But Brontornis might not actually have been a terror bird at all – it may have instead been a giant cousin of ducks and geese.
The known fossil material is fragmentary enough that it’s still hard to tell for certain, but there’s some evidence that links it to the gastornithiformes, a group of huge herbivorous birds related to modern waterfowl.
If it was a gastornithiform, that would mean it represents a previously completely unknown lineage of South American giant flightless galloanserans. And, along with the gastornithids and the mihirungs, it would represent a third time that group of birds convergently evolved this sort of body plan and ecological role on entirely different continents during the Cenozoic.
Aquilarhinus palimentus here was an early hadrosaurid dinosaur known from the Late Cretaceous of Texas, USA, living about 80 million years ago. Around 5m long (16″5″), it had a prominent humped nose that seems to have been an evolutionary prelude to the larger and much more elaborate crests found in later hadrosaurs.
It also had an unusually wide and shovel-like beak, unlike any other known hadrosaur, which was probably a specialization for a different diet than its relatives. Since it lived along coastal marshlands it may have used its broad jaws to scoop up large mouthfuls of soft vegetation – or, much like the “shovel-tusker” proboscideans that were once thought to have a similar lifestyle, it may actually have been doing something else entirely with that beak.
Say hello to the first new non-avian dinosaur of 2021, Shri devi!
Named after a buddhist deity, this little dinosaur was around 2m long (6’6″), roughly the size of a modern peacock or wild turkey. It was a very close relative of Velociraptor, but lived in a slightly different part of the ancient Gobi than its famous cousin, giving us a glimpse of how dromaeosaurid species varied across that region.
The enantiornitheans (“opposite-birds”) were the most diverse and widespread group of Mesozoic birds, existing all around the world throughout the Cretaceous period. They retained claws on their wings and had toothy snouts instead of beaks, and while most of them lacked the lift-generating tail fans of modern birds they appear to have still been very adept fliers.
Known from the Late Cretaceous of Mongolia, about 80 million years ago, this opposite-bird lived alongside famous dinosaurs like Velociraptor and Protoceratops in what is now the Gobi Desert. Only a single partial specimen has ever been found, so its full life appearance is unknown and this reconstruction is somewhat speculative, but it would have been around the size of a pigeon at 25cm long (10″) – not including any decorative tail feathers it may have had, similar to other enantiornitheans.
It wing and shoulder bones were very odd for an opposite-bird, with proportions that don’t match anything capable of competent flight. Instead Elsornis appears to have been a flightless enantiornithean, a representative of a previously unknown terrestrial lineage.
(This is a couple of days late for Halloween, but since this October saw the description of a new dinosaur species with a particularly spooky name, I couldn’t resist putting it into the schedule anyway.)
Spectrovenator ragei was an early member of the abelisaurid lineage, living in southeastern Brazil during the Early Cretaceous, about 120 million years ago. It was one of the smallest known abelisaurids, measuring just 2m long (6’6″), and lacked a lot of the skull specializations seen in larger-bodied Late Cretaceous forms like Carnotaurus, suggesting it was more of a generalist predator.
Its genus name translates to “ghost hunter” due to it being found underneath the fossil remains of another dinosaur entirely – a “ghost” unexpectedly appearing when the specimen was being prepared – but it’s extra appropriate since it also helps to fill in a rather sizeable ghost lineage in the fossil record of abelisaurids.
Named after the mythological bird-like Anzû – and also nicknamed “the chicken from hell” – Anzu wyliei was one of the larger known oviraptorosaurs, measuring about 3m long (9’10”).
Its fossils are some of the most complete for a North American member of this dinosaur group, with four different specimens representing about 80% of the whole skeleton.
Living right at the end of the Cretaceous, about 66 million years ago in North Dakota and South Dakota, USA, Anzu inhabited the ancient floodplains of Hell Creek and appears to have been a fairly fast-moving omnivorous generalist. It had a large crest on its head made of rather fragile thin-walled bone, which may have been used for display or sound amplification similar to the casque of modern cassowaries.
Some of the fossil specimens also show evidence of healed injuries, including a broken rib and an arthritic toe.
Seriemas are part of a lineage known as cariamiformes, highly terrestrial birds that were widespread across most of the world but are today represented today by only two living species in South America. During the Cenozoic this group repeatedly evolved into large predatory flightless forms like the the phorusrhacids and bathornithids, and were probably the closest avians ever got to recreating the “carnivorous theropod” body plan and ecological niche.
And yet none of them ever seem to have experimented with more dromaeosaurid-like claws.
…With one known exception.
Qianshanornis rapax here lived in East China during the mid-Paleocene, about 63 million years ago. It was a small cariamiform, probably around 30cm tall (1″), and is only known from fragmentary fossil material – but part of those fragments was a fairly well-preserved foot. And the bones of its second toe were unlike any other known Cenozoic bird, shaped incredibly similarly to those of dromaeosaurids and suggesting it may have had the same sort of big hyperextendible “sickle claw”.
While it had sturdy legs and short wings, and probably spent a lot of time walking on the ground like other cariamiformes, it was probably also still a fairly strong flier based on the known anatomy of its arms and shoulders.
Unfortunately, though, its head and claws were entirely missing, so without more fossil discoveries it’s hard to say anything definite about its ecology. I’ve restored it here based on other predatory cariamiformes, but since it was also closely related to a herbivorous species it’s not clear whether Qianshanornis was truly a dromaeosaur-mimic or if something else was going on with that unique second toe.
They were fairly small stocky quadrupedal dinosaurs, sort of pig-like, with short deep jaws and powerful beaks adapted for eating fibrous low-level plants like ferns and cycads – and to process such tough food they even evolved a chewing style similar to mammals like rodents.