Birdlike dinosaur Eoneophron infernalis was about the size of an adult human. Credit: Zubin Erik DuttaNew findings, including the discovery of Eoneophron infernalis, recommend that dinosaurs, particularly caenagnathids, were not declining in variety before the asteroid impact, opposing earlier theories of their vulnerability.Were dinosaurs currently on their escape when an asteroid struck Earth 66 million years ago, ending the Cretaceous, the geologic duration that started about 145 million years back? Its a question that has vexed paleontologists like us for more than 40 years.In the late 1970s, debate started about whether dinosaurs were at their peak or in decrease before their big termination. Researchers at that time kept in mind that while dinosaur variety appeared to have increased in the geologic stage that covered 83.6 million to 71.2 million years earlier, the number of types on the scene seemed to decrease throughout the last few million years of the Cretaceous. Some scientists have interpreted this pattern to indicate that the asteroid that struck the Gulf of Mexico was just the final blow for a currently susceptible group of animals.However, others have argued that what looks like a reduction in the variety of dinosaurs might be an artifact of how tough it is to properly count them. Fossil formations may maintain different dinosaurs basically frequently based on factors like their preferred environment and how easily their bodies fossilized there. The availability of numerous outcrops could affect what sort of fossils researchers have so far found. These predispositions are an issue due to the fact that fossils are what paleontologists must rely on to conclusively answer how healthy dinosaur populations were when the asteroid hit.At that important minute, what was really occurring to dinosaur diversity? Discovery, identification and description of new dinosaurs offer vital clues. This is where our work comes in. Close assessment of what we d thought was a juvenile specimen of an already-known types of dinosaur from this time duration exposed that it was actually part of an adult from a totally new species.Our work concentrating on the life phase of our specimen demonstrates that dinosaur variety may not have been decreasing before the asteroid hit, however rather that there are more species from this time duration yet to be found– possibly even through reclassification of fossils currently in museum collections.Kyle Atkins-Weltman holds the femur of the brand-new dinosaur as it was received, with the other fossils in the background. Credit: Kyle Atkins-WeltmanClues Inside the Bones of a Birdlike DinosaurOur new research study concentrated on 4 hindlimb bones– a thigh, a tibia, and 2 metatarsals. They were uncovered in South Dakota, in rocks of the Hell Creek Formation, and date to the last 2 million years of the Cretaceous.When we first analyzed the bones, we recognized them as belonging to a family of dinosaurs known as the caenagnathids– a group of birdlike dinosaurs that had toothless beaks, long legs and brief tails. Direct fossil and presumed evidence indicates these dinosaurs were covered in complex plumes, much like modern birds.The only known types of caenagnathid from this time and region was Anzu, in some cases called the “chicken from Hell.” Covered in feathers and sporting wings and a toothless beak, Anzu was between approximately 450 and 750 pounds (200 and 340 kilograms). In spite of its fearsome label, though, its diet refers argument. It was likely an omnivore, consuming both plant material and little animals.Because our specimen was significantly smaller sized than Anzu, we just presumed it was a juvenile. We chalked up the anatomical differences we saw to its juvenile status and smaller size– and figured the animal would have altered had it continued to grow. Anzu specimens are unusual, and no guaranteed juveniles have been published in the clinical literature, so we were thrilled to possibly find out more about how it grew and altered throughout its life time by looking inside its bones.Just like with a trees rings, bone records rings called lines of arrested growth. Each annual line represents part of a year when the animals growth slowed. They would inform us how old this animal was, and how fast or sluggish it was growing.We cut through the middle of three of the bones so that we might microscopically analyze the internal anatomy of the cross-sections. What we saw entirely uprooted our preliminary assumptions.Teal markers indicate lines of detained development on the cross-section of fossilized bone. Toward the exterior of the bone, the lines are much more detailed together, reflecting less development annually. Scientist counted precisely six lines, implying this animal was between 6 and 7 years of ages when it passed away. Credit: Holly WoodwardIn a juvenile, we would expect lines of arrested development in the bone to be commonly spaced, indicating quick development, with even spacing in between the lines from the within to the outside surface of the bone. Here, we saw that the later lines were spaced progressively better together, indicating that this animals growth had slowed and it was almost at its adult size.This was no juvenile. Rather, it was a grownup of an entirely new types, which we dubbed Eoneophron infernalis. The name means “Pharaohs dawn chicken from Hell,” referencing the label of its larger cousin Anzu. Characteristics distinct to this species include ankle bones merged to the tibia, and a well-developed ridge on one of its foot bones. These werent features a young Anzu would outgrow, however rather unique elements of the smaller Eoneophron.Expanding the Caenagnathid Family TreeWith this brand-new evidence, we started making comprehensive comparisons with other members of the family to identify where Eoneophron infernalis fit within the group.It likewise influenced us to reexamine other bones formerly thought to be Anzu, as we now understood that more caenagnathid dinosaurs resided in western North America during that time. One specimen, a partial foot bone smaller than our new specimen, appeared unique from both Anzu and Eoneophron. Where once there was one “chicken from Hell,” now there were 2, and evidence for a third: one big (Anzu), weighing as much as a grizzly bear, one medium (Eoneophron), humanlike in weight, and one little and yet unnamed, close in size to a German shepherd.Eoneophron infernalis and the smaller unnamed types now sign up with the bigger Anzu as late-Cretaceous caenagnathid dinosaurs from the Hell Creek region. Credit: Zubin Erik DuttaComparing Hell Creek with older fossil formations such as the well-known Dinosaur Park Formation of Alberta that preserves dinosaurs that lived between 76.5 million and 74.4 million years ago, we discover not just the exact same variety of caenagnathid species, but likewise the very same size classes. There, we have Caenagnathus, equivalent to Anzu, Chirostenotes, equivalent to Eoneophron, and Citipes, comparable to the third species we discovered evidence for. These parallels in both species count and relative sizes offer compelling evidence that caenagnathids remained steady throughout the last part of the Cretaceous.Our new discovery recommends that this dinosaur group was not declining in variety at the very end of the Cretaceous. These fossils reveal that there are still brand-new species to be discovered, and support the idea that at least part of the pattern of decreasing diversity is the outcome of tasting and conservation biases.Did big dinosaurs go extinct the way a Hemingway character quipped he went broke: “gradually, then suddenly”? While there are lots of concerns still exceptional in this termination dispute, Eoneophron includes proof that caenagnathids were doing rather well on their own before the asteroid destroyed everything.Written by: Kyle Atkins-Weltman– Ph.D. Trainee in Paleoecology, Oklahoma State UniversityEric Snively– Associate Professor of Anatomy and Cell Biology, Oklahoma State UniversityAdapted from an article initially published in The Conversation.
Credit: Zubin Erik DuttaNew findings, consisting of the discovery of Eoneophron infernalis, suggest that dinosaurs, particularly caenagnathids, were not declining in diversity before the asteroid impact, contradicting earlier theories of their vulnerability.Were dinosaurs already on their way out when an asteroid hit Earth 66 million years back, ending the Cretaceous, the geologic duration that started about 145 million years ago? These predispositions are an issue since fossils are what paleontologists must rely on to conclusively answer how healthy dinosaur populations were when the asteroid hit.At that vital minute, what was really happening to dinosaur variety? Close evaluation of what we d thought was a juvenile specimen of an already-known species of dinosaur from this time period exposed that it was in fact part of an adult from a totally new species.Our work focusing on the life stage of our specimen shows that dinosaur diversity might not have been declining before the asteroid hit, however rather that there are more species from this time period yet to be discovered– possibly even through reclassification of fossils currently in museum collections.Kyle Atkins-Weltman holds the thigh of the new dinosaur as it was gotten, with the other fossils in the background. They were uncovered in South Dakota, in rocks of the Hell Creek Formation, and date to the final 2 million years of the Cretaceous.When we initially took a look at the bones, we recognized them as belonging to a family of dinosaurs understood as the caenagnathids– a group of birdlike dinosaurs that had toothless beaks, long legs and short tails. Credit: Zubin Erik DuttaComparing Hell Creek with older fossil developments such as the well-known Dinosaur Park Formation of Alberta that protects dinosaurs that lived between 76.5 million and 74.4 million years earlier, we find not just the same number of caenagnathid species, but also the very same size classes.
