Lapworthella fasciculata Conway Morris and Bengtson, 1990

Wrona, Ryszard, 2004, Cambrian microfossils from glacial erratics of King George Island, Antarctica, Acta Palaeontologica Polonica 49 (1), pp. 13-56 : 36-40

Lapworthella fasciculata Conway Morris and Bengtson, 1990 in Bengtson et al. 1990

Figs. 12E, 13.

Mitrosagophoran sclerite; Wrona 1989: 542, pl. 10: 3.

Lapworthella fasciculata sp. nov.; Conway Morris and Bengtson in Bengtson et al. 1990: 122, figs. 74–76.

Lapworthella fasciculata Conway Morris and Bengtson in Bengtson et al. 1990; Demidenko in Gravestock et al. 2001: 116, pl. 8: 1–3.

Material.—Four isolated sclerites from erratic boulders Me33 and 66. Figured specimens, ZPAL V. VI /103S11 and 15.

Description.—Mitral pyramidal sclerites, highly elongate and variable in shape. Anterior side (according to the hypothetical scleritome arrangement; e.g., Evans and Rowell 1990) of the sclerite has external (dorsal) sculpture, which consists of pronounced transverse ridges and longitudinal ribs forming characteristic reticular pattern (Figs. 12E and 13A). Posterior sclerite side (ventral) has flat surface covered with steplike growth ridges with longitudinal fine striae in inter−ridge areas ( Fig. 13D ). This posterior area resembles the deltoid duplicature extending onto the posterior slope of some other tommotiid sclerites (e.g., Camenella , Micrina , Kulparina ). Sclerites cross sections are subcircular adapically to triangular in the apertural part. Growth lines, which can be observed on the external and internal sclerite surfaces, reflect lamellar growth of the sclerite wall ( Fig. 13B, C ) by basal−internal accretion. Multilaminar structure of the sclerite can be often seen in the

Fig. 14. Plate−like sclerite of Shetlandia multiplicata gen. et sp. nov., holotype, ZPAL V. VI/36 S3, erratic Me 66. A. Upper (outer) view. B. Oblique lateral Ą view. C. The same sclerite in internal view. D. Upper top (anterior) view. E. Detail of plicate internal surface. F. Detail of plicate internal surface, showing broken thin wall. G. Internal surface of plate, showing growth lines of bands (arrowed). H. Proximal part of sclerite, in top view. I. Ornamentation in detail, showing band and inter−band growth lines. J. Detail of growth band with a weak epithelial pattern. K. Detail of J. L. Broken section of plate and internal surface of flat part (not plicate) of the sclerite, showing lamellar structure and growth lines (arrowed) on internal surface. M. Plicate part of plate in posterior view. N. Plicate growth band in lateral view. O. Detail of N, showing growth band and inter−band grooves. P. Detail of O, showing growth bands with epithelial pattern (similar as in fig. K). R. Detail of M, showing epithelial pattern. S. Detail of growth band with epithelial pattern. T. Detail of plate posterior margin, showing plicate bands. U. Detail of plicate surface in posterior view, showing plicae and interplicate bands .

wall transverse sections ( Fig. 13B, C ). Internal cavity is apex?

separated by septa, which are convex apically.

Remarks.—The Antarctic specimens show great similarities to the Australian type material ( Bengtson et al. 1990) and ad−

ditional material newly recovered from the same Australian localities (Gravestock et al. 2001).

Occurrence.—Allochthonous Early Cambrian (Botomian)

boulders (Me33 and 66), King George Island, Antarctica. a

Superphylum Aschelminthes

Phylum uncertain (?Nemathomorpha)

Order Palaeoscolecida Conway Morris and anterior) Robison, 1986

Remarks.—These are wormlike metazoans with a papillate epidermis, papillae arranged in transverse rows on narrow annuli.

Each annula consists of usually two tubercle rows. This annulation has superficial character and surely not reflect any internal metameric segmentation. The epidermis may form sclerotized cuticular structures—an armour of phosphatic dermal sclerites arranged in array covering the whole integument of animal. The anterior part of the body, if preserved, possesses a usually extended proboscis with rows of spines (scalids) and hooks on the posterior end of the usually coiled trunk. The ali−

mentary canal (gut) is more or less straight with a terminal anus.

These characters are diagnostic features for members of the ventral side (posterior) aschelminthes ( Hou and Bergström 1994), and in particular show their close relationship with the Priapulida (Conway Mor− Fig. 16. Hypothetical reconstruction of sclerite of Shetlandia multiplicata ris 1993, 1997; Müller and Hinz−Schallreuter 1993; Hou and sp. nov., showing the external (A) and internal (B) views. The reconstruction is more interpretative in the apical portion.

Bergström 1994; Zhang and Pratt 1996) or the Nemathomorpha

( Hou and Bergström 1994). The precise systematic position of the Palaeoscolecida is not yet resolved (Hou and Bergström Family Palaeoscolecidae Whittard, 1953

1994; Conway Morris 1997); possibly they represent a link be− Genera included.—For list of genera see Wrona and Hamdi tween nematodes and priapulids ( Hou and Bergström 1994). (2001). Hadimopanella Gedik, 1977 and Kaimenella Mars , The features in common with priapulids (armature, scalids, 1988, known from disarticulated single sclerites, as well as everted spiny proboscis), also suggest that the Palaeoscolecida Milaculum Müller, 1973 and Utahphospha Müller and Miller , can be placed within the newly established Phylum Cephalo− 1976, from complex sclerites.

rhyncha Malakhov, 1980 ( Adrianov and Malakhov 1996). The Brief characterization and remarks.—The family comprises controversy arises also from the differing preservation of com− genera known mainly as external moulds of phosphatized compressed specimens and three−dimensional phosphatized cuticle. plex cuticular structure. Secondary phosphatization might pre− Both styles of preservation provide somewhat different vent disintegration of the sclerite array as the three−dimensional diagnostic characters of the fossil worms. structure of the cuticular armour. Detailed studies by Kraft and Families assigned to this class by Kraft and Mergl (1989) Mergl (1989), van den Boogaard (1989) as well as by Hinz et al. are: Palaeoscolecidae Whittard,1953 and Plasmuscolecidae (1990) and Müller and Hinz−Schallreuter (1993) have docu− Kraft and Mergl, 1989. mented the congeneric nature of all these isolated sclerites with Ą

Palaeoscolecida . The morphology and taxonomy of palaeoscolecide worms and their isolated sclerites was reviewed by Müller and Hinz−Schallreuter (1993), Conway Morris (1997), and more recently by Wrona and Hamdi (2001).

Figures

Fig. 13. Broken sclerite of Lapworthella fasciculata Conway Morris and Bengtson, ZPAL V.VI/30S1, erratic Me33. A. Ornamentation and growth ridges on the dorsal side, anterior view. B. Broken longitudinal section showing septa. C. The same sclerite, posterior view, showing fragment of flat area resembling duplicature. D. Enlargement of posterior side surface, showing growth ribs and interrib areas with longitudinal fluting.