Western Europe

The mammals of the Purbeck Limestone, England, have traditionally been considered to be of Late Jurassic age and, in fact, they are rather similar to those of the Upper Jurassic Morrison Formation, North America (Simpson, 1928a, 1929a). Recent work has shown that the Purbeck and its contained mammalian fauna is probably Berri-asian, or Lower Cretaceous (Allen and Wimbledon, 1991), and it will be so regarded here (see the excellent discussion in Clemens et al., 1979). In the meantime, however,...

Africa

Only two Early Jurassic mammals, both morganucodon-tans (chapter 4), are known from Africa, but they are represented by extraordinary specimens each is based on a nearly complete skull and skeleton from the southern part of the continent (figure 2.6). Two occurrences in Lesotho are in the Red Beds of the Stormberg Group, which is the source for a remarkable fauna of terrestrial vertebrates, including a remarkable diversity of therapsids. The Red Beds and the remainder of the Stormberg Group...

Mammals From The Age Of Dinosaurs

The first 155 million years (Ma) of mammalian history occurred during the Mesozoic. During this vast time span, mammals diversified into many lineages and underwent enormous anatomical evolution. Humans are primates primates are placentals placentals are eutherians and stem eutherians have a long history, which extends well back into the Early Cretaceous. Mesozoic mammals include the trunk and a bewildering bush of basal branches for the entire mammalian family tree. Their fossil records are...

Conventions

As discussed in chapters 1 and 3, we have adopted a traditional, broad-based definition of Mammalia that includes some wholly extinct groups that lie outside the crown clade formed by the three major living groups monotremes, marsupials, and placentals. Under an alternative definition that restricts Mammalia to the mammalian crown group (see Rowe, 1988 McKenna and Bell, 1997), several groups included in this book, such as sinoconodontids, morganu-codontans, docodontans, and Hadrocodium, would...

Asia

An extraordinary wealth of fossil vertebrates has been collected from the Lufeng Basin, Yunnan Province, southern China (figure 2.4). The systematics, assemblages, and stratigraphic and geologic occurrences of the small tetrapods have recently been reviewed by Luo and Wu (1994). The most productive localities are northeast of Lufeng, in the Dachong-Dawa area, in the lower Lufeng Formation, which is about 400 m thick in this region. The lower Lufeng Formation is divided into two distinct...

Evolution In The Shadow Of Dinosaurs

The evolutionary fortune of mammals and the premam-malian synapsids was quite different from those of other land vertebrates during the Mesozoic. Although phyleti-cally diverse, Mesozoic mammals appear to have been relatively rare, even by comparison with other small, non-dinosaurian vertebrates. During the Permian and most of the Triassic, premammalian synapsids thrived in terrestrial vertebrate faunas worldwide. By the Late Triassic, however, premammalian cynodonts were eclipsed by the...

Britain

The other major European occurrence of Late Triassic-Early Jurassic mammals is in southern England and Wales, from sites on either side of the Bristol Channel (figure 2.3). We have drawn from the excellent review of Evans and Kermack (1994) in summarizing these occurrences. During the Late Triassic and Early Jurassic, shallow seas covered parts of the British Isles, transgressing through time, so that major islands transformed into an archipelago. Karst topography developed on the subaerially...

Info

Cimolodonta (Kielan-Jaworowska, Dashzeveg, and Trofi-mov, 1987, see chapter 8). Gobiconodon, a eutriconodon-tan genus shared with the Cloverly Formation of North America (among others elsewhere) and thus implying some degree of interchange among continents, is represented by two species (Trofimov, 1978 Kielan-Jaworowska and Dashzeveg, 1998). Other noteworthy elements of the fauna include a symmetrodontan (Trofimov, 1980, 1997), one or two peramurid-like eupantotherians (Dashzeveg, 1979,1994),...

Introduction

Following our traditional concept of Mammalia, and thus including a number of forms known only by fossils of the Mesozoic, the earliest mammals are from the Late Triassic, a bit over 220 Ma old (figure 2.1). The Meso-zoic record thus spans about 155 Ma of mammalian history more than twice the duration of the entire Ceno-zoic. Yet the Mesozoic record is frustratingly sparse.1 Reasonably complete specimens skulls and skeletons are rare and are known for only a few taxa, while for many groups the...

Book Contents And Format

We see photo above have endeavored to make this book as comprehensive as possible, within practical limitations. Of the 15 chapters that follow, four chapters 1-3 and 15 are of a general nature and apply to the full spectrum of early mammals, whereas the remaining 11 chapters deal with the anatomy, paleobiology, and systematics of the particular groups of mammals known from the Mesozoic, extinct and extant. In chapter 1, we provide some general background on mammals within the context of...

North America

Several previously mentioned occurrences of possible mammals in the Late Triassic of North America specifi-cally North Carolina and Texas Clemens et al., 1979 are now thought more likely to represent therapsids, as noted earlier Sues, 2001 . In the meantime, however, more secure records of mammals from both the Late Triassic and Early Jurassic have been reported from the continent. Adelobasileus cromptoni see Lucas and Hunt, 1990 is known by the posterior part of a skull from Home Creek, Crosby...

Yamanapalli In Adilabad Fossil

A possible mammal, Gondwanadon tapani, has been described from near the village of Tiki, Madhya Pradesh figure 2.5, table 2.3 . Gondwanadon is based on an incomplete, two-rooted, molariform tooth, said to be similar to figure 2.5. Mesozoic mammals of India. Asterisks, Late Triassic-Early Jurassic localities 1-4 diamond, Cretaceous localities 5, 6 . Localities or local faunas 1, Tiki Tiki Formation Carnian, Madhya Pradesh 2, Paikasigudem 3, Manganpalli 4, Yamanapalli Kota Formation Early...

Acknowledgments

We began work on this book on Mesozoic mammals at the beginning of 1999. With support from our colleagues Donald R. Prothero and Hans-Dieter Sues, we signed the contract with Columbia University Press in April 1999. During our five years of work on this book, we greatly benefited from the help and advice of numerous colleagues and friends, who generously offered us enormous assistance in various ways. Primary among them cited in alphabetic order are Alexander O. Averianov and William A....

Eastern Europe

Only one region in Eastern Europe has thus far yielded mammals of Late Cretaceous age, the Halieg Basin, Romania figure 2.16, table 2.17 . A useful account of the geologic setting and microvertebrate fauna in general is given by Grigorescu et al. 1999 . As noted, Europe assumed the form of an archipelago during parts of the Late Cretaceous. Theropods known from Transylvania are generally small, and this seems to be true of other dinosaurs as well, suggesting that the region was, indeed, insular...

Successive Diversifications Of Mesozoic Mammals

Most Mesozoic mammal species are represented only by teeth and incomplete jaws. Inadequate as they are for a comprehensive understanding of whole organisms, teeth and jaws nonetheless provide useful information about the taxonomic richness and diverse feeding adaptations of early mammals. Their records show several major episodes of diversification figure 1.1 . The earliest diversification took place among stem mammals during the Late Triassic to Early Jurassic. From this initial burst of...

Continental Europe

For example, those of the type Lance Formation, eastern Wyoming Clemens, 1963b . We find it neither practical nor desirable to list all such occurrences independently, and instead use composite local faunas admittedly arbitrary in some cases for such assemblages. Faunal lists are grouped together by age and region individual sites or local faunas are keyed to corresponding maps by numbers. Late Triassic through Early Jurassic mammal sites of Western Europe table 2.1, figure 2.2 fall into two...

South America

Mammals of Late Cretaceous age are known from scattered sites in Brazil, Argentina, Bolivia, and Peru figure 2.7, table 2.21 . Collectively, these occurrences rank the Late Cretaceous mammal record from the South American continent as far superior to that of all other Gond-wanan landmasses combined. Yet we still lack sufficient evidence for a reasoned interpretation of mammalian bio-geography and faunal dynamics, both within South America and among the Gondwanan continents. It is especially...

Medernach Triassic

This unit spans the Upper Triassic, but mammalian fossils are restricted to its upper part. Thus far, specimens consist only of isolated teeth or parts thereof. Given the great antiquity of these remains, the affinities of the taxa they represent are sometimes debatable. Tricuspes, for example, occurs at several sites in the Keuper. It may be a mammal Clemens, 1980a, 1986 , but is more generally considered a cynodont Godefroit and Sigogneau-Russell, 1995 , and...

Greenland

A hard-won vertebrate fauna, including mammals, has been collected by Farish A. Jenkins, Jr., and associates from Upper Triassic rocks of Jameson Land, northeastern Greenland, at more than 71 N latitude figure 2.8 . Thus far, the assemblage includes dinosaurs and other archo-saurs, turtles, labyrinthodonts, and fishes, in addition to four mammals. The fauna is very similar to that of the Norian part of the Keuper in Western Europe, sharing such taxa as Gerrothorax, Cyclotosaurus, Proganochelys,...

Australia

Dinosaur Cove Victoria

An island continent with a highly endemic biota sharing certain elements with other southern continents, Australia has long fascinated students of evolution and biogeogra-phy. Until recently, though, no mammalian fossils older than Miocene were known from this important landmass down under. Discoveries in the Early Cretaceous of Australia table 2.12 are now beginning to shed light on the antiquity of mammals there and are raising fundamental new questions on the origin and relationships of some...

Multituberculates From The Woodbine

Arundel Formation Potomac Group Map

Bona fide Early Cretaceous mammals are known from four regions and stratigraphic units in North America the Trinity Group, Texas and Oklahoma figure 2.14 the Cloverly Formation, Wyoming and Montana the Kelvin Formation, Utah figure 2.10 and the Arundel Clay, Maryland figure 2.15 . A fifth, the Cedar Mountain Formation, Utah figure 2.10 , straddles Albian-Cenomanian time Early-Late Cretaceous and is arbitrarily discussed under this heading as well. The Trinity Group in north-central Texas...

Paradigm Shifts In Mesozoic Mammal Evolutionary Studies

A significant conceptual advance from recent studies of early mammals is the understanding that the greatest tax-onomic diversification and morphological divergence tends to appear in the earlier periods of each major clade Rowe, 1993 Cifelli, 2001 Luo et al., 2002 . The most significant diversification of Mesozoic mammals occurred long before the splits of modern lineages of monotremes, marsupials, and placentals. It is near the root of the mammal tree that many basal branches split off, so as...

Premammalian Synapsids

The synapsid lineage that includes mammals split from other amniote vertebrates over 300 Ma ago, during the Late Carboniferous Pennsylvanian in the Paleozoic. Synapsids are characterized by the presence of a lower temporal fen-estra in the skull, among other apomorphies. Their stem taxa, or pelycosaurs, thrived in the Late Pennsylvanian through the Early Permian Kemp, 1982 Carroll, 1988 Hopson, 1994 . Therapsids, a derived subgroup of synapsids, are characterized by enlargement of the temporal...

Major Discoveries Of The Past Two Decades

The first Mesozoic mammal was discovered in 1764, although its significance was not appreciated until almost a century later Owen, 1871 . The first scientifically documented Mesozoic mammal, now known as Phasco-lotherium bucklandi, was discovered in 1812 in a masonry quarry in the Middle Jurassic Stonesfield slates near Head-ington, England. The fossil was later deposited at Oxford University, where it was recognized by Baron Georges Cuvier to be mammalian in 1818, announced as such by William...