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.
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.
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).
SEM micrograph of an autotheca of Wimanicrusta
(Ordovician Geschiebe from Poland).
Lateral view.
a - apertural apparatus,
s - stolon
Isolated autothecae of Bulmanicrusta
(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.
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.
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.

is edited by
Piotr Mierzejewski, the Count of Calmont and Countess Maja Anna Korwin-Kossakowska
since 2002
updated July 7, 2005