A newly discovered ornithopod dinosaur is helping to document faunal turnover in the early Late Cretaceous of North America. The dinosaur, named Iani smithi has been classified as a basal member of the Rhabdodontomorpha. This type of dinosaur is distantly related to the duck-billed dinosaurs (Hadrosauridae), which were to become extremely common by the Late Cretaceous.

The plant-eating I. smithi lived when the Earth was undergoing an intensive period of climate change. Global populations of dinosaurs were changing. Many long-established clades were dying out, being replaced with different types of dinosaur that were to dominate terrestrial environments until the end of the Mesozoic.

Iani smithi

Described from fossils excavated in 2014 from a quarry within the lower Mussentuchit Member of the Cedar Mountain Formation (Utah), the single specimen is thought to represent a juvenile. The fossil material consists of a disarticulated skull, vertebrae, limb elements, parts of the pectoral and pelvic girdles and ribs.

Researchers estimate that Iani lived approximately 99 million years ago (Cenomanian faunal stage of the Late Cretaceous). The Earth was rapidly warming due to increased concentrations of carbon dioxide in the atmosphere. Sea levels were rising and this dramatic period of climate change, known as the Cretaceous Thermal Maximum (KTM), led to extensive faunal turnover.

In North America, sauropods became rarer and eventually extinct (probably). Smaller ornithischian dinosaur clades began to dominate terrestrial environments. Spinosaurids and carcharodontosaurids were in decline. These theropods were eventually replaced by tyrannosaurs and abelisaurids.

This dramatic faunal turnover is reflected in the dinosaur’s name. The genus honours Janus – the two-faced Roman god of change.

The species name honours Joshua Aaron Smith. It is in recognition of his contribution to the discovery and conservation of paleontological resources in Utah.

A Rarity in North America

Iani smithi will help palaeontologists to better understand the transition of the Ornithopoda from Early Cretaceous groups to those bird-hipped dinosaurs that dominated Late Cretaceous terrestrial environments. Early rhabdodontomorphs such as Iani are exceptionally rare in the North American fossil record.

Corresponding author of the scientific paper, Lindsay Zanno (North Carolina State University) commented:

“Finding Iani was a streak of luck. We knew something like it lived in this ecosystem because isolated teeth had been collected here and there, but we weren’t expecting to stumble upon such a beautiful skeleton, especially from this time in Earth’s history. Having a nearly complete skull was invaluable for piecing the story together.”

A Phylogenetic Assessment of Iani smithi

Zanno and her team used the well-preserved skeleton to analyse the evolutionary relationships of Iani and were surprised, and at first sceptical of their findings.

Associate research professor Lindsay Zanno explained:

“We recovered Iani as an early rhabdodontomorph, a lineage of ornithopods known almost exclusively from Europe. Recently, palaeontologists proposed that another North American dinosaur, Tenontosaurus – which was as common as cattle in the Early Cretaceous – belongs to this group, as well as some Australian critters. If Iani holds up as a rhabdodontomorph, it raises a lot of cool questions.”

The picture (above) shows a model of Tenontosaurus from the CollectA Age of Dinosaurs Popular range.

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The research team speculate that Iani could be the last of its line. Studying this fossil specimen, in the context of environmental and biodiversity changes during the Cretaceous will provide insight into the history of our planet.

Lindsay Zanno added:

“Iani may be the last surviving member of a lineage of dinosaurs that once thrived here in North America but were eventually supplanted by duckbill dinosaurs. Iani was alive during this transition, so this dinosaur really does symbolise a changing planet.”

Everything Dinosaur acknowledges the assistance of a media release from the North Carolina State University in the compilation of this article.

The scientific paper: “An early-diverging iguanodontian (Dinosauria: Rhabdodontomorpha) from the Late Cretaceous of North America” by Lindsay E. Zanno, Terry A. Gates, Haviv M. Avrahami, Ryan T. Tucker and Peter J. Makovicky published in PLoS One.

A new taxon of armoured dinosaur has been described from fossils found on the Isle of Wight. The new ankylosaurid has been named Vectipelta barretti (pronounced Vec-tea-pelt-tah bar-rett-ee). The genus name is derived from the Roman name for the Isle of Wight “Vectis” and “pelta” the Latin for shield. The species name honours Professor Paul Barrett of the London Natural History Museum. This is the first dinosaur named honouring Professor Barrett. The name recognises the on-going contribution Professor Barrett has made to vertebrate palaeontology and his support and mentoring of other scientists who also worked on this study.

Vectipelta barretti

Lead author of the paper, published in the Journal of Systematic Palaeontology, Stuart Pond (London Natural History Museum), commented:

“This is an important specimen because it sheds light on ankylosaur diversity within the Wessex Formation and Early Cretaceous England.”

The fossil material consists of a partial skeleton. Cervical, dorsal, sacral and caudal vertebrae have been recovered along with numerous osteoderms, limb elements and a well-preserved but fragmentary pelvic girdle. The first fossils were discovered in the early 1990s, following a landslip west of Chilton Chine (south-western coast of the Isle of Wight). Like many armoured dinosaur fossils associated with the Wessex Formation, the fossils were ascribed to Polacanthus foxii. However, the researchers were able to identify several unique traits in the bones that confirmed that this was a new species.

Not Closely Related to Polacanthus

A phylogenetic analysis demonstrated that Vectipelta was not closely related to Polacanthus. It is more closely related to the geologically younger Chinese ankylosaurids Zhejiangosaurus and Dongyangopelta. This suggests that during the Early Cretaceous there may have been extensive faunal interchange between continents. The picture of ankylosaurid distribution and dispersal may be much more complicated than previously suspected.

To view models of ankylosaurids including Chinese armoured dinosaurs: PNSO Age of Dinosaurs Models and Figures.

Vectipelta is estimated to have measured around four metres in length. It would have been relatively slow-moving with broad hips.

When asked to comment about the spiky, ponderous dinosaur named after him, Professor Barrett stated:

“I’m flattered and absolutely delighted to have been recognised in this way, not least as the first paper I ever wrote was also on an armoured dinosaur in the NHM collections. I’m sure that any physical resemblance is purely accidental.”

More Wessex Formation Armoured Dinosaurs Awaiting Discovery

Although the Wessex Formation is notoriously difficult to date, Vectipelta fossil material is associated with the early Barremian. This armoured dinosaur could have roamed the Isle of Wight around 125 million years ago. The Polacanthus holotype material could be late Barremian in age. This suggests that Vectipelta barretti could be 6-8 million years older than Polacanthus foxii. The other ankylosaurid associated with the Wealden Group is Hylaeosaurus armatus. Hylaeosaurus fossils are associated with even older strata (Valanginian faunal stage). There could be as much as three million years separating Hylaeosaurus from Vectipelta.

The researchers conclude that there were probably lots of different armoured dinosaurs roaming southern England during the Early Cretaceous.

Historically, the assignment of fragmentary ankylosaurid remains to Polacanthus was probably incorrect. There are likely to be several other armoured dinosaurs awaiting discovery in the rocks of southern England and the Isle of Wight. Recent fossil discoveries have led to the revision of the hadrosauriforms and iguanodontids associated with the Wealden Supergroup. It is likely that the Thyreophora will also have to be revised and more taxa erected.

Everything Dinosaur acknowledges the assistance of a media release from the London Natural History Museum in the compilation of this article.

The scientific paper: “Vectipelta barretti, a new ankylosaurian dinosaur from the Lower Cretaceous Wessex Formation of the Isle of Wight, UK” by Stuart Pond, Sarah-Jane Strachan, Thomas J. Raven, Martin I. Simpson, Kirsty Morgan and Susannah C. R. Maidment published in the Journal of Systematic Palaeontology.

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A new study examining diapsid fossil teeth from Lower Triassic sediments in South Africa has provided further evidence of the recovery of terrestrial ecosystems after the end-Permian mass extinction event. The research highlights the growing diversity of archosauromorphs following the extinction of parareptiles and therapsids.

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Picture credit: Everything Dinosaur

Fossil Diapsid Teeth Study

The research team collected teeth from the Driefontein locality in Free State Province, South Africa. The strata represent Lower Triassic deposits (late Olenekian stage). The rocks are part of the Burgersdorp Formation and form part of the Karoo Basin, which provides an extensive geological record, crucially deposition that occurred before and after the end-Permian extinction event.

A total of 102 teeth were collected. The scientists identified 81 diapsid teeth with the remaining teeth classified as coming from temnospondyls. Analysis of the tooth morphology demonstrated that there was a greater diversity of archosauromorphs and other diapsids.

This research suggests that diapsids, especially archosauromorphs benefitted from the mass extinction event. They played an important role in the recovery of terrestrial ecosystems. Archosauromorphs filled many of the niches left vacant after the extinction of therapsids and anapsid reptiles.

For an explanation of the fauna and flora depicted in the image (above): Celebrating the Rise of South African Dinosaurs.

The Rise of the Dinosauria

The fossil teeth from Driefontein provide palaeontologists with an important window into how terrestrial ecosystems recovered. The largest mass extinction recorded in the Phanerozoic occurred approximately 252 million years ago. The end-Permian mass extinction event devastated both marine and terrestrial ecosystems. The Karoo Basin may yield further evidence to help palaeontologists to better understand how life bounced back from the mass extinction event. It may also help scientists to understand how the Archosauromorpha were able to gain an evolutionary advantage over other tetrapods. This may have ultimately helped the Dinosauria and their close relatives to dominate terrestrial habitats.

The scientific paper: “A diverse diapsid tooth assemblage from the Early Triassic (Driefontein locality, South Africa) records the recovery of diapsids following the end-Permian mass extinction” by Devin K. Hoffman, John P. Hancox and Sterling J. Nesbitt published in Plos One.

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