A new species of Early Cretaceous ichthyosaur has been named and described following the study of fossilised remains found in Columbia. The fossils had previously been assigned to the ophthalmosaurian Platypterygius, but researchers from Canada, Germany and Columbia have erected a new species Kyhytysuka sachicarum.

An examination of the teeth in the jaws of the 94-cm-long skull, found that the anterior teeth were small whilst the teeth towards the back of the jaw were much bigger and robust. The researchers, who include Hans Larsson (Director of the Redpath Museum at McGill University), conclude that this ichthyosaur evolved unique dentition that enabled it to despatch large prey such as other marine reptiles.

The First Ichthyosaur Fossils from Columbia to be Described

The fossil specimen, consisting of a relatively uncrushed skull, preserved in three-dimensions, was the first definitive ichthyosaur material to have been found in Columbia (Paja Formation). The material was compared to other South American ichthyosaur fossils and assigned to the Platypterygius genus, being formally described and assigned to a new species – P. sachicarum in 1997.

Writing in the “Journal of Systematic Palaeontology”, the research team concluded that this fossil should really be placed in its own separate genus. The name Kyhytysuka translates from the ancient Muisca culture of central Columbia as “the one that cuts with something sharp”, a nod to the heterodont dentition in the jaw.

Hans Larsson explained:

“This animal evolved a unique dentition that allowed it to eat large prey. Whereas other ichthyosaurs had small, equally sized teeth for feeding on small prey, this new species modified its tooth sizes and spacing to build an arsenal of teeth for dispatching large prey, like big fishes and other marine reptiles.”

A Columbian Researcher Assists with the Study

This is an exciting opportunity for graduate researcher and co-author Dirley Cortés, who hopes to be able to continue to study Columbian marine reptiles, as she grew up in the mountainous area of Columbia close to where this fossil was discovered.

A Fearsome Predator

The dentition of Kyhytysuka sachicarum is unique among ichthyosaurs. This ichthyosaur had heterodont dentition (teeth of different shapes and sizes in the jaw), the teeth at the front of the jaw were small and designed to pierce, further along the jaw the teeth were larger, and adapted to cut flesh, whilst teeth at the back of the jaw were more robust and better at crushing. These teeth and other skull adaptations imply that Kyhytysuka evolved as an apex predator specialising in the hunting and consuming of large vertebrates such as fish and other marine reptiles. As such, this is the first example of a Cretaceous hypercarnivorous ichthyosaur. A hypercarnivore is defined as an organism whose diet consists of at least 70% meat.

The scientific paper: “Re-appearance of hypercarnivore ichthyosaurs in the Cretaceous with differentiated dentition: revision of ‘Platypterygius’ sachicarum (Reptilia: Ichthyosauria, Ophthalmosauridae) from Colombia” by Dirley Cortés, Erin E. Maxwell and Hans C. E. Larsson published in the Journal of Systematic Palaeontology.

Scientists have re-examined fossil bones associated with the Chinese mamenchisaurid dinosaur Hudiesaurus sinojapanorum and propose that the robust limb bone associated with this sauropod represents an entirely different genus which they have named Rhomaleopakhus turpanensis.

The forelimb bones are exceptionally stout and strong, particularly the ulna. The researchers, who include Professor Paul Barrett of the London Natural History Museum, speculate that strong forelimbs could have helped this dinosaur to “push off” from the ground so that it could rear up onto its back legs to feed. Strong forelimbs would also have helped to resist the deceleration forces as the huge dinosaur lowered itself back onto all fours.

Note – the scale bar in the picture (above) equals 20 cm. Although, only described from bones from the right forelimb, it is estimated that Rhomaleopakhus (pronounced Row-ma-lee-oh-pack-hus) could have been between 25 and 30 metres long.

Core Mamenchisaurus-like Taxa

In 1993, a joint Chinese/Japanese field team uncovered sauropod fossil material from the Jurassic-aged Kalazha Formation within Shanshan County in the Xinjiang Autonomous Region of north-western China. The fossils consisted of a single, huge vertebra, four teeth and a nearly complete right forelimb. On the basis of these fossils, a new member of the Mamenchisauridae family of long-necked dinosaurs was erected in 1997 – Hudiesaurus sinojapanorum. This dinosaur’s name translates as Chinese/Japanese butterfly lizard, in recognition of the co-operation between China and Japan in field excavations and because the vertebra had a flat butterfly-shaped process on the front base of the vertebral spine.

Having reassessed the fossil material ascribed to Hudiesaurus the scientists, writing in the “Journal of Vertebrate Palaeontology”, suggest that the bone from the spine, with its unique anatomical characteristics should remain the holotype material for H. sinojapanorum, but the forelimb which was found 1.1 kilometres from the vertebra and the teeth should not be assigned to Hudiesaurus. Indeed, the researchers propose that the robust forelimb with its own unique anatomical characteristics represents a new taxon. The teeth are too poorly preserved and can only be assigned to “core Mamenchisaurus-like taxa”.

Closely Related Mamenchisaurids

The researchers from the Chinese Academy of Sciences, University College London as well as the London Natural History Museum undertook a phylogenetic assessment of the Hudiesaurus and the newly assigned Rhomaleopakhus fossil material. The analysis indicates that Hudiesaurus is closely related to the “core Mamenchisaurus-like taxon” Xinjiangtitan, although differences between them indicate that they should remain separate genera for the time being. The four, poorly preserved teeth cannot be identified with any certainty, but they too probably represent a mamenchisaurid. Rhomaleopakhus too is very likely a member of the Mamenchisauridae family, albeit closely related to Chuanjiesaurus and Analong from the Middle Jurassic and found in Yunnan Province (south-western China).

The scientific paper: “Re-assessment of the Late Jurassic eusauropod dinosaur Hudiesaurus sinojapanorum Dong, 1997, from the Turpan Basin, China, and the evolution of hyper-robust antebrachia in sauropods” by Paul Upchurch, Philip D. Mannion, Xing Xu and Paul M. Barrett published in the Journal of Vertebrate Palaeontology.

This year (2021), has been another bumper year for dinosaur discoveries with over forty new species of dinosaur described, including several from the British Isles such as Pendraig (P. milnerae) from Wales and four new dinosaurs described from fossil finds on the Isle of Wight (Brighstoneus, Ceratosuchops, Riparovenator and Vectiraptor).

New genera are erected based on new fossil discoveries. In addition, a new dinosaur genus or species can be established based on a revision of existing and previously studied fossil material. A new genus of Late Cretaceous, Brazilian titanosaur was announced this year, based on fragmentary remains that had previously been assigned to a titanosaur that roamed Argentina. Time for Arrudatitan maximus to step out of the shadows.

Aeolosaurus maximus

The Aeolosaurus genus was erected by the Argentinian palaeontologist Jaime Powell in 1987 when the first species was named (A. rionegrinus). It was a widespread genus known from numerous individuals collected from Upper Cretaceous deposits, most notably the Angostura Colorada Formation in Río Negro Province, but dinosaur fossils collected from the Bajo Barreal, Los Alamitos and Allen Formations of Argentina have also been assigned to this genus.

The Brazilian fossil remains that led to the erection of the species Aeolosaurus maximus in 2011, have always been regarded as somewhat of an outlier when compared to Aeolosaurus fossil remains discovered in Argentina. A. maximus was described based on vertebrae, ribs, a left ischium, a fragmentary scapula and elements from the limbs including a left femur discovered in 1997 eroding out of an outcrop of the Adamantina Formation in the state of São Paulo state south-eastern Brazil.

Researchers who included Julian Silva Junior (Universidade de São Paulo), reassessed the fossil material following a cladistic analysis in 2019 that challenged the taxonomic placement. Writing in “Historical Biology”, the scientists have confirmed the assertion expressed previously that the Brazilian fossil material represents a distinct genus and the fossils ascribed to Aeolosaurus maximus have been reassigned to the new dinosaur species Arrudatitan maximus.

Commenting on the revision, lead author of the scientific paper, doctoral student Julian Silva Junior stated:

“When analysing the caudal vertebrae, we found that they were different to those assigned to Aeolosaurus and these characteristics served to establish a diagnosis to propose a new genus.”

2021 – A Good Year for Titanosaur Discoveries

Several new titanosaur genera have been erected this year including Menucocelsior (M. arriagadai) and Ninjatitan (N. zapatai), which is the oldest titanosaur known to science.

Everything Dinosaur’s list of new titanosaurs named in 2021

• Arackar licanantay a titanosaur from the Upper Cretaceous Hornitos Formation of Chile.
• Arrudatitan maximus from the Upper Cretaceous Adamantina Formation of south-eastern Brazil.
• Australotitan cooperensis a titanosaur from the Winton Formation of Queensland, Australia.
• Garrigatitan meridionalis from the Upper Cretaceous Argiles Rutilantes Formation of south-eastern France.
• Hamititan xinjiangensis from the Lower Cretaceous Shengjinkou Formation of north-western China which was coeval with the euhelopodid sauropod Silutitan (S. sinensis) which was also scientifically described in 2021.
• Menucocelsior arriagadai from the Upper Cretaceous Allen Formation of Argentina.
• Ninjatitan zapatai the earliest titanosaur known to date described from fossils found in the Lower Cretaceous Bajada Colorada Formation of Argentina.

To read blog posts about some of these newly described titanosaurs:

A new species of titanosaur from the Atacama Desert of northern Chile (Arackar licanantay): A New Titanosaur from Chile – Arackar licanantay.

Australian dinosaur “Cooper” named: “Cooper” – Australotitan cooperensis.

Our article on Hamititan xinjiangensis and Silutitan sinensis: Two New Sauropods from North-western China.

To read the Everything Dinosaur blog post about the earliest titanosaur known to science: Ninjatitan zapatai the Earliest Titanosaur.

The scientific paper: “Reassessment of Aeolosaurus maximus, a titanosaur dinosaur from the Late Cretaceous of Southeastern Brazil” by Julian C. G. Silva Junior, Agustín G. Martinelli, Fabiano V. Iori, Thiago S. Marinho, E. Martín Hechenleitner and Max C. Langer published in Historical Biology.