Ornamentaspis triangularis Geyer 1990

The genus is characterized typically by a midial spine (occipetal spine) on the back of the head (cephalon).  The furrows on the glabella can be seen faintly (O.frequens) or barely discernible (O.angustigena) depending on the species.  The glabella itself is visible unlike Kingaspis.   Typically, the anterior of the glabella is defined and separate from the anterior border area in contrast to Kingaspoides. 

The top three photos are of the cephalon only showing the characteristic occipital spine.  The species triangularis as the name suggests shows a prominent triangular occipital ring on the back (posterior) of the head that precipitates into a spine.  Photo 1 shows the cephalon which has the limonite (orange) rubbed off, missed perhaps by the preparator who was prepping an adjacent trilobite. The third photo shows an adjacent Acadoparadoxides residing on the same layer, betraying the telltale assemblage from which this comes from, the Lower Middle Cambrian.  

 

 

The following photos below are of a fully articulated and prepped O.triangularis. It is rare to find a fully prepped specimen as these are often overlooked being rather small trilobites of 50mm or less. Note the fully prepped spine, how prominent and "fang" like it is.  The second and third photos show the relative convexity of the glabella and palpebral lobes.  The palpebral lobes are prominent and flare outward from the cranidium.  The square trapezoidal glabella with faint furrows is typical of Ornamentaspis and can be seen very well here.  There are thirteen visible thoracic segments but one may be tucked underneath.  The pygidium is not visible.  There is a relatively wide pre-glabellar field and a convex anterior with no rim. The genal spines are short but stout.  Jebel Wawrmast Formation, Tougacht, Morocco.

 

Kenjiro Hakomori 2009.5.5 (Revised 2019.12.2)