| Classification of the Crustoidea |
Bulman, O.M.B. 1970. Graptolithina with sections on Enteropneusta and Pterobranchia. In: C. Teichert (ed.), Treatise on Invertebrate
Paleontology, Part V, Lawrence.
Paleontology, Part V, Lawrence.
Kozlowski, R. 1962. Crustoidea - nouveau groupe de Graptolithes. - Acta PalaeontologicaPolonica 7, 3-52.
Mierzejewski, P. 1985. New aberrant sessile graptolites from glacial boulders. - Acta Palaeontologica Polonica 30, 191-199.
| Graptolite Net | Graptolites & Graptoliters | Evolution of graptolites | Rhabdopleuroidea | Cephalodiscoidea |
| Class Graptolithoidea Beklemishev, 1951 Order Crustoidea Kozlowski, 1962 Family Wimanicrustidae Bulman, 1970 Bulmanicrusta Kozlowski, 1962 Bulmanicrusta latialata Kozlowski, 1962 Bulmanicrusta modesta Kozlowski, 1962 Bulmanicrusta mediocristata Kozlowski, 1962 Ellesicrusta Kozlowski, 1962 Ellesicrusta sombrero Kozlowski, 1962 Holmicrusta Kozlowski, 1962 Holmicrusta sombrero Kozlowski, 1962 Lapworthicrusta Kozlowski, 1962 Lapworthicrusta aenigmatica Kozlowski, 1962 Ruedemannicrusta Kozlowski, 1962 Ruedemannicrusta geniculata Kozlowski, 1962 Urbanekicrusta Mierzejewski, 1985 Urbanekicrusta reversa Mierzejewski, 1985 Wimanicrusta Kozlowski, 1962 Wimanicrusta urbaneki Kozlowski, 1962 Wimanicrusta cristaelingulata Kozlowski, 1962 Family Hormograptidae Bulman, 1970 Hormograptus Ă–pik, 1930 Hormograptus sphaericola (Ă–pik) Hormograptus defensor (Ă–pik) Hormograptus ramulus (Ă–pik) |
Benthic, encrusting graptolites of the order
Crustoidea constitute a group which in some
respects most closely resembles the
Rhabdopleuroidea and at the same time
exhibits a number of features in common with
the Dendroidea. They have been reported
from the Llanvirn to the Upper Ludlow.
Their rhabdosomes comprise autothecae,
bithecae and stolothecae produced, as in
dendroid graptolites, in triads from a
sclerotized stolon similar to that in
Rhabdopleura (Rhabdopleuroidea).
Crustoidea constitute a group which in some
respects most closely resembles the
Rhabdopleuroidea and at the same time
exhibits a number of features in common with
the Dendroidea. They have been reported
from the Llanvirn to the Upper Ludlow.
Their rhabdosomes comprise autothecae,
bithecae and stolothecae produced, as in
dendroid graptolites, in triads from a
sclerotized stolon similar to that in
Rhabdopleura (Rhabdopleuroidea).
| SEM micrograph of an autotheca of Wimanicrusta urbaneki (Ordovician Geschiebe from Poland). Lateral view. |
| s |
| Abbreviations: a - apertural apparatus, s - stolon |
| Isolated autothecae of Bulmanicrusta latialata (Upper Silurian Geschiebe from Poland) From P. Mierzejewski. |
Mitchell, Ch.E., Wilson, M.A. & John, J.M.St. 1993. In situ crustoid graptolite colonies from an Upper Ordovician hardground,
Southwestern Ohio. - Journal of Paleontology 67, 1011-1016.
Southwestern Ohio. - Journal of Paleontology 67, 1011-1016.
Mierzejewski, P. 1977. The first discovery of Crustoidea (Graptolithina) and Rhabdopleurida (Pterobranchia) in the Silurian. - Bulletin
de l'Academie Polonaise des Sciences, Serie des Sciences de la Terre 25, 103-107.
de l'Academie Polonaise des Sciences, Serie des Sciences de la Terre 25, 103-107.
Palaeoecologic knowledge of crustoid graptolites is still insufficient. The main
reason for this situation is that they are extremely rare fossils and their
known record is often limited to tiny fragments of isolated autothecae. Only
in exceptional cases, one can find small fragments of colonies consisting of
uniserial or biserial chains of autothecae.
The morphology of crustoid autothecae suggests that they were attached to
the substrate by their lower, structureless surfaces and formed incrusting
colonies, resembling those of recent Rhabdopleura. One may suppose that
crustoid graptolites built colonies encrusting a firm substrate at moderate
depth in relatively cold water. Chemically isolated crustoids were usually
derived from marly limestones yielding tabulates, bryozoanns, brachiopods,
annelids, molluscs, pterobranchs and various benthic graptolites.
The presence of graptoblasts in crustoids was an adaptation allowing the
species to survive adverse conditions when the rest of colony disintegrated.
reason for this situation is that they are extremely rare fossils and their
known record is often limited to tiny fragments of isolated autothecae. Only
in exceptional cases, one can find small fragments of colonies consisting of
uniserial or biserial chains of autothecae.
The morphology of crustoid autothecae suggests that they were attached to
the substrate by their lower, structureless surfaces and formed incrusting
colonies, resembling those of recent Rhabdopleura. One may suppose that
crustoid graptolites built colonies encrusting a firm substrate at moderate
depth in relatively cold water. Chemically isolated crustoids were usually
derived from marly limestones yielding tabulates, bryozoanns, brachiopods,
annelids, molluscs, pterobranchs and various benthic graptolites.
The presence of graptoblasts in crustoids was an adaptation allowing the
species to survive adverse conditions when the rest of colony disintegrated.
| __________________________________________________________________________ GRAPTOLITE NET is edited by Piotr Mierzejewski, the Count of Calmont and Countess Maja Anna Korwin-Kossakowska since 2002 |
| PORTAL OF GRAPTOLITES AND PTEROBRANCHS SPONSORED BY Artistic Embroidery SZTANDARY FLAGS FAHNEN |
updated July 7, 2005