15 of 15 people found the following review helpful
Tim F. Martin
- Published on Amazon.com
_Dawn of the Dinosaurs_ by Nicholas Fraser is a popular overview of the first period of the Mesozoic Era, the Triassic Period. The author mostly concentrated on the various vertebrate animals that existed during this period though spent a good deal of time on the ecology of various locales as well as invertebrate life and plants. The text is quite readable by the interested layperson though one may have to consult the book's glossary a number of times; at the very least it can be seen as something of a vocabulary builder, as I learned such words as edentulous (lacking teeth) and allochthonous (basically a fossil formed in a place other than where the organism once lived). The anatomical terms like proximal tarsals and elongate ulnare though I had less success with, despite the glossary and the appendix discussing tetrapod anatomy.
Still, the book did introduce me to many animals I knew nothing about and given that I am something of an amateur paleontology buff that is saying something. Also, even if one didn't read a single word of text I would definitely say go and get this book owing to the simply spectacular and gorgeous artwork of Douglas Henderson.
Part one consisted of three chapters and looked at the Early Triassic, setting the stage for the period's climate, geography, geology, fauna, and flora. The world was quite a bit different 240 million years ago; there was only one continent (Pangaea), no polar ice caps, and the world's dry zones were on the equator (not today, where they are centered 30 degrees north and south). Though there is still considerable debate, a megamonsoon system seems to have dominated the world's climate. Although there was considerable regional variation, overall the world was warmer and more arid, particularly in the Early and Middle Triassic.
Fraser did not note that some ideas of the Triassic being a desert planet of sorts is influenced by the knowledge that vast areas of today's world are covered by grasslands, and since grass didn't exist back then; "artists and paleontologists have unwittingly enhanced the view of the Triassic world being an unforgiving place, with sparse ground cover." In reality it is quite likely some other plant filled in the grass niche back then. Also, such desert-dominated depictions don't seem to be able to account for how large herbivores might have survived.
A number of extinct shark groups existed back then, including freshwater species. Amphibians were still a major faunal component particularly in the early Triassic; Fraser discussed very early frogs, gharial-like trematosaurids, suction-gulping bottom-dwelling plagiosaurs, and the alligator-like metoposaurs. One strange group of reptiles he came to again and again in later chapters is the Drepanosauria. Very odd animals, they had barrel-shaped trunks, tails that often had a "compressed leaflike appearance," and sometimes a clawlike bone at the end of the tail (some species may have even had a prehensile tail). Some drepanosaurs were arboreal it seems, maybe pangolin-like, while others were deep-tailed aquatic forms. The first true mammals date back to the late Triassic.
His review of the plant fossil record was interesting; I had no idea of the problems. Many aspects of plant anatomy readily detach from the parent body, such as flowers, fruits, and seeds, and many plants lose their foliage in winter; as a result, it can be hard to link a separate plant part with the parent plant, or a fossilized plant might be missing its most distinguishing characteristics. Plants of the time were non-flowering, dominated by club mosses, horsetails, true ferns, seed ferns, cycads, and conifers. Fraser mentioned in later sections (and in this one) examples of possible Triassic flowering plants, but each time it would seem they are just odd examples of seed ferns.
Part two looked at the Middle Triassic. He noted the excellent insect fossils of Gres a Voltzia in France (including egg clusters, coloration patterns, and plant galls), nothosaurs (including locomotive methods and sexual dimorphism), the possible function of _Tanystropheus_ and its long neck, the sail-backed archosaur _Lotosaurus_, and discussed issues of diversity levels in the fossil record (along the way criticizing a bit "lion lies down with the lamb" depictions that unrealistically cram in as many different organisms as possible into one painting).
Part three detailed the Early Late Triassic. Highlights included the uniquely Triassic insect group known as the titanopterans (some had a wingspan of up to a foot and appear to have had organs to produce loud sounds), _Sharovipteryx_ (an arboreal glider, something apparently common in the Triassic), _Longisquama_ (whose featherlike appendages have been difficult and controversial to interpret), drepanosaurs (were they pterosaur ancestors?), flying fish, the crocodile-like phytosaurs, the huge predatory _Postosuchus_, the armored aetosaurs, the hippo-like _Placerias_, the mysteries of the Ghost Ranch _Coelophysis_, the proposed bird-like genus _Protoavis_, from Scottish sandstones the odd _Scleromochlus_ (it might have hopped and it is debated over whether or not it was related to pterosaurs), and from South America the world's oldest dinosaurs, _Herrerasaurus_, _Eoraptor_, and _Pisanosaurus_.
Part four was on the latest Triassic, how modern ecosystems started to arise though many ancient forms still existed. Highlights include the sphenodontians (which today exist only as the rare tuatara of New Zealand but in the past had a great variety of habits and forms), the gliding kuehneosaurs, the geology of the great Newark rift valley of eastern North American (which like the African Great Lakes possessed species flocks of related fish, though instead of cichlids were instead a group known as the semionotids), a formation noted for numerous trackways and thanks to new prospecting and imaging techniques numerous excellent insect fossils from the Solite Quarry along the Virginia-North Carolina state line. Other interesting items include the freshwater amphibious reptile _Tanytrachelos_ (apparently an aquatic insectivore) and _Uatchitodon_, a reptile that had distinct groves on the sides of it teeth not unlike venomous snake and the Gila monster. The final section of the chapter very briefly reviewed theories over mass extinctions towards the end of the Triassic.