Bennettite Paleoenvironments

Tiaojishan panorama 2wtmk

Bennettites show up in the fossil record first in the Middle Triassic. Late Triassic beds around the world show many fronds of Anomozamites, Pterophyllum, and Zamites.

Throughout the Jurassic bennettites were globally dominant plants. In some ecosystems they accounted for 75% of terrestrial plant life. McLoughlin and Pott (2009) suggested that the Jurassic should be called “The Age of Bennettitales’.

There is a characteristic global plant assemblage for the Jurassic. It includes a lowland vegetation of ferns (Cladophlebis, Coniopteris, Dicksonia, Raphaelia), seed ferns (Pachypteris, Sagenopteris), cycads (Nilssonia), and bennettites (Ptilophyllum, Pterophyllum, Nilssoniopteris, Zamites), riparian ginkgophytes (Czekanowskia, Phoenicopsis, Baiera) and upland conifers (Pityophyllum, Elatocladus). The conifer stands usually include cheirolepid conifers (Classostrobus = cone, Classopolis = pollen, Brachyphyllum, Pagiophyllum, Frenelopsis = leaves), which indicate drier conditions further upland from groundwater. With some local variations, this same basic assemblage is found globally throughout the Jurassic.

Cretaceous floras also include bennettites and many, like the Lower Cretaceous Wealden, Aguilar, and Potomac groups remain dominated by bennettites and the characteristic plant assemblage. The Lower Cretaceous Yixian Formation is more mesic and more wooded and is not dominated by bennettites. Nonetheless the plant community there includes at least three bennettite species, with Tyrmia being especially important, and retains the pattern of lowland ginkgophytes and upland conifer forests including cheirolepids.

Bennettites gradually waned in the Cretaceous, as angiosperms first appeared and then diversified. The spreading angiosperms probably competed with bennettites globally. Bennettites dwindled, finding refugia in Australia and Japan. The last known Mesozoic bennettite was Williamsonia, an ovulate cone from Late Cretaceous (Campanian) British Columbia.

•Rees, P.M., Ziegler, A.M. & Valdes, P.J. 2000. Jurassic phytogeography and climates: new data and model comparisons. In: Huber, B.T., Macleod, K.G. & Wing, S.L. (eds), Warm climates in earth history. Cambridge University Press: 297-318.

•Stockey, R.A. and Rothwell, G.W. 2003. Anatomically preserved Williamsonia (Williamsoniaceae): evidence for Bennettitalean reproduction inthe Late Cretaceous of Western North America. International Journal of Plant Science 164: 251–262.

•McLoughlin, S. and Pott. C. 2009b. Harvesting the extinct Bennettitales. Deposits Magazine 19:16–20.

 Late Triassic Bintan Flora (Indonesia).

Two – thirds of fossil plant taxa were bennettites, mostly small – sized leaves (Pterophyllum and Ptilophyllum, also Anomozamites, Otozamites, Zamites, Williamsonia, Bennetticarpus, Bucklandia) 2 conifers (Brachyphyllum, Podozamites) one cycad (Nilssonia). Wood, scales, large seeds, and fruits were found. No ferns or horsetails.

•Wade-Murphy, J. and Van Konijnenburg-van Cittert. J.H.A. 2008. A revision of the Late Triassic Bintan flora from the Riau Archipelago (Indonesia). Scripta Geologica 136: 73–104.

Middle Jurassic. Tiaojishan Formation (China).

Subtropical to warm temperate, humid, seasonal climate with diverse plant assemblage. 35.5% bennettites (Anomozamites, Bannetticarpus, Cycadolepis, Jacutiella, Pterophyllum, Ptilophyllum, Tyrmia, Williamsonia, Williamsoniella, Zamiophyllum, Zamites), 22.3% ferns (Cladophlebis, Coniopteris, Dicksonia, Raphaelia, Todites), 13.2% cycads (Lioxylon, Nilssonia, Ctenis), 14.5% ginkgophytes and 6.6% conifers. Classopollis indicates cheirolepids which, along with the other conifers, probably grew upland.

•Wang, Y.; Ken, S.; Zhang, W.; Zheng, S. (2006). “Biodiversity and palaeoclimate of the Middle Jurassic floras from the Tiaojishan Formation in western Liaoning, China”. Progress in Natural Science 16 (1): 222–230.

Middle Jurassic. El Consuelo Group, Oaxaca (Mexico).

Freshwater sediments, marine transgression areas with ammonites. Diverse bennettites (Anomozamites, Cycadolepis,  Otozamites, Pterophyllum, Ptilophyllum, Pseudoctenis, Williamsonia, Zamites) seed fern (Sagenopteris),  cycad (Nilssonia), pentoxylean(Taeniopteris).

•Perez-Crespo, V. A. 2011 Estado actual del conocimiento de las plantas fosiles de Oaxaca, Mexico. Naturaleza y Desarrollo vol. 9 no. 1. Pp.47-59.

•Wieland, G.R. 1914–1916. La Flora liásica de Mixteca Alta. Secretaría de Fomento, Boletín del Instituto Geológico de México, 31, 165 p.

Middle Jurassic. Ravenscar Group, Yorkshire and Oxfordshire (UK).

Harris (1952) suggested, and Krassilov (1974) confirmed, that these and other Eurasian floras may have been littoral mangrove thickets. The plant fossils are often found associated with marine plankton. Pachypteris, Stenopteris, Ptilophyllum and Zamites gigas are putatively salt – tolerant species. Above these lowland communities were coniferous forests of diverse shrubs and large trees, growing on the coastal slopes. Bennettites (Anomozamites, Nilssoniopteris, Otozamites, Pterophyllum, Ptilophyllum, Zamites), ferns (Cladophlebis, Todites), seed ferns (Sagenopteris, Pachypteris), cycads (Ctenis, Nilssonia, Pseudoctenis), ginkgophytes (Czekanowskia, Ginkgo, Baiera) and conifers ranging from shrubs to large trees (cheirolepids = Brachyphyllum, Pagiophyllum. Other conifers = Araucarites, Elatides, Cyparissidium, Pityocladus, marskea, Lindleycladus, Bilsdalea and Pelourdea).

•van Konijnenburg-van Cittert, J.H.A., 2008. The Jurassic fossil plant record of the UK area. Proceedings of the Geologists’ Association 119: 59-72.

•Harris, T. M. 1952.The zonation of the Yorkshire Jurassic flora. Palaeobotanist. 1: 207-217.

•Krassilov, V.A.  On the Siberian ‘Endemic’ Cycadophytes with some Phytogeographical Implications.1974. Symposium on Morphological and Stratigraphical Palaeobotany, Ranchi, India: Catholic Pi pp. 28-33.

Late Jurassic. Morrison Formation (USA).

Warm, seasonal, semiarid savannah of mostly herbaceous ferns. Shrubby growth with scattered trees, denser tree growth including Czekanowskia along waterways. Climate grows more humid in the Tithonian, diversity increases, and mesic trees like Podozamites and Pityophyllum, as well as more diverse ferns, proliferate. Cheirolepid leaves (Brachyphyllum) and pollen (Classopolis) may indicate upland stands of conifer trees. Floodplain covered with bennettites (Otozamites, Cycadolepis, Ptilophyllum, Pterophyllum, Weltrichia, Zamites), ferns (Cladophlebis, Coniopteris, Sphenopteris), seed ferns (Sagenopteris), cycads (Nilssonia), ginkgophytes, conifers (Brachyphyllum, Podozamites, Pityophyllum). Big sauropods grazing on low vegetation, cycadeoid leaf fragments found in dinosaur coprolites (Chin and Kirkland, 1998). Tidwell interpreted environment as more forested, and conifers are known, but large root fossils only found along waterways.

•Jurassic “savannah” – Plant taphonomy and climate of the Morrison Formation (Upper Jurassic, Western USA) 2004, Parrish, J. T.; Peterson, F.; Turner, C. E. Sedimentary Geology, 167: 137 – 162

•Chin, K., Kirkland, J.I., 1998. Probable herbivore coprolites from the Upper Jurassic Mygatt–Moore Quarry, western Colorado. Modern Geology 23, 249– 275.

•Tidwell, W.D., 1990a. Preliminary report on the megafossil flora of the Upper Jurassic Morrison Formation. Hunteria 2 (8) (12 pp.).

Late Jurassic. Vega Formation (Spain).

Study of soil around dinosaur footprints: roots, water features, and tracks. Shrubby, subhumid to semiarid habitat, similar to Morrison, but coastal, wetter and more seasonality. Wood and leaf fossils nearby, ferns, horsetails, cycads, conifers spatiotemporally nearby. Diverse dinosaurs, pterosaurs, turtles, and lizards.

•Gutierrez, K.A., and Sheldon, N.D. 2012, Paleoenvironmental reconstruction of Jurassic dinosaur habitats of the Vega Formation, Asturias, Spain: GSA Bulletin, v. 124, p. 596-610.

 Early Cretaceous. Yixian Formation (China).

Subtropical to temperate upland forest. Humid, warm, climate with arid to semi – arid dry season. Cheirolepids and growth rings indicate dry season. One study suggested four distinct zones: 1) intracoastal, waterside, semi-aquatic (Equisetes, Beipiaoa), 2) Lowland (Tyrmia, Coniopteris), 3) intermontane upland ( Liaoningocladus, Baiera) 4) xerophyte (Pagiophyllum, Gurvanella). Bennettites (Baikalophyllum, Rehezamites, Tyrmia, Wilsonia), ferns (Cladophlebis, Coniopteris), more diverse ginkgophytes and conifers.

•Wang, Y., Zheng, S., Yang, X., Zhang, W., and Ni, Q. (2006). “The biodiversity and palaeoclimate of conifer floras from the Early Cretaceous deposits in western Liaoning, northeast China.” International Symposium on Cretaceous Major Geological Events and Earth System, 56A.

•Ding, Q.H., Zhang, L.D., Guo, S.Z., Zhang, C.J., Peng, Y.D., Jia, B.,Chen, S.W. & Xing, D.H. 2003b: Study on the paleoecology of Yixian Formation in Beipiao area, western Liaoning province,China. Geology and Resources 12,9–18. (In Chinese with English abstract)

•Baikalophyllum lobatum and Rehezamites anisolobus: Two Seed Plants with” Cycadophyte” Foliage from the Early Cretaceous of Eastern Asia. C Pott, S McLoughlin, A Lindström, W Shunqing, E Marie Friis. International Journal of Plant Sciences-Botanical Gazette 173, 192-208.

•Wu SQ. A preliminary study of the Jehol flora from western Liaoning. Palaeoworld. 1999;13:7–57.

•Sze, H. C. On the Structure and Relationship of Phoroxylon scalariforme Sze .Acta Palaeontologica Sinica Vol II, No. 4, pp. 347-354, 1954.

Tiaojishan Formation plants, Middle Jurassic

Tiaojishan Formation plants, Middle Jurassic

LEGEND Tiaojishan thicket wtmk

Legend, Tiaojishan Thicket

Foreground, left to right

Cycad

1 Nilssonia, Lioxylon

Bennettites

2 Zamites

3 Pterophyllum festum

4 Anomozamites

5 Ptilophyllum, Williamsonia

6 Tyrmia

7 Ctenis

Ferns

8 Raphaelia

9 Marattia

Ginkgophytes

10 Phoenicopsis (sapling fallen into water)

Overhead, right

11 Sphenobaiera

Conifers

On opposite bank

12 Dicksonia

13 Podozamites

14 Pityophyllum

14 Classopolis (cheirolepid)

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2 responses to “Bennettite Paleoenvironments

  1. I am glad someone is paying attention to the plants!!! Nice pics too. Have you checked out Plants in Mesozoic Time edited by Carole T. Gee. Little hard to get but worth it. There is a chapter in there about the Morrison. They suggest a very diverse flora and find conifers dominant. This makes more sense to me, after all where in the world today do you see conifers sticking to riparian areas only? I think it was probably still fairly open, not closed canopy, but for sure would have been beautifully strange compared to our angiosperm dominated floras. Also keep in mind there are HUGE biases at work in the paleobotanical record. You can’t always trust pollen/spore as a proxy for abundance and the discrete chunks of plants preserved will be biased towards mesic environments.

  2. Thanks Duane. Yes, and Parrish et al. sought to review all of the literature critically. There is a paradox, where some of the conifers are from humid climate groups, while the sediments show semiarid features. Also, the diversity increases greatly as time goes on, and the climate apparently gets more mesic. I reconstructed the Morrison in the past as quite wooded, but the savanna idea definitely has its strengths. Also, I don’t think the conifers were only riparian, but the ginkgophyte leaf beds probably were, the way cottonwoods follow river courses in the American west today.

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