Fremouw Formation

Fremouw Formation
Fremouw Formation
Ma PreꞒ Ꞓ O S D C P T J K Pg N
Type	Approximate paleocoordinates
Region	Transantarctic Mountains of Antarctica
Type section
Named for	Fremouw Peak, Queen Alexandra Range, Antarctica.
Named by	P. J. Barrett
	Fremouw Formation (Antarctica)

The Fremouw Formation is a

riparian

forest at 70–75°S latitude.

Stratigraphy

The Fremouw Formation is mostly Triassic in age, with the oldest rocks dating back to the latest

quartzose sandstone that was deposited in stream beds.^[2] It overlies the Permian Buckley Formation, which consists of coal and Glossopteris fossils.^[3] 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 siltstones and mudstones, coarse-grained channel sandstones, and conglomerates.^[4]

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

fungi. One cycad called Antarcticycas is similar in appearance to the living Bowenia of Australia.^[5] 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 fossils are present around the conifer-like stumps, suggesting that they were the leaves of these large trees.^[6] Based on the geology of the area, the trees grew alongside riverbanks and on floodplains. The structure of the plants shows no adaptation towards cold tolerance, suggesting that the climate was much warmer in the Triassic.^[5]

The Fremouw Formation preserves many tetrapod fossils that span the

Pangea moved northward, putting pressure on populations that could not adapt to the warming climate. Antarctica, while much warmer in the Early Triassic than it is today, was cooler than other parts of Gondwana and may have been more hospitable to tetrapod populations. Antarctica's milder climate allowed many groups to take refuge in the region while other populations experienced decline. In the Early Triassic, many Fremouw Formation tetrapods had smaller body sizes than their Permian ancestors, and many were adapted for burrowing. Both of these characteristics are seen as adaptations to Antarctica's greater seasonal variability and protracted day-night cycles.^[7]

Biota

The first

archosauriform reptiles have all been found in the formation.^[9] These fossils are found around the Shackleton and Beardmore glaciers, in places such as Gordon Valley and Fremouw Peak

.

Tetrapods

Color key

Taxon	Reclassified taxon	Taxon falsely reported as present	Dubious taxon or junior synonym	Ichnotaxon	Ootaxon	Morphotaxon

Notes
Uncertain or tentative taxa are in small text; ~~crossed out~~ taxa are discredited.

Temnospondyls

Taxon	Species	Member	Material	Notes
Austrobrachyops	A. jenseni^[8]	Lower Fremouw	Jaw fragment, pterygoid bone, and other small fragments	A dicynodont, and other animals^[9]
Antarctosuchus	A. polyodon	Upper Fremouw	A mostly complete skull	A capitosaur temnospondyl
Cryobatrachus	C. kitchingi^[8]	Lower Fremouw	A partial skull and other bone fragments	A lydekkerinid temnospondyl
Kryostega	K. collinsoni^[10]	Upper Fremouw	Large snout fragment	A stereospondyl temnospondyl
Micropholis	M. stowi^[11]	Lower Fremouw	A block containing the skeletons of 4 individuals of the taxon, accounting for much of the skeletons.	A Euskelian temnopodyl
Parotosuchus	P. sp.^[9]	Upper Fremouw	Fragment of the right side of the snout.	A temnospondyl
Rhigerpeton	R. isbelli^[12]	Lower Fremouw	Partial skull	A lapillopsid temnospondyl
Rhytidosteidae	R. indet.^[4]	Lower Fremouw		A temnospondyl

Reptiles

Taxon	Species	Member	Material	Notes
Antarctanax	A. shackletoni^[13]	Lower Fremouw	Eight presacral vertebrae, left humerus, ribs, feet	Medium-sized archosauriform
Archosauriformes	Indeterminate.^[14]	Lower Fremouw	Partial presacral vertebra and left humerus	A large-bodied archosauriform reptile
Palacrodon	P. browni^[14]	Lower Fremouw		An enigmatic diapsid reptile; initially named Fremouwsaurus geludens
Procolophon	P. trigoniceps^[14]	Lower Fremouw		A procolophonid reptile
Prolacerta	P. broomi^[14]	Lower Fremouw		A prolacertiform reptile

Synapsids

Taxon	Species	Member	Material	Notes
Cynognathus	Cynognathus sp.^[15]	Upper Fremouw		A cynodont
Impidens	I. hancoxi^[16]	Upper Fremouw	Partial snout	A cynodont, originally described as Diademodontidae indet.^[15]
Ericiolacerta	E. parva^[17]	Lower Fremouw		A therocephalian
Kannemeyeriidae	Indeterminate.^[15]	Upper Fremouw		A dicynodont
Kombuisia	K. antarctica^[7]	Lower Fremouw		A dicynodont
Lystrosaurus	L. curvatus^[18]	Lower Fremouw		A dicynodont
Lystrosaurus	L. murrayi^[18]	Lower Fremouw		A dicynodont
Myosaurus	Myosaurus gracilis^[4]	Lower Fremouw		A dicynodont
Notictoides	N. absens ^[19]			A therocephalian
Pedaeosaurus	P. parvus^[17]	Lower Fremouw		A therocephalian
Rhigosaurus	R. glacialis^[17]	Lower Fremouw		A therocephalian
Thrinaxodon	T. liorhinus^[20]	Lower Fremouw		A cynodont

References

^ ^a ^b Barrett, P.J., 1969, Stratigraphy and petrology of the mainly fluviatile Permian and Triassic Beacon rocks, Beardmore Glacier area, Antarctica. Ohio State University Institute of Polar Studies Report 34, pp1-132 .
S2CID 10995542
.

^
S2CID 28006253
.

^ ^a ^b ^c "Background". Transantarctic Vertebrate Paleontology Project. Augustana College. 2008. Archived from the original on 7 July 2011. Retrieved 13 July 2011.

^ ^a ^b Taylor, E.L.; Taylor, T.N. (1993). "Fossil tree rings and paleoclimate from the Triassic of Antarctica" (PDF). In Lucas, S.G.; Morales, M. (eds.). The Nonmarine Triassic. Albuquerque: The New Mexico Museum of Natural History and Science Bulletin. pp. 453–455.

doi:10.1016/s0031-0182(03)00468-1
.

^
S2CID 20557454
.

^
hdl:2246/2750
.

^
doi:10.1671/0272-4634(2007)27[232:PTMFTT]2.0.CO;2
.

doi:10.1671/0272-4634(2008)28[656:ANTTFA]2.0.CO;2
.

ISSN 0272-4634
.

ISSN 0272-4634
.

S2CID 92116260
.

^
S2CID 129231144
.

^
doi:10.1080/02724634.1995.10011210
.

S2CID 237517965
.

^
hdl:2246/5362
.

^ ^a ^b Colbert, E.H. (1974). "Lystrosaurus from Antarctica" (PDF). American Museum Novitates (2535): 1–44.

ISSN 0272-4634
.

hdl:2246/2011
.

Retrieved from "https://en.wikipedia.org/w/index.php?title=Fremouw_Formation&oldid=1205598658"

[Barrett1969a-1] Barrett, P.J., 1969, Stratigraphy and petrology of the mainly fluviatile Permian and Triassic Beacon rocks, Beardmore Glacier area, Antarctica. Ohio State University Institute of Polar Studies Report 34, pp1-132 .

[Eetal70-2] S2CID 10995542
.

[BBC68-3] 
S2CID 28006253
.

[TVPPB-4] "Background". Transantarctic Vertebrate Paleontology Project. Augustana College. 2008. Archived from the original on 7 July 2011. Retrieved 13 July 2011.

[TT93-5] Taylor, E.L.; Taylor, T.N. (1993). "Fossil tree rings and paleoclimate from the Triassic of Antarctica" (PDF). In Lucas, S.G.; Morales, M. (eds.). The Nonmarine Triassic. Albuquerque: The New Mexico Museum of Natural History and Science Bulletin. pp. 453–455.

[CTTK03-6] :10.1016/s0031-0182(03)00468-1
.

[FAS10-7] 
S2CID 20557454
.

[CC74-8] 
hdl:2246/2750
.

[SSD07-9] 
doi:10.1671/0272-4634(2007)27[232:PTMFTT]2.0.CO;2
.

[SDH08-10] :10.1671/0272-4634(2008)28[656:ANTTFA]2.0.CO;2
.

[11] ISSN 0272-4634
.

[12] ISSN 0272-4634
.

[13] S2CID 92116260
.

[Cetal11-14] 
S2CID 129231144
.

[HWR95-15] 
doi:10.1080/02724634.1995.10011210
.

[Tolchard2021-16] S2CID 237517965
.

[CK81-17] 
hdl:2246/5362
.

[CEH74-18] Colbert, E.H. (1974). "Lystrosaurus from Antarctica" (PDF). American Museum Novitates (2535): 1–44.

[19] ISSN 0272-4634
.

[CK77-20] :2246/2011
.

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