Historical Zoogeography of Land Tetrapods by N. Kalandadze & A. Rautian

Historical Zoogeography of the Land Tetrapods

N.Kalandadze, A.Rautian
Paleontological Institute of the Russian Academy of Sciences
Russia, Moscow

For about twenty years the authors have studied terrestrial tetrapod material and, using some
simple methods, have produced a series of zoogeographical reconstructions from Carboniferous to
Pleistocene.
Some of these results have been published in Russian and we believe that it may be useful
to produce a summary of this work in English.
Some of our results look very unusual, and we thought so at the beginning as well,
but our reconstructions are not imagination.
They are projections of terrestrial tetrapod systematics on to geography (see materials and
methods). And, if our reconstructions are wrong, it means that something is wrong with tetrapod
systematics.
This does not mean, of course, that all of our results are precise.
Some of them can be and must be corrected. But, following A.R.Wallace,
we have studied all the land masses of the Earth and used all available material.
We have received some new results and we may begin to correct them now.
Approximately 1% of mammals "disagree" with our reconstructions.
Some of them are discussed in "Some taxonomical results".
One of the most important aspects of this work is the method used,
as well as some conclusions conserning systematic position of particular groups
that can hardly be obtained by means of standard zoological methods.
The text was written by N.Kalandadze who accepts responsibility for any mistakes.

MATERIALS AND METHODS

We used data on the geographic and stratigraphic distribution of terrestrial tetrapods
(non-marine and non-flying). Each taxonomic group used was considered to be monophyletic,
monotypic and monochronous in origin. Faunas were compared by the degree of their taxonomic
isomorphic characters at the levels from family to genus inclusive.
At the first stage of the work, all faunas were compared with each other in pairs,
regardless of their present or past position on the Earth's surface.
In the analysis of each pair of faunas used two operations :
First, the operation of "falling through" : if a certain taxon showed direct linkage between two
faunas (occured in both faunas at a certain geological time stage), but this linkage could be
explained by the presence of the taxa in the faunas of the previous time, we excluded such taxa
from the consideration concerning the zoogeography of the later time stage.

Second, the operation of reduction : if a direct linkage between the faunas of two regions turned
out to be weak and could be completely reduced to the connection between the two faunas
through a third (or more) fauna (that is, each taxon of the direct linkage corresponds to the same
taxon of the indirect linkage),such a linkage was considered to be false, Reduceable to a set
of other linkage (for additional details of the methods see : Kalandadze, Rautian, 1980-1991.

RESULTS AND DISCUSSION

LATE DEVONIAN

Fossils of Late Devonian tetrapods are known from different territories (Greenland, Russia,
Australia); but their scarcity makes them unsuitable for a reliable zoogeographical investigation.
We tried to use sarcopterygian and dipnoan data, but obtained no satisfactory results; perhaps
owing to that these fishes were not strictly freshwater.

CARBONIFEROUS

Two well-known Carboniferous terrestrial tetrapod faunas of North America, and Western and
Central Europe are so similar that it is possible to consider them as two parts of the same fauna.
This fact is well known and was confirmed in our analyses (Kalandadze,Rautian,1981).

EARLY PERMIAN

High levels of endemism shows that in the Early Permian,
three were three different faunas on three separate land masses:

1. North America + northern part of Eastern Europe.
The most abundant amphibians were Lepospondyli and archaic Labyrinthodonts : Edopida and
Eryopida. Some large amphibians show good adaptation to life away from water. They had a
heavily ossified robust skeletons, with no trace of lateral lines on the skull and lower jaw. As these
kinds of amphibians are known since the Late Carboniferous, we may say, that in the Late
Carboniferous and Early Permian some amphibians tried to "organize" a good terrestrial biota
before the reptiles.
Since the Middle Carboniferous, we know of some groups of reptiles (Cotylosauria, Diapsida,
Theromorpha) had been able to oust amphibians from their ecological niches; thus, we know why,
since Late Permian, most amphibians have become freshwater animals.
The most common terrestrial animals in North America were Pelycosauria, not Therapsida.
Some years ago a few fragments of theromorphs were identified as therapsids.
Based on the historico-zoogeographical data, we suggested that all these fragments
should belong to sphenacodont pelycosaurs (Kalandadze, Rautian,1983)
and Robert Reisz agreed with us (pers.comm.).
At this time we know of no Early Triassic reptiles, and few Middle Triassic reptiles in
North America, however we believe that no therapsids will be found in North America
until the Late Triassic, when all continents were joined and therapsids and primitive mammals
entered North America.
We do not know about any confirmed parareptiles in North America,
but R.Reisz believes that Acleistorhinus is related to Lanthanosuchia.
If this is true, Acleistorhinus is the first known parareptile from North America.
2. West Europe + Middle Asia + China.
The most common labyrinthodonts were the Archegosauroidea and small unusual amphibians,
Discosauriscidae. We follow M.Ivachnenko's suggestion that discosauriscids are amphibian
ancestors of Parareptiles. That separate stock of reptiles - Parareptilia - M.Ivachnenko (after
E.C.alson) traced from Discosauriscidae to Pareiasauria, Procolophonia and Chelonia
(Ivachnenko,1987).
3. South America + Africa + ?.
We know only a few taxa from these territories. But the known genus Mesosaurus, whose
skeletons are abundant in West Africa and Brazil, confirms that these continents were joined in
Early Permian. We do not know of any good Early Permian fossil tetrapods from India and
Australia.

LATE PERMIAN - MIDDLE TRIASSIC

At the beginning of the Late Permian and Early Triassic other parts of Laurasia
(Scotland, Russia and China) were connected with Gondwana.
Previous investigations have shown that the major zoogeographical patterns were the same from
Late Permian to Middle Triassic, when North America and some parts of Western and Central
Europe were isolated.
The faunas of these territories contain some archaic elements; parts of ancient groups.
The differences between these two faunas are not substantial and we believe that they belong to
different provinces of the same Laurasian zoogeographical region.
Some groups of primitive amphibians and captorhinomorphs are known from that region,
especially in North America.
And in all cases both of these faunas show essential differences from the fauna of Gondwana.
Since all other faunas show a high level of similarity, we suppose that all these faunas belong to the
Gondwana zoogeographical region. South America, Africa, India, Antarctica and Australia were
joined at that time, and all the faunas known from those territories were very similar.
The situation with northern faunas is not so clear.
The well-known Scottish Late Permian fauna (from Elgin) includes
only three genera: Geikia, Gordonia (Anomodontia) and Elginia (Pareiasauria).Anomodontia
and Pareiasauria are typical of Gondwana, not Laurasia (Kalandadze, Rautian, 1981).
After the discovering by V.P.Amalitzky the Northern Dvina Faunal Assemblage with large
pareiasaurs, gorgonopsians, therocephals and dicynodonts, the relationships of these faunas with
Gondwanian faunas has become obvious.
Now we can say that large northern continental masses from Scotland to China were joined at that
time. And some provincial differences between these northern faunas and southern faunas confirm
our conclusion that from the Late Permian up to the Middle Triassic the northern continents
adjoined Gondwana at least twice: at the beginning of the Late Permian (Ecca zone or earlier) and
at the beginning of the Early Triassic (Lystrosaurus zone).
The most common animals of the Gondwanian zoogeographical region were Parareptilia
(Pareiasauria and Procolophonia),
Therapsida and freshwater Labyrinthodontia.
One very important group of animals "disagree" with our reconstruction, these are some of the
Triassic Labyrinthodontia. At the beginning of Triassic in Western Europe, (since the Late Permian)
some Gondwana-type labyrinthodonts appeared suddenly on the isolated land masses. In Fig. 2 a,
2b the arrows show the moment of changing amphibian faunas in North America and in Western
and Central Europe. These groups of labyrinthodonts were to have a single peak in both parts of
the Gondwanian zoogeographical region: in the south and in the north.
And that is the reason for North America and Western Europe to display two peaks of
labyrinthodonts. Gondwana and Eastern Europe had one peak of labyrinthodonts
(Kalandadze,Rautian,1983).
As no therapsids appear in North America and Western Europe before the Late Triassic (except
for Procynosuchus sp., from Germany), we examined these labyrinthodonts more carefully and
revealed that all of them had belonged to the families with representatives having been found in the
marine deposits. These families are the Capitosauridae, Benthosuchidae, Trematosauridae and
Plagiosauridae.
We may suggest that, at the beginning of the Triassic, some labyrinthodonts tried to enter salt
marine water (and could cross marine straits). But at the beginning of the Triassic, Ichthyopterygia,
Sauropterygia and Placodontia are known to emerge. This can explain, why after the Late Triassic
one finds only a snall number of fossil Jurassic and Early Cretaceous labyrinthodonts in China,
Mongolia, Middle Asia and Australia. Probably they were ousted by the reptiles.
In the Late Permian, we know one very important change in terrestrial biota. In the beginning of
the Late Permian,there was unique the Ocher Faunal Assemblage (Perm Region, Russia).
All terrestrial animals in this Assemblage were therapsids: small and large, carnivorous and
herbivorous.
Later, in the Northern Dvina Assemblage, all the carnivores were therapsids (gorgonopsians,
therocephals). But the herbivorous animals belong to two groups : dicynodonts (Therapsida) and
pareiasaurs (Parareptilia). Large forms of herbivorous therapsids had died out.
In the terminal Late Permian fauna of Russia (Vjasniky = Daptocephalus zone) there were two
large carnivores: a new Whaitsid therocephal and the first archosaur (Archosaurus). This was a
very important moment in the history of terrestrial tetrapods: large carnivorous therapsids were
being replaced by Archosauria.
Since that time, Theromorpha (and, later, Mammalia) evolved "in the shadow of archosaurs".
It was one of the most important moments in the whole mammalian history.
"The first two-thirds of mammalian history" were spent "in the shadow of dinosaurs" (Lillegraven,
Kielan-Jaworowska, Clemens, 1979).
From then until the Late Triassic we know very few large theromorphs, all belonging to
Dicynodonts. However, small therapsids survived until the Paleocene (Chronoperates in North
America). Having originated from therapsida and being suppressed by dinosaurs in large-size class,
all Mesozoic mammals were small-sized.

LATE TRIASSIC

The time of maximal regression, a zoogeographical Pangaea : when all continents were joined
and North Africa was the centre of the world. This was the time when Chelonia, Crocodylia,
Dinosauria, Pterosauria and Mammalia began to evolve.
Some provincial differences in faunas show that recent oceans began to open by the Late Triassic.
We performed a special study of the Late Triassic using Thecodontia, Dinosauria, Theromorpha
and Mammalia only (Kalandadze, Rautian,1991).
All traces of the previous zoogeography divisions disappeared in Late Triassic Pangaea.
Thus, the Late Triassic is the most ancient time whose historical zoogeography can be
reconstructed with the use of recent materials.

EARLY - MIDDLE JURASSIC

The largest catastrophe of terrestrial biota from the Devonian up to
Recent occured (Kalandadze, Rautian, 1983-1993; Benton, 1985-1989).
This is the reason it is impossible for us to make a reconstruction for this time using our methods
(the materials from all other periods in the history of terrestrial tetrapods from Carboniferous up to
Recent appeared aviable for our reconstructions). Though terrestrial tetrapods were found
everywhere; North America, Europe, Asia, Africa, Madagascar(in Australia, the volume of
material is too small).
Special articles concerning this subject were published (Kalandadze, Rautian, 1993 a, 1993 b).
Many high level taxa became extinct and many high level taxa appeared near the boundary
between the Early and Middle Jurassic; near and during Early and Middle Jurassic.

Some of these taxa are :

Lepospondyli - Apoda
- Urodela
Batrachomorpha - Salientia
Batrachosauria - Chelonia
Eolacertilia - Lacertilia
Thecodontia - Crocodylia
- Pterosauria
- Dinosauria
- Aves
Synapsida - Mamamlia

Dinosauria and Pterosauria are the only two unsuccessful members of this taxa.
Thus, we may say that the Late Jurassic was the time when the Recent biota began to evolve.

LATE JURASSIC

The only but very important difference between the Late Jurassic and Late Triassic
reconstructions is the separation of North America and South America.
It means the Southern and Northern continents were separated.
From that time we know of some groups of mammals : Kuehneotheriidae, Amphidontidae,
Amphitheriidae, Peramuridae (see Table 1).
All of these mammals belong to archaic therians, but not Metatheria and Eutheria.
The oldest fossils of Metatheria and Eutheria are known from the end of the Early Cretaceous
(Aptian-Albian). But in the collection of Paleontological Institute Russian Academy of Science
there are some teeth of Zalambdalestidae and Deltatheridiidae (Reshetov V.J., pers. comm.),
collected in Mongolia (Psittacosaurus zone). All the mammalian fossils were published as "Aptian
- Albian stage"; however, the Psittacosaurus fauna is usually believed to be the Neocomian.
Then, Alex Agadjanian, examining published material from Gumiarotta (Late Jurassic of Portugal)
found that Crusafontia and Henckelotherium resemble Amblypoda and may belong to this order.
In any case we may suggest that the Late Jurassic was the time of separation of Southern and
Northern continents and should be the beginning of divergent evolution of Metatheria (on the
South) and Eutheria (on the North).

LATE JURASSIC - EARLY CRETACEOUS

Some mammalian materials are known from North America, Europe and Africa.
It is important to note here that in the Late Jurassic we know a Multituberculata fauna from North
America (Morrison formation). All that Multituberculat

a had previously died out, and new
Multituberculata from Asia came to North America in the Albian stage.
This fact is very important, because it helps us to find the time of contact of North America with
Asia and South America in the Cretaceous.
We will show later that North America, while being isolated from Asia, in the middle of the Early
Cretaceous, had a short contact with South America.
It was First "Panama" Bridge, which was used, on the one hand, by placental mammals
to occupy South America; and on the other hand, by Didelphidae to reach North America.
This bridge disappeared before the emergence of the First "Bering" Bridge,
which connected North America and Asia.

EARLY CRETACEOUS (middle part)

Placental mammals (some groups of Pantodonta,
Condylarthra, Notoungulata, Xenarthra, Rodentia, and Primates) reached South America.
Some groups of marsupials (Didelphidae) entered North America and then Europe,
North Africa and Asia (Zaissan and Thailand).
Most likely by that time, Australia had been isolated from Antarctica and South America.
We can expect that if Australia had adjoined Antarctica and South America at that time, placental
mammals would have come from South America through Antarctica to Australia.
Thus, Multituberculata and placental mammals (exept bats) will not be found in Australia until the
Pliocene time, when the first terrestrial placentals (Muridae) reached Australia
(Archer,Clyton,1984).
More then ten years ago we proposed that the terrestrial tetrapods of Antarctica must be closer to South American, than to Australian (Kalandadze,Rautian,1982), because, judging by the modern
position of continents on the globe, Antarctica was isolated from Australia earlier than from South
America.
Antarctodolops, the first specimen of terrestrial mammal, confirmed our conclusion.
At present the terrestrial mammalian fauna of Antarctica "include two endemic species of
polydolopid marsupial: Antarctodolops ... and Eurydolops ... and three partly determinate
placentals identified as a tardigrade edentate, a sparnotheriodontid litoptern and a trigonostylopid
astrapothere " (Hooker,1992).

---oOo---

How long was "The Splendid Isolation" of South America?
It is one of the most spectacular questions of historical zoogeography.
The time of South America's isolation, and the problem of origin of Caviomorpha and Platyrrhina
have been previously discussed (Kalandadze,Rautian,1991), but we must return to this subject
here.
G.G.Simpson summarized all results obtained by 1980. He believed that South America was
isolated in the middle of the Cretaceous and mentioned that isolation had lasted through the
Paleocene, maybe up to the first part (but not to the end) of the Eocene.
According to G.G.Simpson, the Caviomorpha and Platyrrhina entered South America
at about the Eocene/Oligocene boundary.
We took the stratigraphical scale for North and South American terrestrial mammal
(Archer,Clyton,1984), added it to the Early Cretaceous and placed on it the main events of
mammalian faunas (Fig. 6). Let us examine the results from the Recent to Cretaceous.
"The Great American Interchange" is the clearest part of this history. A special monograph
concerning this problem was published some years ago (Stehlin, Webb, 1985).
We show all the time intervals of the interchange for all mammalian families,
which come to South America from North and into North America from South
in the Late Miocene-Late Pliocene, Pleistocene and Recent .
The arrow shows the level, on which the first fossils of primates
and rodents were found in South America.
Here is the list of these first South American primates and rodents
(data from Simpson,1980) :

Primates : Cebidae
Rodentia : Cavioidea
Eocardiidae
Erethizontoidea
Erethizontidae
Chinchilloidea
Chinchillidae
Dasyproctidae
Octodontoidea
Octodontidae
Echimyidae

We must to underline two facts.
1. Primates and rodents appeared in South America suddenly and exept for one doubtful family
(Eocardiidae) all og them belong to the recent families.
2. Platyrrhina and Caviomorpha are absolute(ly?) endemic of South America until the Late
Miocene, when some Caviomorpha reached North America.
We beleive that these facts show that not Platyrrhina and Caviomorpha, but their ANCIENT
ANCESTORS reached South America many years before the end of the Paleogene. And their
Early Oligocene representatives appeared as a result of long evolution in isolation.
The time of their invasion to South America is one of the most difficalt questions in this history.

Three groups of mammals are very important in this history:
1) Eutheria. When did they enter South America?
2) Metatheria. When did they enter North America?
3) Multituberculata. When did the first Cretaceous Multituberculata entered North America
and why did not they reach South America?
The first Eutheria appeared in South America in the Late Cretaceous
(Vilquechican stage or equivalent).
The first Metatheria appeared in North America in the Late Cretaceous (Middle Cenomanian).
This means that the First American Interchange began in the Middle Cenomanien or before it.
That is why the situation with Multituberculata is so important.
As far as we know, the first Cretaceous Multituberculata came to North America from Asia in the
Albian (approximately 100 m.y.). If this is true, we know the upper limit of the "First Great
American Interchange", because the absence of typical Multituberculata in South America
suggests that the First American Interchange was finished before their appearance in North
America; otherwise the Multituberculata would have been present in South American faunas.
But the situation with South American Multituberculata is not simple. Three or four South
American endemic genera have been identified as Multituberculata : Gondwanatherium,
Sudamerica, Ferugliotherium and,perhaps, Vucetichia.
Here is the main reason for this identifications :
"similarities in gross dental morphology, enamel microstructure, and inferred direction of jaw
movement between Gondwanatherium and Sudamerica on the one hand and ... multituberculate
Ferugliotherium (which probably includes Vucetichia), on the other, indicates that
Gondwanatherium and Sudamerica are also multituberculates. The Gondwanatheria, including two
families, Ferugliotheriidae (Ferugliotherium) and Sudamericidae (Sudamerica and
Gondwanatherium), are therefore recognized as a new, highly derived suborder of
Multituberculata" (Krause,Bonaparte,1990).
All Cretaceous North American Multituberculata are absolutely ordinary representatives of the
Order Multituberculata and closely related to the Asian ones.
That is why we believe that Multituberculata are realy absent in southern continents.
When we analysed the beginning of "The Splendid Isolation" we examined all mammalian taxa
from the Early Cretaceous to Recent (Fig. 8)(Kalandadze,Rautian,1991).
Two lines of circles reflected the volume of mammalian faunas of South America (below) and
North America (above) from the Early Cretaceous to Recent. External circles show the number of
new genera (see scale); internal black, the number of new families. The upper number near the
circles is the number of new families; the lower, number of new genera in both faunas during that
time.
All the families and genera which did not cross the marine strait between South and North
America (146 families and 1226 genera) are shown in Fig. 8 (large circles).
All the taxa up to the generic taxonomic level from the Early Cretaceous to Middle Miocene in
South America and all other territories of the world are shown on Fig. 8.

The complete list of these taxa are :
South America North America Europe Asia
Alphadon K2 Alphadon K2
Pediomyinae K2 Pediomyinae K2
Pantolambdinae K2 Pantolambdinae P13-P21
Mioclaeninae K2 Mioclaeninae K2
Periptychidae K2 Periptychidae K2
Didelphini P13-P21 Didelphini P13-P21
Notostylopoidea P13-P21 Notostylopoidea P13-P21
Glasbiinae P22-3 Glasbiinae K2
Tardigrada P22-3 TardigradaP13-P21
Primates P31 Primates P13-P21
Rodentia P31 Rodentia P13-P21
Myrmecophagidae N11 Myrmecophagidae P22-3

And that is all.

Complete lists of mammalian orders and families form the Paleocene to Recent, which were found
in South America and North America are too large and we made a special drawing to show the
result of this analyses (Fig. 9). The majority of the data were taken from "Mammalian paleofaunas
of the World" (Savage,Russell,1983).
The only common family has been found in South and North America within the time from the
Paleocene to Middle Miocene is Didelphidae. But they are known from both territories since the
Late Cretaceous (Fig. 9).
We hope that everything is clear within the Cenozoic time. More than 140 families and 1200
genera of mammals are noted which support the supposition that South America was isolated from
Lower Cretaceous (pre-aptian) to Late Miocene.
As we mentioned above, the main reason for divergence of Metatheria and Eutheria was the
isolation of Southern and Northern continents (Fig. 1.4). But the mixed metatherian - eutherian
faunas of South and North America show that this isolation was interrapted. This bridge appeared
in the middle part of the Early Cretaceous (Fig. 1.6) and now we must determine when it
disappeared. For this reason, we must search the Cretaceous material with special care.
In Mesozoic historical zoogeography , the most importnt tetrapods are not mammals,
of course, but dinosaurs, as we have substantially larger material on these huge animals.
Comparative list of Cretaceous dinosaurs of South and North America are not dificalt to compile.
The only dinosaur genus to be found on both continents, is Kritosaurus (Hadrosauridae); it was
described from South America as "Kritosaurus" australis (Weishampel, Dobson, Osmolska,
1990). The majority Hadrosauridae lived in the Late Cretaceous, but some were found in the Early
Cretaceous too. In any case Kritosaurus belong to the most primitive group of the family.
All dinosaurs of South America are very archaic, especially Carnosauria.
Most of them belong to the family Abelisauridae and look like specialised Magalosauridae.
That is why we indicate that the contact between South and North America
in the middle part of the Early Cretaceous ended (Fig. 1.6).
And from that moment until the Albian "The Splendid Isolation" of South America began.
One of the most important result of recent paleotheriology was the discovery of Cretaceous
mammals in South America. J.F.Bonaparte wrote that "Los Alamitos fauna demonstrated strong
compositional differences from all other Late Cretaceous assamblage of mammals"
(Bonaparte,1990,p.63).
Bonaparte believes that "Gondwanatheria may be ancestral to the Xenarthra".
We agree with him, but prefer to remove from Gondwanatheria all brachiodont animals.
The structure of Xenarthral's system may be the following :

Order Xenarthra
Suborder Gondwanatheria
Gondwanatherium,Sudamerica
Suborder Cingulata
Suborder Pilosa

Ferugliotherium and Vucetichia, assigned to Gongwanatheria and (or) to Multituberculata are
brachiodont and the most strange and significant animals in Los Alamitos fauna (Bonaparte, 1986;
Krause, Bonaparte, 1990;
Krause, Kielan-Jaworowsca, Bonaparte, 1992).
It is not the time nor the place to analyse all the opinions, having been expressed concerning that
material. But Alex Agadjanian believes, and we agree with him, that the time has come to look for
the fossils of the Cretaceous Rodentia. Ferugliotherium and Vucetichia are the first two animals to
be examined carefully from that point of view. Especially because the first Cretaceous Pantodonta,
Condylarthra, Notoungulata and Marsupicarnivora (Didelphidae) have been found in isolated
South America.
Since the Early Cretaceous (or earlier, but not later) Australia
had been isolated up to the Early Pliocene.
That is why all Australian groups of dinosaurs belong to the Triassic or Jurassic groups.
We do not know a single dinosaur genera, closely related to well-known Cretaceous dinosaurs of
North America or Asia : Hadrosauridae,Tyrannosauridae, Protoceratopsidae, Ceratopsidae,
Pachycephalosauridae, Psittacosauridae and others. According to T.Rich and P.Vickers-Rich "The
Early Cretaceous vertebrate faunas of Victoria are unusual in being dominated by small ornithopod
dinosaurs. Nowere else in the world is this the case,exept perhaps in the Late Triassic - Early
Jurassic of Southern Africa" (Rich, Vickers-Rich, 1989, p. 16).
It means that in the Cretaceous, Australia was a refuge for the most ancient groups
(Triassic and Jurassic) of dinosaurs.
The presence of the "latest occurence in the world of a labyrinthodont" (Rich, Vickers-Rich, 1989, p. 16) confirms the idea that Australia was isolated since the beginning of the Jurassic.
But because that was the time of Jurassic biotic catastrophe (Fig. 4, 5;Table 1),
there is not enough good material for zoogeographical analysis.
And in the Late Jurassic we have no terrestrial tetrapod material from any southern continents.
We mentioned above that mammalian faunas of southern continents should contain old, primitive
groups of mammals : Prototheria and Metatheria only. And that Australia was isolated before
South and North America junction in the middle of the Cretaceous (Fig. 1.6).
That is why Eutheria andMultituberculata could not reach Australia and Australia has
an unique mammalian fauna : Prototheria + Metatheria.
As rodents (Muridae) reached Australia only in the Early Pliocene, this continent has the most
completely preserved mammalian fauna, which began to evolve in the Jurassic.
And now we can see the results of this evolution in isolation.
That is why it is possible to trace recent families up to the oldest (Oligo-Miocene) Australian
mammalian faunas (Archer, Hand, Godthelp, 1994). And the only Early Cretaceous mammal of
Australia belongs to a recent family, Ornithorhynchidae (Archer, Flannery, Ritchie, Molnar, 1985).
And the same will be with some recent families of Marsupials.*

* In 1994 the second opal jaw was received by Australian Nuseum (Sydney). That jaw was
described as a new genus of Monotremata. Alex Agadjanian examining that jaw carefully.
I am in agreement with him: this jaw belonged to a new specialized Phalangeridae.

Some other structural resemblances of the Australian and Mesozoic faunas can be found.
Australia has no good carnivorous mammals. The biggest was Thylacinus.
Even in the Pleistocene, there were carnivorous diprotodontoids, Thylacoleo; large varanids,
Megalania; and terrestrial crocodyles (Hecht, Archer, 1977; Rich, Monaghan, Baird, Rich, 1991).
Thus, the composition of the Australian fauna (in its essential, carnivorous, part) looks very archaic.
So we may expect that some groups of recent mammals will be traced back to the Cretaceous, as
a line from Ornithorhynchus to Obdurodon and Steropodon indicates. Monotrematum fossils found
in the Early Paleocene of South America confirms that it is posible.
We must underline that Australia is the most interesting continent for paleontologists.
And the most urgent quest is to found Paleogene and Mesozoic mammals, as well as additional
material on dinosaur. Of course it is very important to find good therapsid material, but Australian
therapsids should be more or less closely related to South African, Russian, and others from the
Gondwana zoogeographical region.
After the Late Triassic South America had a short contact with North America in the Early
Cretaceous (pre-Aptian). And then it was isolated from the northern continents until the Late
Miocene.
Australia was isolated (according to terrestrial tetrapod data) by the end of the Early Cretaceous.
And in the Early Pliocene and Pleistocene some placental mammals reached Australia : Muridae,
Homo and Canis .
Africa was isolated for most of the Cretaceous Fig. 1.6-8). In the Paleocene, Africa ajoined
Europe and stayed connected with northern continents til the Recent.
In the middle part of the Early Cretaceous North America was connected first to South America;
than to Asia (Fig. 1.7).
From the end of the Late Cretaceous to the first part of the Paleocene, all continents was isolated.
But after that time, all the Northern continents more or less ajoined one another, as well as Africa
and India.
During the whole Cenozoic, the mammalian faunas of Northern continents were mixed.
And the main results of each contact were extinction and acceleration of divergent evolution.
If we compare the lists of the Paleocene mammalian families in South and North America we will
find a very important fact. In South America we know 16 Paleocene families of mammals.
Half of them died out in the Eocene and Oligocene; the others, after the begining of
The Great American Interchange : Didolodontidae (Late Miocene); Interatheriidae (Pliocene);
Borhyaenidae, Glyptodontidae, Protherotheriidae,
Macraucheniidae (Pleistocene); Didelphidae and Dasypodidae are Recent.
It means that 6 Paleocene mammalian families died out in South America
as a result of mammal invasion from North America.
An absolutely different situation occured in North America.
Here we know 44 Paleocene mammalian families.
Four of them are known before the Great American Interchange; two them died out in the
Pleistocene (Equidae and Erinaceidae); and two are recent (Didelphidae and Soricidae).
And the same situation occurred on all Northern continents.

EARLY-LATE CRETACEOUS

The first direct connection between North America and Asia was the first Bering Bridge.
Since this time, Madagascar has been isolated from Africa.
The recent fauna of Madagascar is a part of old Native African faunas.
Previously we noted that Madagascar was isolateted at least since the Early Cretaceous
(Kalandadze, Rautian, 1983). Here we reproduce some drawings from Cooke (1972), in which
marine deposits are shown along both banks of Macassar strait from the Jurassic to Miocene.
The only question is shown in the Paleocene.
From Madagascar we do not know a mammalian fauna older than the Pleistocene.
But we know recent and Pleistocene faunas of Madagascar and mammalian faunas of Africa since
the Paleocene.
Savage and Russell (1983) published the first list of Paleocene African mammals:
Cimolesta (Palaeoryctidae), Creodonta (Hyaenodontidae) and Carnivora (Miacidae ?).
Since the Paleocene Africa adjoined Europe and and subsequently Eurasia.
And since that time most of the old African mammalian faunas were replaced by Eurasian.
In all cases, in Madagascar we do not know the typical African mammals : Perissodactyla,
Artiodactyla, Carnivora (exept Viverridae), Catarrhina, Hyracoidea, Proboscidea, and others.
Thus, we may say that Madagascar has saved for us some groups of
old, Mesozoic, native African mammals.

LATE CRETACEOUS - MIDDLE PALEOCENE

Maximal transgression. Only South America and Antarctica may have been joined.
All other continents, Madagascar, and New Zealand were isolated.
It means that the dinosaurs died out and mammals began their Cenozoic evolution
on NINE isolated land masses.

LATE PALEOCENE - EALRY EOCENE

India adjoined Asia; Africa become connected with Europe.
Asia has no direct contact with Europe.

MIDDLE - LATE EOCENE

The Northern Atlantic adjoined the Arctic Ocean, separating North America and Europe.
It means that all taxa, which appeared later than the separation of North America and Europe,
which is absent?(but not)? in Asia, must be either older than Middle Eocene or polyphyletic.
Engesser B., (1979) studied some of these taxa and obtained an exellent result.
Polydolopidae, Xenarthra, Litopterna, and Astrapotheria confirm that the Antarctic fauna was
close to the South American, not to the Australian faunas. However, this does not mean that
Antarctic was in contact with South America: the fossil mammalian material is too insufficient.
The glacial-interglacial deposits in Antarctic have been traced back to the Middle or Late Eocene
(Webb, Harwood, 1993).

EARLY OLIGOCENE

Europe and Asia adjoined one another for the first time since the Late Triassic and remained joined up to now.

MIDDLE - LATE OLIGOCENE

The only time since the Middle Paleocene, where we can show disjunction
between North America and Asia.

EARLY - MIDDLE MIOCENE

The Bering Bridge appeared again and remained up to the Pleistocene.

LATE MIOCENE

South America adjoined North America (Panama Bridge):
the beginning of "The Great American Ingerchange" (see above).
One of the most important facts, which additionally confirms impossibility of crossing the Panama
strait is the fact that the level of Atlantic Ocean is about 15-20 meters higher than the Pacific.
The more narrow that strait, the faster its flow and thus the impossibility of its crossing by animals.

EARLY PLIOCENE - PLEISTOCENE

During that time Australia had at least two short contacts with Asia. The Muridae in the
Early Pliocene and then Homo and Canis entered Australia in the late Quaternary.
"Singh, Kershaw and Clark (1979) and Singh (1982), reported that a marked increase in charcoal
dust in cores taken from Lake George, eastern New South Wales, at a level interpreted to be
about 120,000 years BP.
They conclude that the increased charcoal heralds Man's arrival on the, continent." (Archer, 1984).

The glacial shield of Antarctic was not complete up to the Late Pliocene (!), from which good
Nothofagus fossils were found in the Transantarctic Mountins, 500 km from the South Pole
(Webb, Harwood, 1993).

---ooOoo---

Some taxonomical results.

We do not know typical Cretaceous dinosaurs in South America before the invasion of placental
mammals, at which time some Cretaceous dinosaurs from North America appeared there.
The absence of terrestrial animals groups, restricted to the Late Cretaceous, in Australia confirm
this conclusion. This means that the Northern and Southern continants had been separated since
the Late Jurassic or earlier.
Australian mammals could enter Australia only through South America with Antarctica before the
Late Jurassic. Thus, marsupials had to reach Australia before the Late Jurassic.
There are two groups of non-endemic mammals in Australia : Prototheria and Metatheria.
Thus, these mammals should enter South America no later than in the Middle Jurassic.
If we believe that Australia was isolated from South America with Antarctica later than
the Early Cretaceous, Prototheria, and Metatheria should have been present in
Australia and South America with Antarctica before that time.

South America was isolated from North America from the beginning of the Early Cretaceous up to
the Late Miocene. This means that all taxa we know from South America and all other land masses
during all the time of isolation, must be at least of Early Cretaceous age.

These taxa are :

Alphadon; Didelphini; Glasbiinae; Pediomyinae (Didelphidae);
Pantolambdinae (Coryphodontidae);
Tarsiiformes (ancestor of Platyrrhina);
Rodentia;
Myrmecophagidae; Tardigrada;
Mioclaeninae (Hyopsodontidae); Periptychidae;
Notoungulata.

North America was isolated in the Late Cretaceous.
At that time we know Plesiadapiformes from North America. Lemuriformes are numerous on
Madagascar; subsequently, they had to be in Africa in the Cretaceous. Primates had to be in
Africa, Europe, and North America in the Early Cretaceous.
If Madagascar was isolated from Africa no later than the Cretaceous, all mammals, known from
Madagascar and Africa had to be in Africa and Madagascar from the Cretaceous.

These taxa are :

Geogalinae (Tenrecidae);
Hemigalinae; Haepestinae (Viverridae);
Lemuriformes;
Cricetidae;
Tubulidentata.

From the last part of the Late Cretaceous up to the Middle Paleocene Asia was isolated from
North America. This means that all taxa known in Asia and North America at that time, had to be
on both continents no later than the beginning of the Late Cretaceous.

These taxa are :

Coryphodontidae;
Hyopsodontidae; Periptychidae;
Mesonychidae.

Acknowledgments
I would like to thank Dr. Thomas H.V. Rich, for his discussions in Moscow. Dr. Alex Ritchie for
his cordial help. Without whose help this work will not be finished. Dr.Timothy F.Flannery, who
help me with new information. Linda Gibbson and Tish Ennis - for everyday help in the labarotory.
Prof. Michael Archer and Prof. Colin Groves for very interesting discussion. Zerina Johanson for
friendly help. Galina S. Rautian correcte the text. Jennifer Klein read the text ...

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