| Nature of the graptolite order Stolonoidea by Piotr Mierzejewski |
| The order Stolonoidea has been proposed on the basis of material from the Tremadoc in the Wysoczki locality by Kozlowski (1938) without diagnosis, next defined by Bulman (1938) and described adequately by Kozlowski (1949). The stolonoid forms, fairly fragmentary and rare, are placed in a single genus Stolonodendrum Kozlowski, comprising two species, i.e. S. uniramosum Kozlowski, 1949 (type species) and S. parasiticum Kozlowski, 1949. |
| Bulman (1970, p. V53) defined the Stolonoidea as follows: "Sessile or encrusting Graptolithina composed essentially of stolothecae and ?autothecae; stolothecae containing an exaggerated development of stolons dividing at irregular intervals and quite irregular in form". |
| Kozlowski (1949) regarded the Stolonoidea as a group of primitive graptolites, which developed independently of other orders. In turn, Obut (1964) assumed that the Stolonoidea evolved from the same ancestors as dendroid graptolites of the family Dendrograptidae. Urbanek (in: Kuźnicki & Urbanek 1967) noted that there are no marked differences in the morphology of the Stolonoidea and the Rhabdopleuroidea. Similarly the Stolonoidea are characterized by the lack of apertural modifications, the presence of autho- and stolothecae, and a perforational mode of budding. According to him "Stolonoidea presumably represent an offshoot which evolved from a groups close to the Rhabdopleurida, independently of other graptolites, to form a tribe subjected to minor modifications only" (Urbanek in: Kuźnicki & Urbanek 1967, p. 433). |
| The hypothesis of affiliation of the Stolonoidea to graptolites may be very seriously questioned in the light of the present state of knowledge of fossil Rhabdopleurida. It should be noted that colonies of Rhabdopleurites primaevus and Stolonodendrum parasiticum appear strikingly similar. The fragment of Stolonodendrum parasiticum colonies found hitherto have the form of branching creeping tubes. The tubes, initially nonfusellar, gradually widen and smoothly pass into fusellar ones. Nonfusellar parts of the tubes were interpreted by Kozłowski (1949) as stolons and the fusellar - as thecae. Bulman (1955, 1970) also regarded Stolonoidea as graptolites but ne noted that such smooth transition between stolon and theca is not known in other graptolites. It is worth noting here that such transition is also unknown in the Rhabdopleuroidea. |
| I think that the known fragments of S. parasiticum colonies should be interpreted in an entirely different way then in Kozlowski (1949). I regard the supposed stolons of this species as homologues to nonfusellar stolonal tubes in Rhabdopleurites primaevus and the supposed thecae to fusellar stolonal tubes in the latter. Therefore, I do not regard Stolonodendrum parasiticum as a primitive graptolite but rather a rhabdopleurid of the family Rhabdopleuritidae. |
| The above interpretation of fragments of Stolonodendrum parasiticum colony makes it possible to assume that stolons and zooidal tubes of that species are not represented in its type series. I think that stolons have been independently described as such elements of Stolonodendrum sp. A-F by Kozłowski (1949) and erect fusellar parts served as the type material for describing the tuboid graptolite Conitubus siculoides Kozlowski, 1949. The stolons of Stolonodendrum sp. A-F do not differ from those of Rhabdopleurites primaevus. In turn, the presence of a nonfusellar part of periderm in tha basal part of "autotheca" and its transition into the creeping tube, markedly smaller in diameter, were interpreted as characteristic morphological features of Conitubus siculoides Kozłowski (see Kozlowski 1949, fig 46b and pl 15, fig. 9). Doubts concerning the graptolitic nature of Conitubus siculoides Kozlowski and some reservations in relations to the taxonomy of the genus Epigraptus Eisenack (=Idiotubus Kozlowski), put forward elsewhere (Mierzejewski 1978), show that it would be desirable to revise the Tuboidea described by Kozlowski (1949). |
| Based on: Mierzejewski, P. 1986. Ultrastructure, taxonomy, and affinities of some Ordovician and Silurian microfossils.- Palaeontologia Polonica 47, 129-220. |
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| Graptolite Net is edited by Piotr Mierzejewski, the Count of Calmont and Countesss Maja A. Korwin-Kossakowska 2002-2004 |