14. Ptychagnostus.
Sightless agnostids, an early order of minuscule trilobites characterized by their lack of eyes, greatly reduced thoracic (mid-section) segments, and a planktonic, drifting lifestyle in dark, murky marine environments not conducive to vision. From the Middle Cambrian of Utah. Private collection.

15. Gogia kitchnerensis.
Excellently preserved eocrinoids, early ancestral echinoderms from the Middle Cambrian of Utah. Private collection.

16. Cryptozoon proliferum.
This ancient stromatolite, a complete colony of blue-green algae, has been extinct since the appearance of grazing organisms over half a billion years ago. Late Cambrian, New York. Monroe Community College.

The Burgess fauna. An assemblage of early creatures following the sudden widespread appearance of established animal populations known as the “Cambrian explosion.” 4 perfectly preserved victims of a catastrophic undersea mudslide 530 million years ago. From the Middle Cambrian Burgess Shale of British Columbia. U .S. National Museum.

17. Olenoides serratus.
Small and widespread spined trilobite belonging to the corynexochid order. In a rare state of preservation, exhibiting antennae and legs with gills and chewing bases, a passive scavenger of the muddy sea floor characterized by eyes of medium size and a pygidium (tail) of smaller size than its cephalon (head).

Sidneyia inexpectans.
Early predators arthropod, known to feed on small trilobites, characterized by its segmented body and fan-shaped tail, exhibiting combined characteristics of arthropod groups that later diverged (chelicerates and crustaceans).

18. Pikaia gracilens.
Tiny, muscular marine organism, a free-swimming filter-feeder and the earliest known chordate, direct ancestor of the vertebrates.

Waptia fieldensis.
Primitive early arthropod of unique anatomical form, a vaguely shrimplike creature of unknown relationships.

19-36. Trilobites.
A chronological progression of the vastly diversified primordial arthropods, marine Invertebrates comprising 8 distinct orders and representing every period of the Paleozoic Era from their sudden appearance and rapid proliferation in the Early Cambrian to their dwindling extinction in the Permian. From private collections.

37. Isotelus maximus.
A rare, primitive giant trilobite of the ptychopariid order, capable of plowing and digging in the mud, where its life was spent crawling and burrowing. Preserved traces of color patterns in some specimens indicate that the species was elaborately striped. Ordovician, Ohio. Private collection.

38. Homotelus bromidensis.
A spectacular cluster of gregarious ptychopariid trilobites in a mass burial along with cast-off moltings, distinguished by their simple eyes and enlarged cephalons and pygidia. Ordovician, Oklahoma. Private collection.

39. Dalmanites.
A rare, advanced giant trilobite of the phacopid order and early member of the dalmanitid family. distinguished by its complex eyes and diminutive telson (tail spike), a nocturnal bottom-dweller. Silurian, Tennessee. Private collection.

40. Eurypterus remipes.
Primordial sea scorpions preserved together with Eurypterus lacustris, advanced predatory arthropods, ancestors of the scorpion, characterized by their prominent paddles and sharp telsons. A third species, the ferociously armed Pterygotus macrophthalmus, is preserved below. Late Silurian, New York. Private collection.

41. Palaeoscorpius devonicus.
Early amphibious scorpion, among the first creatures to leave the sea, a venomous predator from the Late Devonian deep marine deposits of Germany. University of Bonn.

42. Cephalaspis lyelli.
Primitive jawless fish with a sensory dorsal shield, an armored, mud-filtering marine scavenger exhibiting a tiny but well-preserved pineal opening (“third eye”). Early Devonian, Scotland. Royal Scottish Museum.

43. Acanthocrinus rex.
A magnificent early crinoid, a tentacled filter-feeding animal related to starfish. Early Devonian, Germany. Humboldt Museum.

44. Drepanaspis gemuendensis.
Primitive agnathan (jawless fish), an early vertebrate, an armored and flattened, bottom-dwelling marine scavenger. Early Devonian, Germany. Humboldt Museum.

45. Cheiracanthus.
A “spiny shark”, among the earliest of predatory jawed fishes, from the Middle Devonian of Scotland. Private collection.

48. Phacops africanus.
A giant phacopid trilobite with excellently preserved compound eyes, each composed of over 100 individual lenses, characterized by its large eyes, a granularly decorated glabella (face), and the ability to enroll. Devonian, Morocco. Private collection.

49. Bothriolepis canadensis.
A spectacular school of early placoderms, primitive armored fish with jaws and lungs, from the Late Devonian of Canada. American Museum of Natural History.

50. Dunkleosteus terrelli.
Jaw of the earliest known giant predator, a massive placoderm, from the Late Devonian of Ohio. Private collection.

51. Eusthenopteron foordi.
Advanced crossopterygian fish, an air-breathing, predatory, freshwater lobe-fin, the direct ancestor of tetrapod amphibians. Late Devonian, Canada. Royal Ontario Museum.

52. Ichthyostega.
Skull reconstruction of the earliest known tetrapod amphibian, a 7-toed predator retaining a fishlike tail fin and exhibiting a “third eye” inherited from its fish ancestors. Late Devonian, Greenland. Swedish Museum of Natural History.

53. Paleozoic Sea Floor.
Crinoids, brachiopods, coral, a half-buried trilobite and a trilobite trackway from the Mississippian of Indiana. Private collection.

54. Ulrichicrinus coryphaeus
Actinocrinites gibsoni
Dorycrinus gouldi
Taxodrinus colletti
Sarocrinus nitidus
Agaricocrinites americanus.
Exquisitely preserved crinoids rendered in bouquet, 6 species from the Age of Crinoids. Late Mississippian, Indiana. Private collection.

55. Essexella asherae.
An ancient colonial organism preserved in concretion, this Paleozoic jellyfish is from the Pennsylvanian of Mazon Creek, l1lionois. Private collection.

56. Neuropteris rodgersi.
Early vascular seed fern of the primordial Coal Age swamps, from the Pennsylvanian of Kansas. Private collection.

57. Annularia stellata.
An early scouring rush of the Coal Age swamps, from the Pennsylvanian of Kansas. Private collection.

58. Calamites.
Trunk of the giant, tree-sized scouring rush of the coal forests, from the Pennsylvanian of Utah. Brigham Young University.

59. Lepidodendron aculeatum.
Bark of the arborescent lycopod, among the tallest and most abundant trees of the coal forests. Pennsylvanian, Utah. Brigham Young University

60. Stigmaria.
Prior to their recognition as the root systems of lycopods, these isolated fossils were separately described as Stigmaria. From the Pennsylvanian of Michigan. Brigham Young University.

61. Lepidophyllum.
This genus was established to describe the fossilized foliage of lycopods not found in association with the rest of the plant. Pennsylvanian, Utah. Brigham Young University.

62. Urogomphus giganteus.
Large advanced dragonfly from the Late Jurassic of Germany and direct descendant of the primitive winged insects of the Carboniferous coal swamps. Humboldt Museum.

63. Eoscophus lockardi.
Near complete skeleton of an early terrestrial amphibian, from the Pennsylvanian of Kansas. Private collection.

64. Mylacris.
Early giant cockroach, an advanced winged insect of the coal forests, ancestral to beetles, ants, and bees. Pennsylvanian, Kansas. Private collection.

65. Cephalerpeton ventriarmatum.
Near complete skeleton of an early cotylosaur, one of the oldest vertebrates recognized as a reptile, able to lay eggs on dry land and ancestral to birds, mammals, and all other subsequent reptile groups, with preserved ventral scales, from the Pennsylvanian of Illinois. Yale Peabody Museum.

66. Eocaptorhinus laticeps.
Skull of the advanced captorhinomorph, among the earliest and most primitive reptiles, with a very conspicuous “third eye.” from the Early Permian of Oklahoma. Oklahoma Museum of Natural History.

67. Seymouria baylorensis.
Skeletons of the terrestrial amphibian exhibiting features characteristic of reptiles, from the early Permian of Texas. U.S. National Museum (Smithsonian Institution.)

68. Eryops megacephalus.
Skulls of the large terrestrial amphibian, an advanced predator, able to walk without crawling on its belly. Early Permian, Texas. Private collection.

69. Diplocaulus magnicornis.
Skulls of the small, aberrant pond-dwelling amphibian, uniquely equipped for combative head-butting during mating competition. Early Permian, Texas. Private collection.

70. Dimetrodon limbatus.
Magnificent skeleton of the primitive fin-backed pelycosaur, a giant predatory mammal-like reptile equipped with an archaic system for regulating its blood warmth and exhibiting a ferocious arcade of palatine teeth. Early Permian, Texas. Brigham Young University.

71. Aerosaurus wellesi.
Skeleton of a juvenile pelycosaur (including partial skeletons of Sphenacodon and Eryops), an archaic mammal-like reptile with a largely aquatic lifestyle. Early Permian, New Mexico. University of California, Berkeley.

72. Mesosaurus brasiliensis.
Skeleton of the primitive web-footed marine reptile of Africa and South America, evidence of the former union of the 2 continents. Early Permian, Brazil. University of California, Los Angeles.

73. Mesosaurus africanus.
Skeleton of the early marine reptile of Africa, the earliest known aquatic animal descended from terrestrial ancestors. Early Permian, South Africa. Private collection.

74. Dicynodon grimbeeki.
Skulls of the advanced, tusked mammal-like reptiles, from the Middle Permian of South Africa. University of California, Berkeley.

75. Broomisaurus laticeps.
Skull of the large, saber-toothed gorgonopsid, an advanced predatory mammal-like reptile, possibly warm-blooded. Middle Permian, South Africa. University of California, Berkeley.