C O R N U P R O E T I N A E

 

Here is presented an important sub-family for the collectors that present difficulties to identify its members. This is an attempt to summary of a work of PILLET 1972 : Les trilobites du Dévonien inférieur et du Dévonien moyen du Sud-Est du Massif Armoricain. Soc. Et. Sci. Anjou. Mém N°1.

One will note that PILLET classified the cornuproetinae in the proetidae (today in the Tropidocoryphidæ).

 

Order

Proetida

FORTEY & OWENS 1975

Typically small trilobites, recently separated from Ptychopariida (different larval development). One of the Libriostomate orders (natant hypostome or derived therefrom). Exoskeleton sometimes with pits or small tubercles.

Occurrence : Ordovician (Tremadoc) to Permian (Tartarian). The last of the trilobites was of this order (Phillipsiinae).

  • Cephalon : Opisthoparian sutures.
  • Glabella large, vaulted, well-defined, typically narrowing forward.
  • Typically 4 pairs of glabellar furrows with posterior-most pair longest and deepest, those anterior shorter and fainter.
  • Eyes, usually present, holochroal, often medium, convex, medial or posterior.
  • Rostral plate narrow and backward tapering.
  • Occipital ring well defined, typically bearing a median tubercle.
  • Long hypostome, most species natant, but some secondarily conterminant (e.g., late Proetidæ & Bathyuridæ).
  • Typically with genal spines.
  • Thorax : 6 – 22 (typically 8 - 10) segments.
  • Tips variable, blunt to long-spined.
  • Pygidium : Micropygous to subisopygous.
  • Often spineless.
  • Usually with 4 – 10+ distinct pleural furrows.

Superfamily

Proetoidea

SALTER 1864

 
  • Cephalon : Opisthoparian sutures.
  • Rostral plate narrow.
  • Glabella tapering or inverse pyriform, mostly suboval, with 3-4 pairs of lateral furrows, sometimes indistinct (e.g., Proetinae), or glabella long, expanding forward to anterior border furrow or beyond, with lateral preoccipital lobes present (e.g., Phillipsiinae).
  • Eyes, when present, typically holochroal, convex, close to the glabella.
  • Fixigenæ narrow, librigenæ broad, except in blind species.
  • Hypostoma typically natant, but secondarily conterminent in advanced Proetidæ.
  • Genal angle spined or blunt rounded.
  • Thorax : 8-10 segments (typically 10 in Proetinæ, 9 in Phillipsiinæ).
  • Pleuræ with furrows.
  • Tips blunt or spined.
  • Pygidium : Typically semicircular, with few segments, but some large, long, parabolic, with up to 33 axial segments.
  • Margin typically smooth, but some with terminal axial spine or pleural spines.
  • 6 - 11 axial rings.

Family

Proetidæ

SALTER 1864
  • Cephalon : Glabella large and gibbous.
  • Glabella smooth or incised by 1 to 4 pairs of glabellar furrows.
  • Glabellar lobes L1 sometimes isolated by very oblique S1 furrows.
  • Rostral plate of normal ptychopariid type, with junction sutures usually diverging.
  • Thorax : 8 to 10 segments.
  • Præannulus and distal ends rounded.
  • Pygidium : isopygous to mesopygous.
  • Rachis moderately long to long.
  • 5 to 30+ axial rings.
  • Pleural lobes to 14 pairs of ribs.
  • Limb frequently well developped.

Sub-family

Cornuproetinæ

RICHTER., RICHTER & STRUVE 1959

Flattened global shape.

  • Cephalon : Broad.
  • Glabella narrowing at its middle part, "violin-shaped."
  • Preglabellar field not very broad but always distinct.
  • Lateral furrows (3 pairs) distinguished by faint ornamentation, sometimes not apparent.
  • Occipital ring broad, not narrowing laterally.
  • Occipital lobes not – or only slightly – distinct.
  • Preocular sutures slightly divergent.
  • Palpebral lobes and eyes large to middle-sized.
  • Librigenae broad, ending in long genal spines.
  • Cephalon border striated.
  • Thorax : 10 segments (except Sculptoproetus with 9).
  • Pleurae smooth (except Xiphogonium).
  • Pygidium : Short.
  • 4 to 6 axial rings.
  • 3 pleurae, of "Gerastos type."
Occurence : Wenlockien – Frasnien.
Genus Cornuproetus (RICHTER 1919)

Type-species : Gerastos cornutus GOLDFUSS 1843.

Sub-genera according to PILLET 1972 :

  • Cornuproetus (Cornuproetus) RICHTER 1919
  • Cornuproetus (Buchiproetus) PILLET 1969
  • Cornuproetus (Macroblepharum) ALBERTI 1964
  • Cornuproetus (Tafilaltaspis) ALBERTI 1966
  • Cornuproetus (Voigtaspis) ALBERTI 1967
  • Cornuproetus (Sculptoproetus) ERBEN 1951
  • Cornuproetus (Richteraspis) ALBERTI 1969
  • Cornuproetus ? (Francenaspis) ALBERTI 1969
  • Cornuproetus ? (Proetopeltis) PRIBYL 1965
  • Xiphogonium HAWLE & CORDA 1847
  • Vicinoproetus ALBERTI 1967
  • ? Quadraproetus ALBERTI 1967
  • ? Phaetonellus NOVAK 1890
  • ? Cyrtosymboloïdes ALBERTI 1967

 

Observations : The genus Cornuproetus includes numerous species today split into several sub-genera. These sub-genera are extremely similar to each other and can be distinguished by details only. Nevertheless, this classification is important to help in identifying important species from a stratigraphic point of view.

Note : Diademaproetus was not considered by Pillet as a sub-genus of Cornuproetus, but of Lepidoproetus.

 

Sub-genus Cornuproetus (Cornuproetus) (RICHTER 1919)

Type-species : Gerastos cornutus GOLDFUSS 1843. Granulous exoskeleton.

  • Cephalon : Outline regularly rounded anteriorly.
  • Preglabellar field very narrow, almost lacking.
  • Limb striated only in periphery.
  • Palpebral lobes middle-sized.
  • Preocular sutures not very divergent.
  • Single occipital tubercle.
  • Pygidium : Strongly marked pygidial axial rings.
  • Pleural fields with 3 pleurae.
  • Limb broad, distinctly separated/marked.

Occurrence: Silurian – Mesodevonian. Europe, North Africa, Asia (Australia ?). Arctic Canada ? (see C. tozeri ORMISTON 1967) USA - Oklahoma ? ( see C. pictus contractus ORMISTON 1968) These 2 forms might belong to the genus Eremiproetus.

 

 

Sub-genus Cornuproetus (Buchiproetus) PILLET 1969

Type-species : Proetus buchi HAWLE & CORDA 1847. Granulous exoskeleton.

  • Céphalon : Anterior border ogival.
  • Concentric striations invading almost the totality of the limb.
  • Preglabellar field narrow, but distinct.
  • Palpebral lobes long and narrow.
  • Single tubercle on the occipital ring.
  • Preocular sutures not, or very slightly, divergent.
  • Pygidium : Strong axis, similar to Cornuproetus (Cornuproetus).

Occurrence: Upper Lower Devonian, lower MiddleDevonian.

 

 

Sub-genus Cornuproetus (Macroblepharum) ALBERTI 1964

Type-species : Cornuproetus (Macroblepharum) africanus ALBERTI 1964. Striated exoskeleton.

  • Céphalon : Anterior border rounded.
  • Glabella similar to Cornuproetus (Cornuproetus).
  • Preglabellar field narrow.
  • Limb striated at its periphery.
  • Palpebral lobes (and visual surfaces) very large, reaching ahead the former quarter of the glabella.
  • Single occipital ring.
  • Preocular sutures strongly divergent.
  • Pygidium : Limb hardly distinct.
  • Only the first two pleurae are distinct.

Occurrence: Upper Praguian. Eifelian, Morocco.

 

 

Sub-genus Cornuproetus (Tafilaltaspis) ALBERTI 1966

Type-species : Cornuproetus (Tafilaltaspis) creber ALBERTI 1966. Granulous exoskeleton.

  • Cephalon : Anterior border ogival.
  • Limb striated on three quarters of its surface.
  • Preglabellar field broad.
  • Palpebral lobes long and narrow.
  • Preocular sutures hardly diverging.
  • Single occipital ring.
  • Pygidium : Axis short.
  • Limb broad, defined by a thin concentric furrow.

Occurrence: Upper Praguian. Eifelian, Morocco.

 

 

Sub-genus Cornuproetus (Voigtaspis) ALBERTI 1967

Type-species : Cornuproetus (Voigtaspis) voigti ALBERTI 1967. Granulous exoskeleton.

  • Pygidium : Short and broad.
  • Axis trapezoidal with 4-5 rings.
  • Pleurae extend to and indent the posterior border.
  • Limb indistinct.

Occurrence: Praguian, Morocco.

 

 

Sub-genus Cornuproetus (Sculptoproetus) ERBEN 1951

Type-species : Proetus sculptus BARRANDE 1846. Striated exoskeleton.

  • Cephalon : Slightly ogival.
  • Glabella similar to Cornuproetus.
  • Preglabellar field rather broad.
  • Limb striated only on its peripheric edge.
  • Palpebral lobes middle-sized.
  • Single occipital ring.
  • Preocular sutures very divergent.
  • Thorax : 9 rings.
  • Pygidium : Relatively lengthened, with trapezoidal axis.
  • Limb indistinct.

Occurrence: Upper Silurian. Eiffelian. Bohemia, Germany, Morocco.

 

 

Sub-genus Cornuproetus (Richteraspis) ALBERTI 1969

Type-species : Cornuproetus bivallatus RICHTER 1913. Granulous exoskeleton.

  • Céphalon : Ogival.
  • Glabella definitely longer than broad.
  • Limb almost entirely striated.
  • Preocular sutures clearly divergent.
  • Palpebral lobes convex, middle-sized.
  • Two occipital tubercles.

Occurrence: Frasnian. Germany.

 

Sub-genus Cornuproetus ? (Francenaspis) ALBERTI 1969

Type-species : Prodrevermania ? deubeli ALBERTI 1967. Unknown exoskeleton.

  • Céphalon : Rounded.
  • Glabella tapering forward.
  • Border rolled up, striated.
  • Preglabellar field broad.
  • Single occipital tubercle.
  • Outline of eye ridges.
  • Palpebral lobes lengthened and slightly convex, the alpha point[*] being distant from the dorsal furrow.

Occurrence: Praguian. Germany.

Observation : This sub-genus might belong to Lepidoproetinae, due to its anterior border rolled up and concave.

[*] : what I translated "alpha point" is the point where the facial suture reaches anteriorly the cephalic border. It should be written in greek, but yahoo won't accept it.

 

Sub-genus Cornuproetus ? (Proetopeltis) PRIBYL 1965

Type-species : Proetus neglectus BARRANDE 1852. Granulous exoskeleton.

  • Cephalon : Hardly ogival.
  • Very distinct glabella.
  • Limb entirely striated.
  • Preglabellar field very narrow.
  • Palpebral lobes very long and very narrow, reaching the former anterior quarter of the glabella.
  • Preocular sutures converging.
  • Single occipital tubercle.
  • Librigenae narrow with simple acute genal angle, without spine.
  • Pygidium : Similar to Cornuproetus.

Occurrence : Upper Lower Devonian ? – Middle Devonian. Bohemia, Germany, Morocco.

Observation : the attribution to the Cornuproetus genus is doubtful because of the narrow preglabellar field and the absence of genal spines. This sub-genus doesn't belong tohte genus Proetus, but the cephalon is very similar to Quadraproetus. The pygidia are very different though.

 

 

Jean PILLET. Les trilobites du Dévonien inférieur et du Dévonien moyen du Sud-Est du Massif Armoricain. Soc. Et. Sci. Anjou. Mém N°1. 1972

 

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