Nematocrania Grant, 1976

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 : 493-494

Genus Nematocrania Grant, 1976 Remarks.—The specimens from China are characterized by

Type species: Nematocrania crassa Grant, 1976 ; upper Artinskian, distinct costellate ornament. The costellae are very strong,

Permian; Ko Muk, Thailand. rather loosely spaced with wide intertroughs, and terminate

Nematocrania pilea sp. nov. at growth lamellae as protruding spinous outgrowths. Gen−

Fig. 5D–G, K, M, P, Q. eral character of the ornamentation is reminiscent of that ob−

?1999 Acanthocrania sp. ; Baliński 1999: 441, fig. 3A. served in the early Permian Nematocrania Grant, 1976 and some Carboniferous craniids attributed to Philhedra Koken ,

Etymology: Latin pileus, kind of head cover; referring to the subconical shape of the dorsal valve. 1889. The type species of the former genus N. crassa Grant ,

Holotype: Complete dorsal valve PKUM02−0196 illustrated on Fig. 1976 was originally described from the late Artinskian (early

5M. Permian ) of southern Thailand. The specimens described

Type locality: GB site, Muhua section near village of Gedongguan, here share with it large dorsal anterior adductor scars and

Changshun County, Guizhou, China. strong external radial costellation of the dorsal valve. In both

Type horizon: Upper part of the Muhua Formation, Siphonodella crenu− forms the costellae are interrupted by growth lamellae and as lata Zone (middle Tournaisian). can be seen from some illustrations of the Thailand’s species (e.g., Grant 1976: pl. 1: 12, 27), they give rise of short

Diagnosis.—Small sized, subconical dorsal valve with strong spinous projections. N. pilea sp. nov. differs from N. crassa

radial ribbing interrupted by growth lamellae and terminat− mainly in having more loosely spaced costellae.

ing as short spinous projections. From Nematocrania crassa The specimens studied here are also

very

similar to

Phil− Grant, 1976 and Philhedra trigonalis (M’Coy, 1884) differs hedra trigonalis (M’Coy, 1884) re−described in detail from

mainly by loosely spaced costellae.

the Viséan of County Fermanagh, Northern Ireland by

Material.—Seven complete and 10 slightly damaged dorsal Brunton (1968; see also M’Coy 1844: pl. 20: 2). They differ

valves. by the total number of costellae which in the Chinese species

Description.—Shell rather small, attaining up to 4.8 mm in is lower. Costellae in N. pilea are added by intercalation diameter, with subrounded, subelliptical to slightly irregular whereas in specimens from Fermanagh both intercalation outline; sometimes with short, flattened posterior margin. and branching have been noted ( Brunton 1968: 8). In its

Ventral valve unknown; dorsal valve subconical, apex usu− costellate ornament P. trigonalis differs markedly from the ally slightly posterior to centre, rarely subcentral. type species of the genus, i.e., Philhedra baltica (Koken,

Apical region of ca. 1 mm in diameter rather smooth; rest 1889) which possesses radially arranged thick hollow spines of valve ornamented with strong radial costellae, 3–5.5 in ( Bassett 2000). In this respect, P. trigonalis seems to be

1 mm at the valve margins, separated by wide interspaces; closer to Nematocrania . Nematocrania pilea sp. nov. closely costellae added by intercalation, branching not observed; the resembles Crania rowleyi Gurley, 1883 described by Rodri−

total number of costellae at the outer margin averages from guez and Gutschick (1967: 369, pl. 41: 6–9) from the Sap−

about 27 (on small specimens) to 57 (on the largest valve); at pington Formation (earliest Mississippian) of Western Mon−

some distance from the apex they are interrupted by growth tana, USA in general character of shell ornamentation. The lamellae and terminate as protruding tubercles or short spines; specimens described here attained smaller shell dimensions usually, on the next growth lamella new costella appears in and have somewhat less closely spaced costellae.

continuation of the old one. Some costellae appear to be Nematocrania pilea sp. nov. differs from Deliella delie curved. On well preserved specimens the spinous projections Halamski, 2004 from the Late Eifelian of the Holy Cross of the costellae seem to protrude beyond the valve margins. Mountains ( Poland) in having widely spaced costellae,

Internal features of the dorsal valve poorly preserved; whereas the latter is characterized by dense parvicostellate only a pair of large anterior adductor scars can be distin− ornamentation (see Halamski 2004). A single dorsal valve reported as Acanthocrania sp. and described from nearby locality at Muhua section ( Baliński 1999) may be better assigned to Nematocrania pilea . This questionable juvenile specimen, measuring 2 mm in diameter, is poorly preserved but reveals rudiments of weak radial costellae at the valve periphery.

Stratigraphic and geographic range.—This is a rather rare species in samples GB, GT, and D4 collected near the Gedongguan and Daposhang localities. One questionable specimen come from sample Mu−42 from the section near Muhua village (see Baliński 1999).