. The animans and man; an elementary textbook of zoology and human physiology. Cambrian Algonkian.tian. Lauren- Birdlike reptiles; flying reptiles; toothed birds; first snakes; bony fishes abound; sharks again numerous.First birds; giant reptiles; am-monites; clams and snails abundant.First mammals (a marsupial); sharks reduced to few forms; bony fishes appear. Earliest of true reptiles. Amphi-bians; lung fishes; fringe fins;first crayfishes; insects abun-dant; spiders; fresh-watermussels. First amphibians (froglike ani-mals); sharks; ostracophores;first land shells (snails); mol-luscs abundan

- Image ID: 2AFPE15
. The animans and man; an elementary textbook of zoology and human physiology. Cambrian Algonkian.tian. Lauren- Birdlike reptiles; flying reptiles; toothed birds; first snakes; bony fishes abound; sharks again numerous.First birds; giant reptiles; am-monites; clams and snails abundant.First mammals (a marsupial); sharks reduced to few forms; bony fishes appear. Earliest of true reptiles. Amphi-bians; lung fishes; fringe fins;first crayfishes; insects abun-dant; spiders; fresh-watermussels. First amphibians (froglike ani-mals); sharks; ostracophores;first land shells (snails); mol-luscs abundan
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Image ID: 2AFPE15
. The animans and man; an elementary textbook of zoology and human physiology. Cambrian Algonkian.tian. Lauren- Birdlike reptiles; flying reptiles; toothed birds; first snakes; bony fishes abound; sharks again numerous.First birds; giant reptiles; am-monites; clams and snails abundant.First mammals (a marsupial); sharks reduced to few forms; bony fishes appear. Earliest of true reptiles. Amphi-bians; lung fishes; fringe fins;first crayfishes; insects abun-dant; spiders; fresh-watermussels. First amphibians (froglike ani-mals); sharks; ostracophores;first land shells (snails); mol-luscs abundant; first crabs.First truly terrestrial or air-breathing animals; first in-sects; corals abundant; mailedfishes. First known fishes, ostracophores,mailed and with cartilaginousskeleton; brachiopods; trilo-bites, molluscs, etc. Invertebrates only. Simple marine invertebrates. 282 THE ANIMALS AND MAN species of all the great groups from simplest to higher areliving today. Most of these species are however modernin their origin. The original or first species in all the great ,. FIG. 153. Skeleton of Hesperornis regalis, the Giant Toothed Bird ofthe Kansas Cretaceous. (In the American Museum of Natural History;after Sternberg.) groups are gone; and some whole families and orders ofspecies are extinct. For example in the class of reptilesthere existed in the Mesozoic era many enormous kinds FOSSIL ANIMALS 283 called Dinosaurs, Ichthyosaurs, Pterodactyls, etc., of whichno living representatives are left. Some of these reptileshad wings (Pterodactyls) and seem more like great birdsthan true reptiles. In the bird class, too, there were, in thesame era, various enormous kinds now extinct, some of whichhad teeth. An interesting example of the geologic succession ofrelated animals and one often referred to in books aboutextinct animals, is that of the horse series. In lower Eocenerocks is found an animal called Eohippus, about the sizeof a fox, with four hoofed toes and the rudiment of a f

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