#janavis

A new paper I'm on is out today! Led by Daniel Field, we review the fossil record of Late Cretaceous birds and their close relatives from the Maastricht Formation of Belgium and the Netherlands. These include the recently described Asteriornis and Janavis, which made waves for yielding exceptional insights into the origins of modern birds!

We also present new data on the growth stage and hindlimb proportions of the type specimen of Asteriornis, confirming it to be a small but long-legged bird, a body plan that has been implicated in modern bird survival across the end-Cretaceous extinction.

Factfiles:

Falcatakely forsterae

Artwork by @otussketching, written by @zygodactylus

Name Meaning: Forster’s Small Scythe Beak 

Time: 70 to 66 million years ago (Maastrichtian stage of the Late Cretaceous) 

Location: Maevarano Formation, Mahajanga Province, Madagascar 

We like to joke that the different types of protobirds in the Mesozoic were just like modern birds with teeth, and that’s obviously an oversimplification, but sometimes it’s just true. This is one of those times. Falcatakely was an Enantironithine - an Opposite bird - very distinct from living birds, and yet, it convergently evolved a toucan beak, essentially rendering it a toothed toucan! Don’t get your hopes up, though - the teeth were few in number, concentrated in the front of the beak. But, still, that’s not going to stop me from calling this an Opposite Toucan. Unfortunately, only the skull is known, so it is uncertain how large the rest of the body was - the beak itself was 9 centimeters in length. Falcatakely lived in the seasonally arid Maevarano Formation, which transitioned between a swampy floodplain and a semidesert depending on the season. Here there were a LOT of weird animals, not just Falcatakely - this is the home of the herbivorous croc Simosuchus, the toothy dinosaur Masiakasaurus, giant stem-mammals like Adalatherium, the giant frog Beelzebufo, the weird protobird Rahonavis, and more normal things like Majungasaurus and Rapetosaurus. Honestly, we should stop being surprised at the strange things islands manage to produce, but I’m not quite ready to give up that shocked feeling yet. 

Janavis finalidens

Artwork by @otussketching, written by @zygodactylus

Name Meaning: Janus’ final toothed bird 

Time: 66.8 million years ago (Maastrichtian stage of the Late Cretaceous) 

Location: Maastricht Formation, Eben-Emael, Belgium 

Janavis was another inhabitant of the Maastricht Formation, living alongside the modern bird Asteriornis, which it would have appeared very similar to - except Janavis was a protobird, specifically a cousin of Ichthyornis, featuring teeth (like other protobirds) and serving as an interesting juxtaposition living alongside Asteriornis - a strange play of the past and the future, living alongside one another, just before the asteroid hit. Janavis is known from fossils embedded in hard rock that were primarily examined via CT scan, which revealed vertebrae and parts of the limb bones, where only the skull and some fragments had been known previously from the exposed parts of the fossil. Fairly large, with a wingspan of five feet, it was much bigger (nearly twice) than its cousin Ichthyornis. It had greatly pneumatisied vertebrae, and a very kinetic skull allowing for a wide variety of movement in the jaws. This is interesting, as the earliest derived modern birds - the Paleognathes - all have non-kinetic skulls like most dinosaurs, indicating that it is possible that group had a trait reversal, rather than kinetic skulls only first evolving in Neognathes. It mainly fed on seafood along the coast, like its relatives, and spent its time in the tropical forests along the coast. Many invertebrates, ammonites, corals, echinoderms, sharks, mosasurs, turtles, elasmosaurs, and marsupials shared its environment, as well as dinosaurs such as Asteriornis, Orthomerus, and as-yet unnamed taxa. 

(Select bones of Janavis finalidens with comparisons to those of Ichthyornis [scale bars = 10 mm], from Benito et al., 2022)

Meaning of name: Janavis = [Roman deity of beginnings, endings and transitions] Janus's bird [in Latin]; finalidens = final teeth [in Latin]

Age: Late Cretaceous (Maastrichtian), 66.9–67 million years ago

Where found: Maastricht Formation, Liège, Belgium

How much is known: Partial skeleton of one individual, including parts of the skull, several vertebrae, and limb bones.

Notes: Janavis was a euornithean, a group including modern birds and some of their closest extinct relatives. Living near the end of the Cretaceous, Janavis was among the last of the toothed euornitheans to have gone extinct. It was similar to the slightly older Ichthyornis, a seagoing euornithean known from numerous specimens primarily from the Late Cretaceous of North America. However, Janavis differed from Ichthyornis in having extensive chambers for air sacs in its back vertebrae as well as being much larger (estimated as having weighed about 1.5 kg, comparable in size to the largest extant gulls). Within Euornithes, Janavis and Ichthyornis were among the closest known Mesozoic relatives to modern birds.

The type specimen of Janavis had been described briefly in 2002, but was left unnamed at the time. A new study not only investigates its anatomy and affinities in greater detail, but also reinterprets several bones preserved in the specimen that had been previously misidentified. One of these newly recognized bones is a pterygoid (one of the bones in the palate), among the few known examples of this bone being preserved in a Cretaceous euornithean. The structure of this pterygoid indicates that Janavis had a mobile palate, a feature previously thought to have originated in modern neognath birds. Combined with recently reported evidence for a potentially mobile palate in Ichthyornis, Janavis suggests that a flexible palate evolved prior to the origin of modern birds, overturning longstanding assumptions about avian evolution.

(Schematic skeletal showing preserved bones of Janavis finalidens, with newly reported bones in yellow and reinterpreted bones in blue, from Benito et al., 2022)

New avian dinosaur discovery might rewrite the evolution of modern birds

The discovery suggests some modern birds, like emus and ostriches, evolved “backwards”

A new dino-bird fossil has overturned more than a century of accepted wisdom about how modern birds evolved. It comes down to a key beak feature.

Modern birds fall into two infraclasses: neognaths and palaeognaths.

Almost all of today’s roughly 11,000 bird species are neognaths, or “modern jaws”. The palate (roof of mouth) structure of neognath jaws is connected by a mobile joint, and a number of the jawbones are reduced. This makes their beaks more dextrous, which is helpful in nest-building, grooming, food gathering, and defence.

Palaeognathae palates are considered more primitive and reptilian, with fused palate bones. There are only a few dozen living birds which fall into this second clade, including emus, ostriches and kiwis...