Mississippian sponge, heteractinid?, from UK

[TqB]

The axes look interesting, how much is calcite overgrowth or is it just recrystallised?:

Sp. 3

 

And a tangential section (preservation getting woolly towards the left):

Sp. 3

[Spongy Joe]

Excellent!

 

This is looking to me very like a Talpaspongia species, which I've just been digging out the literature for. These are wewokellid heteractinids, and the axes are the actual spicules; the rest is hypercalcification, which explains why the shapes are so odd! The spicules in described Talpaspongia are triactins and monaxons (without any heteractine spicules), and the body form is tubular with a deep central cloaca. So far as I know (at this stage; I've not looked comprehensively yet!) the genus is only known from the mid-western USA. 

 

I will say there seems to be some really interesting concentric stuff going on in some of those spicules; definitely worth getting a thin section done!

 

So... that's three species: two heteractinids (probably new genus, and a ?Talpaspongia) and a demosponge (Haplistion). Anything else?

 

p.s. no worries on mixing up the mineralogies - happens to us all! At the moment I can't seem to tell nautiloids from arthropods, but that's another (currently secret) story...

 

Ref:

Donald H. Lokke. Calcareous spicules in Talpaspongia clavata R. H. King, Lower Permian of Concho County, Texas. Journal of Paleontology (1964) 38 (4): 778-781

[doushantuo]

miscellaneous sponge needles,to show morphological diversity in poriferan spicules(Paleozoic to the right ,from Reitner/Mehl,1995): 

 

[Spongy Joe]

Hi Ben - thanks for posting these. Some spicules are truly amazing things...

 

I really need to explain these a bit, though, otherwise they're going to be a bit incongruous. First thing is that in modern siliceans (demosponges and hexactinellids) there are two fundamentally different sorts of spicules: megascleres and microscleres. The other classes (Calcarea and Homoscleromorpha) don't have microscleres. As you might guess, microscleres are a little bit on the teeny side: often less than 50 microns, and hardly ever preserved in fossils. This is an absolute pain, because they're critical to modern taxonomy, and when you have fossils that you're trying to relate taxonomically to, say, living families... well, not having microscleres is a bit of a curse. (I'll tell you the story of that sometime... once the paper's published!)

 

What you have on the left are some such microscleres: various forms of hexasters. These are basically limited to the hexactinellid subclass Hexasterophora (hence the name), and you won't find them in anything else.

 

On the left are dermal armour megascleres from Thoracospongia (I think..?), with weird inflated rays. These are really limited to a few taxa in the Stiodermatidae (plus one or two oddballs that might be unrelated), an extinct family of probable hexactinellids (but affinity uncertain, and could well be stem-group).

 

There's really enormous diversity in these spicules, with many families having developed their own subtly (or not-so-subtly) different morphologies, but generally based on the same few basic forms. In hexactinellids, the basic spicule is the hexactin: a three-dimensional cross. Trace the ancestry backwards, and simple variations of hexactins go back a long, long way.

        In demosponges, there are fundamental diactins (needles) and later tetractins (caltrops). Trace these back to Burgess Shale genera like Hazelia and Vauxia, and diactins were where they started... although they seem to have originated first in a hexactinellid-like beastie that lost its hexactins!

 

        In calcareans, diactins, tetractins and probably primitive triactines (three-rayed spicules in one plane) are what we've got. What we're seeing in Talpaspongia is probably something like the ancestral condition for living calcareans: diactins and triactins. Go further back, though, deep into the stem group, and you find the heteractinids: often with hexaradiate heteractins. The new genus on the first page has some of these, but is dominated by pentaradiate heteractins, which do turn up occasionally (including in one living calcarean, Sycon pentactinoides).

 

Go right back to the beginning, and you get to the Burgess Shale icon Eiffelia, which had hexaradiate heteractins... but also hexactins. This is where it gets really interesting, since this combines things that today are diagnostic of two entirely separate classes. This is why unusual spicule combinations are so interesting: they can tell us something about the 'missing links' between the living classes, and what the first sponges were really like...

 

Sorry, long ramble. Feel free to ignore.

 

Oh, and I've no idea what the last figure was meant to be showing!

[Jesta384]

I have nothing informative to add - just came here to say this is so cool. Reading the comments between you two is fascinating!!! I say one of the new species should be fossilforumis

[TqB]

3 hours ago, Spongy Joe said:

Excellent!

 

This is looking to me very like a Talpaspongia species, which I've just been digging out the literature for. These are wewokellid heteractinids, and the axes are the actual spicules; the rest is hypercalcification, which explains why the shapes are so odd! The spicules in described Talpaspongia are triactins and monaxons (without any heteractine spicules), and the body form is tubular with a deep central cloaca. So far as I know (at this stage; I've not looked comprehensively yet!) the genus is only known from the mid-western USA. 

 

I will say there seems to be some really interesting concentric stuff going on in some of those spicules; definitely worth getting a thin section done!

 

So... that's three species: two heteractinids (probably new genus, and a ?Talpaspongia) and a demosponge (Haplistion). Anything else?

 

p.s. no worries on mixing up the mineralogies - happens to us all! At the moment I can't seem to tell nautiloids from arthropods, but that's another (currently secret) story...

 

Ref:

Donald H. Lokke. Calcareous spicules in Talpaspongia clavata R. H. King, Lower Permian of Concho County, Texas. Journal of Paleontology (1964) 38 (4): 778-781

-

That's a fascinating and satisfying answer, Joe! I've just looked through the Lokke paper which seems to match these very well, apart from the absence of polyactines.  I see there's only the one species described, Talpaspongia clavata, which is Permian plus one Pennsylvanian record?  By the way, I checked the Treatise too and it expands the range to China

 

I'm looking hard at my material (thirty odd specimens) and so far, apart from the one Haplistion, now that I've got my eye in they're all looking like one or other of the heteractinids.

 

A lot of them are extensively silicified and rather blobby but some patches are replaced and weathered quite nicely and show spicules including pentaradiates on the surface, with some fusing. The ones on the bowl shaped form appear to have a long proximal ray (and a short distal one) that produces a layer of widely spaced pillars below the surface. These show up well in transverse section. Somewhat like Tholiasterella perhaps?

 

Outer surface of Talpaspongia type:

Sp. 14

 

Bowl type, largest specimen (15cm across), convex surface:

Sp. 7 a

 

Bowl type, in same block as Sp. 7 a above

Sp. 7 b

 

 

 

[TqB]

1 hour ago, Jesta384 said:

I have nothing informative to add - just came here to say this is so cool. Reading the comments between you two is fascinating!!! I say one of the new species should be fossilforumis

 

Thank you! Glad you're finding it interesting.

[TqB]

Just one more new bowl shaped specimen, only lightly silicified.

A starry, tangential slice very near the outside of a convex bit (see pics 3 & 4 for location).

Sp. 4

 

 

Vertical section. Previous tangential section is from the top of this.

Sp. 4