Colpocoryphe grandis

 

 

Here is a page created after a discussion on the Yahoo Trilobite Club about "Diacalymene ouzregui : a Colpocoryphe, a Diacalymene or a Flexicalymene ?" (See message #191 and replies) One thing seems almost certain : this is not a Colpocoryphe, as this page will demonstrate it.

To my mind, Dicrano reporting J. Destombes, H. Hollard & S. Willefert (1966) is right when he proposes Flexicalymene ouzregui (DESTOMBES 1966) (J. Destombes, H. Hollard & S. Willefert. Lower Palaeozoic rocks of Morocco. in Holland C.H.. 1985. Lower Palaeozoic of north-western and west-central Africa. John Wiley & Sons.)

Inside the genus Colpocoryphe, C. grandis and C. rouaulti are 2 very similar species both in morphology and distribution. This is why I do present C. rouaulti here too.

 

Nice specimen to come

very soon :)

Specimen description

 

Diagnosis :

 

Order

 

 

 

 

 

 

 

 

 

Phacopida

 

 

 

 

 

 

 

 

 

SALTER 1864

 

 

 

 

 

 

 

 

 

Occurrence: Lower Ordovician (Tremadoc) to Upper Devonian (Famennian).

  • Cephalon: Proparian (Phacopina and Cheirurina), gonatoparian (Calymenina) or opisthoparian (Calymenina),
  • Preglabellar field often very short or absent.
  • 4 or fewer pairs of glabellar furrows.
  • Eyes : when present, schizochroal (Phacopina) or holochroal (Cheirurina and Calymenina).
  • With rostral plates (Calymenina and Cheirurina) or without (some Phacopina).
  • Hypostome conterminant (all suborders) to impendent (some devonian Phacopina).
  • Exosqueletton generally granulous.
  • Thorax: 8 – 19 segments, sometimes distinctly furrowed.
  • Axis sometimes broad (e.g., Homalonotidae).
  • Pygidium : Typically micropygous (most Calymenina and Phacopina), but variable (e.g., subisopygous in Dalmanitoidea and Acastoidea).
  • May be lobed or spiny (e.g., Cheirurina, some Dalmanitoidea, Acastoidea), or smooth-margined, with round or subtriangular outline (e.g., Calymenina, Phacopoidea).
Suborder Calymeninæ SWINNERTON 1915
  • Cephalon: Semicircular to subtriangular.
  • Typically with gonatoparian sutures (a few opisthoparian, e.g., Bathycheilidae, primitive Homalonotidae).
  • Glabella narrowing forwards.
  • Eyes holochroal, often small.
  • Hypostome conterminant.
  • Rostral plate present.
  • Thorax: 11 – 13 (typically 13) segments with rounded tips.
  • Pygidium: Semicircular or triangular.
  • Without spinose margin.

Family

 

Calymenidæ

 

BURMEISTER 1843

 
  • Cephalon : Semicircular and convex.
  • Glabella bell-shaped or parabolic
  • Glabella widest across occipital ring or preoccipital.
  • May or may not project in front of genae.
  • 2 to 4 pairs of lateral furrows.
  • Lateral lobes of glabella diminishing in size forward, tending to be isolated by shallow furrows from median lobe and independantly convex (2nd and 3rd lateral lobes - L2 and L3 - may be papillate).
  • Axial furrows bordering lateral glabellar lobes deep.
  • Anterior pit deep.
  • Relatively small eye lobes, situated on the highest part of genae opposite to L2 or L3.
  • Low eye ridges may be present.
  • Convex lateral border clearly defined by broad furrows.
  • Frontal area variable in length (sag.), in some form extending into frontal spine.
  • Connective sutures converging backwards.
  • Doublure rolled under borders and not extending inside them.
  • Hypostoma longer than wide, with subovate middle body.
  • Posterior lobe of the hypostoma crescentic.
  • Large anterior hypostomal wings.
  • Thorax : 12 ou 13 segments.
  • Axis convex .
  • Deep articulating furrows and apodemal pits.
  • Pygidium : Axis extending almost to posterior margin.
  • Axis sloping steeply backward and sideward.

Subfamily

 Colpocoryphiinæ

HUPÉ 1855
  • Cephalon : Semicircular to semielliptical, much wider than long.
  • Border defined in front only, very narrow, touching front of glabella. in anterior view, strongly bent down at sides.
  • Glabella narrowing forward considerably, with smoothly convex sides, anterior end truncate.
  • Circumglabellar furrows sharp and rather deep.
  • 2 - 4 pairs of lateral glabellar furrows.
  • Eyes usually far forward.
  • Eye lobes strinkingly small, not elevated above genæ, hardly interrupting general course of facial sutures.
  • Weak eye ridges may be present.
  • Fixigenæ very wide (tr.)
  • Posterior sections of facial sutures forming evenly convex curves that cut margins of cephalon near genal angles.
  • Rostral suture apparently on anterior margin.
  • Thorax : Well-marked moderately wide axis.
  • Pygidium : Transversely elliptical or subtriangular, wider than long.
  • Trilobation distinct.
The Subfamily includes 2 genera : Colpocoryphe and Salterocoryphe (Plaesiacomia has been revised as a Kerfonellinae).

Genus

Colpocoryphe

NOVAK in PERNER 1918

Occurence : Llanvirn - Llandeilo. Europe, N. Afriqua, N. America, Asia.

  • Cephalon : Convex.
  • Trapezoidal glabellea, frequently distinctly furrowed and surelevated compared to the axis.
  • Dorsal furrows slightly convergent forwardly with almost linear anterior parts.
  • Broad dorsal furrows, deep and not well defined.
  • 3, rather 4, well defined lateral furrows
  • Librigenæ without lateral area or lateral furrow.
  • Preglabellar field very short (sag.), downward oriented.
  • Inflated occipital ring with smooth lateral ends.
  • Occipital furrow broad and deep.
  • Eye ridges rather weak.
  • Anterior cephalic notch marked, with frequently parallel edges.
  • Thorax : Strongly convex axis.
  • Pygidium : Triangular.
  • Convex axis, with segmentation well defined.
  • 6 - 8 axial rings.
  • Pleurae with deep border furrows.
  • Axis extending nearly to posterior margin (large posterior terminal piece), connected to it by short postaxial ridge.
  • Pleural fields behind articulating half-ribs nearly smooth, with 2 - 3 very indistinct ribs.
  • Wide border distinctly set off by marked change in convexity.

Species

grandis

(SNAJDR 1956)

 

Average sized trilobite, to 11 cm in length.

  • Cephalon : Strongly convex glabella, with parabolic outline, forwardly bent.
  • Very short (sag.) preglabellar area.
  • Wide anterior notch of the cephalon (tr.).
  • Eyes located very forwardly.
  • Posterior angles of L2 obliqued to the antero-border angles (resulting in a sharpening of L2 laterally).
  • Broad posterior fields of the fixigenae (sag.).
  • Pygidium : General outline with 5 angles.
  • Axis funnel-shaped, about half the pygidium in width.
  • 7 axial rings.
  • Posterior terminal piece barely widening.
  • Inner part of the pleurae bearing a hardly noticeable rib.
  • Border furrows broad and flat.
  • Posterior edges angle of convergence acute.

 

Discussion :

Colpocoryphe differs from Salterocoryphe HAMMANN 1977 by a shorter, downward oriented, preglabellar area; by more posterior eyes, on proeminent eyestalks situated; by a pygidium, which reminds for Salterocoryphe the one of Neseuretus (Neseuretus) with thin border furrows, crossed by the pleural segmentation.

Colpocoryphe differs from Plaesiacomia HAWLE & CORDA 1847 by a more convex glabella and by more distinct lateral furrows. The glabella of Plaesiacomia is bell-shaped, and, on the pygidium, the border furrows are distinctly situated after the end of the rachis (Remind that Plaesiacomia has been included in the Kerfonellinae).

Colpocoryphe grandis differs from C. rouaulti mostly by its larger size and a wider anterior notch of the cephalon, by longer glabellar furrows S2, by eyes located farther from the dorsal furrows and, on the pygidium, by narrower and less deep dorder furrows and by a more developped terminal axial piece, flanked by distinct aliform outgrowths.

To illustrate another (classical) mistake between Colpocoryphe and Flexicalymene, one will recall C. poronai (PELLIZARI 1913) of China, which is indeed a Flexicalymene. (cf. HAMMANN 1983).

 

Complementary pictures :

Colpocoryphe grandis

 

Lateral and frontal view of specimen SMF 27938a. (After HAMMANN 1983)

 

Dorsal view of specimen SMF 27938a. (After HAMMANN 1983)
Frontal view of specimen SMF 27938a. (After HAMMANN 1983)

 

Type-scheme of the cephalon. a - dorsal view . b - frontal view. c - Hypostoma. (After HAMMANN 1983)
Type-scheme of the pygidium. d- dorsal view. e - lateral view. f - rear view. (After HAMMANN 1983)

 

Colpocoryphe rouaulti

 

Type-scheme of the cephalon. a - dorsal view adult stage. b - dorsal view immature stage. c - Hypostoma. (After HAMMANN 1983)
Type-scheme of the pygidium. d- dorsal view. e - lateral view. f - rear view. (After HAMMANN 1983)

 
Complete rolled specimen. Frontal and lateral views. See coaptation structures. SMF 27931. (After HAMMANN 1983).

 

Dorsal view. Specimen SMF 27931 (After HAMMANN 1983)

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