Scientists writing in the journal “Nature” have announced the discovery of a new species of Late Cretaceous ankylosaur from southernmost Chile. The dinosaur named Stegouros elengassen evolved a large tail weapon, unlike any other tail weapon known in the Dinosauria. Stegouros had a flat, frond-like structure formed by seven pairs of laterally projecting osteoderms. This formidable tail weapon superficially resembles a macuahuitl, a frightening war club used by Aztec warriors.

A life reconstruction of the newly described Gondwana ankylosaur Stegouros elengassen. Picture credit: Mauricio Álvarez.

Picture credit: Mauricio Álvarez

A Combination of Stegosaur and Ankylosaur Anatomical Characteristics

The researchers from the University of Chile (Universidad de Chile) in Santiago report on an articulated, nearly complete fossil specimen representing a single animal that was excavated by a field team in February 2018 from sediments relating to the Dorotea Formation in the province of Ultima Esperanza in southern Chile. Stegouros was very small for an ankylosaur, measuring around two metres in length and weighing approximately 100 kilograms.

It shows ankylosaurian cranial characters, but a largely ancestral postcranial skeleton, with some stegosaur-like characters.

A phylogenetic analysis places Stegouros in the Ankylosauria and the research team postulate that it is closely related to other ankylosaurs known from southern Gondwana such as Kunbarrasaurus from Australia and Antarctopelta, fossils of which were found on James Ross Island off the Antarctic Peninsula.

Field team members jacket the fossilised remains of Stegouros. Picture credit: Universidad de Chile.

Picture credit: Universidad de Chile

The Parankylosauria Clade

The researchers propose the establishment of a new clade of ankylosaurs – the Parankylosauria which consists of basal ankylosaurs that split from the main ankylosaurian lineage during the Middle Jurassic, although the fossil evidence for this is currently lacking with Stegouros, Antarctopelta and Kunbarrasaurus forming part of a ghost lineage of basal ankylosaurs with origins back in the mid-Jurassic.

The posterior of the Stegouros specimen with the armoured tail clearly shown. Picture credit: Universidad de Chile.

A Transitional Ankylosaur

Commenting on the significance of this fossil discovery, lead author of the scientific paper, Sergio Soto, a researcher at the University of Chile stated that the fossilised remains of S. elengassen represent a “Rosetta Stone” for deciphering the fragmentary fossils of other ankylosaurs from southern Gondwana.

He added:

“Stegouros is an evolutionary link between ankylosaurs and other older lineages of armoured dinosaurs. Stegouros has only some of the features normally found in ankylosaurs, particularly the skull, but many others are absent. It also has some traits similar to stegosaurs, inherited from a common ancestor with them, but that other ankylosaurs lost in evolution.”

Picture credit: Universidad de Chile

Stegouros roamed the Chilean Patagonia around 74 million years ago. The genus name translates as “roofed tail”, whilst the species name comes from a mythical armoured monster from the folklore of the indigenous Tehuelche people.

Note

CollectA introduced a 1:6 scale figure of this remarkable dinosaur in 2023.  Safari Ltd also added a Stegouros model to their range in 2024.

The CollectA Deluxe 1:6 scale Stegouros elengassen dinosaur model – due to be available mid 2023.

To view the range of CollectA Deluxe prehistoric animal figures available from Everything Dinosaur: CollectA Deluxe Prehistoric Life Models.

The scientific paper: “Bizarre tail weaponry in a transitional ankylosaur from subantarctic Chile” by Sergio Soto-Acuña, Alexander O. Vargas, Jonatan Kaluza, Marcelo A. Leppe, Joao F. Botelho, José Palma-Liberona, Carolina Simon-Gutstein, Roy A. Fernández, Héctor Ortiz, Verónica Milla, Bárbara Aravena, Leslie M. E. Manríquez, Jhonatan Alarcón-Muñoz, Juan Pablo Pino, Cristine Trevisan, Héctor Mansilla, Luis Felipe Hinojosa, Vicente Muñoz-Walther and David Rubilar-Rogers published in the journal Nature.

The Everything Dinosaur website: Dinosaur Toys and Models,

Known from a single specimen discovered in Spain back in 1993 Pelecanimimus (P. polyodon) from the Las Hoyas lagerstätte was the first unambiguous ornithomimosaur described from Europe. Although the scientific paper erecting the genus was published in 1994, no detailed examination of the holotype fossil material (LH 7777) had been undertaken.

A re-examination of the holotype fossil has been carried out by a team of international scientists, which included Francisco Ortega, one of the authors of the original scientific paper describing this 2-metre-long theropod. They conclude that Pelecanimimus was remarkably bird-like although as a member of the Ornithomimosauria it was not that closely related to the dinosaur lineage that led to the evolution of the birds.

An Ossified Sternum

Pelecanimimus when it was named, was the only ornithomimosaur that had a preserved ossified sternum. The sternum is not usually preserved in theropods, it has been suggested that this part of the skeleton was not ossified and therefore it did not fossilise well, or perhaps the absence of this structure was due to preservational bias. The distance observed between the coracoids in articulated theropod specimens led to many palaeontologists inferring its presence. In this new paper, the researchers examined the shape of the sternum and concluded that its morphology was similar to the sternums of dinosaurs more closely related to birds such as Velociraptor and Oviraptor (the Maniraptora clade).

Pelecanimimus Breathed Like a Bird

Furthermore, the research team found evidence of the presence of uncinate processes. These small, hook-shaped bones are linked to the ribs and are also present in extant and extinct birds. Pelecanimimus is the only known representative of the Ornithomimosauria with these structures and this is the first time that uncinate processes have been found in a non-maniraptoran theropod. If maniraptorans evolved these structures, along with the distantly related Pelecanimimus, this suggests convergent evolution.

In birds, uncinate processes function to increase the mechanical advantage for movements of the ribs and sternum during respiration. They make breathing more efficient. In summary, the research team suggest Pelecanimimus, breathed like a modern bird.

Elena Cuesta, the lead author of the study from the Fukui Prefectural University, Japan explained:

“The fact that Pelecanimimus preserved these processes suggests that it also had a bird-like breathing mechanism. Apparently, the origin of such avian-like features is older and more widespread than thought. However, the evolutionary history of both the ossified sternum and uncinate processes is still unclear. Nevertheless, their detection in Pelecanimimus confirms that these elements were present in Ornithomimosauria as well as in other dinosaurs.”

Distinctive Features on the Hands

The joint Japanese/Spanish research team also discovered distinctive features on the hands. The manus of Pelecanimimus has conspicuously elongated metacarpals, particularly metacarpal I and lengthened distal phalanges, a feature also found in some later, more derived ornithomimosaur species. The authors of the study conclude that these anatomical features require the erection of a new clade, the Macrocheiriformes. This clade is defined as including Pelecanimimus and more derived ornithomimosaurs. The term Macrocheiriformes, means “forms with large hands.”

The scientific paper: “Pelecanimimus (Theropoda: Ornithomimosauria) postcranial anatomy and the evolution of the specialized manus in Ornithomimosaurs and sternum in maniraptoriforms” by Elena Cuesta, Daniel Vidal, Francisco Ortega, Masateru Shibata and José L Sanz published in the Zoological Journal of the Linnean Society.

A new dinosaur from Appalachia – Parrosaurus missouriensis.

For much of the Cretaceous the North American landmass was effectively divided into two, by a shallow sea (Western Interior Seaway). At its greatest extent it was around 1,000 kilometres (600 miles) wide, the long, narrow landmass that represented the western part of North America is known as Laramidia and palaeontologists have amassed a huge amount of data about the abundant dinosaurs that roamed these ancient shores. The eastern landmass, Appalachia, stretched from Newfoundland in the north, to the mid-west American states, but in comparison little is known about the Appalachian dinosaur fauna.

A new species of duck-billed dinosaur has been added to the Appalachian biota, named Parrosaurus missouriensis and as the species epithet suggests, this Late Cretaceous herbivore was found in Missouri.

Very Rare Dinosaur Discovery

In contrast to the extensive, rapidly eroding “Badlands” of Montana, Wyoming and North/South Dakota, rocks of Cretaceous age from the ancient landmass of Appalachia are not exposed to any great extent in eastern North America. Dinosaur fossil bearing units are not being eroded, they remain buried under other strata and to add to this dilemma, much of the eastern part of the USA is conurbation. However, there are bright spots for palaeontologists looking for dinosaur bones.

Mines, eroding rivers and construction sites can all provide opportunities for fossil discoveries. Indeed, it was the digging of a well near to the village of Glen Allen in Bollinger County, south-eastern Missouri back in 1942 that led to the finding of several dinosaur bones, the first time such fossils had been reported from the “Show Me State”.

The caudal vertebrae that were excavated from the site were thought to represent a sauropod and it was scientifically described and named Neosaurus missouriensis in 1945 (Gilmore and Stewart). It was noted that the genus name was already occupied, Neosaurus having been erected in 1869 for a Palaeozoic synapsid from France, so the scientific name was changed to Parrosaurus missouriensis.

Duck-billed Dinosaur Fossils

Ironically, duck-billed dinosaur fossils had been found in North Carolina and the species Hypsibema crassicauda was erected in 1869, a review of the Glen Allen material (Baird and Horner), led to the erection of the species Hypsibema missouriensis as the Missouri fossils were confirmed to be hadrosaurid and showed similarities with the fossils that had been found in North Carolina.

More recent excavations carried out at the Glen Allen site, led by fossil expert Guy Darrough and with the support of the Field Museum of Chicago has led to the discovery of at least four individual hadrosaur specimens. The fossils found in close association in black clay represent three adults and juvenile.

The site has yielded other fascinating fossils, providing a glimpse into the fauna of Appalachia. For example, a scute (dermal armour) from a giant crocodilian has been found, fossils of turtles discovered and even the tooth of a tyrannosaur has been uncovered.

Parrosaurus missouriensis

The extensive fossil material found as led to the establishment of a new species Parrosaurus missouriensis. This very notable fossil location might just prove to be a headache for the State administration, as in 2004 these fossils had been declared Missouri’s official State dinosaur when they were assigned to Hypsibema missouriensis.

The story has been widely reported and team members at Everything Dinosaur are optimistic that once the fossil material has been studied in detail and more of the specimens cleaned and prepared, then new discoveries will be made.

This month has seen another new species of sauropodomorph named and described. Issi saaneq (pronounced is-y sa-ah-neq), roamed what is now eastern Greenland around 214 million years ago (Late Triassic), this new dinosaur has been named based on two fossil skulls believed to represent one juvenile and one older animal possibly a sub-adult. Ascribed to the Plateosauridae family and showing affinities to South American sauropodomorphs I. saaneq helps to extend our understanding of the evolution and development of these important early dinosaurs.

Originally Assigned to Plateosaurus

The skull fossils were found in the early 1990s, during excavations of sediments representing lake shore deposits that make up part of the of the Malmros Klint Formation in Jameson Land, Greenland. The larger skull was found in 1991, the smaller skull, now believed to represent the same species was found subsequently along with numerous other fossils including skull material that has yet to be catalogued and described.

The two skulls (specimen numbers NHMD 164741 and NHMD 164758), are now part of the vertebrate fossil collection of the Natural History Museum of Denmark. Postcranial material was also found in association with the smaller skull (NHMD 164758) and this could have come from the same animal, but these bones have also not yet been examined in detail.

When first found, it was thought that these fossils were examples of Plateosaurus (P. engelhardt which is now regarded as nomen dubium with fossil material assigned to P. trossingensis). As several new sauropodomorphs had been described in recent years, the researchers were able to tap into the wealth of new fossil data and confidently assign the skulls to a new genus.

Commenting on the significance of the find, lead author of the scientific paper, published in the journal “Diversity”, Doctor Victor Beccari (Universidade Nova de Lisboa), stated:

“The anatomy of the two skulls is unique in many respects, for example in the shape and proportions of the bones. These specimens certainly belong to a new species.”

“Cold Bone” – Issi saaneq

Issi saaneq is the first non-avian dinosaur to be named from fossils found in Greenland. The name comes from the local Inuit language, with “issi” meaning cold and “saaneq” meaning bone. This is a reference to the harsh and very unpleasant weather conditions associated with the fossil site. The bones of this dinosaur were cold to the touch and the field team were often “frozen to the bone” as they worked in the extremely chilly conditions.

Affinities with South American Sauropodomorphs as well as Plateosaurus

Phylogenetic assessment indicates that Issi saaneq has affinities to Brazilian plateosaurids such as Macrocollum (M. itaquii) and the European Plateosaurus, being recovered as the sister clade of Plateosaurus in this study. It is the northernmost record of a Late Triassic sauropodomorph.

To read Everything Dinosaur’s blog post about the naming and scientific description of Macrocollum itaquii: How Did Some Dinosaurs Get Long Necks?

The discovery of Issi saaneq expands the known geographical range of these dinosaurs and broadens our knowledge about the evolution of the Sauropodomorpha.

The scientific paper: “A New Sauropodomorph Dinosaur from the Late Triassic (Norian) of Jameson Land, Central East Greenland” by Victor Beccari, Octávio Mateus, Oliver Wings, Jesper Milàn and Lars B. Clemmensen published in Diversity.