The Chirostenotes was an oviraptorosaur that belonged to the late Cretaceous Period. Oviraptorosaurians were dinosaurs that resembled birds quite substantially in structure and function. Some scientists believe them to be more closely related to birds than dinosaurs, but most paleontologists contend that they shared a common ancestor with birds but yet belong to clade Dinosaurian.
The fossils of this animal were discovered in Canada. They were about 80 to 75 million years old. This would place the timeline of existence of the Chirostenotes at the Campanian age of the Cretaceous. Although its remains have not been found anywhere except Canada, scientists believe that it could have lived all across North America.
The most prominent features of the Chirostenotes were its slender appendages. Its built was slender too; its length was about 7 feet yet it weighed only about 25 to 30 kilos. Its feeding habits have not been properly defined yet, but researchers postulate that it was either an herbivore or an omnivore.
The name Chirostenotes is a juxtaposition of two words. The term 'chiro' is derived from the Greek word 'cheir' which denotes 'hand'. The suffix 'stenotes' is takes inspiration from the Greek word 'stenos' which means 'narrow' or 'closed'. Thus, the name Chirostenotes translates to 'narrow hands'.
The specific name C. pergracilis had Latin origins. The word 'per' denotes 'everywhere' and the word 'gracilis' is Latin for 'gracefully slender'. 'Pergracilis' indicates 'slender all throughout', which was selected for this dinosaur in view of its lean physique.
The name for this reptile was suggested by scientist Lawrence Lambe, but he passed away before he could finish his research on it. Paleontologist Charles Gilmore picked up the research where Lambe had left it and defined the type species in 1924.
Discovery of fossils
The remains of the Chirostenotes were discovered part by part in various expeditions.
- The holotype of the dinosaur was discovered in the year 1914 in the Little Sandhill Creek region of the Dinosaur Park Formation of Alberta, Canada. It comprised of a pair of hands of the dinosaur. These were found by George Sternberg and were examined by Lambe.
- As Lambe could not finish his work, they were described by Charles Gilmore in 1924.
- In the year 1934, Charles Sternberg found foot fossils in the same Dinosaur Park Formation and classified them under a new genus, Macrophalangia. He believed them to belong to a carnivorous dinosaur.
- In 1936, a jaw specimen was found in Alberta which had small sharp teeth. This was discovered by Raymond Sternberg and he presumed it to belong to a bird. He defined a new genus for it, the Caenagnathus.
- Gilmore also ascribed a jaw which bone to the Chirostenotes which had teeth present on it. It is known today that the Chirostenotes was a toothless dinosaur.
- By 1981, a complete specimen of the dinosaur Elmisaurus was described is Asia. It was an oviraptorosaurid, and based on these finding, all of the above mentioned fossils were classified under genus Chirostenotes.
- A few larger skeletons from the Maastrichtian Horseshoe Canyon Formation have also been ascribed to genus Chirostenotes.
- In the 1990, scientists finally cleared up much of this mess. They deemed the Macrophalangia synonymous with the Chirostenotes. However, the Caenagnathus was declared a separate genus.
- The Maastrichtian bones were separated from the Chirostenotes, as were the jaws which contained teeth.
- Even today, the information about oviraptorosaurids is incomplete. But scientists understand them much better than they did a hundred years ago.
Nature of the hand and leg bones
The hand of the Chirostenotes had long and slender digits, which were three in number. The middle digit was considerably larger than the ones flanking it, and had a sharp claw on it. Scientists believe that this adaptation could have been for grappling on rocky hills. It could possibly have been used for impaling prey, but only delicate organisms could be seriously damaged by it.
Its feet also had three digits and it was tall at the hips. Its posture may be described as similar to the chicken used for cock fights.
The Chirostenotes is classified under suborder Theropods, clade Oviraptorosauria, family Caenagnathidae and subfamily Caenagnathinae. It is obvious that the type genus of the family is the Caenagnathus.
The clade Oviraptorosauria was defined in 1976 and before that, dinosaurs similar to the Chirostenotes were presumed to be similar to the ornithomimids.
- The Chirostenotes, as its name suggests, was a delicate dinosaur. It grew to about 2 to 2.2 meters but weighed only around 45 to 60 pounds.
- Its jaw was shaped like a beak. The beak lacked teeth. It is believed that modern day birds eventually lost their through intermediate species like the Chirostenotes (the Chirostenotes was not a bird or an ancestor of birds. Modern birds and the Chirostenotes may have had a common ancestor).
- It is debatable whether this dinosaur had feathers. No feather fossils have yet been ascribed to it. But many of its contemporaries possessed feathers.
- The feet of this dinosaur were long, with slender toes. It probably stood 3 feet tall.
- The tail of this reptile was lean and slender as well.
Habits and habitat
- The Chirostenotes was most likely a terrestrial dinosaur. Its bones did not show any clear indication that it could fly.
- The feeding habits of the animal are again a matter of contention. Its beak did not have teeth so it could not tear its prey. It likely is d the length of its beak to reach in the cracks and crevices of rocks and feed on smaller insects or reptiles. It is also possible that the dinosaur ate grasses and leaves, or was an omnivore.
- The function of the claw on its hand is also unclear. It could only trap unarmored creatures with it as it was not very strong. The other alternative would be that it trapped its hunt with its beak and killed it with the claw.
Some paleontologists also believe that the claw was used or gaining a hold on the rocks of cliffs, like a grappling hook.
- The habitat of this reptile consisted of rocky plains and valleys which were rich in vegetation.
The Chirostenotes was closely related to the genera Anzu and Caenagnathus.
The discovery of the Chirostenotes was a breakthrough in understanding oviraptorosaurid dinosaurs. Their intermediate nature between birds and dinosaurs stills amazes scientists.