My trilobite of the week.

[piranha]

28 minutes ago, DPS Ammonite said:

The ICZN code requires that the name be in Latin letters; ł needs to be rendered into a Latin letter. I am going to assume that an l is used instead.

 

Correct....I inadvertently overlooked it with a quick copy/paste from Google translate!

[rew]

Correction noted.  Another label to rewrite.

[rew]

Trilobite of the week #271 is Cybeloides loveni girvanensis of Late Ordovician age (Upper Rawtheyan Stage) from "Harper's Trench", S.E. bank of Lady Burn, near Girvan, Ayrshire, Scotland.

 

This is a showy Encrinurid.  Even the little brachiopod has been identified -- it's Skenidioides asteroideus.

 

 

Edited March 12, 2023 by rew

[piranha]

2 hours ago, rew said:

Trilobite of the week #271 is Cybeloides loveni girvanensis of Late Ordovician age (Upper Rawtheyan Stage) from "Harper's Trench", S.E. bank of Lady Burn, near Girvan, Ayrshire, Scotland.

 

 

Hupé 1955 designated this trilobite as a subgenus: Cybeloides (Paracybeloides). 

 

Jell & Adrain 2003 elevated it from subgeneric to generic rank: Paracybeloides.

 

text from: Morris 1988

 

 

Hupé, P. 1955
Classification des Trilobites.

[Classification of Trilobites.]
Annales de Paléontologie, 41(4):91-325

 

Jell, P.A., Adrain, J.M. 2003
Available Generic Names for Trilobites.

Queensland Museum Memoirs, 48(2):331-551  PDF LINK

 

Morris, S.F. 1988
A Review of British Trilobites, Including a Synoptic Revision of Salter's Monograph.
Palaeontographical Society Monograph: London, 140(574):1-316

[rew]

Does the subspecies still apply?  I.e., is this Paracybeloides loveni girvanensis, or just Paracybeloides loveni?

[piranha]

12 hours ago, rew said:

Does the subspecies still apply?  I.e., is this Paracybeloides loveni girvanensis, or just Paracybeloides loveni?

 

 

They are now classified separately: Paracybeloides loveni – Paracybeloides girvanensis

 

"During the last hundred years or so Cybele loveni  Linnarsson or C. rugosa (Pordock) have been frequently included in faunal lists accompanying papers dealing with British Ordovician stratigraphy and palaeontology. Scottish material, described as 'varieties' of Cybele loveni by Reed (1906, 1930), was referred to Cybeloides Slocom (Reed 1928). Hupé (1955) created a new genus Paracybeloides with Reed's var. girvanensis as type species and more recently north of England specimens have been compared with Paracybeloides girvanensis (Dean 1962; Ingham 1966). An examination of specimens in old collections and of new material, mainly from north British localities, shows that many British specimens are not only inseparable generically but also specifically: they are identified with Reed's 'var.' girvanensis which is here reassigned to Cybeloides. A comparison of the original, and topotype, specimens of Cybele loveni Linnarsson (1869) with C. girvanensis shows that the Swedish species is a distinct but closely allied form."

 

text & figures from:

 

Ingham, J.K. 1968
British and Swedish Ordovician Species of Cybeloides (Trilobita).
Scottish Journal of Geology, 4(4):300-316

 

 

 

text from:

 

Peers, S. 1997

The Taxonomy, Phylogeny and Palaeobiogeography of the Trilobite

Families Pliomeridae and Encrinuridae: Reconstructing the Ordovician

World using Evolving Lineages. PhD Thesis, Glasgow University, 410 pp. 

PDF LINK

[rew]

Okay, it looks like I have a Paracybeloides girvanensis.

 

The frustrating thing is, despite getting expert corrections on the names I have for my trilobites, I know that in ten years at least 5% of them will still be misnamed, because of continued work in reclassifying that class.

[rew]

I'm sure you've all been waiting for this one...

 

Trilobite of the week #272 is Elrathia marjumi of Middle Cambrian age from the Marjum Formation at Millard County, Utah.  This is not a rare trilobite, but is less ubiquitous than its cousin, Elrathia kingii.  E. marjumi lived later than E. kingii.  The two trilobites are very similar, one difference is that the profile of the pygidum of E. kingii shows a slight concavity at the bottom, which is lacking in E. marjumi.

 

 

[rew]

Trilobite of the week #273 is Struveaspis bignoni, of Middle Devonian age (Eifelian Stage) and from the Jorf Red Formation at Jorf, Erfoud, Morocco.

 

This member of the Phacopidae has a plasticy appearance, like many of the fossils found at Jorf, where the rocks are semi-metamorphised.

Edited March 25, 2023 by rew

[rew]

An update.  I called trilobite #160 posted January 22, 2021 Crotalocephalus maurus.  Piranha pointed out that I had misidentified the species because Crotalocephaus maurus does not the the two little spines at the front of the head.  Now I see trilobite I posted called Pilletopeltis maurus.  I'm not sure that one's right either.

 

 

Edited March 25, 2023 by rew

[piranha]

2 hours ago, rew said:

An update.  I called trilobite #160 posted January 22, 2021 Crotalocephalus maurus.  Piranha pointed out that I had misidentified the species because Crotalocephaus maurus does not the the two little spines at the front of the head.  Now I see trilobite I posted called Pilletopeltis maurus.  I'm not sure that one's right either.

 

 

Crotalocephalus maurus  is the most recent assignment for the taxon: "Pilletopeltis maurus". The taxonomy has shuffled around over the years with Pilletopeltis ranked as a subgenus: Cheirurus (Pilletopeltis) maurus – Crotalocephalus (Pilletopeltis) maurus. However, according to Jell & Adrain 2003: Pilletopeltis is classified as a junior subjective synonym of: Crotalocephalus.

 

Jell, P.A., Adrain, J.M. 2003
Available Generic Names for Trilobites.

Queensland Museum Memoirs, 48(2):331-551  PDF LINK

[rew]

So is it really Crotalocephalus maurus, despite the little spines?  Or do I still have an undescribed Cheirurid?

[piranha]

15 minutes ago, rew said:

So is it really Crotalocephalus maurus, despite the little spines?  Or do I still have an undescribed Cheirurid?

 

 

Nothing has changed:

 

Crotalocephalus maurus Alberti 1966, does not have anterior cephalic spines.

 

Your trilobite is Crotalocephalus sp.  It has not been been formally described. 

[rew]

Okay. 

[Mark Kmiecik]

18 hours ago, rew said:

Okay. 

 

Yup -- gotta love progress! 

[rew]

Trilobite of the week #274 is Drotops megalomanicus megalomanicus, of Middle Devonian age from the Bou Dib Formation at Mrakib, Morocco.  Unlike its super spiny cousin, D. armatus, this is a conventionally conservative member of the Phacopidae, but it is big.  At 16 cm my specimen is of respectable size but by no means the largest example found.   BTW, the Phacopidae lived right to the end of the Devonian.  This family was outlived only by a few families in the order Proetida.

 

 

Edited April 4, 2023 by rew

[rew]

Trilobite of the week #275 is Drotops megalomanicus subornatus, of Middle Devonian age and from Issoumour, Morocco.  Yes, this is just a different subspecies of the same species that you saw last week.

Like all Drotops, Drotops megalomanicus subornatus has a pustulose glabella, but it lacks the small pustules scattered over the thorax and pygidium that Drotops megalomanicus megalomanicus has.  This variant has a smooth thorax and a smooth pygidium.

 

My specimen is 9.9 cm long, a respectable size for most trilobites but on the small side for a Drotops.

 

This is the last Drotops you'll see in this thread.  Next week's bug won't be in the Phacopidae at all.

 

[rew]

Trilobite of the week #276 is Whittardolithus radiatalis of Middle Ordovician (Darriwilian stage) age, from the Middleton Formation, LLandelian Stage, at Shropshire, England.  This is in the family Trinucleidae and like all members of that family, it was blind, with no eyes.

 

 

[rew]

Trilobite of the week #277 is Eudolalites maiderensis of Late Ordovician (Late Katian Stage) age from the Upper Ktaoua Formation at Erfoud, Morocco.  This is 14.5 cm long so is a large member of the Dalmanitoidea.  Although trilobites in this family have schizochroal eyes the lenses are rarely well preserved with this species and my specimen is no exception.

 

 

[rew]

Trilobite of the week #278 is Greenops widderensis of Middle Devonian age from the Widder Formation, Hamilton Group at Arkona, Ontario, Canada.  This is about 1 inch (2.5 cm) long, typical for this genus.  Greenops trilobites are small but are nice examples of the subfamily Asteropyginae.

 

There is some pyritization of the lenses of the right eye.

 

Edited April 29, 2023 by rew
The right, not the left, eye is pyritized.

[Kane]

Brings back memories. We used to pull many of these before the "changes." Know that your specimen is likely the result of our work. Here's one of mine (up to my back teeth in these buggers). It was crazy as we were working a spot maybe ten metres before we tapped out and the local farmer shouted us off, since we were undercutting his land. Cherish your specimen as the site is mostly done. Arkona is not what it used to be.

[rew]

Trilobite of the week #279 is Ampyxina bellatula of Late Ordovician age from the Maquoketa Formation at Pike County, Missouri.

 

 

[rew]

Trilobite of the week #280 is Tapinocalymene nodulosa of Middle Silurian age from the Wenlock Series of the Coalbrookdale Formation, at Ape Dale, Stropshire, U.K.  This Calymenid has a short upturned rostrum.  I am the only one on my block with this bug.

 

 

[ClearLake]

16 minutes ago, rew said:

I am the only one on my block with this bug.

Maybe even your whole state!  Very nice!  I continue to marvel at this thread.  Keep it going!

Edited May 13, 2023 by ClearLake

[rew]

Trilobite of the week #281 is Ptychagnostus punctuosus of Middle Cambrian age from the Marjum Formation at Millard County, Utah.  I still have some agnostids to get through.