Graptolite Net | Graptolites & Graptoliters | Rhabdopleuroidea | Cephalodiscoidea | Crustoidea | Camaroidea | Tuboidea | Dendroidea | Graptoloidea
Crustoidea rea regarded as encrusting graptolites, morphologically intermediate between the extant pterobranch
Rhabdopleura and extinct Dendroidea. Recently, crustoid stolons have been etched from upper Tremadoc chert
nodules in Wysoczki (Poland) by Mierzejewski et al. (in press). This finding is very significant for graptolite
research because it sheds a new light on the budding patterns in graptolites and their evolution, extends the
lower stratigraphic range of Crustoidea from the Llandeilo to the upper Tremadoc, and clears up the puzzle of the
presence of graptoblasts in the upper Tremadoc. According to Kozłowski (1949, 1962), there are two main
lineages in the graptolite evolution leading from a common ancestors, namely: (1) Crustoidea > Dendroidea >
Graptoloidea and (2) Tuboidea > Camaroidea; lineage (1) is characterized by regular triad budding resulting in
alternating triads of autotheca, bitheca and stolotheca, whereas lineage (2) exhibits diad budding with no regular
succesion and variably distributed nodes. Kozłowski left open the question of what of mode budding and thecal
succesion has been adopted by the common ancestor of graptolites. Our observations make distinct
disturbances in Kozłowski's schemes of stolon system budding because the crustoid system is more complicated
and somewhat sophisticated than that in Dendroidea. The crustoid trifurcation in the material from Wysoczki is
only apparent in character and composed of two bifurcations following in rapid succesion: the first diad of "triad"
forms due to bifurcation of the parental stolothecal stolon into the very long descendant stolon and extremely
short prezooidal stolon, whereas the second diad bifurcates into the autothecal and bithecal stolons. Identical
structures were illustrated but not discussed by Kozłowski. At the present state of knowledge, it seems possible
that the regular triad succesion of thecae in Crustoidea and Dendroidea are different and highly specialized
modes of budding.
Rhabdopleura and extinct Dendroidea. Recently, crustoid stolons have been etched from upper Tremadoc chert
nodules in Wysoczki (Poland) by Mierzejewski et al. (in press). This finding is very significant for graptolite
research because it sheds a new light on the budding patterns in graptolites and their evolution, extends the
lower stratigraphic range of Crustoidea from the Llandeilo to the upper Tremadoc, and clears up the puzzle of the
presence of graptoblasts in the upper Tremadoc. According to Kozłowski (1949, 1962), there are two main
lineages in the graptolite evolution leading from a common ancestors, namely: (1) Crustoidea > Dendroidea >
Graptoloidea and (2) Tuboidea > Camaroidea; lineage (1) is characterized by regular triad budding resulting in
alternating triads of autotheca, bitheca and stolotheca, whereas lineage (2) exhibits diad budding with no regular
succesion and variably distributed nodes. Kozłowski left open the question of what of mode budding and thecal
succesion has been adopted by the common ancestor of graptolites. Our observations make distinct
disturbances in Kozłowski's schemes of stolon system budding because the crustoid system is more complicated
and somewhat sophisticated than that in Dendroidea. The crustoid trifurcation in the material from Wysoczki is
only apparent in character and composed of two bifurcations following in rapid succesion: the first diad of "triad"
forms due to bifurcation of the parental stolothecal stolon into the very long descendant stolon and extremely
short prezooidal stolon, whereas the second diad bifurcates into the autothecal and bithecal stolons. Identical
structures were illustrated but not discussed by Kozłowski. At the present state of knowledge, it seems possible
that the regular triad succesion of thecae in Crustoidea and Dendroidea are different and highly specialized
modes of budding.
| GRAPTOLITE NET is edited and periodically updated by Piotr Mierzejewski, Count of Calmont and Countess Maja Korwin-Kossakowska since 2002 |
| DISCOVERY OF THE OLDEST REMAINS OF CRUSTOID GRAPTOLITES AND ITS PHYLOGENETIC SIGNIFICANCE PIOTR MIERZEJEWSKI, ADAM URBANEK and CYPRIAN KULICKI North American Paleontology Convention 2005, Abstracts, pp. 48-49 |
