A. Kozlowska-Dawidziuk, A.C. Lenz & D.E.B. Bates
Proceedings of the 7th International Graptolite Conference, Ed. by G.Ortega & G.F.Acenolaza 2003, 49-53
"The development mode and proximal structures are commonly accepted as the best for classification of
higher taxa within Graptoloidea. The retiolitids and petalolithids are unique in possesing a virgellar ancora
and /or distal ancora development. The ancora structures are considered homologous, and they are
regarded as synapomorphic features on which the new superfamily Retiolitoidea has been founded. The
ancora structures are considered homologous, and they are here regarded as synapomorphic features on
which the new superfamily Retiolitoidea has been founded. The ancora is defined by Bulman (1970) as
"anchor-shaped initial growth stage of retiolitids, apparently formed of virgella with two distal bifurcations"
emphases are ours). Now we know that the true ancora is developed in diplograptid Pattern I forms (Melchin,
1998) and retiolitids Pattern R. The first true ancora, beginning with a bifurcation, was developed in
petalolithids representing Pattern I forms. Some evolution of the ancorae from small and simple to more
complex is observed, although there has been no detailed study of the petalolithid group focusing on the
astogenetic and historic development of ancorae. In Petalolithus and Pseudorthograptus there is sometimes
considerable distal growth beyond the ancora umbrella to the point of partial envelopment of the post-sicular
region of the rhabdosome (e.g., Koren' and Rickards, 1996; see Figure 1 A, B). The most studied ancorate
petalolithid Hercograptus Melchin, 1999 possesses an ancora umbrella connected to the thecae (Figure 1C).
The next and the most advanced stage of the ancora development occurs in the Retiolitidae in the form of an
ancora sleeve (Fig. 1 D, E). In this case the ancora sleeve is deeply integrated with thecal skeleton, which in
addition, is built mostly by lists similar to those of the ancora. These two features: ancora sleeve and thecal
wall and thecal framework are critical and unique for the retiolitids. The ancora sleeve may form walls, outside
the thecal skeleton, making an additional internal environment. The retiolitid ancora sleeve wall may possess
orifices and some additional structures as large stomas or long spines on the obverse and reverse sides of
rhabdosomes (Bates and Kirk, 1997; Kozlowska-Dawidziuk, 2001; Lenz and Kozlowska-Dawidziuk, 2001)."
Suborder Virgellina Fortey and Cooper, 1986
Superfamily Retiolitoidea Kozlowska, Lenz & Bates, 2003
Family Petalolithidae Bulman, 1955
Family Retiolitidae Lapworth, 1873
Subfamily Pseudoretiolitinae Kozlowska-Dawidziuk, Lenz & Bates, 2003
Subfamily Rotaretiolitinae Kozlowska-Dawidziuk, Lenz & Bates, 2003
Subfamily Retiolitinae Lapworth, 1973
Subfamily Paraplectograptinae Kozlowska-Dawidziuk, Lenz & Bates, 2003
Subfamily Sokolovograptinae Kozlowska-Dawidziuk, Lenz & Bates, 2003
Subfamily Gothograptinae Obut & Zaslavskaya, 1983
Subfamily Cometograptinae Kozlowska-Dawidziuk, Lenz & Bates, 2003
Subfamily Neogothograptinae Kozlowska-Dawidziuk, Lenz & Bates, 2003
Subfamily Spinograptinae Kozlowska-Dawidziuk, Lenz & Bates, 2003
Subfamily Plectograptinae Boucek & Munch, 1952
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