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Hypagnostus parvifrons Trilobite


House Range, Marjum formation of central Utah
Cambrian Period (570-540 million years ago)
Trilobites of the order Agnostida are mmall trilobites (usually only a few mm long) with cephalon and pygidium strongly similar in outline and size (isopygous); enrollment typical. Cephalon: cephalic shield with deeply parabolic outline, maximum width usually anterior of genal angle, sutures proparian or lacking; border convex; glabella fusiform, widest at base (except in Condylopygidae), glabellar segmentation highly variable, sometimes complex, but in some species entirely effaced; most species eyeless; hypostome natant, specialized with ribbon-like wings; rostral plate lacking (or uncalcified).  Thorax: segments 2 (Agnostina) or 3 (some Eodiscina), axis typically broad, short fulcrate pleurae.  Pygidium: strongly isopygous; pygidial margin typically closely matching cephalic margin.  Occurrence: L. Cambrian to U. Ordovician (Ashgill).
Kingdom: Animalia
Pylum: Arthropoda
Class: †Trilobita
Order:  †Agnostida
Family: †Spinagnostidae
Genus: †Hypagnostus
Species: †parvifrons

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