Bajadasaurus pronuspinax – Sauropod Defences

A newly described sauropod from northern Patagonia (Argentina), has provided palaeontologists with evidence to help explain why some of these long-necked dinosaurs evolved long, paired spines on the necks.  These features may have had a primary role as defensive structures helping to deter attacks from theropod predators.  The dinosaur has been named Bajadasaurus pronuspinax and it has been assigned to the Dicraeosauridae family, a sister family to the Diplodocidae within the Sauropoda.  Dicraeosaurids are characterised by having relatively shorter necks and distinctive vertebrae which had long, paired neural spines.  The function of these spines has long been debated.  They have been interpreted as playing a role in visual communication, sexual display and thermoregulation, however, this newly described dinosaur suggests that within this family of long-necked dinosaurs they evolved as a form of defence.

Illustrating Bajadasaurus pronuspinax and the Fossil Find Location

Picture credit: Gallina et al published in Scientific Reports

The image (above), shows a skeletal reconstruction of the head and neck of Bajadasaurus (A), with the preserved fossil material shown in white.  On the right of the image is a location map (B), showing the site of the fossil find, close to the Ezequiel Ramos Mexía lake in Neuquén Province, Argentina.  A line drawing is provided (C), that shows the association and the location of the fossils found at the dig site.

Interpreting Fossils One Cervical Vertebra at a Time

The authors of the scientific paper, propose that the elongated neural spines of this dinosaur always faced forward, presenting a formidable obstacle for any meat-eating dinosaur wanting to attack the animal’s neck.  However, it is worth noting that if the image (above), is studied, the theory of Bajadasaurus having a neck topped with defensive spikes, like some sort of Victorian railings is based on the discovery of a single neck bone, in the skeletal illustration placed in the position of the fifth cervical vertebra.  The appearance of B. pronuspinax is inferred by comparing these fossils to the better-known Amargasaurus (A. cazaui).  Until more fossils are found the appearance of Bajadasaurus and the orientation of those neural spines can only be speculated.

A Model of the Dicraeosaurid Amargasaurus

Lead-author of the study, Pablo Gallina and his colleagues, propose that these neural spines may have been covered with keratin and therefore much longer than the spines themselves.  The extent of the neural spines, the length of the keratin sheaths that covered them and the direction they pointed in, remains unknown.  Until more fossils of Bajadasaurus are found, those elongated neural spines remain a mystery.

Naming a New Dinosaur

That one cervical spine forms the basis for the species epithet.  The genus honours Bajada (Spanish for downhill), a reference to the fossil find location – Bajada Colorada.  The species name means “bent over, forward spines”, we shall see if more fossil discoveries reaffirm this interpretation.  Importantly, the fossil material assigned to Bajadasaurus includes much of the skull, thanks to these fossils, the palatal bones, the braincase and a nearly complete left dentary, palaeontologists have a much better idea about the size and morphology of dicraeosaurid dinosaur skulls.

Skull Material Associated with Bajadasaurus pronuspinax and Line Drawing

Picture credit: Gallina et al published in Scientific Reports

The skull is quite small for a sauropod, dicraeosaurids described to date were not as big as some of their diplodocid cousins.  Size estimates range from around 10 to 13 metres in length.  The size of Bajadasaurus is unknown, but based on these fossils, it is likely that this dinosaur was within this size range too.  The orbits are quite large and their position on the top of the skull suggests that when this dinosaur had its head down and it was feeding, it was capable of seeing ahead (forward-directed, stereoscopic vision).

Comparing Bajadasaurus to the Geologically Younger Amargasaurus

The strata of the Bajada Colorada Formation represent sediments laid down at the very beginning of the Cretaceous (Lower Cretaceous, Berriasian/Valanginian faunal stages).  Bajadasaurus roamed Patagonia some 140 million years ago.  Amargasaurus, lived in the same part of South American but around fifteen million years later.

A Model of the Sauropod Dinosaur Bajadasaurus

Picture credit: Everything Dinosaur

The picture (above) shows a CollectA Deluxe Bajadasaurus dinosaur model.

To view this model range: CollectA Deluxe Age of Dinosaurs Models.

The researchers suggest that the temporal difference between Bajadasaurus and Amargasaurus, supports the idea that the development of an array of defensive spines was likely adaptive over a long time period.  How effective these spines may have been against predators, is once again, open to speculation.  However, the presence of elongated neural spines would have given the impression of a larger animal with a thicker neck.  To a hungry, carnivorous dinosaur the appearance of a bigger more robust adversary may have been enough of a deterrent.

The scientific paper: “A New Long-spined Dinosaur from Patagonia Sheds Light on Sauropod Defence System” by Pablo A. Gallina, Sebastián Apesteguía, Juan I. Canale and Alejandro Haluza published as an open access article in the journal “Scientific Reports”.

Visit the Everything Dinosaur website: Everything Dinosaur.

Single Feather Not From Archaeopteryx

One of the most significant fossils to have ever been found, an iconic fossil in vertebrate palaeontology – a single fossilised feather from the Upper Jurassic Solnhofen limestone, is not quite what it seems.  The feather, long thought to be from an Archaeopteryx, is probably not from the “urvogel” at all.  The feather most likely was lost by a dinosaur, before it was blown into a shallow, calm lagoon and preserved as a carbonised film for 150 million years.

The Iconic Single Feather Fossil – Once Synonymous with Archaeopteryx is Not What it Seems

An international research team which included Dr Michael Pittman (University of Hong Kong), have applied a novel, high-tech, imaging method called Laser-Stimulated Fluorescence (LSF), to  help solve a 150-year-old mystery and to confirm that this feather was not from Archaeopteryx.

Discovered in 1861

The specimen was discovered in 1861 and actually consists of a slab and counter slab component, housed in museums located in Berlin and Munich.  A year later, the fossil feather was formally described and heralded as coming from an Archaeopteryx (A. lithographica), although unlike most feather impressions associated with the dozen or so Archaeopteryx specimens known to science, this feather was preserved as a dark, carbonised film.  This was the first fossil feather ever discovered and at the time fossils of Archaeopteryx were heralded as evidence of a “missing link”, supporting Darwin’s recently published theory of natural selection.

The detailed scientific description published in 1862 commented upon a rather long quill visible on the fossil, but this is unseen today.  Even recent X-ray fluorescence and UV (ultraviolet), imaging studies did not end the controversy of the “missing quill”.  The original existence of this quill has therefore been debated and it was unclear if the single feather represented a primary, secondary, or primary covert feather from Archaeopteryx.

Archaeopteryx

Writing in the academic journal Scientific Reports, the researchers outline their work using the LSF technology and demonstrate its potential for providing new information about extensively studied fossil specimens.  The application of Laser-Stimulated Fluorescence is being developed by Thomas G Kaye of the Foundation for Scientific Advancement, Sierra Vista, Arizona (USA) and Dr Pittman.

Dr Pittman stated:

“My imaging work with Tom Kaye demonstrates that important discoveries remain to be made even in the most iconic and well-studied fossils.”

Detecting the Geochemical Presence of the Lost Quill

The application of LSF technology permitted the scientists, which included lead-author of the study Tom Kaye, to detect the geochemical halo from the rachis, matching the 1862 description.

Views of the Isolated Solnhofen Feather – Not from Archaeopteryx

Picture credit: University of Hong Kong

Not Archaeopteryx but Probably from a Feathered Dinosaur

The shape of the feather has led the researchers to discount the idea that it came from an Archaeopteryx.  Instead, they conclude that it probably came from an unknown species of feathered dinosaur that lived alongside Archaeopteryx in the Solnhofen Archipelago.

Daniela Schwarz, a co-author of the scientific paper based at the Museum für Naturkunde, Berlin, commented:

“It is amazing that this new technique allows us to resolve the 150-year-old mystery of the missing quill.”

This new insight into an iconic fossil specimen also suggests that the diversity of feathered dinosaurs was likely higher in the ancient island archipelago than previously thought.

Tom Kaye added:

“The success of the LSF technique here is sure to lead to more discoveries and applications in other fields.  But, you’ll have to wait and see what we find next!”

Visit the award-winning Everything Dinosaur website: Everything Dinosaur.