The Pitkin Formation, or Pitkin Limestone, is a fossiliferous geologic formation in northern Arkansas that dates to the Chesterian Series of the late Mississippian. This formation was first named the "Archimedes Limestone" by David Dale Owen in 1858, but was replaced in 1904. The Pitkin conformably overlies the Fayetteville Shale and unconformably underlies the Pennsylvanian-age Hale Formation. Some workers have considered the shales at the top of the Pitkin Formation to be a separate formation called the Imo Formation. More recently, others have considered the Imo to be informal member of the Pitkin Formation.
Paleofauna Early work aimed at creating a comprehensive list for all fossils found in the Pitkin Formation was done by Easton in 1943. Unless otherwise stated, all species below can be found in his 'Fauna of the Pitkin Formation.'
Foraminifera
Archaediscus A. stilus Asteroarchaediscus A. rugosus Earlandia Endothyra E. kleina E. phrissa Endothyranella Eosigmoilina E. explicata E. rugosa Eostaffella Eotuberitina Monotaxinoides Neoarchaediscus Nodosarchaediscus Paramillerella Planospirodiscus Plectogyra Priscella Pseudoammodiscus P. priscus Pseudoglomospira Tetrataxis T. corona Trepeilopsis Zellerina Z. designata Z. discoidea
Porifera, Sponges
Cliona
Scyphozoa Conularia Originally considered to be a gastropod.
Anthozoa, Corals
Amplexus Aulopora A. gracilis Caninostrotion C. variablilis Kinkaidia LesliellaWebb, Gregory., 1987., The Coral Fauna of the Pitkin Formation (Chesterian), Northeastern Oklahoma and Northwestern Arkansas. Journal of Paleontology vol. 61:3 Leonardophyllum Lonsdaleia L. major L. minor MichelliniaWebb., Gregory., 1990., A New Tabulate Coral Species from the Pitkin Formation (Chesterian) of north-central Arkansas. Journal of Paleontology vol. 64:4. M. macerimuris Parvaxon Pleurodictyum P. eugenei P. meekanum Syringopora Triplophyllum
Blastoidea
Pentremites P. elongatus P. godoni P. laminatus P. obesus P. platybasis
Crinoidea, Sea Lilies
Agassizocrinus (see unidentified section) A. patulus Aphelecrinus A. planus Bronaughocrinus B. figuratus Camptocrinus Carinocrinus C. stevensi Castillocrinus Catillocrinus Cosmetocrinus C. eventus Cromyocrinus Culmicrinus Cyathocrinus Delocrinus Dichocrinus Hydreionocrinus Linocrinus L. floweri Onychocrinus O. pulaskiensis Pachylocrinus Paianocrinus P. aptus P. durus Paracymbiocrinus P. pitkini Pelecocrinus P. stereostoma Pentaramicrinus P. modulus Phacelocrinus Phanocrinus P. cooksoni P. irregularis Poteriocrinus Pterotocrinus P. tridecibrachiatus Scytalocrinus (see unidentified section) S. braggsi S. dunlapi S. garfieldi Taxocrinus T. whitfieldi Telikosocrinus T. caespes T. residuus Zeusocrinus Z. foveatus
Ophiuroidea, Brittle Stars This group was originally place under Stelleroidia in early studies. Aganaster A. singulatus Schoenaster
Echinoidea, Sea Urchins
Archaeocidaris
Worms Previous studies have grouped these diverse animals into a single, obsolete taxon: Vermes. Spirorbis
Bryozoa, "Moss-animals"
Anisotrypa A. solida Archimedes (called Archimedipora in early studies) A. communis A. compactoides A. compactus A. distans A. fosteri A. fragilis A. intermedia (A. intermedius) A. invaginata (A. invaginatus) A. lunatus A. magnus A. meekanus A. moorei A. pitkinensis A. proutana (A. proutanus) A. sublaxus A. swallovana (A. swallovanus) A. terebriformis Batostomella Chellotrypa C. distans Chilotrypa C. regularis Dichotrypa D. levis Dyscritella Fenestella F. cumingsi F. matheri F. rectangularis F. serratula F. tenax Fistulipora F. introspinosa Glyptopora G. crassa G. michilinia Lyropora L. solida Meekopora M. abrupta M. tenuis Polypora P. whitei Rhombopora Septopora S. biserialis S. cestriensis S. subquadrans Tabulopora T. cestriensis T. microfistulata T. poculoformis T refiexa T. subtilis
Brachiopoda
Adectorhynchus A. suspectum Athyris A. cestriensis Buxtonia B. arkansana Camarophoria C. cestriensis C explanata Chonetes C. oklahomensis C. sericeus C. tumescens Cliothyridina C. sublamellosa Composita (See unidentified section) C. subquadrata C. trinuclea Crania C. infimbriata Diaphragmus Dielasma D. arkansanum D. formosum D. illinoisensis D. shumardanum D. whitfieldi Echinoconchus (See unidentified section) E. alternatus Eumetria E. costata E. pitkinensis E. vera Girtyella G. indianensis Hustedia H. multicostata Krotavia K. lucerna Lingula Lingulidiscina L. newberryi var. moorefieldana and ovata Linoproductus L. pileiformis Martinia Orthotetes O. kaskaskiensis O. stenopsis O. subglobosus (var. protensa) O. uspectum Productus P. cestriensis P. fasciculatus Pustula Reticularia R. setigera Spirifer S. leidyi S. pellaensis Spiriferina S. spinosa Streptorhynchus Syringothyris S. aequalis Tetracamera T. neogenes
Bivalvia, Bivalves This group was also referred to by another name in earlier studies: Pelecypoda.
Allorisma A. walkeri Astartella Aviculopecten A. batesvillensis A. eurekensis A. keoughensis A. morrowensis A. multilineatus A. pitkinensis Conocardium C. peculiare Cypricardella (See unidentified section) Edmondia E. crassa (Along with E. crassa var. suborbiculoidea) E. pitkinensis Leda L. vaseyana Leiopteria Leptodesma Myalina M. compressa M. longicardinalis Nucula N. illinoisensis Parallelodon Pteronites Schizodus (See unidentified section) S. arkansanus S. chesterensis S. depressus S. insignis Solenomya Sphenotus S. cherokeense S. gibsonense S. quadriplicatum
Scaphopoda, Tusk Shells Laevidentalium
Gastropoda, Snails
Bellerophon (See unidentified section) B. pitkinensis Bucanella Colpites Euphemites E. incarinatus Clabrocingulum Gosseletina (See unidentified section) Helcionopsis H. reticulatus Hemizyga Holopea H. newtonensis Latischisma Leptoptygma (See unidentified section) Microptychis Mourlonia M. angulata Naticopsis Neilsonia Phanerotremas Platyceras P. subrotundum Pseudozygopleura Sphaerodoma S. subcorpulenta Stegocoelia Straparolus S. planidorsatus S. triliris Strobeus (See unidentified section) Strophostylus
Cephalopoda
Arcanoceras A. furnishi Coloceras (see unidentified section) Cravenoceras C. hesperium C. richardsonianum Cycloceras C. randolphensis C. equoyahensis Dolorthoceras (See unidentified section) D. eurekensis Eoasianites E. globosus Eumorphoceras E. bisulcatum Metadimorphoceras Mooreoceras Syngastrioceras Trizonoceras
Trilobita Grifithides G. pustulosus Kaskia K. chesterensis K. pitkinensis Paladin P. mucronatus
Ostracoda Glyptopleurain G. optina Paraparchites Primitia P. fayettevillensis
Vertebrata Cladodus Deltodus Petalodus
Plantae, Plants "Encrusting Algae" has been reported but not assigned to any genus. Archaeolithophyllum Asphaltina A. cordillerensis Girvanella Rectangulina
Unidentified Following is a list of fossils also found in the Pitkin by Easton in 1943 that have gone unidentified. A "Cup Coral" A member of the genus Pentremites Three species within Agassizocrinus Two species within Scytalocrinus A totally unidentifiable Crinoid Two species of Bellerophon Two species of Gosseletina Two species of Leptoptygma Two Species of Strobeus One species each of Composita and Echinoconchus Two species of Cypricardella Two species of Coloceras, one of which may actually be Leuroceras One species of Dolorthoceras An unnamed shark spine
See also
List of fossiliferous stratigraphic units in Arkansas Paleontology in Arkansas
References