My trilobite of the week.

[Kermit72]

Here is the full piece 

[Kermit72]

[rew]

Welcome to the forums.  Yes, the Hollardops trilobites often have great eyes.  And the holochroal eyes of the scutellids are preserved surprisingly often, although they typically require magnification to see.

[piranha]

1 hour ago, rew said:

This week's bonus triloblite, #49, is Ptychagnostus germanus from the Middle Cambrian Marjum Formation in Millard County, Utah.  It is a fairly typical agnostid trilobite.  As is usual with these trilobites, I'm not sure if this picture is heads up or heads down.

 

 

Time to make a new label.. ..this one was reclassified as Ptychagnostus cuyanus in:

 

Tortello, M.F., Bordonaro, O.L. 1997

Cambrian Agnostoid Trilobites from Mendoza, Argentina: A Systematic Revision and Biostratigraphic Implications.

Journal of Paleontology, 71(1):74-86

 

 

 

figure 131 from:

 

Robison, R.A., Babcock, L.E., Gunther, V.G. 2015
Exceptional Cambrian fossils from Utah: A Window into the age of Trilobites.
Utah Geological Survey Miscellaneous Publication, 15-1:1-97

 

[rew]

Once again piranha forces me to relabel my stuff.  Thanks for the info, this bug apparently had wide distribution. 

[rew]

For trilobite #50, the official trilobite of the week, I have another agnostid trilobite, Glyptagnostus reticulatus, from the Furongian Series, Ogon’or Formation at the Lena River basin of Siberia, Russia.  This species has a very wrinkled carapace.  At 17 mm in length this specimen is not only large for the species but large for the order as a whole.

 

This trilobite is used as as an index fossil. Its first appearance in the Huaqiao Formation in Hunan, China is used to define the start of the Paibian, the 8th stage of the Cambrian, which is taken as the start of the Late Cambrian.

 

I make no guarantee that this specimen is heads up.

 

[rew]

This week's mid-week bonus trilobite, #51, is a proetid from the Rochester Shale of Caleb's Quarry, New York, so is of Silurian age.  It is allegedly Dechenella microcephalus.  I say allegedly, because when I Google that name nothing comes up, which makes me wonder if the species has been renamed.  The usual proetids that come from Caleb's quarry are Radnoria bretti and Decoroproetus corycoeus.  This is certainly not a Radnoria and doesn't really match the shape of the D. corycoeus either.  So it does seem to be a proetid at the obscure end of the scale for Caleb's quarry.

[rew]

I did find this other trilobite called Dechenella macrocephalus (in contrast to this bug, which is D. microcephalus):

 

Note that that bug is Middle Devonian, and has a pustulose glabella, unlike this one.  Most Dechenella species appear to be Devonian, although its certainly possible that some species lived during the Silurian.

[piranha]

On 6/11/2019 at 10:59 PM, rew said:

This week's mid-week bonus trilobite, #51, is a proetid from the Rochester Shale of Caleb's Quarry, New York, so is of Silurian age.  It is allegedly Dechenella microcephalus.  I say allegedly, because when I Google that name nothing comes up, which makes me wonder if the species has been renamed.  The usual proetids that come from Caleb's quarry are Radnoria bretti and Decoroproetus corycoeus.  This is certainly not a Radnoria and doesn't really match the shape of the D. corycoeus either.  So it does seem to be a proetid at the obscure end of the scale for Caleb's quarry.

   

 

 

This one matches well with: Pseudodechenella rowi

 

 

 

figures from:

 

Lieberman, B.S. 1994

Evolution of the trilobite subfamily Proetinae Salter, 1864, and the origin, diversification, evolutionary

affinity, and extinction of the Middle Devonian proetid fauna of eastern North America.

American Museum of Natural History Bulletin, 223:1-176  PDF LINK

[rew]

It's certainly very similar.  But Pseudodechenella rowi is Middle Devonian, I'd never seen any indication that that species extends back to the Silurian.  Do you know if Dechenella microcephalus is a valid species?

[piranha]

46 minutes ago, rew said:

It's certainly very similar.  But Pseudodechenella rowi is Middle Devonian, I'd never seen any indication that that species extends back to the Silurian.  Do you know if Dechenella microcephalus is a valid species?

 

 

Dechenella microcephalus is not a valid species and Pseudodechenella rowi is Middle Devonian.  I received some follow-up info from a friend.  Apparently the trilobite (attached below) was sold elsewhere with the same info that was provided to you.  The seller later said he was only given the name and assumed it was from the same formation as some other trilobites he received.  He said it was actually from the Middle Devonian, Ludlowville Formation, Livingston County, New York.  All of these clues appear to point to an ID of Pseudodechenella rowi.

 

[rew]

That makes sense.

[rew]

Well, I'd like to make the trilobite of the week be one where I get the identification right.  This one is as unmistakable as Arctinurus boltoni.  Trilobite #52 is Bristolia insolens, an Early Cambrian bug from the Latham Shale of San Bernardino County, California.

[Coco]

Could be interesting if you put size

 

Coco

[rew]

That bug is about 35 mm long (including the telson) and about 40 mm wide.  I think that's a pretty typical size, though no where near the maximum size for the species.  Just getting a complete example of this species was enough for me.

[rew]

There are two bonus midweek trilobites.  Both are smooth carapaced members of the Styginidae, and are believed to have been burrowing trilobites.  The first, #53, is Bumastus ioxus.  This really is a Silurian trilobite from the Rochester Shale of Caleb's Quarry. 

[rew]

Trilobite #54 is Failleana indeterminata, a late Ordovician trilobite from the Verulam Formation of Simcoe County, Ontario.  This bug is a bit crude, a chip of shell is missing where the right eye should be and although the living bug had a domed carapace this specimen is crushed quite flat, which is often the case for trilobites preserved in shale.  I couldn't be too picky, you don't get too many opportunities to get this species.

 

[rew]

Continuing this week's theme of Styginidae, the official trilobite of the week, #55, is a Middle Devonian scuttelid from Alnif Morocco called Thysanopeltis speciosa.  This bug has a lot of iron staining on the pygidium, but does show well the fringe of small spines on the pygidium that define the species.  I took a close up of the left eye.  Many of the lens of the holochroal eyes are preserved, but it's not as nice as the preservation on my Scutellum trilobite.  If you have a scutellid trilobite I recommend that you look at the eyes under magnification.  You may find that the lenses are better preserved than you thought.

[rew]

This week's midweek bonus trilobite, #56, is Neltneria termieri, a late Atdabanian Redlichid from Issafen, Morocco.  The Atdabanian stage (3rd stage of the Cambrian) was when trilobites first appeared, so this is a pretty early bug.  The trilobite was photographed straight on, the skew you see is partly because the head is bent slightly to the right but mainly due to some stretching of the rock that took the fossil with it.  (You can see this in more extreme form with those Portuguese Ordovician bugs.)

[rew]

Continuing the theme of late Atdabanian trilobites from Issafen, Morocco, this week's trilobite of the week, #57, is Gigantopygus papillatus.  At over 18 cm in length it is a large trilobite, but the "Giganto" refers to the large pygidium, not the trilobite as a whole.  The pygidium is big only for a Redlichid, as with all bugs in that order the head is much bigger than the pygidium.

 

This trilobite has no restoration (it is all real shell) but has lots of repair.  It was found in numerous pieces that had to be glued back together.

 

[rew]

The trilobite of the week, #58, is a large Ordovician Ondontopleurid from the Ktaoua Formation of Morocco, generally called Selenopeltis buchii, after its closest European equivalent.  This is a large specimen, 18 cm long, and has decent, although as you can see, definitely not perfect, shell preservation.   This may be the most faked trilobite on the planet.  I don't think I've ever seen a real one offered on our favorite auction site.   This one is real.

 

[rew]

For trilobite of the week #59 I have another Devonian scutellid.  This is Septimopeltis clementina from Jorf, Morocco.  Like some other bugs from this site it has a somewhat plastic appearance due to the rock being semi-metamorphosed.   Despite this this is still some preservation of the lenses in the eyes.

 

[Wrangellian]

Amazing collection.

You could post just one a week and I think they would all deserve to be the 'trilobite of the week', but I'm not complaining about you posting all the bonuses!

[rew]

The dearth of mid-week bonus trilobites has been due to some technical difficulties at the photography end.  They seem to have been resolved.  Anyhow, this week's trilobite of the week, #60, is an unusual early Devonian (Pragian) Acastid, Lanceaspis hammondi, from Mjane, Morroco.  This bug's chief feature is of course its huge, wide rostrum.  The brownish pygidium is due to staining by iron rich water; the nearby rock is stained the same way.  At 68 mm in length, this is near the upper end of the size range for the species.

[rew]

This week's mid week bonus trilobite is a bit of a mystery.  I got it a few years back at one of those Paleochic auctions.  Jake Skabelund dug it up.  He said it comes from the lowest part of the Latham shale near Cadiz, California.  Its a species of Olenellus that resembles O. gilberti but is apparently too early for that species.  The macropleural spines are too long for it to be a Mesonacis fremonti.  So any informed opinions as to the identity of this bug but are welcome.

 

The trilobite is of good size, about 8.8 cm.  The shell is well preserved but the color is so close to that of the rock that it's not the most displayable bug.