A bird that lived alongside dinosaurs may have used its beak to preen its feathers, as modern birds do. But it also had a full mouth of teeth. These let it chew like a dino. The finding provides new clues to how birds evolved from dinosaurs.
Scientists made a new 3-D reconstruction of the skull of Ichthyornis (Ick-thee-OR-nis) dispar. This bird lived during the Late Cretaceous, some 87 million to 82 million years ago. The new reconstruction shows this creature had a small, primitive beak. Its upper jaw would have moved around easily. Such traits would have let the bird use its beak to precisely groom itself and grab things, much as modern birds do. But I. dispar also kept some features from its dino ancestors. These included teeth and strong jaw muscles.
This ancient bird shows up often in textbooks. Paleontologist Othniel C. Marsh first described the animal some 150 years ago. It was a water bird, similar to a tern. Much like a duck, its wings spanned about 60 centimeters (24 inches). The shape of those wings and its breastbone suggested this bird could fly.
Another famous fossil flyer is Archaeopteryx (Ar-kee-OP-tur-ix). This extinct reptile lived about 70 million years before I. dispar. Archaeopteryx had a more reptilian skull, notes Bhart-Anjan Bhullar. He’s a vertebrate paleontologist at Yale University in New Haven, Conn. With a beak and fairly large head, the skull of I. dispar much better resembles those in modern birds, he says.
Several skulls of I. dispar existed at various museums. Still, there was much science didn’t know about these birds, Bhullar says. One reason: Fossils dug up in the 19th century had been smashed flat in places. This made it hard to see a lot of important details. Then, in 2014, researchers unearthed a new I. dispar fossil. It contained a nearly perfect skull.
The researchers combined that fossil with three partial skulls from museum collections. They also took a closer look at the skull found 150 years ago. Bhullar’s team input details from all of these skulls into a computer. It helped to recreate a 3-D image of what the ancient bird would have looked like. Those researchers published it May 3 in Nature.
An in-between head
The reconstruction showed these birds could raise their upper jaw separately from the lower jaw, as modern birds can. This range of motion would have let I. dispar use its tiny beak like tweezers to peck or preen or grasp objects. Large holes in the sides of its skull show where jaw muscles attached. The size of those holes suggests those muscles would have been strong. Says Bhullar, this suggests that “it was pecking like a bird and biting down like a dino.”
His team also made detailed measurements of the inside of the skull. This showed them the brain’s shape. And again, in many ways it looked like those of modern birds.
For example, the forebrain is an area in the front related to thinking. In I. dispar it was large. This brain also had big optic lobes — regions that process images sent from the eyes. “This [creature] was thinking like a bird, and had sensitive vision and motor coordination,” Bhullar concludes. It might have needed these traits to handle the intense physical challenges of flying.
The new study offers the first in-depth look at the skull of this ancient species, says Lawrence Witmer, who was not part of the new study. This vertebrate paleontologist at Ohio University in Athens says the study gives important new details on how dino jaws morphed into today’s bird beaks. Dinosaur jaws were toothy and covered in skin. A modern bird’s beak lacks teeth and is covered in keratin, the same stuff from which human hair is made.
Luis Chiappe praises the careful way researchers studied this important historical fossil. Chiappe, too, is a vertebrate paleontologist. He works at the Natural History Museum in Los Angeles, Calif. Still, he is not convinced that the size of the brain and other traits are related to the bird’s flying ability. He’s also not sure that I. dispar’s in-between features offer general clues to the way all birds would have evolved from dinosaurs.
“We have big questions about what was happening with birds in the Late Cretaceous,” he says. Scientists don’t know much about these animals’ skulls. “It could be that what we see in Ichthyornis might not be representative of an evolutionary trend,” he says.
3-D Short for three-dimensional. This term is an adjective for something that has features that can be described in three dimensions — height, width and length.
birds Warm-blooded animals with wings that first showed up during the time of the dinosaurs. Birds are jacketed in feathers and produce young from the eggs they deposit in some sort of nest. Most birds fly, but throughout history there have been the occasional species that don’t.
Cretaceous A geologic time period that included the end of the Age of Dinosaurs. It ran from roughly 145.5 million years ago until 65.5 million years ago.
dinosaur A term that means terrible lizard. These ancient reptiles lived from about 250 million years ago to roughly 65 million years ago. All descended from egg-laying reptiles known as archosaurs. Their descendants eventually split into two lines. For many decades, they have been distinguished by their hips. The lizard-hipped line are believed to have led to the saurichians, such as two-footed theropods like T. rex and the lumbering four-footed Apatosaurus (once known as brontosaurus). A second line of so-called bird-hipped, or ornithischian dinosaurs, appears to have led to a widely differing group of animals that included the stegosaurs and duckbilled dinosaurs. But a new 2017 analysis now calls into question that characterization of relatedness based on hip shape.
evolutionary An adjective that refers to changes that occur within a species over time as it adapts to its environment. Such evolutionary changes usually reflect genetic variation and natural selection, which leave a new type of organism better suited for its environment than its ancestors. The newer type is not necessarily more “advanced,” just better adapted to the conditions in which it developed.
extinct An adjective that describes a species for which there are no living members.
fossil Any preserved remains or traces of ancient life. There are many different types of fossils: The bones and other body parts of dinosaurs are called “body fossils.” Things like footprints are called “trace fossils.” Even specimens of dinosaur poop are fossils. The process of forming fossils is called fossilization.
groom (in zoology) The practice of some animals to clean oneself or another.
keratin A protein that makes up your hair, nails and skin.
lobe A rounded and somewhat flat projection. Many leaves, for instance, have lobed edges.
motor (in biology) A term referring to movement.
muscle A type of tissue used to produce movement by contracting its cells, known as muscle fibers. Muscle is rich in protein, which is why predatory species seek prey containing lots of this tissue.
paleontologist A scientist who specializes in studying fossils, the remains of ancient organisms.
physical (adj.) A term for things that exist in the real world, as opposed to in memories or the imagination. It can also refer to properties of materials that are due to their size and non-chemical interactions (such as when one block slams with force into another).
preen (in biology) A verb for the way birds straighten and clean their feathers.
range The full extent or distribution of something. For instance, a plant or animal’s range is the area over which it naturally exists.
reptile Cold-blooded vertebrate animals, whose skin is covered with scales or horny plates. Snakes, turtles, lizards and alligators are all reptiles.
skull The skeleton of a person’s or animal’s head.
species A group of similar organisms capable of producing offspring that can survive and reproduce.
trait A characteristic feature of something. (in genetics) A quality or characteristic that can be inherited.
vertebrate The group of animals with a brain, two eyes, and a stiff nerve cord or backbone running down the back. This group includes amphibians, reptiles, birds, mammals and most fish.
Journal: D. J. Field et al. Complete Ichthyornis skull illuminates mosaic assembly of the avian head. Nature. Vol. 557, May 3, 2018, p. 96. doi: 10.1038/s41586-018-0053-y.
Journal: K. Padian. Evolutionary insights from an ancient bird. Nature. Vol. 557, May 3, 2018, p. 36. doi: 10.1038/d41586-018-04780-3