Petriellaceae

Petriellaceae; Temporal range:
	Illustration of Kannaskoppianthus telemagnus and Rochipteris telefolia And. & And. 2023
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Clade:	Gymnospermae
Class:	†Pteridospermopsida
Order:	†Petriellales; (Taylor, 1994)
Family:	†Petriellaceae; (Taylor, 1994)
Genera
	Rochipteris foliage; Kannaskoppianthus pollen organ; Kannaskoppia ovulate structure;
Synonyms
	Kannaskoppifolia And. & And. 2023

Petriellales is an extinct order of gymnosperms known from Middle Triassic (Olenekian) to Late Triassic (Rhaetian) floras of Gondwana, with fossil findings from Antarctica, Australia, southern Africa and South America. The family Petriellaceae is the only known family in the order. The order is characterized by fan-shaped leaves with anastomosing veins and forked reproductive structures represented by separate female ovulate and male microsporangiate organs. Petriellales plants are thought to have been part of humid understory vegetation of Triassic temperate forests, with fossil occurrences on the high latitudes of Southern Hemisphere.^[1]

Taxonomy and classification

Petriellales foliage and reproductive structures are most often found separately, which has made classification difficult.^[1]

The foliage genus Rochipteris was established in 2001 to define fan-shaped leaves with sparsely reticulate anastomosing venation from Triassic floras across southern Gondwana.^[2] Specimens now considered to fall under Rochipteris, have historically been assigned to Chiropteris and Psygmophyllum.^[3]Rochipteris differs from Chiropteris by apetiolate leaves (leaves directly attached to the stem) and sparse reticulate veining.^[3]

The genus Rochipteris was originally defined to include only isolated leaves and was noted as having no known reproductive structures.^[2] Connection between foliage genus Rochipteris (junior synonym: Kannaskoppifolia) and reproductive structures Kannaskoppia and Kannaskoppianthus was made when co-occurring fossil specimens were found in 2003.^[4]

Morphology

Foliage (Rochipteris)

General habit of Rochipteris has been described as "slender, erect, woody shrubs".^[1] The leaf form varies between cuneate (wedge-shaped) and flabellate (fan-shaped). Attachment to the stalk varies between genus with some leaves attached directly to the stalk and some leaves within the genius having a short leaf stalk. Veination is fine, forking, radiating from the base, subparallel to the segment margins and anastomosing. Lamina ranges from entire, trifid and segmented into narrow lobes.^[1]^[3]^[5]

Female ovulate (Kannaskoppia)

The ovulate organs of the Petriellales are represented by the genus Kannaskoppia, which compromise of fine proximally forked strobilus. On each strobilus, there are 8-12 megasporophylls adaxially with 90 degree angle between the two rows. Each megasporophyll carries one cupule that is bent backwards from the stalk. Cupules curve inwards and divide to three lobes when open. No seeds or ovules have been found.^[4]

Male microsporangiate (Kannaskoppianthus)

Microsporangiate organs of the Petriellales are represented by the genus Kannaskoppianthus, a ginkgoopsid strobilus characterized by proximally forked axis carrying up to 20 microsporophylls that are divided equally and arranged adaxially with 90 degree angle between the rows (similar to Kannaskoppia). Microsporophylls have a spathulate shape and are flattened, and host 5-10 elliptic microsporangia per unit. Pollen has not been observed. Diagnostic characters between Kannaskoppianthus species are 1) size and forking of the strobilus, 2) number of microsporophylls per limb, 3) number of microsporangia per head.^[1]

Paleoecology

Molteno Formation, southern Africa

Petriellales fossils from Upper Triassic Molteno Formation, southern Africa, are though to have occupied a wide range of habitats, but are most often associated with Heidiphyllum thicket, floodplain wetlands, riverine sandbanks and fern meadows.^[1]

Fremouw Formation, Antarctica

Fossils of Petriellales from the Fremouw Formation of Antarctica indicate that the group was part of a warm polar forest biome that experienced extreme seasonality in daylight. During the Triassic, high-latitude regions of Gondwana supported humid, densely vegetated forests under greenhouse conditions with extreme polar light regime.^[5]

Phylogeny

Paleogeographic occurrences

South America

La Profeta-Ternera Basin
Calingasta Basin
Malargue Basin
El Querco Los Molles Basin
Cuyo Basin
Biobio-Temuco Basin
El Tranquilo Basin^[5]

Southern Africa

Molteno Formation^[1]

Antarctica

Fremouw Peak, Central Transantarctic Mountains
Allan Hills, South Victoria Land^[5]

Australia

Telford Basin
Springfield Basin
Tasmania Basin
Council Trench deposits
Ipswich Basin
Esk Trough^[5]^[3]

Gallery

Information about the fossils can be found when clicking on the image.

R. rolleri
R. penensis
R. komifolia
R. vincularis
R. telefoila
R. matatifolia
R. sp
♂ K. lutinumerus
♂K. aasvoelensis
♂K. irregularis
♀ K. vincularis
♀K. vincularis, R. vincularis
♀K. vincularis

References

^ ^a ^b ^c ^d ^e ^f ^g Anderson, John Heidi (2023). Molteno Kannaskoppia Mid-Triassic gymnosperm case study for whole-plant taxonomy. ANNALS OF THE EVOLUTIONARY STUDIES INSTITUTE, UNIVERSITY OF THE WITWATERSRAND: PALAEONTOLOGIA AFRICANA.
^ ^a ^b Herbst, R.; Troncoso, A.; Gnaedinger, S. (2001). "Rochipteris nov. gen. leaf incertae sedis (= Chiropteris pro parte) Upper Triassic of Argentina and Chile". Ameghiniana. 38: 257–269 – via ResearchGate.
^ ^a ^b ^c ^d Barone-Nugent, E.D.; McLoughlin, S.; Drinnan, A.N. (1903). "New species of Rochipteris from the Upper Triassic of Australia". Review of Palaeobotany and Palynology. 123: 273–287 – via Elsevier Science Direct.
^ ^a ^b ANDERSON, J.M.; ANDERSON, H.M. (2003). "Heyday of the gymnosperms: systematics and biodiversity of the Late Triassic Molteno fructifications". Strelitzia. 15. National Botanical Institute, Pretoria.
^ ^a ^b ^c ^d ^e Bomfleur, Benjamin; Decombeix, Anne-Laure; Schwendemann, Andrew B.; Escapa, Ignacio H.; Taylor, Edith L.; Taylor, Thomas N.; McLoughlin, Stephen (2014). "HABIT AND ECOLOGY OF THE PETRIELLALES, AN UNUSUAL GROUP OF SEED PLANTS FROM THE TRIASSIC OF GONDWANA". Int. J. Plant Sci. 175 (9) – via ResearchGate.

[:0-1] ^ ^a ^b ^c ^d ^e ^f ^g Anderson, John Heidi (2023). Molteno Kannaskoppia Mid-Triassic gymnosperm case study for whole-plant taxonomy. ANNALS OF THE EVOLUTIONARY STUDIES INSTITUTE, UNIVERSITY OF THE WITWATERSRAND: PALAEONTOLOGIA AFRICANA.

[:1-2] Herbst, R.; Troncoso, A.; Gnaedinger, S. (2001). "Rochipteris nov. gen. leaf incertae sedis (= Chiropteris pro parte) Upper Triassic of Argentina and Chile". Ameghiniana. 38: 257–269 – via ResearchGate.

[:2-3] Barone-Nugent, E.D.; McLoughlin, S.; Drinnan, A.N. (1903). "New species of Rochipteris from the Upper Triassic of Australia". Review of Palaeobotany and Palynology. 123: 273–287 – via Elsevier Science Direct.

[:3-4] ANDERSON, J.M.; ANDERSON, H.M. (2003). "Heyday of the gymnosperms: systematics and biodiversity of the Late Triassic Molteno fructifications". Strelitzia. 15. National Botanical Institute, Pretoria.

[:4-5] Bomfleur, Benjamin; Decombeix, Anne-Laure; Schwendemann, Andrew B.; Escapa, Ignacio H.; Taylor, Edith L.; Taylor, Thomas N.; McLoughlin, Stephen (2014). "HABIT AND ECOLOGY OF THE PETRIELLALES, AN UNUSUAL GROUP OF SEED PLANTS FROM THE TRIASSIC OF GONDWANA". Int. J. Plant Sci. 175 (9) – via ResearchGate.

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