Lingulepis malongensis Rong

Zhang, Zhifei, Han, Jian, Zhang, Xingliang, Liu, Jianni & Shu, Degan, 2004, Soft-tissue preservation in the Lower Cambrian linguloid brachiopod from South China, Acta Palaeontologica Polonica 49 (2), pp. 259-266 : 261-262

Lingulepis malongensis Rong ; Rong 1974: 114, pl. 44: 27, 32. Lingulepis malongensis Rong ; Jin et al. 1993: 794, figs. 5.1, 5.6, 5.7,

8.1–8.4, 9.4. Lingulepis malongensis Rong ; Luo et al. 1994: pl. 37, figs. 11–14. Lingulepis malongensis Rong ; Chen et al. 1996: 135, figs. 165–167. Lingulellotreta malongensis ; Homer et al. 1997: figs. 4.1–4.14. Lingulellotreta malongensis Rong ; Holmer and Popov 2000: 72, figs.

1a–d.

Lophophore.—The shells of Lingulellotreta malongensis are small, pedicle valve ranging from 2.28–8.09 mm long

(see Table 1), the average length is 6.32 mm. The pseudointerarea of pedicle valve extends anteriorly to 30–40% of valve length. Inside the shell (No: ELI L−0014A), an undulant, transverse reddish brown strand correlates with the position of the anterior body wall ( Figs. 1A , 2A ). It divides the space inside the shell into two parts, the anterior portion putatively representing mantle cavity (about 80% of the volume/length), and a posterior 20% representing viscera. In the mantle cavity, the lophophore appears as imprints of a pair of ear−shaped spiral brachial arms, disposed symmetrically about the midline ( Figs. 1 , 2 ). They extend antero−laterally, then converge inward. The brachial arms are markedly hollow or tubiform, delineated by a pair of parallel curved threads in reddish brown ( Fig. 1E, D 2 ), which are probable marginal doublures of the tubular brachial axes. The brachial arms are sometimes impressed in the internal mould of the dorsal valve ( Figs. 1B–D, E, G , 2B, C ), or in some specimens are directly exposed in a lamina of sediment filling the mantle cavity ( Figs. 1A, F , 2A ). It is within such a lamina of sediment that filaments of the lophophore are three−dimensionally preserved, ( Figs. 1A , 2A ). The filaments project along the spiral brachial axes, bowing antero−laterally ( Figs. 1A, C , 2A, B ). On a single brachium, about 23–34 tentacles can be counted ( Figs. 1A, C , 2A, B ). They are arranged apparently in a single palisade, are elongate and coarse, and distinctly visible in the hitherto known four specimens (e.g., Figs. 1A, C , 2A, B , 4A ). In the other specimens ( Fig. 1B, D–F, G ) only impressions of brachial axes were seen. At the base of a pair of brachia, a circular mark occurring in some specimens ( Figs. 1A–D, G , 2A–C ), could represent the position of the mouth. In more than 40 specimens with preserved lophophore impressions, no trace of any skeletal lophophore support was evident. It is, therefore, assumed that the lophophores of these linguloids were supported alone by a hydrostatic skeleton as in Recent lingulids.

Ll [mm]

The digestive system.—The configuration of the alimentary canal of L. malongensis is completely revealed in one informative specimen ( Fig. 4A, B ). It is marked by a recurved, “mud−filled” tube, showing considerable relief ( Fig. 4A, B ). Mouth is represented by a circular mark at the base of the lophophore ( Figs. 1 , 2 , 4A ), which is followed by a short esophagus ( Fig. 4A ). This leads posteriorly into a pouchlike distended stomach ( Fig. 4A ). A transverse belt−like impression across the stomach could represent the gastroparietal band ( Fig. 4A ). Several protuberances with considerable relief at or near the posterior part of the stomach are interpreted as digestive diverticula ( Fig. 4A ). Beyond the stomach the digestive canal continues as a narrow intestine filled with muddy sediment and extending posteriorly. Then, it recurves in front of the posterior body wall, and extends forwards toward the right anterior body wall, finally terminates in an anal opening some distance postero−lateral to the mouth ( Fig. 4A, B ).

Figures

Fig. 1. The lophophore of Lingulellotreta malongensis from the Yu’anshan Member of the Qiongzhusi (Chiungchussu) Formation, Lower Cambrian, China. A. ELI L−0014A, dorsal view of ventral interior, showing lophophore, with a series of definitive filaments, three−dimensionally preserved in a lamina of sediment between valves. B. ELI L−0033, showing paired imprints of brachia and depression of distinctive visceral cavity. C. ELI L−0052A, a specimen strongly compressed, showing lophophore with filaments. D. ELI L−0056A. D1, parallel specimen with straight pedicle strongly compressed, and with paired spiral brachial imprints; D2, details of the brachial imprints of D1. E. ELI L−0073, a lateral oblique view of strongly compressed specimen, showing detail of a hollow brachial tube. F. ELI L−0101, lateral oblique view of the lophophore three−dimensionally preserved in sediment in valves. G. ELI L−0081, a parallel, possible juvenile specimen strongly compressed; note the relatively small brachia. Scale bars 2 mm. See Fig. 2 for some interpretations.

Fig. 2. Interpretative drawings of the interiors of Lingulellotreta malongensis shown in Fig. 1. A. Sketch of Fig. 1A. B. Sketch of Fig. 1C. C. Sketch of Fig. 1G. Scale bars 1 mm.

Fig. 4. Two linguloid brachiopods, Lingulellotreta malongensis and Lingulella chengjiangensis, from the Yu’anshan Member of the Qiongzhusi (Chiungchussu) Formation, Lower Cambrian, South China. A. Lingulellotreta malongensis, ELL L−0017. A1, photograph of the dorsally and right laterally compressed specimen, showing the interiors, including the digestive system and paired imprints of brachia; A2, explanatory drawing of the same. B. ELI L−0091A, a parallel specimen of Lingulellotreta malongensis, note the faint brachial contour and digestive tract with considerable relief. C. Lingulella chengjiangensis, ELI C−0029. C1, photograph (dorsal view) of dorsal interior, showing the digestive tract with an anterior anus, and with impression of visceral cavity; C2, explanatory drawing of the same. D. Lingulella chengjiangensis, ELI C−0027, anterodorsally compressed specimen, showing the position of the mouth. Scale bars 2 mm.