The Fremouw Formation is a Triassic

Triassic

The Triassic is a geologic period and system that extends from about 250 to 200 Mya . As the first period of the Mesozoic Era, the Triassic follows the Permian and is followed by the Jurassic. Both the start and end of the Triassic are marked by major extinction events...

-age rock formation in the Transantarctic Mountains

Transantarctic Mountains

The three largest mountain ranges on the Antarctic continent are the Transantarctic Mountains , the West Antarctica Ranges, and the East Antarctica Ranges. The Transantarctic Mountains compose a mountain range in Antarctica which extend, with some interruptions, across the continent from Cape Adare...

 of Antarctica. Fossils of prehistoric reptiles and amphibians have been found in the formation. Fossilized trees have also been found. The formation's beds were deposited along the banks of rivers and on floodplains. During the Triassic, the area would have been a riparian forest at 70–75°S latitude.

Stratigraphy

The Fremouw Formation is Triassic in age, although the oldest rocks date back to the latest Permian

Permian

The PermianThe term "Permian" was introduced into geology in 1841 by Sir Sir R. I. Murchison, president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with Edouard de Verneuil; Murchison asserted in 1841 that he named his "Permian...

. Much of the formation is quartzose sandstone that was deposited in stream beds. It overlies the Permian Buckley Formation, which consists of coal and Glossopteris

Glossopteris

Glossopteris is the largest and best-known genus of the extinct order of seed ferns known as Glossopteridales ....

fossils. The formation is informally divided into lower, middle, and upper units. Most fossils are found in the Lower Fremouw Formation. Here, bones are preserved in fine grained siltstone

Siltstone

Siltstone is a sedimentary rock which has a grain size in the silt range, finer than sandstone and coarser than claystones.- Description :As its name implies, it is primarily composed of silt sized particles, defined as grains 1/16 - 1/256 mm or 4 to 8 on the Krumbein phi scale...

s and mudstone

Mudstone

Mudstone is a fine grained sedimentary rock whose original constituents were clays or muds. Grain size is up to 0.0625 mm with individual grains too small to be distinguished without a microscope. With increased pressure over time the platey clay minerals may become aligned, with the...

s, coarse grained channel sandstones, and conglomerate

Conglomerate (geology)

A conglomerate is a rock consisting of individual clasts within a finer-grained matrix that have become cemented together. Conglomerates are sedimentary rocks consisting of rounded fragments and are thus differentiated from breccias, which consist of angular clasts...

s.

Biota

The first tetrapod

Tetrapod

Tetrapods are vertebrate animals having four limbs. Amphibians, reptiles, birds and mammals are all tetrapods; even snakes and other limbless reptiles and amphibians are tetrapods by descent. The earliest tetrapods evolved from the lobe-finned fishes in the Devonian...

 or land-living vertebrate from Antarctica was found in the Fremouw Formation and described in 1968. It was represented by a small bone fragment that is probably part of the left mandible

Mandible

The mandible pronunciation or inferior maxillary bone forms the lower jaw and holds the lower teeth in place...

 of a temnospondyl amphibian. The bone was found the previous year by a researcher from Ohio State University

Ohio State University

The Ohio State University, commonly referred to as Ohio State, is a public research university located in Columbus, Ohio. It was originally founded in 1870 as a land-grant university and is currently the third largest university campus in the United States...

 who was studying the geology of the Transantarctic Mountains. The animal was later named Austrobrachyops jenseni. After its discovery, paleontological expeditions were launched to the area around the Beardmore Glacier

Beardmore Glacier

The Beardmore Glacier in Antarctica is one of the largest glaciers in the world, with a length exceeding 160 km . The glacier is one of the main passages from the Ross Ice Shelf through the Queen Alexandra and Commonwealth ranges of the Transantarctic Mountains to the Antarctic Plateau, and was one...

 to uncover more fossils. Since then, fragmentary remains of temnospondyls, therapsids, and archosauriform reptiles have all been found in the formation. These fossils are found around the Shackleton

Shackleton Glacier

Shackleton Glacier is a major Antarctic glacier, over long and from 8 to 16 km wide, descending from the polar plateau from the vicinity of Roberts Massif and flowing north through the Queen Maud Mountains to enter the Ross Ice Shelf between Mount Speed and Waldron Spurs. The Roberts Massif...

 and Beardmore glaciers in places such as Gordon Valley

Gordon Valley

Gordon Valley is a small valley, the western half of which is occupied by a lobe of ice from Walcott Neve, lying west of Mount Falla in Queen Alexandra Range. Named by Advisory Committee on Antarctic Names after Mark A. Gordon, United States Antarctic Research Program aurora scientist at Hallett...

 and Fremouw Peak

Fremouw Peak

Fremouw Peak is a prominent peak, 2,550 m, forming the south side of the mouth of Prebble Glacier, in Queen Alexandra Range. Named by Advisory Committee on Antarctic Names for Edward J. Fremouw, United States Antarctic Research Program aurora scientist at South Pole Station, 1959....

.

Amphibians

Taxon	Member	Material	Notes	Images
Austrobrachyops jenseni	Lower Fremouw	Jaw fragment, pterygoid bone, and other small fragments	A nomen dubium Nomen dubium In zoological nomenclature, a nomen dubium is a scientific name that is of unknown or doubtful application... based on a combination of material from brachyopid Brachyopidae Brachyopidae is an extinct family of Temnospondyl labyrintodonts. They evolved in the early Mesozoic and were mostly aquatic. A fragmentary find from Lesotho, Africa is estimated to have been 7 meter long, the largest amphibian ever known to have lived besides Prionosuchus.-External links:*...  amphibians, a dicynodont Dicynodont Dicynodontia is a taxon of anomodont therapsids or mammal-like reptiles. Dicynodonts were small to large herbivorous animals with two tusks, hence their name, which means 'two dog tooth'... , and other animals
Cryobatrachus kitchingi Cryobatrachus Cryobatrachus is an extinct genus of prehistoric amphibian.-See also:* Prehistoric amphibian* List of prehistoric amphibians...	Lower Fremouw	A partial skull and other bone fragments	A temnospondyl
Kryostega collinsoni Kryostega Kryostega is a large temnospondyl amphibian from the Early or Middle Triassic of Antarctica. The genus is based on a single specimen collected in 1986 by a team led by paleontologist William H. Hammer of Augustana College, and now housed in the collections of the American Museum of Natural History...	Upper Fremouw	Large snout fragment	A temnospondyl
Parotosuchus Parotosuchus Parotosuchus is an extinct genus of capitosauroid temnospondyl within the family Capitosauridae. It was a two-metre-long giant salamander-like predator that lived during the Early Triassic inhabiting lakes and rivers... sp.	Upper Fremouw	Fragment of right side of snout	A temnospondyl
Rhytidosteidae Rhytidosteidae Rhytidosteidae is a family of Temnospondyli that lived in the Permian and Triassic.-References:*Yates, AM , A new tiny rhytidosteid from the Early Triassic of Australia and the possibility of hidden temnospondyl diversity. J. Vert Paleontol. 20:484-489.-External links:*...  indet.	Lower Fremouw		A temnospondyl

Reptiles

Taxon	Member	Material	Notes	Images
Archosauriformes Archosauriformes Archosauriformes is a clade of diapsid reptiles that developed from archosauromorph ancestors some time in the Late Permian...  indet.	Lower Fremouw	Partial presacral vertebra and left humerus Humerus The humerus is a long bone in the arm or forelimb that runs from the shoulder to the elbow....	A large-bodied archosauriform reptile
Palacrodon broomi	Lower Fremouw		An enigmatic diapsid Diapsid Diapsids are a group of reptiles that developed two holes in each side of their skulls, about 300 million years ago during the late Carboniferous period. Living diapsids are extremely diverse, and include all crocodiles, lizards, snakes, and tuatara...  reptile; initially named Fremouwsaurus geludens
Procolophon trigoniceps Procolophon Procolophon was a genus of lizard-like procolophonid reptiles with at least eight species that persisted through the Permian–Triassic extinction event, but became extinct in the later Triassic....	Lower Fremouw		A procolophonid Procolophonid The Procolophonids - family Procolophonidae - are a group of small reptiles. Skulls have been discovered, roughly 5 cm in diameter....  reptile
Prolacerta broomi	Lower Fremouw		A prolacertiform reptile

Synapsids

Taxon	Member	Material	Notes	Images
Cynognathus Cynognathus Cynognathus crateronotus was a meter-long predator of the Early to Middle Triassic. It was among the more mammal-like of the Synapsids, a member of a grouping called Eucynodontia. The genus Cynognathus had an almost worldwide distribution... sp.	Upper Fremouw		A cynodont Cynodont Cynodontia or cynodonts are a taxon of therapsids which first appeared in the Late Permian and were eventually distributed throughout all seven continents by the Early Triassic . This clade includes modern mammals and their extinct close relatives. They were one of the most diverse groups of...
Diademodontidae indet.	Upper Fremouw		A cynodont
Ericiolacerta parva Ericiolacerta Ericiolacerta was a small therocephalian therapsid from the early Triassic of South Africa and Antarctica. It was around in length, with long limbs and relatively small teeth. It was probably fairly active, and ate insects and other small invertebrates....	Lower Fremouw		A therocephalia Therocephalia Therocephalians are an extinct suborder of carnivorous eutheriodont therapsids that lived from the middle and late Permian into the Triassic 265.0—245.0 Ma existing for approximately .... n
Kannemeyeriidae Kannemeyeriidae Kannemeyeriidae is a family of large, stocky, beaked and sometimes tusked dicynodonts. They were the dominant large terrestrial herbivores through most of the Triassic period...  indet.	Upper Fremouw		A dicynodont Dicynodont Dicynodontia is a taxon of anomodont therapsids or mammal-like reptiles. Dicynodonts were small to large herbivorous animals with two tusks, hence their name, which means 'two dog tooth'...
Kombuisia antarctica Kombuisia Kombuisia is a genus of dicynodont from Early to Middle Triassic of South Africa and Antarctica. Two species was described for the genus: Kombuisia frerensis and Kombuisia antarctica....	Lower Fremouw		A dicynodont
Lystrosaurus curvatus Lystrosaurus Lystrosaurus was a genus of Late Permian and Early Triassic Period dicynodont therapsids, which lived around 250 million years ago in what is now Antarctica, India, and South Africa...	Lower Fremouw		A dicynodont
Lystrosaurus murrayi Lystrosaurus Lystrosaurus was a genus of Late Permian and Early Triassic Period dicynodont therapsids, which lived around 250 million years ago in what is now Antarctica, India, and South Africa...	Lower Fremouw		A dicynodont
Myosaurus gracilis Myosaurus Myosaurus is an extinct genus of dicynodont....	Lower Fremouw		A dicynodont
Pedaeosaurus parvus Pedaeosaurus Pedaeosaurus is an extinct genus of non-mammalian synapsid. Fossils have been found from the Fremouw Formation in the southern Transantarctic Mountains of Antarctica. Padaeosaurus has traditionally been classified as a scaloposaurid and more recently as an ericiolacertid closely related to...	Lower Fremouw		A therocephalian
Rhigosaurus glacialis Rhigosaurus Rhigosaurus is a genus of therocephalian therapsid.-References:*...	Lower Fremouw		A therocephalian
Thrinaxodon liorhinus Thrinaxodon Thrinaxodon was a cynodont, an ermine-sized therapsid. Pits on the skull suggest that Thrinaxodon may have had whiskers, and by extension a protective covering of fur. There are suggestions that it was warm-blooded...	Lower Fremouw		A cynodont

Paleoenvironment

Well-preserved plants are common in the Fremouw Formation. Logs have been found in channel deposits and roots and stems have been found in permineralized

Permineralization

Permineralization is a process of fossilization in which mineral deposits form internal casts of organisms. Carried by water, these minerals fill the spaces within organic tissue...

 soil. Smaller fossils on Fremouw Peak include cycad

Cycad

Cycads are seed plants typically characterized by a stout and woody trunk with a crown of large, hard and stiff, evergreen leaves. They usually have pinnate leaves. The individual plants are either all male or all female . Cycads vary in size from having a trunk that is only a few centimeters...

s, horsetail

Horsetail

Equisetum is the only living genus in the Equisetaceae, a family of vascular plants that reproduce by spores rather than seeds.Equisetum is a "living fossil", as it is the only living genus of the entire class Equisetopsida, which for over one hundred million years was much more diverse and...

s, seed ferns, Osmundaceae

Osmundaceae

The Osmundaceae is a family of four genera and 15-25 species. It is the only fern family of the order Osmundales; an order in the class Pteridopsida or in some classifications the only order in the class Osmundopsida...

 ferns, and even fungi. One cycad called Antarcticycas is similar in appearance to the living Bowenia

Bowenia

The genus Bowenia, includes two living and two fossil species of cycads in the family Stangeriaceae, sometimes placed on their own family Boweniaceae. They are entirely restricted to Australia...

of Australia

Australia

Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

. In 2003, 99 fossilized tree trunks were described from Gordon Valley. These trunks comprise an intact fossilized forest, allowing for an estimation of the distribution of plants and tree cover. Dicroidium

Dicroidium

Dicroidium is an extinct genus of fork-leaved seed ferns that were distributed over Gondwana during the Triassic . Their fossils are known from South Africa, Australia, New Zealand, South America and Antarctica...

fossils are present around the conifer-like stumps, suggesting that they were the leaves of these large trees. Based on the geology of the area, the trees grew alongside riverbanks and on floodplains. The structure of the plants show no adaptation toward cold tolerance, suggesting that the climate was much warmer in the Triassic.