A New Medium-sized Abelisaurid – Niebla antiqua

A new species of Late Cretaceous abelisaurid theropod has been named based on fragmentary fossils found in northern Patagonia (Argentina).  The dinosaur has been named Niebla antiqua and it represents one of the most derived of all the abelisaurids described to date.  With an estimated body length of around 4 to 4.5 metres, Niebla is smaller than the roughly contemporaneous abelisaurid Quilmesaurus (Q. curriei), known from the same formation and considerably smaller than Carnotaurus sastrei.

Niebla antiqua

Described recently in a scientific paper published in the Journal of South American Earth Sciences, the description being based on ribs, weathered vertebrae, a near complete braincase, lower jaw fragments (dentary) and teeth plus a relatively intact scapulocoracoid (pectoral girdle), Niebla helps to strengthen the fossil record of abelisaurids known from the Maastrichtian.

The Location of the Niebla antiqua Fossil Discovery in Río Negro Province (Patagonia) and a Skeletal Drawing

Picture credit: Rolando et al (Journal of South American Earth Sciences)

The fossil material was found during excavation of exposed Allen Formation strata located near Matadero Hill in the province of Río Negro by CONICET researchers.  Their study suggests that abelisaurid evolution may be more complex than previously thought.

A Size Comparison Between Niebla antiqua and Carnotaurus sastrei

Picture credit: Everything Dinosaur

Adding to the Diversity of South American Members of the Abelisauridae

Abelisauridae dinosaurs are very well known from South America.  However, the fossil record of the very youngest members of this theropod family (abelisaurids associated with the Maastrichtian faunal stage of the Late Cretaceous), is relatively poor.  The researchers describe a new species (Niebla antiqua), although the fossils are highly fragmentary, they conclude that the material represents an adult animal and therefore this dinosaur was a medium-sized abelisaurid, much smaller than other coeval abelisaurids such as Carnotaurus and Abelisaurus.

The genus name is from the Spanish for “mist” a reference to the foggy conditions that the field team encountered when conducting the excavation, whilst the trivial or specific name refers to the great age of the strata.

A Medium-sized Abelisaurid

The braincase shows autapomorphic features (unique characteristics), such as a dorsoventrally tall basal tuber and postemporal foramen enclosed by parietal and exoccipitals.  The scapulocoracoid is notably similar to that of Carnotaurus (C. sastrei), the research team note a number of features including having a posterodorsally oriented glenoid, a dorsoventrally expanded and wide coraco-scapular plate and the blade of the scapula is very narrow and straight.  These anatomical traits are very different from those of other abelisaurids.  This might indicate a unique conformation of the pectoral girdle among these South American members of the Theropoda.

The scientific paper: “A new medium-sized abelisaurid (Theropoda, Dinosauria) from the late cretaceous (Maastrichtian) Allen Formation of Northern Patagonia, Argentina” by Mauro Aranciaga Rolando, Mauricio A. Cerroni, Jordi A. Garcia Marsà, Federico l. Agnolín, Matías J. Motta, Sebastián Rozadilla, Federico Brisson Eglí and Fernando E. Novas published in the Journal of South American Earth Sciences.

Visit the user-friendly Everything Dinosaur website: Everything Dinosaur.

Thalassodraco etchesi – A New Species of Ichthyosaur is Described

A new kind of ichthyosaur has been named and described (Thalassodraco etchesi) following the discovery of a partial, articulated skeleton preserved in a limestone concretion on the Dorset coast (southern England).   The fossil material consisting of the anterior portion of the marine reptile was discovered by renowned amateur fossil hunter Dr Steve Etches MBE, the founder of the Etches Collection museum, located on Kimmeridge Bay, not too far from where this new species was discovered.

This new species has been named Thalassodraco etchesi, the name translates as “Etches Sea Dragon”.

A Life Reconstruction of Thalassodraco etchesi

Picture credit: Megan Jacobs/University of Portsmouth

Unusual Dentition

Noticing the numerous, small teeth in the jaws, there are more than seventy teeth in the upper jaws alone, Steve passed his find onto researchers at the University of Portsmouth.  The scientific paper on the fifth known ichthyosaur from the Late Jurassic has been published in the on-line, open-access journal PLOS One.

Corresponding author of the paper, University of Portsmouth Masters student, Megan Jacobs, comments that at an estimated two metres in length, it is the smallest ichthyosaur from the Late Jurassic to be described to date.

The location of the fossil discovery – Kimmeridge Bay is part of the Jurassic Coast World Heritage Site.  The material comes from a limestone layer known as the White Stone Band.  When it died, the seafloor would have been a very soft ooze, allowing the front half of the animal to sink into the mud, before scavengers came along and ate the tail end.

The Beautifully Prepared Fossilised Remains of T. etchesi with an Interpretative Line Drawing

Picture credit: Jacobs and Martill (with permission to use the photograph from the Etches Collection)

As the anterior portion of the carcass was partially buried it was protected from being scavenged and the fine particles of mud which encased it provided conditions for exceptional preservation.  Stomach contents along with ligaments and some other soft tissues have been preserved.

Commenting on the specimen, Megan stated:

“Skeletons of Late Jurassic ichthyosaurs in the UK are extremely rare, so, after doing some research, comparing it with those known from other Late Jurassic deposits around the world, and not being able to find a match was very exciting.  Thalassodraco etchesi is a beautifully preserved ichthyosaur, with soft tissue preservation making it all the more interesting.  Steve’s incredible collection contains many new and exciting animals, and being given the chance to describe this ichthyosaur was a real privilege.”

A Deep Body but Small Forelimbs

The researchers noted the unusual body shape of the small ichthyosaur, it had a deep ribcage, small forelimbs and jaws lined with dozens of tiny, conical teeth.  It may have filled a slightly different niche in the Late Jurassic marine ecosystem compared to other ichthyosaurs.

Co-author of the paper, Professor David Martill, who leads the vertebrate palaeontology research unit at the University of Portsmouth commented:

“Steve is an exceptional fossil collector and although he is sometimes referred to as an amateur collector, he has done so much for palaeontology that he has been awarded an MBE, and is truly a pro.  If it were not for collectors like Steve, scientists would have very few specimens to work on.”

A Skeletal Reconstruction of Thalassodraco etchesi

Picture credit: Jacobs and Martill (PLOS One)

With the publication of the scientific paper formally naming this new species of marine reptile, the research does not end.  The team hope to study the specimen, which is part of the Etches Museum collection, learning more about the reptile’s biology.

Professor Martill explained:

“There are a number of things that make this animal special, not least of which is its unusual rib cage and small flippers.  It may have swum with a distinctive style from other ichthyosaurs.”

Our congratulations to Dr Steve Etches and all the team at the amazing Etches Collection museum on the Dorset coast.

The scientific paper: “A new ophthalmosaurid ichthyosaur from the Upper Jurassic (Early Tithonian) Kimmeridge Clay of Dorset, UK, with implications for Late Jurassic ichthyosaur diversity” by Megan L. Jacobs and David M. Martill published in PLOS One.

Visit the Everything Dinosaur website: Everything Dinosaur.