Zilantophis schuberti –  A New Species of Snake from the Gray Fossil Site

A newly described species of prehistoric snake is helping herpetologists to better understand the evolution of modern snakes.  The new species, named Zilantophis schuberti is described in a scientific paper published this week in the “Journal of Herpetology”, it lived approximately five million years ago, a time when our planet’s global average temperature was rising.  Scientists hope that this new discovery will provide helpful information so that they can better understand the ways in which today’s fauna will adapt with the onset of global warming.

An Illustration of the Newly Described Snake – Zilantophis schuberti

A speculative drawing of the tiny snake – Zilantophis.

Picture credit: Steven Jasinski (University of Pennsylvania)

A Famous Fossil Site

Co-author of the paper, Steven Jasinski (PhD student at the University of Pennsylvania), explained that the fossils come from the famous Gray Fossil Site, close to East Tennessee State University, Jasinski and fellow author David Moscato (State Museum of Pennsylvania), report the discovery of highly modified, snake vertebrae, with wing-like struts, most probably to anchor strong back muscles.  The morphology (shape) of these bones do not match any living species of snake, it has been speculated that these snakes developed specialised vertebrae to help them push through compacted leaf litter as they hunted for insects and other small prey.  The specialised vertebrae may also have been an adaptation for digging or possibly swimming.  The idea that Zilantophis was aquatic is difficult to rule out.

Photograph and Line Drawing of a Highly-Modified Vertebra

The arrow notes the location of wing-like projections that gave the species its name (Zilantophis schuberti).

Picture credit: Steven Jasinski (University of Pennsylvania)

PhD student Steven commented:

“Snakes don’t have arms or legs,* but they have high numbers of vertebrae.  These are often the bones that palaeontologists use to identify fossil snakes.”

*Snakes and lizards belong to the Order Squamata, snakes evolved from limbed reptiles and recently Everything Dinosaur reported on the chance discovery of a 115-million-year-old fossil that provides evidence of the transition from reptiles with limbs to the serpentine form.

To read the article: First Fossil Snake with Four Limbs Described.

Named After a Mythical Creature

The genus name is derived from Zilant, a winged serpent from Tatar mythology.  The trivial name honours Blaine Schubert, the executive director of East Tennessee State’s Don Sundquist Centre of Excellence in Palaeontology, who acted as mentor and adviser to the authors whilst they studied there.  The ancient snake’s name translates as “Schubert’s winged snake”.

At only a few centimetres in length, Zilantophis was no monster, the tiny vertebrae had to be meticulously separated from the dark clay sediment of the Gray Fossil Site.  The researchers conclude that this Late Miocene/Early Pliocene snake is most closely related to rat snakes (Pantherophis) and kingsnakes (Lampropeltis), both of which are relatively common in North America today.  In total, the field team found evidence of seven different snake genera at the dig site, the descendants of which can still be found in east Tennessee today.

Field Team Members Working at the Sinkhole Dig Site

Field team members excavating the sinkhole (Gray Fossil Site).

Picture credit: Steven Jasinski (University of Pennsylvania)

Snake genera identified include:

• Garter snakes (Thamnophis)
• Rat snakes (Pantherophis)
• Pine snakes (Pituophis)
• Whip snakes (Masticophis)
• Water snakes (Nerodia)

Zilantophis schuberti and all the snakes listed above, are members of the Colubridae snake family, the largest and most specious group of extant snakes.  The authors comment that the Late Miocene was seeing a transition in snake fauna.  Boas had dominated the serpentine fauna of North America, but gradually the boas went into decline and they were replaced by the colubrids, which are typically much smaller and more mobile than boas.  This faunal change coincided with extensive climate change, with forests being replaced by open prairies as a result of a drying climate.

Steven Jasinski explained:

“Zilantophis was part of this period of change.  It shows that colubrids were diversifying at this time, including forms that did not make it to the present day.”

The Importance of the Gray Fossil Site

The Gray Fossil Site, located close to the town of Gray in Washington County (Tennessee), represents deposits from a sinkhole that accumulated in the Late Miocene to the very Early Pliocene Epochs.  As the clay deposits straddle the Miocene/Pliocene boundary, the strata and the fossils contained therein have provided researchers with an opportunity to study changing biodiversity at a time when the Earth’s climate was undergoing rapid change.  Discovered seventeen years ago, during the construction of a road, the site represents the accumulated debris from the bottom of a large pond, that occasionally dried out.  A wide variety of vertebrate fossils have been excavated from the site, including several large mammals, transitional forms of the American alligator, turtles, snakes and amphibians.

Excavating the Skull of a Tapir from the Dig Site

A tapir skull from the Gray Fossil Site (eastern Tennessee).

Picture credit: University of Pennsylvania

The Gray Fossil Site, has yet to be fully explored but it has already provided a hugely important window into the changing environment of North America between 7 million years ago and 4.5 million years ago (approximately).  This new research represents the first formal survey of snake fossils at the location, the discovery of Zilantophis, which dates from the Hemphillian stage of the North American Land Mammal Ages (NALMA), is helping scientists to understand evolutionary change at a crucial time in the history of the fauna of North America, a time when modern animals and plants were becoming established.

Ammonite Fossil Captures Brief Moment in Deep Time

Every once in a while, a fossil is found that provides a remarkable insight into life in the past.  An example of this is an Ammonite fossil that dates from the Late Jurassic.  The shell of the dead ammonite was rolled along the floor of a shallow lagoon, before it finally came to rest on the finely grained sediment.  An event that lasted for perhaps just a few seconds has been preserved within the fossil record, it has persisted for over 150 million years.

An Artist’s Illustration of the Ammonite Shell Drag

Capturing a moment in the Late Jurassic (cephalopod shell trackway).

Picture credit: Manchester University

The Solnhofen Plattenkalk (Solnhofen limestone)

Located in the southern German State of Bavaria, the world-famous limestone beds that form the Solnhofen Lagerstätte, preserve, in exquisite detail, a remarkable fossil record of animals and plants including soft-bodied creatures such as jelly fish and delicate insects such as dragonflies.  Many vertebrate fossils have also been excavated, perhaps the most famous of which are the fossils of the theropod Archaeopteryx, referred to as “Urvogel”, German for “first bird”.

The international team of scientists, which includes palaeontologist Dean Lomax (Manchester University), have been studying the 8.5-metre-long trackway a fossil of an ammonite shell as it was rolled along the soft, carbonate mud by the lagoonal currents.  At the end of the track, the cricket ball-sized ammonite (Subplanites rueppellianus) came to rest.

The Team of Scientists Mapped the Progress of the Ammonite Shell Across the Bed of the Lagoon

Mapping the path of the Ammonite shell across the floor of the lagoon.

Picture credit: Manchester University

The picture above shows the track of the ammonite (left to right), with line drawings of each element of the highlighted “tool mark” fossil shown below.  The ammonite itself can be found at the end of the track (extreme right).  The ammonite, a specimen of S. rueppellianus was already dead when the track was made, although fossils such as this have been found before, it is an extremely rare find.  Technically, although the shell left a drag mark in the sediment and the body fossil is preserved, the track itself can’t really be regarded as a trace fossil.

Studying Ammonite Trace Fossils

Trace fossils such as trails, footprints, burrows and borings preserve evidence of the activity of animals.  As the ammonite was dead when the track was created, it should not really be referred to as a trace fossil.  A more accurate term might be “tool mark” to describe the fossilised movement of the shell across the lagoon floor.

Dean, lead author of the scientific paper published in the on-line academic journal PLOS One, commented:

“With fossils, we usually find body fossils, such as bones, teeth or shells, or trace fossils, such as tracks and burrows.  However, the drag mark has not been made by the ammonite in life and does not reflect behaviour.  Instead, the drag mark was created by the lake’s current moving the ammonite shell.  It is easy to understand why such fossils have been misinterpreted as the traces of living organisms.”

Visit the website of Dr Dean Lomax: British Palaeontologist Dr Dean Lomax.

A Spectacular Record of a Late Jurassic Ecosystem

During the Late Jurassic, much of western Europe was covered by a warm, tropical sea.  There were islands and these were home to an array of dinosaurs and other exotic creatures.  The landscape included stagnant lagoons that had limited access to the open sea.  These shallow bodies of water were extremely saline and very few organisms could tolerate the harsh conditions.

As a result, if animal or plant remains were washed into the lagoon from the land, or if, in this case, an ammonite was washed into the lagoon from the sea, there were very few scavengers or micro-organisms around to ingest the organic material.  The still waters, devoid of life, helped the preservation of these animal and plant remains. Slowly, they would have become buried in the soft, finely grained mud at the bottom of the lagoon, or in this case a rare current had disturbed the rotting ammonite and rolled the shell along the lagoonal floor, before the shell finally fell over and came to rest.

Subplanites rueppellianus Fossil Preserved at the End of the Trackway

Subplanites rueppellianus preserved at the end of the track.

Picture credit: Manchester University

Plotting the Movement of the Ammonite

How exactly did the fossil move after it had already died?  Ammonites had gas chambers, which they used to control their buoyancy and movement, similar to a submarine.  However, the shell of the ammonite was probably empty and the authors of the study speculate that some of the gas remained present in the shell.  This meant the ammonite did not sink straight to the bottom and fall over.  Instead, the S. rueppellianus shell was dragged along the bottom of the tropical lagoon by what must have been a calm and steady current.

Dean Lomax Provides a Scale for the 8.5-metre-long Fossil Drag Mark

Dean Lomax (University of Manchester) examines the trace fossil.

Picture credit: Manchester University

The start of the drag mark is not preserved, so the shell may have been rolling for much longer.  The mark was created by contact of the ammonite’s ribs (ridges on the shell), with the lagoon floor.  The mark begins with just two lines, suggesting only two of the ammonite’s ribs were in contact with the bottom of the lagoon.  The number of ribs increases along the drag marks length.

Dean Lomax added:

“Fossils such as this are super rare and provide a snapshot of an unusual moment in deep time.”

Revolutionising the Way Palaeontologists Can Showcase Fossil Material

Intricate digital photogrammetry and three-dimensional modelling was used by the research team to create a detailed video of the fossil, showing the progression of the ammonite until its final resting place.

Dean Lomax Carefully Maps the Final Movements of the Ammonite Shell

Analysing the final movements of the ammonite shell.

Picture credit: Manchester University

Palaeontologist Peter Falkingham, (Liverpool John Moores University) and one of the co-authors of the study explained:

“We created a virtual model of the fossil by compiling over 600 photographs of the specimen.  We then created a video, which shows the drag mark and the preserved Ammonite.  Such modern techniques, like the photogrammetry method we used, have really revolutionised the way palaeontologists can study fossils.”

Everything Dinosaur acknowledges the help of the University of Manchester Press Team for their help in the compilation of this article.

Visit the Everything Dinosaur website: The Everything Dinosaur Website.