TABULAR SUMMARY OF PALEOZOIC LIFE — Continued 



Molluscoids 



Mollusks 



Arthropods 



Vertebrates 



Bryozoans: 

 - Abundant. 



- Brachiopods: Still 

 common, with new 

 species; straight- 

 hinged forms still 

 prevail. 



Bryozoans: 

 ^ Jk Common. 



Brachiopods: Still 

 declining, but 



y fairly common; 



- straight-hinged 

 forms prevail. 



Pelecypods: Greatly in- 

 creased in numbers and 

 species. 

 Gastropods: Common: 

 Cephalojoods: Somee^rj, 



^noceras7 now common 

 and more, complex. 



Trilobites: Very rare and 

 become extinct, 

 rypterids: 

 ecome extinct. 



{sects: Much like the 

 Pennsylvanian. 



Fishes and Amphib- 

 ians: Much like the 

 Pennsylvanian, but 

 with new species. 



Reptiles: Many rep- 

 resentatives of the 

 lower orders. 



Pelecypods: Still increas- 

 ing. 



Gastropods: Common and 

 first land forms appear. 



Cephalopods: Similar to 

 Mississippian, but Nauti 

 loids declining and Am 

 monoids more comp" ' 



Bryozoans: More 

 abundant than in 

 the Devonian. 

 , .• Brachiopods: De- 

 \j dining but still 



common and with 

 ^ many new species; 

 ., mostly straight- 



hinged forms. 



lecnning anu aiii 

 4s more complix. 



Trilobites: Rare. 



Eucrustaceans: Present. 



Arachnids: Eurypterids 

 still declining; first Spi- 

 ders appear. 



Myriapods: Common. 



Insects: Common and 

 large; simpler types 

 only. 



Fishes: Much like 

 Mississippian. 



Amphibians: Culmin- 

 ate, e.g. Stegocepha- 

 lans. 



Reptiles: Present? 



Pelecypods: More com- 

 mon than before. 



Gastropods: Common. 



Cephalopods: Much like 

 the Devonian, but coiled 

 Nautiloids culminate 

 and Ammonoids are 

 more complex. 



Trilobites: Rare. 

 Eucrustaceans? 

 Arachnids: Eurypterids 

 declining. 



Myriapods: Present. 



Insects: No fossils. 



Fishes: Selachians in- 

 creasing; Dipnoans 

 declining; Arthrodi- 

 rans declining; Gan- 

 oids increasing. 



Amphibians: Present. 



:P, 



? Bryozoans: Present. 



|J Brachiopods: Cul- 

 minate in numbers 

 and species; many 

 new forms added; 

 mostly straight- 

 hinged forms. 



Pelecypods and Gastro- 

 pods: Much like the Si- 

 lurian. 



Cephalopods: Most earlier 

 forms persist, but Am- 

 monoids first appear, e.g. 



Goniatite. 



Trilobites: 

 Decline markedly. 



Eucrustaceans ^Common. 



Arachnids: Eurypterids 

 declining, but still not- 

 able for size. 



Myriapods: First known. 



Insects: Unknown. 



Ostracoderms: Culmi- 

 nate and become 

 extinct. 



Fishes: Very profuse, 

 e.g. Selachians, 

 Dipnoans, Arthrodi- 

 rans and Ganoids. 

 Amphibians? 



K 



Bryozoans: 

 Abundant. 



Brachiopods: Prom- 

 inent in numbers 

 and species ; nearly 

 all straight-hinged 

 forms. 



Pelecypods and Gastro- 

 pods: Common and much 

 like Ordovician. 



Cephalopods: Common 

 and much like Ordovi- 

 cian, but coiled Nauti- 

 loids predominate. 



Trilobites: Diminished 

 but still common. 



Eucrustaceans: Similar 

 to Ordovician. 



Arachnids: First Scorp- 

 ions ; Eurypterids culmi- 

 nate in numbers, species 

 and size (?). 



Ostracoderms: Rare, 

 small and primitive. 



Fishes : Selachians 

 of primitive charac- 

 ter and rare. 



Bryozoans: 

 Abundant. 



Brachiopods: More 

 complex, larger.and 

 abundant ; Articu- 

 lates prevail; and 

 nearly all are 

 straight-hinged 

 forms. 



Pelecypods: Larger and 

 more common. 



Gastropods: Common. 



Cephalopods: Very prom- 

 inent and all are Nauti- 

 loids, e.g. Orthoceras, 

 Cyrtoceras, Trochoceras 

 and Trocholites. 



Trilobites: Culminate in 

 numbers and species. 



Eucrustaceans: Few and 

 simple. 



Eurypterids: Present. 



Ostracoderms: Mark- 

 ing first appearance 

 of Vertebrates; speci- 

 mens rare and very 

 fragmentary. 



Bryozoans: Absent. 



Brachiopods: Small 

 thin-shelled; Inar- 

 ticulates prevail; 

 some Articulates in 



I the Upper Cam- 

 brian. 



Pelecypods: Very 

 and rare. 



Gastropods: Rare, simple 

 and mostly an the Upper 

 Cambrians 



Cephalopods: Rare, small 

 and simple; all Nauti- 

 loids e.g., Orthoceras an 

 Cyrtoceras. 



Crustaceans : Trilobites 

 common and usually 

 highly segmented and 

 with small tail plates; 

 some very simple forms. 



Eurypterids: Rare. 



None. 



d\^-.. 



^'/Wiv, 



