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WEEKS FORMATION
Upper Middle Cambrian ~ 501 Mda
Carlo Kier Collection II
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The genus Modocia is one of the mostest common trilobites found in the Weeks Formation.
In this page are visible two type of Modocia: Modocia weekensis type 1 and Modocia weekensis type 3.
M. weekensis type 3 (upper left and center images, with meraspid and probably holaspid forms) has a free genal spine longer than M.weekensis type 1 and a a small suite of nodes are visibles on the axial rings.
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Modocia n.sp.
Ord.: PTYCHOPARIIDA
Fam.: MARJIMIIDAE
Gen.: Modocia WALCOTT, 1924b
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Norwoodia sp. (Shanan Peters dissertation, 2003, unpubl.)
Ord.: PTYCHOPARIIDA
Fam.: NORWOODIIDAE
Gen.: Norwoodia WALCOTT, 1916a
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On the upper left N. sp. is associated with Cedaria.
The agnostid near the fixigenal spine in the upper right image belong to Triadaspis bigeneris specie.
Ventral view of N. sp. (lower right image); in the center of the cephalon is visible the hypostome plate.
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Selenocoryphe platyura (nomen nudum)
(Shanan Peters dissertation, 2003, unpubl.)
Ord.: PTYCHOPARIIDA
Fam.: -
Gen.: Selenocoryphe BEEBE 1990
In the upper righ image is visible Genevievella granulatus. Particular is the axial spine due probably to abnormality development (follow the link above for a better image resolution of the specimen).
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Tricrepicephalus coria
Ord.: PTYCHOPARIIDA
Fam.: TRICREPICEPHALIDAE
Gen.: Tricrepicephalus KOBAYASHI, 1935c
Tricrepicephalus species referred to as T. coria, have been synonomized with T. texanus (see Pratt, 1992, Peters, 2003), although this is not as yet universally accepted. The jury is still out until more specimens of Tricrepicephalus are found (extracted from http://westernta.com/Formations/Weeks.htm
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Weeksina unispina (Walcott, 1916)
Ord.: PTYCHOPARIIDA
Fam.: LONCHOCEPHALIDAE
Gen.: Weeksina RESSER, 1935
The specimen showed in the center and upper righ show a double spine in correspondance of the axial spine. This can be due to a growing abnormality or belong to a new specimens not yet studied.
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Order: CORYNEXOCHIDA
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Cephalon with opisthoparian sutures; glabella elongate, sides often concave (pestle-shaped), furrows (when not effaced) typically with splayed arrangement, the hind pair pointing sharply backwards, and anterior pairs tending more and more forward directed; sometimes furrows pit-like; cranidial borders often ledgelike; hypostome conterminant or (in derived forms) impendent; eyes typically large, in some gently arcuate. Thorax typically with 7-8 segments (but range for order is 2-12, rarely more), pleural tips often spinose. Pygidium typically large (isopygous or subisopygous), of variable form, sometimes spinose.
From: http://www.trilobites.info/ordcorynexochida.htm
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Olenoides sp.
Ord.: CORYNEXOCHIDA
Fam.: DORYPYGIDAE
Gen.: Olenoides MEEK, 1877
Big incomplete specimens of pigydium of Olenoides. Extremely rare are these specimens and only two are found complete in the Weeks formation.
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Undescribed trilobite
Ord.: -
Fam.: -
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This species of trilobite is extremely rare and scientists don’t know at what genus or species this trilobite belong. Other particularity is the dimension (compared with the other trilobite fauna of Weeks frm.), that makes “Undescribed” one of the largest trilobites found in the Weeks Formation.
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 "Trilobites distribution pour my site_Corynexochida_icone")
Club Paleontologico Italiano
