Kulindadromeus zabaikalicus
Etymology: Runner from Kulinda
First Described By: Godefroit et al., 2014
Classification: Dinosauromorpha, Dinosauriformes, Dracohors, Dinosauria, Ornithischia, Genasauria, Neornithischia
Time and Place: 173 million years ago; in the Aalenian of the Middle Jurassic
Kulindadromeus was found in the Ukureyskaya Formation of Southwestern Siberia, Russia
Physical Description: Kulindadromeus was a small, bipedal dinosaur, built well for running on its hind limbs, while its forelimbs remained available for grasping food. Kulindadromeus had a squat body, a long tail, long legs, short arms, and a small head. It had a small, triangular snout that ended in a beak which was used to snip off plant material. It was about 1.5 meters long from head to tail, making it around average size for small bipedal herbivores at the time. Compared to an average person, it only would have come up to their knees and lower thighs in terms of height. It is distinguishable from its closest relatives primarily due to differences in its skull, namely having different sized holes in its snout, having a somewhat differently shaped upper jaw, and more slender bones in its hips. The differences in its head potentially aided in keeping its head cool, or in eating freshwater plants that it would have specialized in. In addition, it had more extensive muscles in its feet, which would have aided in running, along with the differences in musculature in its hips.
Coloring by the author; line art by Diane Remic
The most notable feature of Kulindadromeus is its extensive network of feathers and scales, which were preserved in great detail in the many fossils found of the species. Single-stranded protofeathers (meaning, precursors to feathers found in modern birds) are found all over the main body, neck, and head of Kulindadromeus. These protofeathers, usually reaching up to 3 centimeters in length, resemble those feather precursors found in dinosaurs more closely related to birds, such as Sinosauropteryx. In addition, there were groups of up to seven long filaments extending from the same location in the skin, extending down along the upper arms and thighs and reaching up to 1.5 centimeters in length. Finally, the last type of feather present on Kulindadromeus were bundles of ribbon-shaped feathers, up to two centimeters in length, extending in parallel along the lower legs.
Kulindadromeus features a variety of scale types preserved as well. Overlapping hexagon shaped scales are found on the lower legs below the ribbon shaped feathers. Round, non-overlapping scales are on the hands, ankles, and feet. The top of the tail has five rows of rectangular scales, arched and locked together with only a little overlap. Small spurs jut out on the middle of the tail, giving a bumpy surface to the midline. These scales then taper off to small, round scales at the end of the tail that no longer overlap.
Color in these structures is not known at this time.
Diet: Herbivorous; primarily a low-level browser of freshwater plants such as horsetails and moss, as well as potentially some coniferous trees (though these were rarer in the region). Kulindadromeus would have used its beak to snip off this plant material, which it then chewed with its teeth (a unique behavior for the group of dinosaurs Kulindadromeus belonged to).
Behavior: Given its small size, adaptations for running, and lack of adaptations for defense, it is likely that Kulindadromeus would have been fairly skittish, running at any sign of danger in its environment. As in other dinosaurs, it was probably warm-blooded and active. Preserved as it was in a large bone bed with many individuals (including adults and juveniles), it is likely it was somewhat social; probably living in groups to aid in protection from predators or other sources of danger. Most dinosaurs are known to have taken care of their young, including those most closely related to Kulindadromeus; as such, though there is no direct evidence of parental care in Kulindadromeus, it is likely that it took care of its young in some capacity.
Ecosystem: Freshwater lake environment near an active volcano system, filled with freshwater plants and invertebrates. Given the high position of Siberia at the time, it probably would have been no warmer than subtropical climates today; potentially even reaching temperate climate conditions, with seasonal changes in water and temperature. At least one other kind of dinosaur lived in the region, a theropod of some sort - probably a Coelurosaur (a group of dinosaurs that includes birds, Tyrannosaurs, and everything in between) - that may have preyed upon Kulindadromeus. Other herbivorous dinosaurs were probably present as well, though they have not been studied yet in great detail.
Other: Though Kulindadromeus is fascinating in its own right due to the adaptations it shows for running compared to its relatives (which were already very fast on their own), as well as what it can show us about Middle Jurassic environments (which are not very well known compared to the Early or Late Jurassic), Kulindadromeus is most notable for what it tells us about the evolution of feathers in dinosaurs.
Prior to Kulindadromeus, the only confirmed feather remains in dinosaurs were in the group that included birds and their closest relatives - the Coelurosaurs. These dinosaurs showcase the evolution of feathers from single-stranded structures, sort of like hair in their shape, to the branched and barbed structure we’re familiar with in modern birds. Though single-stranded filaments were known from two dinosaurs distantly related to this group - Psittacosaurus and Tianyulong - they were poorly understood and not easily connected to feathers, as opposed to, say, just being another sort of fluff evolved in dinosaurs separate from the feather line.
Kulindadromeus, on the other hand, not only showed extensive fluffy covering nearly identical to that found in Coelurosaurs, but it also showed a diversity in fluffy covering not seen in dinosaurs outside of the Coelurosaur group before. This diversity matched many of the ideas proposed as intermediaries in feather evolution. This, combined with increasing evidence that the fluffy covering found in closely related pterosaurs is also a form of protofeather, indicates that feathers not only were ancestral to dinosaurs, but to the group of animals more closely related to birds than to Crocodilians. This indicates that fluffiness was one of the things that set early bird relatives apart from other reptiles, as reptile evolution exploded in the wake of the end-Permian extinction.
This fluffy covering would have helped small dinosaurs in general to keep warm, as well as aid in display and other social cues. Kulindadromeus, living in a slightly cooler environment, as well as being small in size, would have definitely benefited from the fluff in keeping warm. In addition, small warm-blooded animals such as Kulindadromeus utilize fluffy covering in maintaining their internal body temperature - most cold-blooded animals don’t really require fluff in this way.. Studies indicate that most smaller dinosaurs probably had such covering, and feathers were primarily lost in the larger dinosaurs that no longer needed them to keep warm.
Thus, though Kulindadromeus is not much to look at in terms of spikes, horns, teeth, and other monstrous structures; it does provide an important clue in our understanding of how birds evolved, as well as what dinosaurs looked like in life. This makes it one of the most important dinosaur discoveries of the 2010s, as well as one of the cutest! Hopefully, as it is studied further, we can glean more about how it looked and lived.
~ Article by Meig Dickson
