A study of the fossilised remains of an as yet unnamed species of ankylosaurid suggests that these dinosaurs were adapted for digging. Whilst it seems unlikely that these large herbivores could have lived in burrows, they may have been able to dig for roots and tubers, excavate wells in dried up rivers to reach subsurface water and dig into sediments to obtain supplementary minerals in a similar way that extant elephants do today.

Picture credit: Everything Dinosaur

The model (above) is a Pinacosaurus armoured dinosaur from PNSO.

To view the range of PNSO dinosaur models: PNSO Prehistoric Animal Figures.

Digging Pits to Protect Their Undersides

Furthermore, many palaeontologists have postulated that these armoured herbivores might have been able to hunker down to defend their limbs and undersides from theropod predators. If these animals dug shallow pits they might have been able to protect themselves from attack and make it difficult for carnivorous dinosaurs to spot them when they were partially buried. Horned lizards (Phrynosoma) have a similar flat body and lateral fringe scales as seen in some types of ankylosaurid, these extant reptiles adopt these types of defensive strategies.

Discovered in the Early 1970s

Remains of an armoured dinosaur was first reported by a joint Soviet-Mongolian expedition to the southern Gobi Desert of Mongolia in the early 1970s. The skeleton consisting of dorsal vertebrae, elements from the limbs, ribs parts of the pelvis and the pectoral girdle along with several armoured scutes, was partially prepared for removal, but the excavation was not completed. The fossil specimen remained uncollected but crated up until 2008 when it was taken away for preparation by members of a Korean/Mongolian research team.

Probably a New Species of Armoured Dinosaur

The sandstone sediments of the Upper Cretaceous (Middle to Late Campanian stage), Baruungoyot Formation have yielded the remains of three ankylosaurid taxa, namely Saichania chulsanensis, Tarchia kielanae and Zaraapelta nomadis. Writing in the journal “Scientific Reports” the researchers which include such luminaries as Phil Currie and Eva Koppelhus (University of Alberta), Michael Ryan (Canadian Museum of Nature) and corresponding author Yuong-Nam Lee (Seoul National University, South Korea), state the unnamed ankylosaurid has some similarities to S. chulsanensis, but there are anatomical differences. Unfortunately, very little postcranial fossils of Tarchia kielanae and Zaraapelta nomadis have been found making it impossible to undertake a direct comparison with this specimen (MPC-D 100/1359).

Adapted for Digging

The scientists speculate that several anatomical features identified in MPC-D 100/1359 could indicate that this ankylosaurid was adapted for digging. The bones in its front feet are arranged in a shallow arc, which could have enabled it to dig soft earth. The fused vertebrae and the reduced number of bones in its hind feet, compared to other dinosaurs, may have helped anchor the ankylosaurid when digging or moving its tail. The body shape of MPC-D 100/1359, which is wider in the middle and narrower at the front and rear, may have helped its body to remain straight when digging. These traits such as the narrow-wide-narrow body shape and the manus (hand) and pes (foot) bone configuration are also known in other ankylosaurids.

Dig Those Ankylosaurs

Digging for resources out of reach from other animals and excavating shallow pits as part of a defensive strategy might have been prevalent amongst these armoured dinosaurs.

To read Everything Dinosaur’s article from 2014 about the discovery of Zaraapelta nomadis: New Species of ankylosaurid in Praise of Victoria Arbour.

The scientific paper: “A new ankylosaurid skeleton from the Upper Cretaceous Baruungoyot Formation of Mongolia: its implications for ankylosaurid postcranial evolution” by Jin-Young Park, Yuong-Nam Lee, Philip J. Currie, Michael J. Ryan, Phil Bell, Robin Sissons, Eva B. Koppelhus, Rinchen Barsbold, Sungjin Lee and Su-Hwan Kim published in Scientific Reports.

A team of international scientists including Steve Brusatte (University of Edinburgh), have confirmed the presence of troodontids in the Late Cretaceous of Europe. A new species of troodontid has been erected based on the discovery of a single metatarsal bone (the second metatarsal bone from the right foot), from Late Cretaceous strata in the Talarn Formation exposed at the Sant Romà d’Abella site in the southern Pyrenean region of Spain. This new dinosaur has been named Tamarro insperatus.

Picture credit: Oscar Sanisidro

Found in 2003

The single fossil bone indicating the presence of troodontids in Europe was found in September 2003 by a team of palaeontologists from the Museu de la Conca Dellà (Lleida, Isona, Spain) at the Sant Romà d’Abella site (Spain). It was found in fluvial floodplain deposits believed to have been laid down just 200,000 years or so before the K-Pg mass extinction event.

The fossil bone was found in the same horizon as plant fossils and the type specimen of the lambeosaurine Pararhabdodon isonensis, the metatarsal was found in close proximity to the Pararhabdodon type specimen, these are the only two vertebrates known from this site.

The Dinosaurs from the Late Cretaceous of Europe

During the Late Cretaceous, high sea levels ensured that much of the European landmass we know today was underwater. Numerous islands existed, creating an extensive archipelago and several dinosaurs associated with these islands exhibit dwarfism or other unusual features associated with isolated ecosystems. Very little is known about the Theropoda that inhabited these islands. For example, the presence of troodontids in Europe has been debated for a long time. Several troodontid-like and Paronychodon teeth (a nomen dubium taxa referred by some to the Troodontidae), were recovered from the Campanian and Maastrichtian deposits of the ancient Hateg (Romania) and Ibero-Armorican (Portugal, France and Spain) islands, but this fossil bone provides definitive, unequivocal proof of these theropods being present in the Late Cretaceous of Europe.

Picture credit: Albert G. Sellés (Institut Català de Paleontologia Miquel Crusafon/Museu de la Conca Dellà)

A Basal Troodontid with Asian Origins

An analysis of the bone and a phylogenetic assessment suggests that Tamarro is a basal member of the Troodontidae family and most likely a representative of the Asian subfamily the Jinfengopteryginae. The research team speculate on how a dinosaur with relatives in Asia could have become established in Europe. Maastrichtian troodontids like Tamarro could have reached Europe during the Cenomanian faunal stage and persisted on these islands until the K-Pg extinction event.

Estimated at around two metres in length Tamarro is around twice the size of other related troodontids. A close examination of the bone (cross-sectional histology), reveals that the metatarsal came from a subadult animal that was growing rapidly. Although troodontids are known to have fast growth rates, Tamarro seemed to be growing much quicker than other members of the Troodontidae, perhaps reaching full maturity in around two years.

The genus name is derived from the Catalan word “Tamarro” which refers to a small, mythical creature from local folklore. The species or trivial name “insperatus” is from the Latin for unexpected, a reference to the unexpected discovery of the fossil bone.

The scientific paper: “A fast-growing basal troodontid (Dinosauria: Theropoda) from the latest Cretaceous of Europe” by Albert G. Sellés, Bernat Vila, Stephen L. Brusatte, Philip J. Currie and Àngel Galobart published in Scientific Reports.

The Everything Dinosaur website: Dinosaur Models and Gifts.