Hintzespongiidae Finks, 1983

Botting, Joseph P. & Muir, Lucy A., 2014, First post-Cambrian records of the reticulosan sponges Valospongia and Hintzespongia from the late Tremadocian of North Wales, Acta Palaeontologica Polonica 59 (1), pp. 241-252 : 248-249

Family Hintzespongiidae Finks, 1983

Emended diagnosis.—Thin-walled, obconical, ovate or vasiform Reticulosa in which an inner, gastral layer of parallel, slender-rayed hexactines or derivatives, as in Protospongioidea, is overlain by a layer of slender-rayed hexactines or derivatives in nonparallel orientation that surround closely spaced, circular gaps or aporhyses.

Discussion.—The only material of Hintzespongia consists of the holotype of H. bilamina Rigby and Gutschick, 1976 , and additional fragments of Hintzespongia from the Wheeler and Marjum formations described by Rigby et al. (2010).Another potential specimen is the holotype of Ratcliffespongia wheeleri Rigby and Church, 1990 , if that species should be placed in the genus. A fragment of a similar sponge from the Burgess Shale was described by Rigby and Collins (2004), and assigned to H. bilamina , but re-examination (JPB, personal observations) shows this specimen to be a different, undescribed sponge with a single spicule layer. The only non-Laurentian sponge recorded as Hintzespongia ( Yang et al. 2010) appears to show no evidence of a secondary spicule layer, and is likely to represent instead Ratcliffespongia or a related genus.

The relative positioning of the two spicule layers in H. bilamina could not be stated with certainty by Rigby and Gutschick (1976) due to the fragmentary nature of the specimen, and none of the subsequent discoveries provides a near-complete specimen in which the two layers are clearly distinct. As a result, the dermal and gastral placement of the two spicule layers has never been confirmed.

Genus Hintzespongia Rigby and Gutschick, 1976 Type species: Hintzespongia bilamina Rigby and Gutschick, 1976 , from the middle Cambrian Marjum Formation of Utah, USA.

Species included: Hintzespongia bilamina Rigby and Gutschick, 1976 , Hintzespongia wheeleri ( Rigby and Church, 1990) .

Diagnosis (emended after Finks and Rigby 2004b).—Sponge thin-walled, conical to barrel-shaped, with a probably gastral layer of parallel, slender-rayed stauractines of at least four orders of size, underlying a layer of slender-rayed stauractines and hexactines in nonparallel orientation.

Discussion. —Definition of this monospecific genus is complex, and requires a re-evaluation of similar and related taxa. Finks and Rigby (2004b) list Hintzespongia , Ratcliffespongia , Cyathophycus , and Stephenosphongia as being assigned to the family, but some of these assignments are perhaps unsound. Cyathophycus is a complex, widely distributed genus that is in need of revision (and probably subdivision), but the inner layer of at least some species appears to be composed of monaxons (discussed by Botting 2003, 2004). Stephenospongia is a poorly known genus that may not even have an outer spicule layer, although there are traces of reticulation in some parts ( Rigby 1986) that might resemble the reticulating outer mesh of Valospongia , discussed above. None of these genera are particularly similar to Hintzespongia bilamina , but there are definite similarities between it and Ratcliffespongia wheeleri ( Rigby and Church 1990) .

The taxonomy of Ratcliffespongia is complicated, despite being based on only two specimens. Rigby (1969) described R. perforata based on a unique, semi-complete specimen from the Wheeler or Marjum formations, of a sponge with prominent, somewhat transversely elongate parietal gaps in a thin wall that was constructed from large, thin-rayed but clearly defined stauractines. The spicule rays do not generally demark the margins of the gaps, which were visible as a soft tissue impression. The sponge apparently consisted of a single layer of spicules, and was assigned to the Teganiidae . Another unique specimen from the upper Wheeler Formation was described by Rigby and Church (1990) as R. wheeleri , but although showing prominent parietal gaps, this species differs substantially. The gaps are more circular and irregularly arranged, and the spiculation of the wall is rather obscure, with small hexactines or their derivatives often marking very clearly the margins of the gaps. Most fundamentally, R. wheeleri appears to have possessed two layers, with a homogeneous, sub-reticulate grid of small spicules overlying(?) the pariety-bearing layer. The diagnosis of Ratcliffespongia was emended by Rigby and Church (1990) to include the double-layered wall, and both species were thereby assigned to the Hintzespongiidae . The similarity was accepted only through the assumption that the holotype of R. perforata represents a decorticated inner layer of a hintzespongiid ( Finks 1983; Rigby and Church 1990). However, the holotype is apparently well preserved, near-complete (the only damage appears to be due to erosion and distal breakage of the loose block containing the specimen), and fully articulated, even showing traces of the soft tissues marking the margins of the parietal gaps. Decortication seems very unlikely in this case, especially as the fragment forming the holotype of R. wheeleri is much less intact and appears to be less well preserved in some areas than others.

The skeletal architecture is fundamentally different in the two Ratcliffespongia species, and they have little in common except for being reticulosan hexactinellids with parietal gaps. We therefore do not recognise these two species as belonging to the same genus, and restrict the use of Ratcliffespongia to the type species R. perforata . Instead, the fundamental structure of R. wheeleri is identical to that of Hintzespongia , and we therefore reassign it to that species. The separation from Hintzespongia by Rigby and Church (1990) was on the basis of differences in the regularity of spicule organisation in the reticulate layer, and parietal gap dimensions; these are superficial differences that do not obscure a close relationship. We therefore include both R. wheeleri and the new (open nomenclature) sponge described here in Hintzespongia .

Stratigraphic and geographic range. —The confirmed range for Hintzespongia is restricted to the middle Cambrian Wheel- er and Marjum formations of Utah, USA, together with the probable new record from the Tremadocian of Wales, UK.