Specimen description :

• Positive.
• On matrix.
• Complete specimen up to 99 %.
• Total size : 41 mm.
• Middle Devonian - Upper Eifelian.
• "Barre de calcaire grèseuse, zone à Pinacites jugleriI".
• Assa, Morocco.

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."

• Cephalon : Cephalic anterior border anteriorly prolonged in a tongue.
• Anterior furrows converging toward this tongue in front of the anterior border of the glabella.
• Pre-sulcal depression, basin-like, delimited by the cephalic anterior border and the anterior furrows, which is prolonged either in flat and narrow furrows into the librigenæ, either in suture into the moderatly inflated anterior border, thus participating into the cranidium delimitation.
• Preglabellar area very narrow (sag.) or lacking.
• Subquadratic glabella, contracted at middle.
• Eyes large, close to the posterior furrows.
• Genal points very long, backward oriented, almost reaching the distal part of the pygidium in projection.
• Thorax : 10 segments.
• Pygidium : very broad (tr.) and short (sag., exsag.).
• Subtrapezoidal rounded outrim.

• Cephalon : Strongly vaulted (tr.).
• Inflated anterior border.
• Librigenæ vaulted, smooth.
• Pre-sulcal depression distinct and broad (sag.).
• Distinct anterior furrows narrow, in continuity of the preglabellar furrows.
• Preglabellar area lacking (sag.).
• Subquadratic glabella, contracted at middle, the anterior distinctly diverging backward.
• Frontal glabellar area of the glabella relatively flat.
• Very thin sculptures on the exosqueletton of the glabella and on the occipital ring ("scale-like").