In the rugged terrains of what is now Argentina, a unique dinosaur roamed the earth over 230 million years ago. Chromogisaurus, known as the “Earth-Colored Lizard,” thrived during the Carnian Epoch of the Late Triassic Period. This (likely) herbivorous dinosaur, a basal member of Sauropodomorpha, offers a fascinating glimpse into the diverse prehistoric life that once dominated our planet.

Discovered in the Valle Pintado locality of the Ischigualasto Formation. Chromogisaurus was originally unearthed in 1988 during a joint field trip carried out by the Natural Sciences Museum of Argentina, the National University and Museum of San Juan, and the University of Chicago. This find had to wait over twenty years until it was finally given formal description by Martín Ezcurra in 2010. It has provided valuable insights into the early evolution of Basal Sauropodomorph dinosaurs. Let’s delve into the world of Chromogisaurus, exploring its origins, physical characteristics, and the environment it once inhabited.

Chromogisaurus Key Facts

Chromogisaurus Origins, Taxonomy and Timeline

The name Chromogisaurus, meaning “Earth-Colored Lizard,” is derived from the Greek words “chroma” (color), “gi” (ground), and “sauros” (lizard). This name pays homage to the vibrant Valle Pintado (Painted Valley) locality in the Ischigualasto Formation, where its fossils were discovered. Pronounced KROH-mo-gee-SORE-us, the name encapsulates the essence of its earthy origins.

Taxonomically, Chromogisaurus is classified within the basal sauropodomorph group and has been resolved as a member of the saturnaliine family in most recent cladistic analyses. As is often the case with most long-extinct taxa, the type species, Chromogisaurus novasi, stands alone within its genus. Residing at the very base of Sauropodomorpha, Chromogisaurus and its saturnaliine clademates were little differentiated from the primitive dinosaur condition – with these small, bipedal lizards barely hinting at the colossal sauropods they would later give rise to.

Chromogisaurus lived during the Late Triassic Period, specifically towards the end of the Carnian Epoch, which spans from 237.0 to 228.0 million years ago (MYA). This era was a time of significant evolutionary changes, when the early ancestors of many later dinosaur groups began to emerge. The presence of Chromogisaurus in this period provides crucial insights into the early stages of sauropodomorph diversification, as well their adaptation to changing environments and evolving dietary habits.

Discovery & Fossil Evidence

Chromogisaurus was first discovered in 1988 at the northern margin of the Valle Pintado site in the Ischigualasto Formation, located within the Ischigualasto-Villa Union Basin in San Juan Province, Argentina. A team of South and North American paleontologists unearthed the holotype specimen, cataloged as PVSJ 845. This initial find included partial skeletal remains, providing a foundation for understanding its anatomy and classification.

The formal description of Chromogisaurus was published in 2010 by Martín Ezcurra. There is a limited number of fossils. However, the available specimens have been critical in reconstructing the dinosaur’s physical characteristics and evolutionary significance. The preservation of these fossils has allowed paleontologists to study the anatomical details, contributing to our knowledge of early Sauropodomorphs.

The fossils of Chromogisaurus include isolated tail vertebrae, fragmentary forelimb material, and most of the hindlimb and pelvis. These remains have been instrumental in identifying key features that distinguish it from other early sauropodomorphs. Despite the limited amount of material, the degree of preservation has enabled detailed studies, providing insights into its morphology and lifestyle.

Chromogisaurus Size and Description

Short Description of Chromogisaurus

Chromogisaurus was a small basal sauropodomorph dinosaur, characterized by its relatively lightweight and agile build. Its elongated body was supported by strong, slender limbs, facilitating bipedal locomotion. Like other sauropodomorphs the head would have been proportionally small, with a mouth full of small, coarsely-serrated teeth ideal for snipping at the low-hanging vegetation that was forming an increasingly large part of its diet.

The vertebral column of Chromogisaurus was flexible yet sturdy, supporting its overall body structure. Its forelimbs were shorter than the hind limbs but robust enough to assist in foraging and possibly in brief quadrupedal movement. The tail was long and balanced, aiding in its bipedal stability. No direct evidence of skin is available. However, it is presumed to have been covered in scales, typical of early dinosaurs.

Size and Weight of Type Species

The type species, Chromogisaurus novasi, measured approximately 6.5 feet in length and stood about 1.6 to 2.5 feet tall at the hips. Weighing between 44.0 to 66.0 pounds, this dinosaur was a veritable pipsqueak compared to its later sauropod relatives. This smaller stature would have been advantageous in the diverse and possibly densely vegetated environments of the Late Triassic, allowing it to navigate through various terrains with ease.

The available fossil evidence, though partial, provides a reliable basis for these size and weight estimates. These measurements are crucial for understanding its role in the ecosystem, its interactions with other species, and its survival strategies. The relatively small size of Chromogisaurus underscores the adaptability of sauropodomorph dinosaurs, especially when considered against the unprecedented jump in size that the group would undergo over the ensuing 20 million years. 

The Dinosaur in Detail

Chromogisaurus exhibited several curious features that set it apart from later sauropodomorphs. One of its most distinctive traits was its lightweight and agile build, which allowed for efficient bipedal locomotion. This agility would have been essential for foraging and evading predators, highlighting its adaptability in a dynamic environment.

Based on closely related species, the dental structure of Chromogisaurus alluded to the increasing amounts of plant material that these fledgling herbivores were beginning to consume. While still retaining the small, pointed teeth primitive to early dinosaurs, the serrations along the edges of early sauropodomorph teeth were larger and coarser. This likely represents an adaptation for cropping and processing tough vegetation. This dietary habit, while novel for dinosauria, would prove enormously successful for the group – both figuratively and literally! 

Furthermore, Chromogisaurus likely had a well-developed sensory system, with keen vision and possibly a strong sense of smell. These sensory adaptations would have been crucial for detecting predators and locating food sources. The combination of these sensory and physical traits enabled Chromogisaurus to thrive in the diverse environments of the Late Triassic, showcasing its evolutionary success and adaptability.

Contemporary Dinosaurs

During the Late Triassic, Chromogisaurus shared its environment with several other notable dinosaurs, creating a vibrant and competitive ecosystem. Among these contemporaries were Saturnalia, Panphagia, Eoraptor, and Pampadromaeus, each contributing to the dynamic interactions within their habitat, while underscoring the incredible rates of diversification that Sauropodomorpha was experiencing at the time.

Saturnalia, a fellow member of the saturnaliid family, is known from slightly further north in the Late Triassic Santa Maria Formation of Brazil. This dinosaur was similar in size and likely shared similar herbivorous habits. The overlap in their habitats suggests they might have competed for similar food resources, but slight differences in feeding strategies could have allowed them to coexist without direct competition.

Panphagia, another early sauropodomorph, was also part of this ancient ecosystem. Its name means “All Eater,” reflecting its likely omnivorous diet. This diverse diet would have reduced direct competition with Chromogisaurus. However, it’s very possible the latter also engaged in opportunistic omnivory when the occasion presented itself. The presence of Panphagia highlights the varied dietary adaptations that existed among early dinosaurs, promoting ecological diversity.

Pampadromaeus, another small sauropodomorph, shared similarities with Chromogisaurus in terms of size and diet. The coexistence of these two dinosaurs suggests a rich and varied plant life in their environment, supporting multiple herbivorous species. Their interactions would have contributed to the ecological complexity of the Late Triassic landscapes.

A sauropodomorph Theropod?

Eoraptor was originally considered one of the earliest known theropods. It is now also considered to be one of the earliest sauropodomorphs. This ambiguity highlights just how minimally the two main herbivorous and carnivorous branches of saurischian dinosaurs had diverged at this early point in time – with some sauropodomorphs still retaining a superficially ‘carnivorous’ aspect. While still likely a facultative omnivore, the presence of Eoraptor indicates a complex food web where herbivory likely still had to be supplemented by these primitive dinos more ‘traditional’ foodstuffs.

Interesting Points about Chromogisaurus

Chromogisaurus in its Natural Habitat

Chromogisaurus thrived in the varied and dynamic environments of the Late Triassic Period. The climate during this time was generally warm and semi-arid, with seasonal rainfall influencing the types of vegetation and water sources available. The Ischigualasto Formation, where Chromogisaurus was discovered, was characterized by a mix of floodplains, river systems, and forested areas, providing a rich habitat for diverse plant and animal life.

As a herbivore, Chromogisaurus primarily fed on the abundant vegetation, possibly augmented by a spot of opportunistic omnivery. Its numerous, coarsely-serrated teeth likely allowed it to crop a wide variety of plants, including ferns, cycads, and conifers. The dinosaur’s ability to move efficiently on two legs enabled it to forage effectively, reaching different types of plant material depending on its immediate needs and surroundings.

Although the social dynamics of most extinct taxa can only be speculated upon, Chromogisaurus may have been social creature for at least the early part of its like, possibly living in small groups for protection. The dinosaur’s sensory adaptations, such as keen vision and a strong sense of smell, would have been essential for detecting predators and locating food. These adaptations not only ensured its survival but also allowed it to thrive and play a significant role in shaping its ecosystem.

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 Chromogisaurus.

Article last fact checked: Joey Arboleda, 06-07-2024

Featured Image Credit: dinosaurpictures.org