Pinacosaurus – Plank Lizard from Mongolia

Pinacosaurus lived during the Late Cretaceous in the ancient land of what is now Mongolia. It was a type of ankylosaur, which coexisted with various other dinosaur species. This herbivorous dinosaur, known for its armored plates, was not the largest of its kind but was nonetheless a significant presence in its habitat. Its contemporaries included Protoceratops, Saichania, Sinocephale, and Turanoceratops, each occupying different niches within the same environment and contributing to the diverse dynamics of their prehistoric ecosystem.

Pinacosaurus Key Facts

Pinacosaurus Origins, Taxonomy and Timeline

Pinacosaurus, or “plank lizard,” derives its name from the Greek words ‘pinax’ (plank) and ‘sauros’ (reptile/lizard). This name hints at its unique armor system. Belonging to the Ankylosauria group, specifically the ankylosaurid family, Pinacosaurus grangeri stands as its type species with an additional species, P. mephistocephalus. 

Taxonomically, this dinosaur finds its roots firmly in the ankylosaurid family tree, a lineage known for their armored bodies. The timeline of this herbivore spans the Late Cretaceous Period, specifically from the Early/Lower Cretaceous to the Campanian Agw. This timeline places it in a dynamic era of Earth’s history where many iconic dinosaurs thrived.

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Discovery & Fossil Evidence

The discovery of Pinacosaurus is a tale as intriguing as the dinosaur itself. It began in the Gobi Desert’s “Flaming Cliffs.” In 1923, Walter Granger, through the support of the American Museum of Natural History’s Central Asiatic Expeditions, unearthed the first remains of this genus in the Djadokhta Formation in Shabarakh Usu (Bayn Dzak), Mongolia. A decade later in 1933, Charles Whitney Gilmore officially labeled these remains as Pinacosaurus grangeri as a nod to Granger’s pioneering discovery. The holotype, AMNH 6523, included a partially crushed skull and other skeletal fragments.

In 1999, the narrative expanded with the naming of Pinacosaurus mephistocephalus, a second potentially valid species, by Pascal Godefroit. It is currently distinguished by nuances in its skull armor. This addition of a mostly articulated skeleton hinted at a more complex and diverse genus than initially thought.

Bonebeds at Alag Teeg

Remarkably, the fossils found to date are predominantly juveniles–possibly the highest number for any ankylosaur. These discoveries primarily occurred in bonebeds at Alag Teeg, now part of the Alagteeg Formation. Soviet-Mongolian expeditions in the late 1960s and early 1970s reported thirty skeletons, with subsequent Mongolian-Japanese and Canadian expeditions between 1993 and 2006 adding seventy more.

The abundance of juvenile remains offers a unique window into the early life stages of Pinacosaurus, painting a picture of a once thriving species. Each fossil discovery, from the initial find to the latest, contributes to piecing together the fascinating story of this Late Cretaceous marvel.

Pinacosaurus Size and Description

This medium-sized ankylosaurine measured approximately 16.0 feet in length and weighed up to 2.1 tons. This lightly built dinosaur was not as heavily constructed as some of its ankylosaur cousins. Its body was flat and low-slung, designed for a life close to the ground. Compared to an average human male, Pinacosaurus would have been quite imposing in size, roughly equivalent to the body mass of a horse.

The Dinosaur in Detail

The head of Pinacosaurus was a fortress in itself and protected by bone tiles. This is reflected in its name, meaning “plank lizard.” Each nostril was a large depression, intriguingly pierced by three to five smaller holes. The purpose of the holes remains a subject of speculation to this day. Its smooth beak was adept at biting off low-growing plants, which were then sliced by rows of small teeth and processed by its enormous hind gut.

The neck, back, and tail were shielded by an armor of keeled osteoderms, providing robust protection against predators. Moreover, this dinosaur wasn’t just passively armored; it could actively defend itself with a tail club. This combination of physical characteristics and defense mechanisms paints a picture of a creature well-adapted to its environment, capable of both enduring and responding to the challenges of its time.In 2015, Arbour and Currie identified some distinguishing traits of this genus. Notably, the upper snout armor didn’t consist of distinct tiles but rather a fused mass. Additionally, adult individuals possessed a skull that was longer than wide, a trait shared with distant relatives like Gobisaurus and Shamosaurus.

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Interesting Points about Pinacosaurus

Pinacosaurus in its Natural Habitat

Imagine an Asian landscape marked by the unique climate and geography of the Late Cretaceous. This herbivore roamed lands rich in vegetation, a crucial element of its diet. Its four-legged locomotion suggests a stable and deliberate movement, possibly aiding in foraging.

In terms of social behavior, concrete evidence is scarce. A group of skeletons representing a group of juveniles was found oriented in the same direction. This suggests a possible herd dynamic in Pinacosaurus. The discovery of a fossilized larynx–the oldest known so far from dinosaurs–implies that this dinosaur was capable of making loud vocalizations. This form of communication could be important in herds, allowing members to announce threats.

Contemporary Dinosaurs

In the ancient, sun-drenched lands that would one day be known as Mongolia, the sturdy Pinacosaurus meandered through the arid landscape, its armored back glinting under the relentless sun. This herbivorous Asian dinosaur, not the largest but certainly formidable, shared its world with a cast of contemporaries.

Imagine a scene where our main dinosaur encounters a Protoceratops. The Protoceratops, smaller and less armored, might have eyed Pinacosaurus warily–knowing full well that a competition for the sparse vegetation could ensue. Meanwhile, the Saichania, roughly the same size as our main dinosaur, could have been both competitor and companion. Their interactions may have been a mix of competitive foraging and mutual acknowledgment of each other’s armored prowess, adding a layer of complexity to Pinacosaurus’ existence.

Not all contemporaries were mere competitors, though. The domed head of the Sinocephale might have been an odd sight for Pinacosaurus. While not direct competitors due to different dietary preferences, their paths likely crossed. On the other hand, the smaller Turanoceratops might have steered clear of Pinacosaurus, understanding the unspoken hierarchy within their shared ecosystem.

In this ancient world, Pinacosaurus was not just an isolated creature; it was part of a vibrant tapestry of life. Each interaction, whether a competition for a patch of ferns or a peaceful coexistence, shaped its days. This armored giant amidst the dust and the heat played a central role in a prehistoric drama where survival was the main act, and its contemporaries were both co-stars and audience in the ever-unfolding story of life on Earth.

Frequently Asked Questions

Sources

The information in this article is based on various sources, drawing on scientific research, fossil evidence, and expert analysis. The aim is to provide a comprehensive and accurate overview of Pinacosaurus. However, please be aware that our understanding of dinosaurs and their world is constantly evolving as new discoveries are made.

This article was last fact-checked: Joey Arboleda, 11-03-2023