Permian Tropical Lowlands – A Hot Spot for Plant Evolution

Over recent days, team members at Everything Dinosaur have been reviewing the breadth and scope of the articles posted on this blog in the last twelve months.  The number of Sauropodomorpha themed articles (sauropods and their ancestors), has been commented upon.  There have certainly been some amazing early, long-necked dinosaur discoveries, but we have also had a lot of exciting fossil discoveries concerning the Plantae Kingdom to write about too.  In 2019, we have reported on research that suggests the very first land plants evolved earlier than previously thought.  We have also written about new compelling evidence that suggests that flowering plants (angiosperms), were present during the Middle Jurassic.

The Preserved Remains of a Seed Fern (Upper Permian Deposits – Jordan)

Picture credit: Palaeobotany Research Group, University of Münster/Blomenkemper et al

It seems fitting that our last post for 2019, once again looks at some remarkable plant fossil discoveries.

Scientists led by palaeobotanists from the University of Münster (western Germany), have uncovered a series of well-preserved fossils representing important plant groups from Upper Permian rocks at a site in Jordan.  The location, on the Dead Sea, has revealed the fossils of three major plant lineages:

1. Podocarpaceae – a type of conifer, an evergreen tree
2. Corystospermaceae – a type of seed fern (Pteridosperm)
3. Bennettitales – cycad-like plants which produced seeds in cone-like structures

All the fossils pre-date the End-Permian extinction event that wiped out around 95% of all the life on our planet and the fossils prove that all three plant groups evolved millions of years earlier than previously thought.  For example, the now extinct Bennettitales were thought to have evolved sometime in the Triassic.  These fossils confirm that their evolution took place much earlier and that all three types of plant evolved before and persisted through the greatest mass extinction event known in Phanerozoic Eon.

A “Hidden Cradle of Plant Evolution”

Fossilised twigs representing the Podocarpaceae, commonly referred to as southern conifers, as the vast majority of extant species are found in the Southern Hemisphere, have been found.  These fossils represent the oldest record of any living conifer family.  In collaboration with colleagues from the Smithsonian Institute (USA) and scientists from the University of Jordan, the team also discovered the preserved, carbonised leaves and reproductive organs of Corystospermaceae, a group of seed ferns that went extinct some 150 million years ago, as well as remains of Bennettitales, a peculiar lineage of extinct seed plants with flower-like reproductive organs.

Trekking Through the Wadis on the Dead Sea Coast Looking for Plant Fossils

Picture credit: Palaeobotany Research Group, University of Münster/Blomenkemper et al

Evidence for the unexpectedly early occurrence of Corystospermaceae in the Permian of Jordan was first published about ten years ago by a research team led by Prof Dr Hans Kerp.  Since then, researchers have uncovered not only the well-preserved leaves but also the characteristic reproductive organs of this group of plants.  Like Bennettitales and Podocarpaceae, these plants were believed to have evolved millions of years later during the Early Mesozoic.

One of the co-authors of the scientific paper, published in the journal “Science”, Benjamin Bomfleur (Palaeobotany Research Group, University of Münster), stated:

“Analysis of characteristic epidermal cell patterns enabled us to resolve the systematic relationships of the plant fossils more precisely.  The study area is really exceptional, like a melting pot of floral provinces.”

An Unusual Mix of Plant Taxa

The researchers noted that the plant fossils at the site represent a diverse and very mixed assemblage of plant types.  The sedimentary deposits were laid down in an equatorial coastal environment with a distinct dry season – an ecosystem that rarely preserves delicate plant fossils.  The scientists conclude that, early evolutionary innovations can occur in drought-prone tropical habitats which rarely offer the conditions needed for fossil preservation.

Dr Bomfleur added:

“The occurrence of no less than three major ‘modern’ plant groups in deposits of just this single rock formation may indicate that such stressed and disturbance-prone tropical environments may have acted as evolutionary cradles also for other plant groups.”

Exquisite Details Revealed by Acid Etching

Once the fossil material had been collected by the field team, a variety of methods were employed in the preparation laboratory to help identify the plant types the fossils represented.  Powerful acids were used on some specimens to prepare plant cuticles for detailed microscopic analysis.  It can be very difficult to distinguish pteridosperms from ferns based on foliage alone.  Similarly, the fossil leaves of cycads are very difficult to tell apart from those of true Bennettitales.  Identification is usually confirmed by examining microscopic details preserved in cells and on the cell wall of the cuticle, hence the need to use a variety of delicate techniques to reveal fine details.

Careful Exposure to Acids Helps Prepare Delicate Fossils for Microscopic Analysis

Picture credit: Palaeobotany Research Group, University of Münster/Blomenkemper et al

Survivors of a Mass Extinction Event

The plant fossils have been dated to approximately 255 million years ago (Lopingian Epoch of the Late Permian), so this ecosystem existed just a few million years prior to the “Great Permian Dying”, a mass extinction event that devasted both marine and terrestrial ecosystems.  The unexpected discovery of these three main groups of plants prior to this extinction event, not only pushes back the origins of these plant types in time, but also proves that all three groups survived the End-Permian extinction event.

Some of these lineages appear to span the mass extinction event, which suggests that the communities they supported may have been more stable than expected over this period of dramatic transition and change.  Thus, early evolutionary innovations can occur in drought-prone tropical habitats, which rarely offer the conditions needed for fossil preservation.  Seasonally dry tropical environments could be described as “cradles of evolution”.

The scientific paper: “A Hidden Cradle of Plant Evolution in Permian Tropical Lowlands” by Patrick Blomenkemper, Hans Kerp, Abdalla Abu Hamad, William A. DiMichele and Benjamin Bomfleur published in the journal Science.

Everything Dinosaur acknowledges the assistance of a press release from the University of Münster in the compilation of this article.

To read Everything Dinosaur’s blog post on the idea that the first land plants evolved millions of years earlier than once thought: Plants May Have Originated 100 Million Years Earlier.

To read Everything Dinosaur’s article about the discovery of fossils representing very early flowering plants: The First Flowering Plants Originated in the Early Jurassic.

Visit the Everything Dinosaur website: Everything Dinosaur.

Fourteen Years of Work to Tell the Story of “Little Foot”

Christmas is a time for family get togethers and spending time with relatives.  Today, we feature the astonishing story of the remarkable and nearly complete fossilised skeleton of an australopithecine nicknamed “little foot” a member of the Hominidae family and as such, a long, distant relative of us all.  The Sterkfontein Caves in South Africa are located around twenty-five miles north-west of Johannesburg in Gauteng Province (South Africa).

Numerous fossils of hominids are known from the Caves and the surrounding area, which is called the Cradle of Humankind and Everything Dinosaur has reported on several recent and highly significant australopithecine fossil finds, however, at an estimated 3.67 million years of age, “little foot” is the oldest australopithecine specimen ever found in southern Africa.

The Partially Uncovered Remains of the Australopithecine Nicknamed “Little Foot”

Picture credit: PAST/Paul Myburgh

Lead researcher Professor Ron Clarke and his team have published the first, formal scientific description of the fossil material in the “Journal of Human Evolution”.  Such is the completeness of the skeleton, that anthropalaeontologists confidently predict that many more papers will be written, as this is the only known, virtually complete fossil skeleton of an Australopithecus discovered to date.  It has taken fourteen years of painstaking work to excavate the fossils and six years to clean and prepare them for detailed study.

Dedicated Research Leads to Scientific Breakthrough

In 1994 and 1997, Professor Clarke identified twelve foot and lower leg bones of one Australopithecus individual misidentified as animal fossils in boxes stored at Sterkfontein and at the University of Witwatersrand (Johannesburg).  Clarke and his assistants, Nkwane Molefe and Stephen Motsumi, then looked for and located the very spot where the bones had been blasted out by lime miners, probably sometime in the 1920s deep inside the Sterkfontein Caves.  It was a real case of detective work, as Nkwane and Stephen worked in the caves to try to identify the very spot where the fossils that had been stored in the boxes, actually came from.

After one and a half of days of carefully searching the caves, they found that the pieces matched with two broken-through shin bones in a concrete-like cave infill and started the excavation process, first with hammer and chisel to remove the overburden, before turning to the painstaking process of locating and exposing the bones with an airscribe.

The Researchers were Able to Locate the Rest of the Skeleton by Matching Pieces Together

Picture credit: PAST/Paul Myburgh

Unusual Taphonomy of the Female Australopithecine

The taphonomy of “little foot” is unusual.  The female (identified by the shape of the pelvis), fell into a cave and the body became mummified in the exceptionally dry conditions.  The absence of predators allowed the body to remain undisturbed but at some time in the past there was a slight displacement of some skeletal parts through slippage on the rock-strewn talus slope in the cave, crushing and breaking of some bones through rockfall and pressure, calcification after a change to wet conditions, and then slight downward collapse of part of the cave infill.  This partial collapse left voids that were later filled with stalagmitic flowstone that encased breaks through the femurs.

When the first attempts to date the fossils was made, an analysis of the stalagmite flowstone encasing the fossil was made.  However, the flowstones were later infills in voids created by the collapse that had broken and displaced parts of the skeleton.  The data gave a more recent date for the fossil, “little foot” was actually much older, having lived during the Zanclean stage of the Pliocene Epoch.

Professor Ron Clarke Demonstrates the Use of an Airscribe

Picture credit: PAST/Paul Myburgh

Commenting on the earlier attempts to date the skeleton, Professor Clarke stated:

“The flowstones do not date the skeleton.  In 2015, cosmogenic isochron dates using 26Al and 10Be were published in Nature, showing that the age of the actual breccia containing the skeleton dates back ca 3.67 million years.  This is consistent with the original age estimates of around 3.5 million years that were proposed based on the low stratigraphic position of the deposit within the cave.”

Helping to Reassess the Australopithecus Genus

Study of the anatomical features of “little foot” suggests that the skeleton is most similar to the australopithecine known as A. prometheus, which was proposed as a species in 1948 by the famous anthropologist Raymond Dart.  The phylogeny of the australopithecines and related genera is controversial.  It is hoped that the virtually complete skeleton, so painstakingly excavated, will shed new light on taxonomic relationships, helping to fill in a number of evolutionary gaps.

Professor Ron Clarke and the Skull of “Little Foot”

Picture credit: PAST/Paul Myburgh

Everything Dinosaur acknowledges the assistance of a press release from the University of Witwatersrand and supporting materials in the compilation of this article.

Visit the Everything Dinosaur website: Everything Dinosaur.