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is edited by
Piotr Mierzejewski, the Count of Calmont and Countess Maja A. Korwin-Kossakowska
|REVIEW OF CLAIMED GRAPTOLITE SOFT PARTS
P.R. Crowther, R.B. Rickards and A. Urbanek
|'Graptolite eggs and embryos have been claimed by Kozłowski (1949, 1971). A summary of this work can be found in Rickards (1979, pp. 398-401). The thin tube-like structures described by Bulman & Rickards (1966) may be comparable to the possible embryos illustrated by Kozłowski. More recently Rickards & Stait (1984) have described pyritized zooids in a Tremadoc species of Psigraptus from Tasmania.'
'Apart from the above claims there has been a number of reported occurences of soft parts
and zooids which have not received widespread acceptance by paleontologists. Most notable among those were the claims by Hundt: his 1965 paper illustrates his main thesis and gives reference to earlier contributions. We regard his various soft tissues as misinterpretations of peridermal structures such as nemal vanes or vesicles, or as misunderstandings of varied, badly preserved yet otherwise normal skeletal features. More sophisticated claims were made by Decker & Gould (1957) and by Decker & Hassinger (1958) who, we feel completely misinterpreted indifferently preserved, flattened graptolites of various genera. The periderm itself was carbonized and, in places, fragmented. Thus we cannot accept that supposed nematothecal and gonothecal zooids are actually preserved in the specimens illustrated; one of us (R.B.R.) has seen some of the specimens and remains unconvinced. Obut (1950) illustrated that he believed to be zooids in the thecal tubes of Monoclimacis. Two of us (R.B.R. and A.U.) had an oppurtunity, with Obut's guidance, to examine the illustrated specimens and concluded that the supposed zooids were the thickened bases of interthecal septa (normal in Monoclimacis) which had rotated to the bedding plane upon diagenetic flattening of the rhabdosome. That, combined with a bedding plane tectonic lineation and pyritospheres on the bedding surfaces adequately explains Obut's illustrations.'
'More recently X-ray studies such as those carried out by Bjerreskov (1978) and unpublished work at Cambridge (by P.R.C. and S.J. Baker) have suggested the presence of decaying soft parts within the thecal tubes at the time of formation of the pyrite internal moulds. Pyritization normally almost wholly fills the thecal cavity, usually without disrupting the periderm, but occasionally it is concentrated in a very suggestive manner as depicted by Bjerreskov (1978). However, in such material no trace of zooidal morphology or stolons has been claimed, in contrast to the work of Rickards & Strait (1984), where pyritized stolons connect three dimensional pyritized zooids within the thecal cavities, the surrounding periderm having then been diagenetically flattened around them. Thus the possible mechanism proposed by Bjerreskov (1978) has actually preserved zooids, prior to decay, in at least some cases.'
[...] 'Urbanek & Mierzejewski (1984, p. 82) noted 'loose organic material' fused with the thecal walls and filling part of the erect neck and apertural apparatus cavity of the crustoid Bulmanicrusta latialata Kozłowski. They described it as 'filaments and patches of varying electron density separated by empty spaces' and inferred a probable origin from the decomposition of 'either organic secretions or of tissues filling the thecal cavities during the life of the colony'. They briefly related their observations with the (then unpublished) 'cellular' complex of the present authors [...].'
Discoveries on graptolites by X-ray studies
Graptolite soft tissues
Collagen in pterobranch skeleton