page_title: List of the Paleozoic life of Pennsylvania
section_title: O
hierarchical_section_title: List of the Paleozoic life of Pennsylvania / O
caption_attribution_description: Orthacanthus seckenbergianus, pencil drawing
context_page_description: This list of the Paleozoic life of Pennsylvania contains the various prehistoric life-forms whose fossilized remains have been reported from within the US state of Pennsylvania and are between 541 and 252.17 million years of age.
context_section_description: †Octonaria
  †Octonaria bifurcata
  †Octonaria dicristata
  †Octonaria quadricostata
  †Ogygopsis
  †Ogygopsis klotzi
  †Olenellus
  †Olenellus alius
  †Olenellus similaris
  †Olenellus wanneri
   †Olenoides
  †Olenoides buttsi – type locality for species
  †Olenoides pennsylvanicus – type locality for species
  †Olenoides serratus
  †Olethroblatta
  †Olethroblatta americana – type locality for species
  †Orbiculoidea
  †Orbiculoidea tullia
  †Orsadesmus – type locality for genus
  †Orsadesmus rubecollus – type locality for species
   †Orthacanthus
  †Orthacanthus compressus
  †Orthacanthus platypternus
  †Orthacanthus texensis
  †Orthoceras
  †Orthograptus
  †Orthograptus quadrimucronatus
  †Orthomylacris
  †Orthomylacris alutacea – type locality for species
  †Orthomylacris analis – type locality for species
  †Orthomylacris cordiformis – type locality for species
  †Orthomylacris mansfieldi – type locality for species
  †Orthomylacris pauperata – type locality for species
  †Orthomylacris pennsylvaniae – type locality for species
  †Orthomylacris pittstoniana – type locality for species
  †Orthomylacris pluteus – type locality for species
  †Orthonota
  †Orthonota parvula – tentative report
  †Orthonota undulata
  †Orthonychia
  †Orthonychia parva
  †Orthotetes
  †Orthotheca
  †Orthotheca shriveri – type locality for species
  †Oryctocephalus
   †Osteolepis
  †Oulodus
  †Ovatia
  †Oxynoblatta
  †Oxynoblatta vicina – type locality for species
  †Ozarkodina
caption: Life restoration of the Carboniferous-Permian freshwater shark Orthacanthus
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