hypothesis that suspension feeding is the ancestral state for the major clade Deuterostomia.
... Each C-shaped unit is inclined to the branch axis, and the free tips follow the thin tubular structure located on the internal side of the adaxial wall. It is tempting to homologize the serial units with fuselli, as their way of merging on one side is similar in size and morphology to the zigzag suture in the creeping parts of the theca of the pterobranch Rhabdopleura (e.g., Mierzejewski & Kulicki 2001, 2003, and the tubular structure inside the tube with the stolon (e.g., Urbanek & Dilly 2000). The difference in preservation between the Tianjialing organism and associated graptolites may be due to the predominance in the graptolites of fusellar tissue, which forms a spongy meshwork instead of cortical, densely ordered fibrils (Mierzejewski & Kulicki 2001; but both kinds of tissues are present in the rhabdopleurids according to Mierzejewski & Kulicki 2003). ...
... It is tempting to homologize the serial units with fuselli, as their way of merging on one side is similar in size and morphology to the zigzag suture in the creeping parts of the theca of the pterobranch Rhabdopleura (e.g., Mierzejewski & Kulicki 2001, 2003, and the tubular structure inside the tube with the stolon (e.g., Urbanek & Dilly 2000). The difference in preservation between the Tianjialing organism and associated graptolites may be due to the predominance in the graptolites of fusellar tissue, which forms a spongy meshwork instead of cortical, densely ordered fibrils (Mierzejewski & Kulicki 2001; but both kinds of tissues are present in the rhabdopleurids according to Mierzejewski & Kulicki 2003). Also, the hemispherical base of the tube and its emergence from the black stolon closely resemble the stolon system of extant Rhabdopleura. ...
An enigmatic clonal organism from the earliest Floian (Arenig) Fenxiang Formation at Tianjialing in Hubei Province, China and here named Crinisdendrum sinicum gen. et sp. nov., shows a puzzling combination of anatomical characters. Lateral colony branches that originate from tubular stolons are built of C-shaped serial oblique units resembling fuselli and merging along a zig-zagged suture, a set of features generally believed to be unique to pterobranch hemichordates. At least most branches taper near their tips and are closed in a manner resembling the termination of thecae previously reported in the extant pterobranch Rhabdopleura normani. The main drawback of the pterobranch model is that previous observations of terminating thecae in R. normani have neither been confirmed by more recent zoological studies nor explained in functional and developmental terms. Pyritized Crinisdendrum specimens preserved in shale were scanned using X-ray microtomography, enabling restoration of early stages of colony development (astogeny). Pyritic internal moulds of probable thecae, showing their interiors in negative relief, and phosphatized walls of thecae overgrown by black corals were recovered chemically from samples of calcareous intercalations in the Fenxiang Formation. Both sets of specimens exhibit a thread-like cylindrical structure resembling a stolon inside the theca and located below the zigzagged suture. A similar organization of branches also characterizes the feathery colonies of Webbyites from the Early Ordovician Klabava Formation of Bohemia, although these colonies are known in less detail. A new family, Crinisdendridae is proposed to encompass these two genera. Further testing of the hypothesis of a pterobranch affinity for these 470-million-year-old organisms will require a better understanding of the anatomy and growth of extant clonal hemichordates.
... There is no information on mucus production in modern pterobranchs. Interestingly, non-fusellar tissue occurs in some rhabdopleurids (e.g., kuLicki, 1971;Mierzejewski, 1986;Mierzejewski & kuLicki, 2003) and may be indicative of early development of tubarium secretion. ...
... The construction of the collagenous tubarium and asexually budded colonial zooids are synapomorphies of the Pterobranchia (Cameron 2005) and these features are shared with the graptolites, along with many details of the composition and fusellar mode of construction of the tubarium (Andres 1977;Dilly 1993;Mierzejewski & Kulicki 2003). Despite these similarities, Bulman (1970) regarded the Pterobranchia and Graptolithina as distinct classes. ...
... They also omitted taxa, especially Epigraptus, about which a wealth of structural detail is known (Kozłowski 1971). In addition, their study did not incorporate information from a number of recent ultrastructural studies of pterobranchs and benthic graptolites (e.g. Bates & Urbanek 2002;Mierzejewski & Kulicki 2003;Maletz et al. 2005). Rickards & Durman (2006) three classes in the subphylum Pterobranchia: Rhabdopleurina, Cephalodiscina and Graptolithina. ...
... Bulman 1937; Bulman & Rickards 1966;Kozłowski 1949;Urbanek & Towe 1974;Wiman 1901Koremagraptus Bulman 1927, 1947Anisograptus Cooper et al. 1998Maletz 1992;authors' unpublished observations Rhabdinopora Bulman 1949;Legrand 1974Dictyonema Bulman 1933Kozłowski 1949;Urbanek & Mierzejewski 1984;Urbanek & Towe 1974Dendrograptus Kozłowski 1949Urbanek & Mierzejewski 1986Mastigograptus Andres 1977, 1980Bates & Urbanek 2002;Bates et al. 2009;Urbanek & Mierzejewski 1984;Urbanek & Towe 1974Reticulograptus Whittington & Rickards 1968Kozlowskitubus Kozłowski 1963Mierzejewski 1978Dendrotubus Kozłowski 1949, 1963Bulmanicrusta Kozłowski 1962Urbanek & Mierzejewski 1984;Mierzejewski et al. 2005Bithecocamara Kozłowski 1949Cysticamara Kozłowski 1949Epigraptus Eisenack 1941Kozłowski 1949Kozłowski , 1971Urbanek & Mierzejewski 1982Rhabdopleura Dilly 1985a,b, Dilly 1986Mierzejewski & Kulicki 2003;Stebbing 1970;Urbanek & Dilly 2000Cephalodiscus Andersson 1907Dilly 1993;Gilchrist 1915Gilchrist , 1917Harmer 1905;John 1931John , 1932Schiaparelli et al. 2004;Urbanek 1976;Urbanek & Mierzejewski 1984;authors' unpublished observations are inapplicable in that instance. We describe the effects of these alternate codings in the results section below. 1 -Helical line. ...
A phylogenetic analysis of morphological data from modern pterobranch hemichordates
(Cephalodiscus, Rhabdopleura) and representatives of each of the major graptolite orders
reveals that Rhabdopleura nests among the benthic, encrusting graptolite taxa as it shares
all of the synapomorphies that unite the graptolites. Therefore, rhabdopleurids can be
regarded as extant members of the Subclass Graptolithina (Class Pterobranchia). Combined
with the results of previous molecular phylogenetic studies of extant deuterostomes,
these results also suggest that the Graptolithina is a sister taxon to the Subclass
Cephalodiscida. The Graptolithina, as an important component of Early–Middle Palaeozoic
biotas, provide data critical to our understanding of early deuterostome phylogeny.
This result allows one to infer the zooid morphology, mechanics of colony growth and
palaeobiology of fossil graptolites in direct relation to the living members of the clade.
The Subdivision Graptoloida (nom. transl.), which are all planktic graptolites, is well supported in this analysis. In addition, we recognize the clade Eugraptolithina (nov.). This
clade comprises the Graptoloida and all of the other common and well-known graptolites
of the distinctive Palaeozoic fauna. Most of the graptolites traditionally regarded as
tuboids and dendroids appear to be paraphyletic groups within the Eugraptolithina;
however, Epigraptus is probably not a member of this clade. The Eugraptolithina appear
to be derived from an encrusting, Rhabdopleura-like species, but the available information
is insufficient to resolve the phylogeny of basal graptolites. The phylogenetic
position of Mastigograptus and the status of the Dithecoidea and Mastigograptida
also remain unresolved.
Biodiversity, Cambrian, Hemichordata, Deuterostomia, Ordovician.
... The construction of the collagenous tubarium and asexually budded colonial zooids are synapomorphies of the Pterobranchia (Cameron 2005) and these features are shared with the graptolites, along with many details of the composition and fusellar mode of construction of the tubarium (Andres 1977;Dilly 1993;Mierzejewski & Kulicki 2003). Despite these similarities, Bulman (1970) regarded the Pterobranchia and Graptolithina as distinct classes. ...
... They also omitted taxa, especially Epigraptus, about which a wealth of structural detail is known (Kozłowski 1971). In addition, their study did not incorporate information from a number of recent ultrastructural studies of pterobranchs and benthic graptolites (e.g. Bates & Urbanek 2002;Mierzejewski & Kulicki 2003;Maletz et al. 2005). Rickards & Durman (2006) treated both Cephalodiscus and Rhabdopleura as outgroups and their classification recognized three classes in the subphylum Pterobranchia: Rhabdopleurina, Cephalodiscina and Graptolithina. ...
... Bulman 1937; Bulman & Rickards 1966;Kozłowski 1949;Urbanek & Towe 1974;Wiman 1901Koremagraptus Bulman 1927, 1947Anisograptus Cooper et al. 1998Maletz 1992;authors' unpublished observations Rhabdinopora Bulman 1949;Legrand 1974Dictyonema Bulman 1933Kozłowski 1949;Urbanek & Mierzejewski 1984;Urbanek & Towe 1974Dendrograptus Kozłowski 1949Urbanek & Mierzejewski 1986Mastigograptus Andres 1977, 1980Bates & Urbanek 2002;Bates et al. 2009;Urbanek & Mierzejewski 1984;Urbanek & Towe 1974Reticulograptus Whittington & Rickards 1968Kozlowskitubus Kozłowski 1963Mierzejewski 1978Dendrotubus Kozłowski 1949, 1963Bulmanicrusta Kozłowski 1962Urbanek & Mierzejewski 1984;Mierzejewski et al. 2005Bithecocamara Kozłowski 1949Cysticamara Kozłowski 1949Epigraptus Eisenack 1941Kozłowski 1949Kozłowski , 1971Urbanek & Mierzejewski 1982Rhabdopleura Dilly 1985a,b, Dilly 1986Mierzejewski & Kulicki 2003;Stebbing 1970;Urbanek & Dilly 2000Cephalodiscus Andersson 1907Dilly 1993;Gilchrist 1915Gilchrist , 1917Harmer 1905;John 1931John , 1932Schiaparelli et al. 2004;Urbanek 1976;Urbanek & Mierzejewski 1984;authors' unpublished observations are inapplicable in that instance. We describe the effects of these alternate codings in the results section below. 1 -Helical line. ...
A phylogenetic analysis of morphological data from modern pterobranch hemichordates (Cephalodiscus, Rhabdopleura) and representatives of each of the major graptolite orders reveals that Rhabdopleura nests among the benthic, encrusting graptolite taxa as it shares all of the synapomorphies that unite the graptolites. Therefore, rhabdopleurids can be regarded as extant members of the Subclass Graptolithina (Class Pterobranchia). Combined with the results of previous molecular phylogenetic studies of extant deuterosto-mes, these results also suggest that the Graptolithina is a sister taxon to the Subclass Cephalodiscida. The Graptolithina, as an important component of Early-Middle Palaeo-zoic biotas, provide data critical to our understanding of early deuterostome phylogeny. This result allows one to infer the zooid morphology, mechanics of colony growth and palaeobiology of fossil graptolites in direct relation to the living members of the clade. The Subdivision Graptoloida (nom. transl.), which are all planktic graptolites, is well supported in this analysis. In addition, we recognize the clade Eugraptolithina (nov.). This clade comprises the Graptoloida and all of the other common and well-known grapto-lites of the distinctive Palaeozoic fauna. Most of the graptolites traditionally regarded as tuboids and dendroids appear to be paraphyletic groups within the Eugraptolithina; however, Epigraptus is probably not a member of this clade. The Eugraptolithina appear to be derived from an encrusting, Rhabdopleura-like species, but the available information is insufficient to resolve the phylogeny of basal graptolites. The phylogenetic position of Mastigograptus and the status of the Dithecoidea and Mastigograptida also remain unresolved. h Biodiversity,
... Fuselli enclose a fabric typically composed of fusellar fibrils that are characteristically wavy, branching and anastomosing, forming a spongy three-dimensional meshwork (Urbanek and Towe 1974). Fusellar fibril diameters vary between 60 and 110 nm (Mierzejewski and Kulicki 2003) (Table 1). The cortex is composed of sheets that are separated by an electron-lucent material that typically contains cortical fibrils that are straight, thick (100 nm -1 µm) and arranged in parallel (referred to as a eucortex) (Table 1). ...
... An alternative hypothesis would be that the typical graptolite-like pattern is the result of taphonomic changes. However, this also seems unlikely because the same fibril pattern was found in living Rhabdopleura (Mierzejewski and Kulicki 2003). The most probable explanation is that the fibril characterizations of both Dilly and Mierzejewski and Kulicki were cor-rect, but incomplete because they did not employ both SEM and TEM. ...
The ultrastructure of the coenecia of Cephalodiscus (Cephalodiscus) hodgsoni Ridewood, 1907, Cephalodiscus (Idiothecia) nigrescens Lankester, 1905, and Cephalodiscus (Orthoecus) densus Andersson, 1907 was characterized using light microscopy, transmission electron microscopy, and scanning electron microscopy. The coenecium of Cephalodiscus is composed of layers of coenecial material of variable thickness laid down one upon the next and separated by sheets. Thick fusellar-like layers (up to 160 μm thick) and thin cortical-like layers (down to 15 nm thick) are present, but do not form two distinct components. Instead, a continuum exists in the thickness and shape of these layers. At the ultrastructural level, both fusellar-like and cortical-like layers are composed of thin (16–23 nm) long and straight fibrils, similar to the fibrils described in extant Rhabdopleura Allman, 1869. In C. densus, fibrils in the outer secondary deposits show a parallel arrangement, similar to the arrangement of fibrils in the graptolite eucortex. Although similarities in the shape and arrangement of growth increments between Cephalodiscus, Rhabdopleura, and graptolites probably reflect homologous zooidal behaviors and secretion mechanisms, differences at the ultrastructural level show that fibril types and fibril arrangement can evolve independently from larger scale features of the coenecium.
... Debajo y en primer término, se representa el domo de un oozooide, de cuyo lateral surge el tubo inicial del primer blastozooide de una nueva colonia. ción zoológica dentro de los graptolitoideos (Urbanek, 1986(Urbanek, , 1994Mierzejewski & Kulicki, 2003;Maletz et al., 2005;Rickards & Durman, 2006). Tanto la mayoría de los pterobranquios actuales como los graptolitos secretan un exoesqueleto colonial o tubario de naturaleza orgánica, llamado cenecio en el primer grupo y rabdosoma en el segundo. ...
