The Middle Cambrian Jince Formation of the Příbram-Jince Basin (Fig. 1) is globally renowned as a classical repository of well preserved and diverse skeletal fauna (e.g. Barrande, 1846, Barrande, 1852 and Šnajdr, 1958). Richly diversified associations of trilobites, agnostids, echinoderms, brachiopods, hyoliths, palynomorphs and ichnofossils associated with generally rare bivalved arthropods, molluscs and foraminifers have been studied for nearly two hundred years (summary see Fatka et al., 2004). Recently, rare specimens of poorly biomineralized and/or soft-bodied Burgess Shale-type fauna have been also described (e.g. Chlupáč and Kordule, 2002, Maletz et al., 2005, Mikuláš et al., in press and Mikuláš and Kordule, 1998).

General overviews of the stratigraphy and depositional setting of the Jince Formation are available in Havlíček (1971), Kukal (1971), Geyer et al. (2008) and Fatka and Mergl (2009). Most of the specimens of S. kozaki sp. nov. were collected in the lower part of the Jince Formation from an artificial excavation at the Rejkovice–“ve žlutých” locality (= Rejkovice “in yellow” of Fatka and Kordule, 1992), one specimen was found at the Felbabka–Ostrý vrch Hill locality. Both specimens of ?Sphenothallus kordulei sp. nov. come from the natural outcrops at the Vinice slope near the Jince locality (Figs. 1 and 2).

Phylum: CNIDARIA Hatschek, 1888

Class, Order, Family Uncertain

Genus Sphenothallus Hall, 1847

Type species: Sphenothallus angustifolius Hall, 1847.

Discussion: Phosphatic tubes of Sphenothallus have been documented only rarely from Cambrian sediments. Five occurrences have been published from the Lower Cambrian of China. Li et al. (2004) reported an occurrence of up to 3 mm long specimens of Sphenothallus sp. from the Guojiaba and Xiannudong formations in Shaanxi Province of China, which represents the earliest known record of Sphenothallus. Zhao et al. (1999) and Zhu et al. (2000) established S. taijiangensis Zhu et al., 2000 from the Upper Kaili Formation in Guizhou Province of South China. Nakagavi (2009) briefly discussed morphology and chemical composition of Sphenothallus from the Shuijingtuo Formation of the Hubei and Hunan provinces (South China). Peng et al. (2005) described S. songlinensis Peng et al., 2005 from the Niutitang Biota (Nangaoan Stage) of eastern Guizhou and reported also S. taijiangensis? from the Kaili Formation (Duyuanian Stage). Li et al. (2007) listed occurrences of Sphenothallus ranging from the Qiongzhushian to Longwangmiaoan stages of South China. Skovsted and Holmer (2006) briefly reported the presence of Sphenothallus in the Lower Cambrian Harkless Formation of Esmeraldina County in southern Nevada. An undetermined species of Sphenothallus was recently described by Van Iten et al. (2002) from the Mount Stephen trilobite beds of the lower Middle Cambrian Burgess Shale Formation near Field in British Columbia, Canada.

Remarks: The Lower Cambrian Cambrovitus Mao et al., 1992 from Guizhou Province of China, originally classified as a hyolith, is in agreement with Zhu et al. (2000, p. 236) and Li et al. (2007, p. 240), regarded as separate genus. Aceñolaza (2004) figured and briefly discussed Sphenothallus sp. from the Late Cambrian Puncoviscana Formation, La Higuera outcrops in the Province of Tucumán, NW Argentina. More recently, this specimen was determined as Selkirkia sp. by Aceñolaza and Aceñolaza (2007, p. 8).

Sphenothallus kozaki sp. nov.

Fig. 3, 1–11

Holotype: Almost complete tube L40903± partly flattened, illustrated on Fig. 3-1, 3-2 and 3-11.

Paratype: Incomplete tube L40904± preserved in relief, Fig. 3-3, 3-4 and 3-10.

Material: Nine specimens preserved as internal and external moulds in green and purple fine greywacke to shale.

Occurrence: Příbram-Jince Basin; Jince Formation; Rejkovice–“ve žlutých” locality, lower levels of the Paradoxides (E.) pussilus trilobite Zone, upper levels of the Acadolenus snajdri trilobite Zone (corresponding to the Cambrian Stage 5, equal to the Ptychagnostus gibbus Biozone) and slope of the Felbabka–Ostrý vrch Hill locality, lower levels of the Paradoxides (P.) paradoxissimus gracilis trilobite Zone (Drumian Stage)

Etymology: In honour of Vladislav Kozák, collector of Lower Palaeozoic fossils of the Barrandian area.

Diagnosis: Several centimeters long, narrow, phosphatic conical tube. Perpendicular cross-section of the shell is circular. Expansion angle 5° to 9°. Longitudinal thickenings are weak and situated on the inner shell surface.

Description: All specimens are incomplete, preserved in purple-green shale and are oriented parallel to bedding. The fragments range from 20 to 35 mm in length and are from 2.8 to 4.3 mm wide at the apertural end (Table 1). The width strongly reflects the degree of flattening. In specimens with the apertural part preserved in high relief, the apertural width is lower, while partly flattened specimens show a slightly wider aperture. The dimensions of complete cones may be envisaged to be more than 40 mm in length and 4.5 mm in maximal width. All cones have been broken at their apexes and thus no holdfast is known. Some specimens are very slightly curved in the proximal portion and straight distally; however most of specimens are straight throughout their length. Aperture is straight and smooth without any distinct structures.

A perpendicular cross-section of the shell is circular or almost circular in its outer outline as is clearly visible in the specimens L40904 (Fig. 3-3, 4, 10) and L40899 (Fig. 3-7), both preserved in a high relief. Longitudinal thickenings are visible in flattened specimens or parts of shells, the apical portions are often slightly more flattened than the apertural ends. Thus, it is inferred that the thickenings were located inside the shell and the inner outline was narrowed in one direction. Very slightly developed imprints of thickenings on the inner casts indicate that they were thin and weak. Remains of the shell wall in the specimen L40901 (Fig. 3-9, 12) illustrate a multilayered, lamellar wall structure.

Remarks: Typical feature of S. kozaki is the circular outline of the shell with the internal thickenings, which differentiate the new species from the other known forms of Sphenothallus.

?Sphenothallus kordulei sp. nov.

Fig. 4, 1–3

Holotype: Fragment of tube L40902+ illustrated on Fig. 4-1a.

Paratype: Fragment of tube L40902+ on the same bedding plane as the holotype illustrated on Fig. 4-1b.

Occurrence: Příbram-Jince Basin; Jince Formation; Vinice slope near Jince locality, higher levels of the Paradoxides (E.) pusillus trilobite Zone, (corresponding to the Cambrian Stage 5, equal to Ptychagnostus atavus Biozone).

Etymology : In honour of the late Vratislav Kordule, collector of Cambrian fossils of the Barrandian area.

Diagnosis: Giant, smooth and partly flexible organo-phosphatic conical shell, with narrow, slender and thin pair of opposite thickenings. Expansion angle exceeds 10° in the apical portion of the shell; the angle decreases to its minimum distally.

Description: Both known specimens are preserved as flattened moulds in brown-green fine greywacke and are oriented parallel to the bedding. Preserved fragments range from 91 mm to 100 mm in length and from 16 mm to 17 mm in width (Table 1); complete specimens are estimated to reach about 140 mm in length and up to 20 mm in apertural width. The tubes studied are broken at both ends. The expansion angle reaches 13.5° in apical portion of the cone. It decreases to 3.5° distally. The original organo-phosphatic material of the wall is not preserved. The imprints of the inner and outer surfaces show entirely smooth character. The material was flexible and is preserved irregularly rumpled. Thickenings are narrow and thin. They are preserved as poorly distinct low, flat rounded ridges. Their width ranges between 1.3 mm to 1.75 mm. The aperture preserved in the holotype shows no conspicuous structures or swellings. Its rim is smooth, the wall is of the same thickness as in other parts of the cone. The aperture outline is not straight but curved, and expanded in the axial part of the cone forming a low lobe.

Remarks: The new form is typified by a large apical angle forming rapidly widening cone. The angle decreases distally and the cone turns into an almost cylindrical tube. The apertural widening is distally suppressed and increases very gradually. The thickenings are minute related to the shell size in comparison to other Cambrian species of Sphenothallus. However, the thickenings were apparently robust enough and/or the body internally structured so firmly that strong reinforcements were not required to keep the shell upright above the substrate.

All studied specimens have been deposited in the collection of the National Museum Prague, numbered sequentially from L40897 to L40904.

Sphenothallus shows a simple morphology and its phylogenetic affinities have been controversial. It was regarded as an annelid or other “worm” tube (e.g. Mason and Yochelson, 1985 and Neal and Hannibal, 2000) or to be of a cnidarian affinity (e.g. Peng et al., 2005 and Zhu et al., 2000). It also has been interpreted as a sessile predator (Peng et al., 2005). The very simple morphology of sphenothallids makes any interpretation of their affinities difficult.

However, there are some key features that make it possible to distinguish separate species. The organo-phosphatic composition of cones combined with the smooth surface and marks of weak thickenings indicate some morphological relationship of the Bohemian specimens to the genus Sphenothallus.

S. kozaki is typified by its unusual circular cross-section (Fig. 5). We consider ?S. kordulei as a giant sphenothallid. It fits with a very wide size range of Sphenothallus as large or long specimens are not exceptional in younger material. However, ?S. kordulei is the biggest Cambrian sphenothallid and one of the largest altogether. We classify this species provisionally as Sphenothallus; we are convinced, that its morphology is so unique to indicate a separate new genus. However, the collected material is not sufficient to erect it now.

Sphenothallus is considered to be an opportunistic generalist inhabiting a wide range of marine environments (Neal and Hannibal, 2000). It was repeatedly documented attached by holdfast to shells of brachiopods (Bolton, 1994, Neal and Hannibal, 2000 and Wang et al., 2003), rarely also to the enigmatic genus Byronia (Zhu et al., 2000), as well as to cephalopods (Bolton, 1994 and Van Iten et al., 1992), to crinoid stems (Mason and Yochelson, 1985) and/or to other sphenothallid tubes (Neal and Hannibal, 2000; re-interpretation of older material of Feldmann et al., 1986). In addition, Sphenothallus was able to colonize hardgrounds (Bodenbender et al., 1989) and even soft, muddy bottoms (Wang et al., 2003). Despite the absence of any sphenothallid-like holdfasts, either isolated or attached to any shell surface in the Jince Formation, S. kozaki can be considered to have the usual mode of life.

In the case of ?S. kordulei, the discussion on mode of life is quite speculative, because of the limited material and the very simple morphology. However, by analogy to other phosphatic conical fossils, a benthic mode of life may be envisaged for ?S. kordulei. The partly flexible material of the cones supports an epifaunal nature rather than a semi-infaunal or infaunal mode of life.

Discovery of Sphenothallus in the classical Cambrian of the Příbram-Jince Basin is surprising. Fossil collections, intensively assembled since the end of 18th century did not include, for a long time, any rests of groups with organo-phosphatic shell, e.g. conulariids. The only other groups of organo-phosphatic fossils are represented by the linguliformean brachiopods (Fatka and Mergl, 2009 and Mergl and Šlehoferová, 1990) and the problematic plates (Elicki et al., in preparation), which, however, do not represent conulariids.