Problematica:
Amusingly, this really is a technical term, and it has a precise meaning. You might expect it to be anything that we don’t know what to do with, but alas! no – or, rather, yes, but it’s more complicated than that. There are numerous fossils that we can’t do much with, but normally the reason is that they’re too poorly preserved. Small fragments, abraded bits or specimens overgrown by other fossils or by crystals, can all be entirely obscure. However, none of these are actually ‘problematic’ – they’re just useless.
To be really problematic, we have to be able to see it quite clearly, be able to describe it… and still have no idea what to do with it. In practice, this problematicalness can operate on several levels. The ultimate is something that we can’t certainly identify as animal, vegetable or mineral, but these are pretty unusual. There are a few things, such as the receptaculitids (which might well turn up at Builth one day), which could be plant or animal, but in most cases we’re pretty sure that the problematica are animals. They include some very well known groups like hyolithids and tentaculitids, and large numbers of rather more obscure ones that we can’t yet assign to phylum level. On a smaller scale, one can talk about things like ‘problematic echinoderms.’ In this case, it would be a fossil that shows clearly diagnostic characters of one large-scale group, but doesn’t seem to fit into any sub-group within it, or for which the subgroup has an uncertain relationship to other sub-groups. In other words, it’s all a bit arbitrary, and depends on the context. In the list here, I’ve put things into problematica if they really don’t fit into any of the other categories, and are also unclear at phylum level among fossils that are not yet known from Builth. In other words, ‘problematica’ here refers to *real* problematica. The only exceptions are some things included in ‘microfossils,’ such as the phosphatic spines.
As well as being subjective, the category is a rather fluctuating one. Things enter and depart as our understanding of the fossils improves. For example, the strange Marcusodictyon was long thought to be the earliest bryozoan, but well-preserved material showed that the skeleton was unlike that of any other bryozoans, and it’s now generally regarded as problematic. It may still be a bryozoan, with an independently-evolved skeleton, but we’re really no longer certain. In contrast, Sphenothallus was for a long time regarded as problematic, but better material showed tetra-radial symmetry of the phosphatic tube, and it’s now almost certainly a cnidarian, which is where I’ve put it.
The problematica that I’ve included here include small conical fossils, a small worm-like thing, and something truly bizarre that might show some similarity to echinoderms… but is totally unlike any yet described! In fact, all the examples included, with the exception of Marcusodictyon, are undescribed, and do not fit into established problematic groups. We’re also keeping a few oddities up our sleeves as we look at them, so it’s likely that there will be several more in due course.
The Ordovician being an interestingly early time, between the Cambrian faunas and the diverse Palaeozoic faunas, there are likely to be a whole series of early forms of well-known groups (e.g. corals, bryozoans, molluscs). Problematica have a unique fascination, which is partly just the appeal of the bizarre, and partly because they can often tell us very important things about evolution, once we work out what they’re saying!
[1]Marcusodictyon? sp. Colony up to 10 mm across.
[5]Problematicum A, with early growth stage(?) below. There are multiple specimens of this fossil, including some reasonably complete ones. Better preserved ones show a stereom-like microstructure that closely resembles that of echinoderms, although it is very difficult to fit the thing into any known sort of echinoderm. Although the 'arms' are often broken in a brittle manner, there is no clear plate structure, and it appears to be a single unit. It seems to grow from a three-pronged blob, with the prongs extending to form the 'arms' and 'tail'. When the arms join together, a tuft of spicular-looking fibres is produced; these, however, do show some evidence of being made of minute plates, and resemble pinnules. A similar tuft appears near the end of the 'tail' at some point. The species is often associated with crescentic echinoderm-like plates with roughly the same diameter as the 'body' of this species, and in one example, is also associated with a xenomorphic column fragment (i.e. one with alternating wide narrow and ossicles ) of some other echinoderm. The only almost believable interpretation so far is a new echinoderm group allied to the 'carpoids...' all suggestions welcomed! Up to 30 mm.
Update!! The reconstruction is wrong. Actually, it appears to be the plates of a cornute (indeed a type of carpoid), stuck together in the wrong way, and missing quite a lot of bits. There's an essay appearing on what went wrong - and right - in the reconstruction process (see the introduction page), and a new cornute ('cornute indet.') on the echinoderms page which gave us the information that was needed. It's still a very weird thing, though, even for a cornute.
[2]Problematicum B. Only specimen is 1.5 mm long.
[2]Problematicum C. Only specimen is 3 mm long.
[1]Problematicum D. Looks like it should have been a cone, but unlike everything else at the locality, it is flattened. Possibly a weakly sclerotised organic structure; perhaps a fragment of something larger. Length 5 mm.
[1]Problematicum E. Possibly a scolecodont, but it so, it's a weird one. Looks organic in composition. Only specimen is 0.3 mm long.
[1]Problematicum F. Two specimens, preserved vertically in the sediment, of what appears to have been a lightly phosphatised cone with regular transvere ribs (growth increments?) and slightly meandering, irregular radial ridges. height 6 mm.
To be drawn:
[4] hyolithid; these are conical shells with an operculum and two spines ('helens' - after the wife of the discoverer, Charles Walcott - but alas rarely preserved). Thought to be molluscs, or possibly sipunculans.
[2] This is just too weird to describe. It resembles a strange internal bit from a certain type of living crustacean, but probably isn't.
[2] A complex radial branch network with a vertical spine in the centre of the slightly concave surface. Concave surface of branches slightly tuberculate, convex surface with faint longitudinal ridge resembling those of early fenestellid bryozoans. This will probably end up as a bryozoan itself, but the growth form is very different from any others in the area, and so far there's only one specimen.
[5]lobopod?!? It's certainly a weird one, and despite being in 3D, we're sure it's soft bodied. It's a partial specimen from inside a pyrite nodule, and is basically a worm-like creature with a ridged cuticle, and what looks horribly like a hooked appendage. We need another one to be sure, though.
[5]Small polyp-like organism, probably either sponge or cnidarian.
[5]Putative entoproct.
[5]Conical tube-dwelling organism.
[1]branching network of curved struts - looks like burow, but can't be; tube-worm? Resembles Buphotrephis.
