Curious Early Cambrian Conical Critters From The Harkless Formation, Nevada

[Virgilian]

Here's an image I received the other day from a paleo-enthusiast acquaintance who with impressive regularity continues to pull interesting material for study out of his numerous digs in Nevada. Thought I might "get a kick out of it."

 

I certainly did.

 

The specimens come from the Lower Cambrian Harkless Formation of Nevada. Largest is about a quarter inch long (a little over 6mm). The back-story here is that they were rather confidently identified in the field as Salterella--an extinct member of the phylum Agmata, a phylum erected in 1977 by the late paleontologist Ellis L. Yochelson. They are of unestablished zoological affinity, which is to say that Agmatans cannot be definitely categorized with any modern organismal analog.

 

What's especially fascinating about Salterella and its Agamatan Early Cambrian "cousin" Volborthella (which occurs in geologically older Early Cambrian strata, below Salterella's stratigraphic range) is that the Agmatan animal agglutinated minute mineral grains, incorporating them into its growing shell--that is to say, the actual soft-bodied creature who constructed the shells made a "conscious" decision about which specific minerals in its environment were best suited to include in its expanding shell-home.

 

Back at home, though, identification dubiety set it. Now, he's not so certain. Thinks they could well be assigned to the extraordinarily rare Early Cambrian genus Lidaconus--which is not an Agmatan, apparently, though it bears a striking external superficial resemblance to Salterella--originally described from a couple of Nevada localities situated not too far from where these curious specimens were recovered.

 

By the way--Just in case one speculates whether such specimens referred to Salterella, Volborthella, or Lidaconus could possibly be sclerites--in other words, the conical curiosities do not represent products of individual animals, but rather they're the dissociated components of a larger creature (fragmented "spikes" of some kind of "armored worm," for example)--that idea has already been proposed in the scientitic literature; and it's already been falsified, completely discredited.

 

So, Salterella--or Lidaconus?

 

Some uncertainly now exists, admittedly. Both Salterella and Lidaconus occur within the Bonnia–Olenellus trilobite Zone, in the upper part of the Harkless Formation. Lidaconus is slightly younger, stratigraphically speaking. The paleo-acquaintance also mentioned that he'd probably have to resort to cross-sectioning a few of the specimens; Salterella and Lidaconus can be distinguished on the basis of distinctive internal morphological differences. We'll see what transpires.

 

[Arizona Chris]

Awesome!  Kind of looks like a cross between a monoplacophoran and hyolithid.  

[Oxytropidoceras]

Given the resistance to weathering of the pictured fossils and their color, they look like they are silicified. If they are silicified, it would be an atypical mode of preservation for such fossils. Go read;

 

Skovsted, C.B., 2003. Unusually preserved Salterella from the Lower Cambrian Forteau Formation of Newfoundland. GFF, 125(1), pp.17-22.

https://www.researchgate.net/publication/240545628_Unusually_preserved_Salterella_from_the_Lower_Cambrian_Forteau_Formation_of_Newfoundland

 

If they are silicified and if the matrix is carbonate (two significant "ifs"), a person might be able extract some by dissolving the limestone. That would provide an interested professional a very rare opportunity to study this Agmatan in detail and up close.

 

An interesting paper about these fossils is:

 

Signor, P.W. and Ryan, D.A., 1993. Lower Cambrian fossil Volborthella: The whole truth or just a piece of the beast?. Geology, 21(9), pp.805-808.

 

"These agglutinated fossils are traditionally interpreted as the complete skeleton of individual animals. However, a newly discovered fossil from the White-Inyo Mountains of eastern California demonstrates that Volborthella was a bilaterally symmetrical animal..."

 

and "Lower Cambrian fossil Volborthella: The whole truth or just a piece of the beast?: Comment and Reply"

https://www.researchgate.net/publication/236000331_Lower_Cambrian_fossil_Volborthella_The_whole_truth_or_just_a_piece_of_the_beast_Comment_and_Reply

[Plax]

are the little rounded objects the narrow terminations of the animal in life position? In that case we would be looking from bottom up from a minor break in deposition or storm? event with a renewal of normal deposition. Perhaps the other side of the rock would show larger circles.

[Virgilian]

Just over-the-transom: Some additional photographs sent to me, fossil material recovered from the Lower Cambrian Harkless Formation, Nevada, by said paleo-enthusiast acquaintance referenced in first post in this thread.

 

First up: A chunk of limestone from the upper portions of the Harkless Formation, bearing multitudes of Salterella--a member of the extinct phylum Agmata. Most about a quarter inch long--a little over 6mm. Several thin carbonate layers in the upper third section of the Harkless are composed almost entirely of such Salterella specimens.

 

 

Second--Two genus Ogygopsis trilobite specimens on the same bedding plane, from the Lower Cambrian Harkless Formation, Nevada. A pygidium (tail-hind section) at lower right. The other specimen reveals the pygidium and a partial thoracic segment (middle portion of the three-lobed trilobite anatomy) still articulated. Students of Cambrian paleontology might recognize the name Ogygopsis from its occurrence in the world-famous Middle Cambrian Burgess Shale, Canada, where it is by far the most abundant fossil represented in the spectacular fossil deposit, noted for its plentiful soft-bodied preservations.

 

 

And third--A mostly complete ptychopariid trilobite from the Lower Cambrian Harkless Formation, Nevada. Syspacephalus, perhaps? He's not sure.

 

[piranha]

6 hours ago, Virgilian said:

Students of Cambrian paleontology might recognize the name Ogygopsis from its occurrence in the world-famous Middle Cambrian Burgess Shale, Canada, where it is by far the most abundant fossil represented in the spectacular fossil deposit, noted for its plentiful soft-bodied preservations.

 

 

Actually, only partial antennae are known from a few Ogygopsis klotzi from the Burgess Shale.  The Burgess Shale trilobite with abundant soft-bodied preservation is Olenoides serratus.  Of the 31 trilobite species described with soft-bodied anatomy, Olenoides serratus is one of only 6 trilobites with a complete record of the antennae and post-antennal limbs.

 

 

Hofmann, H.J., & Parsley, R.L. (1966)

Antennae of Ogygopsis.

Journal of Paleontology, 40(1):209-211

 

Whittington, H.B. (1975) 

Trilobites with appendages from the Middle Cambrian, Burgess Shale, British Columbia.

Fossils and Strata, 4:97-136

[Wrangellian]

Interesting stuff.. Oh to live in an area where Cambrian oddities occur (or have a friend who does and is willing to send you samples!)...

[doushantuo]

some shapes to be expected in SSF's: