Muhuarina haeretica Baliński and Sun, 2005

Sun, Yuanlin & Baliński, Andrzej, 2008, Silicified Mississippian brachiopods from Muhua, southern China: Lingulids, craniids, strophomenids, productids, orthotetids, and orthids, Acta Palaeontologica Polonica 53 (3), pp. 485-524 : 510-512

Muhuarina haeretica Baliński and Sun, 2005

Fig. 18 .

1999 Productoid gen. et sp. indet. 2; Baliński 1999: 442; fig. 4P, S.

2005 Muhuarina haeretica gen. et sp. nov.; Baliński and Sun 2005: 450–453, text−figs. 1A, B, 2, 3.

2008 Muhuarina haeretica Baliński and Sun, 2005 ; Baliński and Sun 2008: 106–107, fig. 1.

Material.—Seven almost complete and one fragmentary shell, nine ventral and nine dorsal valves.

Remarks.—This micromorphic aulostegoid productid was recently described in details ( Baliński and Sun 2005, 2008). As it was suggested by the authors Muhuarina haeretica seems to be the oldest and most primitive representative of a highly specialized Permian family Cooperinidae . The Permian members of the family are characterized by an evolutionary trend to complicate a structure of the lophophore support and in consequence, as it can be deduced, to modify the lophophore itself. The subperipheral ridge of the middle Tournaisian Muhuarina may indicate the possession of a simple trocholophe type of the lophophore ( Baliński and Sun 2005). The Late Permian Falafer Grant, 1972 and Ceocypea Grant, 1972 have highly folded subperipheral ridges or platforms suggesting a very complex multilobate lophophore, termed a falafer by Grant (1972).

The recently recovered specimens of M. haeretica show that the brachiopod used its numerous rhizoid spines to cement to some hard substrate (mainly to brachiopod shells; Fig. 18C, D ; see also Baliński and Sun 2008) in the same way as the Permian Cooperina Termier, Termier, and Pajaud, 1966 from West Texas ( Cooper and Grant 1975).

Stratigraphic and geographic range.— The species has been recovered from samples Mu−42, M2/2, M2/3, M2−8, GB, GT taken from the Muhua Formation.

Productidina gen. et sp. indet.

Fig. 19 .

Remarks.—As was mentioned in the general section of this paper the most characteristic feature of the studied material is the disarticulation and fragmentation of skeletal material, especially when larger specimens are involved. As a result, there are several dozens of fragments of large valves of productoids, echinoconchoids, and linoproductoids in the collection which are not possible to determine taxonomically with confidence. A few of them are presented herein ( Fig. 19 ) in order to illustrate more adequately the high taxonomic variability of the fauna from Muhua. The following forms could be represented:

– Semicostellini gen. et sp. indet. ( Fig. 19A–F ). There are several fragments of dorsal and ventral valves in the collection coming from sample M2−8. Spines are developed only on ventral valve. Low cardinal process and distinct lateral ridges are developed in dorsal valve interior.

– Strophalosiidina gen. et sp. indet. ( Fig. 19G ). A single fragmentary ventral valve was found in sample M2−8. The valve is thin−shelled, flat, and has well marked wide interarea and convex pseudodeltidium. Rudimentary teeth are also present ( Fig. 19F 4 ).

– Productininae gen. et sp. indet. ( Fig. 19R ). Morphological features of a very fragmentary material are suggestive of Avonia Thomas, 1914 or Overtonia Thomas, 1914 .

– Orbinaria ? sp. ( Fig. 19L ). The illustrated fragment of the productellid dorsal valve is similar to Orbinaria Muir−Wood and Cooper, 1960 .

– Spinocarinifera ? sp. ( Fig. 19K, M ). These leioproductine specimens show cardinalia and shell ornamentation similar to Spinocarinifera Roberts, 1971 .

– Acanthocosta sp. ( Fig. 19H–J ). Internal structure of the dorsal valve and external shell ornamentation agree with those of Acanthocosta Roberts, 1971 .

– Echinoconchoidea gen. et sp. indet. ( Fig. 19O, P ). Several small fragments in the collection do not preserve cardinalia but show characteristic shell ornamentation.

– Auriculispininae gen. et sp. indet. ( Fig. 19N ). This rather incomplete ventral valve is very suggestive of Undaria Muir−Wood and Cooper, 1960 . Similar form was reported as monticuliferid gen. et sp. indet. by Wang et al. (2006: 545, fig. 4.10–4.11) from the Tournaisian of northern Guangxi, South China.

– Juresaniinae gen. et sp. indet. ( Fig. 19Q ). Interior of the illustrated dorsal valve reminds that of some juresaniines, e.g., Parajuresania Lazarev, 1982 . The genus, however, occurs in upper Carboniferous (Pennsylvanian), so our specimen represents most probably another form.

Figures

Fig. 18. Aulostegoid brachiopod Muhuarina haeretica Baliński and Sun, 2005 from the Muhua Formation. A. Slightly damaged ventral valve, PKUM02−0290, in interior (A1), anterior (A2), lateral (A3, posterior to the left), and enlarged interior (A4) views; notice well preserved teeth (arrowed) and interarea. B. Shell, PKUM02−0046, in dorsal view. C. Incomplete juvenile ventral valve, PKUM02−0080, (posterior to top) cemented to the chonetoid shell; notice well preserved rhizoid spines and muscle platform (after Baliński and Sun 2008: fig. 1E). D. Incompletely preserved ventral valve, PKUM02−0047, in lateral view (posterior to the left) showing rhizoid spines (after Baliński and Sun 2008: fig. 1D). Sample M2−8 (A) and GB (B–D). Scale bars 0.5 mm.

Fig. 19. Productidines from the Muhua Formation. A–F. Semicostellini gen. et sp. indet. A, B, F. Incomplete dorsal valves, PKUM02−0291 (A), PKUM02−0292 (B), and PKUM02−293 (F), in exterior (A1, B1, F1) and interior (A2, B2, F2,) views. C–E. Fragments of ventral valves, PKUM02−0294 (C), PKUM02−0295 (D), and PKUM02−0296 (E), in exterior view. G. Strophalosiidina gen. et sp. indet., incomplete ventral valve, PKUM02−0297, in exterior (G1), interior (G2), and posterior (G3) views, and SEM enlargement of G2 showing rudimentary teeth (G3). H–J. Acanthocosta sp. H, I. Incomplete dorsal valves, PKUM02−0298 (H) and PKUM02−0299 (I), in exterior (H1, I1) and interior (H2, I2) views. C. Fragment of ventral valve, PKUM02−0300, showing external ornamentation. K, M. Spinocarinifera? sp.; incomplete dorsal valves, PKUM02−0301 (K) and PKUM02−0302(M), in exterior (K1, M1), interior (K2, M2), and enlarged posterior (K3) views. L. Orbinaria? sp.; fragmented dorsal valve, PKUM02−0303, in exterior (L1), interior (L2), and enlarged interior (L3) views. N. Auriculispininae gen. et sp. indet., probably belonging to Undaria Muir−Wood and Cooper, 1960; ventral valve, PKUM02−0304, in exterior (N1), lateral (N2), and anterior (N3) views. O, P. Echinoconchoidea gen. et sp. indet.; fragments of ventral valve, PKUM02−0305 (O) and dorsal valve, PKUM02−0306 (P), showing external ornamentation. Q. Juresaniinae gen. et sp. indet., incomplete dorsal valve, PKUM02−0307, in exterior (Q1) and interior (Q2) views. R. Productininae gen. et sp. indet.; fragment of dorsal valve, PKUM02−0308, probably representing Avonia Thomas, 1914 or Overtonia Thomas, 1914. Samples M2−8 (A–J), GB−GT (K–M, O–R), and MH1 (N). Scale bars 2 mm.

Fig. 4. Different results of the silicification of brachiopod valves from the Muhua Formation. A. Subradial lamellae of silica arising along fibres of the secondary shell layer as seen on the external surface of shell. B. Net−like pattern formed by silica on the internal surface of the terebratulid valve reflecting the mosaic of the terminal faces of fibres (see text for further explanation). C. Punctate shell microstructure preserved on a silicified terebratulid valve. D. Spiriferoid ventral valve silicified with “spongy” silica; general view (D1) and enlargement (D2).