Once the Cenozoic had begun, the only remaining dinosaurs were modern birds. That means raptors (or dromaeosaurs) would never again stalk the Earth, right? Wrong! Raptor dinosaurs get their name from modern raptors: eagles, hawks, owls and the like; and they are in fact some of the closest relatives of birds. So during the Paleogene period when predatory birds started to radiate, they weren't reinventing being a raptor. They continued being raptors.
Palaeoglaux: An early owl from Germany's Messel Lake, about 40 million years ago. Unlike modern owls, it had strange ribbon-like feathers on its body, likely used in display.
Horusornis: A strange relative of hawks and eagles that lived in France 35 million years ago. Like modern harrier-hawks, it had flexible feet to dig out prey from tree cavities.
Antarctoboenus: An early relative of falcons found from Antarctica, about 35 million years ago. It may have prowled near the edges of giant penguin colonies.
Danielsraptor: Another early falcon from the 50 million year old London Clay formation. It had a large jagged beak and long legs, which helped it catch prey on the ground.
Dynamopterus: A relative of Seriemas and terror birds from Messel lake, about 40 million years ago. It likely caught small vertebrates from the forest floor.
Paleopsilopterus: One of the earliest known terror birds, it lived in Brazil about 50 million years ago. It was already flightless and similar to later small terror birds.
Bathornis: A distant relative of terror birds that was remarkably successful. This flightless predator and its relatives lived in North America from the Late Eocene to the Oligocene.
Messelastur: A falcon-like bird of prey that was closely related to parrots and passerines instead of raptors. It lived in Messel Lake about 40 million years ago.
Masillaraptor: A tiny true falcon also known from Messel Lake. It had a relatively long beak from a falcon, and it may have fed mostly on large insects.
Tynskya: Another small raptor related to parrots and passerines, this falcon-like predator lived around 50 million years ago. Its remains have been found in North America and Europe.
Palaeoglaux – рід вимерлих сов, єдиний в родині Palaeoglaucidae. Жив в еоцені в Європі. Скам’янілі рештки виду знайдені в Мессельському кар’єрі в Німеччині і фосфоритах Керсі у Франції.
Time and Place: Palaeoglaux lived from 48 to 37 million years ago, from the Ypresian age to the Priabonian age of the Eocene in the Paleogene
Palaeoglaux is known from the Messel Pit of Darmstadt-Dieburg, Germany; as well as the later Quercy Fissure Formation of Occitanie, France
Physical Description: Palaeoglaux was a very early form of owl, and one of the most complete early owls known - which means we know quite a bit about it! It is known from multiple individuals, including full skeletons on slabs; though, at this time, its skull is not known, so it is uncertain if it looked quite as weird as living owls in terms of facial structure. Like living owls, it has extra air holes in its shoulders, showing that this unique trait of living owls evolved very early on. However, it doesn’t show a bony arch in the foot like living owls, meaning it probably didn’t use its feet as much in hunting as living owls do - since that bony arch helps to strengthen the feet in gathering prey.
In general, Palaeoglaux was a fairly small owl, about the size of the modern Little Owl - so, able to fit in the palm of the hand. This makes sense, given that most animals from the global rainforest of the Messel Pit were quite small, due to the density of vegetation. In addition, the later species - from the late Eocene, when the rainforest was transitioning to drier, more open environments - is significantly larger than the earlier species, thus pointing to its size being directly related to its environment. One distinctive thing about Palaeoglaux, at least the earlier Messel species, are its feathers - long, ribbon like feathers are known from its back, which were originally interpreted as display structures. This would have made Palaeoglaux a rare, but not unique, example of a diurnal (daytime) owl. However, these sorts of feathers are actually quite common in Messel Pit fossils - so it actually could be an example of a preservational thing. Thus, more fossils are necessary to determine if these feathers are actually a display structure or just regular old feathers. Since there are many diurnal birds of prey in the Messel Environment, it would make sense for there to be at least one nighttime hunter such as Palaeoglaux. Still, the jury is out.
Diet: As an owl, Palaeoglaux was probably a bird of prey - feeding on small animals such as rodents, lizards, and smaller birds. Still, we do not have the head of Palaeoglaux at this time; this means we can’t be certain that it was exclusively carnivorous, like modern owls. It is more likely because the common ancestor of owls and many other birds such as mousebirds, rollers, parrots, and songbirds was probably a bird of prey; so owls (and animals like hawks, eagles, falcons, and seriemas) just retained that lifestyle while other groups lost it. Still, it’s possible Palaeoglaux may have had a different diet than living owls, and more fossils are necessary to confirm that it was a predator. Given that Palaeoglaux was quite small in the Messel environment, it wouldn’t have been able to eat very big animals; though its prey size would have increased as it did later in the Eocene.
Behavior: Owls today utilize keen eyesight and hearing to hunt food at night, using silent flight to sneak up on prey and catch them unawares. Many of the features necessary for this probably evolved in the Eocene, as some of the earliest representatives of modern owls evolved in this time. However, Palaeoglaux shows a unique mixture of early and derived traits, and thus, it may not have been ask exceptionally adapted for hunting as living owls. Much of Palaeoglaux’s behavior remains a mystery because we do not have fossils of its head at this time - and we’re not sure whether or not it was diurnal, meaning active in the day, or nocturnal, aka active at night.
Given that it does have more air-filled shoulder bones, it probably was in the process - if not already there - of evolving those silent flight mechanics of living owls. This would have aided it in hunting prey, allowing it to sneak up on other animals. However, its less strengthened toe bones would mean that it wasn’t quite as good at holding down its prey and catching it with its feet as living owls; it possible that it would have used its mouth more, though of course, without head fossils that’s difficult to say. Still, it would have dwelled in trees, using its high vantage point to look for food.
If Palaeoglaux’s ribbon feathers were for display, rather than just regular feathers, then Palaeoglaux would have probably been diurnal - active and hunting during the day. It may have puffed up those ribbon feathers in threat displays or sexual displays as well. If they weren’t for display, Palaeoglaux may have still been diurnal; or it could have been nocturnal, hunting small animals at night.
By Scott Reid
Ecosystem: The Messel Pit was a diverse and important ecosystem from the middle Eocene, with many different transitional forms of animals to showcase how life began to evolve into modern forms. Palaeoglaux is one of many transitional dinosaurs, living in the Global Rainforest environment of the time; the Messel Pit was warm and wet and covered with dense vegetation, which rendered Palaeoglaux and essentially all other tree-dwelling birds extremely small. The forest surrounded a large lake, which was filled with trapped volcanic gas; these gases would have released periodically and overwhelmed the animals of the environment, leading ot mass deaths. These animals would have then drifted down to the bottom of the lake, allowing for the unique preservation that allows for us to have a unique glimpse into this environment. Palaeoglaux probably spent most of its time in the trees, rather than closer to the lakeshore.
Many other dinosaurs filled the environment with Palaeoglaux, including the early roller Eocoracias, the early songbird Primozygodactlyus, other roller and Kingfisher relatives Messelirrisor and Primobucco, the parrot of prey Messelastur, the seriema-like Strigogyps, and the large herbivore Gastornis. Messelastur and Strigogyps, being much, much larger than Palaeoglaux, may have even fed upon it. The early flamingo relative Juncitarsus was also present in the pit, and probably was a wading bird within the lake of the Messel. Early forms of hummingbirds and other weird fliers were present (such as early relatives of potoos and nightjars), as well as an early woodpecker relative Gracilitarsus, other seriema relatives like Idiornis, and falcons like Masillaraptor. As such, diurnal birds of prey were heavily present in the Messel; and this points more to Palaeoglaux potentially being nocturnal after all.
Palaeoglaux was also present in the Quercy Fissure Formation. This was a later Eocene formation, showcasing how life began to transition along with the general environment. The global rainforest was drying up as the world was cooling; ice caps were forming at the poles, and ecosystems in general were becoming more open, dry plains. As such, Palaeoglaux got somewhat larger - as did other birds. Still, the Quercy Formation represents an environment that was still fairly warm and wet - it was probably an estuary environment, near to the shore but not quite associated fully, given that very few fish are preserved there. The environment was littered sinkholes and caves, leading to its unique preservation of animals. Many salamanders and some frogs are known form the area; though, by far, lizards are some of the most common animals there, and were probably a major source of food for Palaeoglaux. Here, Strigogyps was still present, and may have still been a problem for Palaeoglaux; parrots closer to modern forms such as Quercypsitta were present, as was the early woodpecker relative Sylphornis. Pigeons, water birds, and landfowl were also common frequenters of this environment.
Other: Palaeoglaux, though complete, is often extremely crushed; the fossil slabs of the species are difficult to interpret, and one of the best known slabs has not yet been fully described.
Species Differences: P. perrierensis is the later species from Quercy - so it is younger, from France, and larger than P. artophoron, the species from the Messel. In addition, P. perrierensis did have somewhat stronger feet than P. artophoron, indicating further evolution of traits involved in catching prey as the genus continued through the Eocene.
~ By Meig Dickson
Sources under the cut
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The phosphorate beds of Quercy, France preserve a wealth of fossils from the late Eocene and Oligocene epoch, about 35-25 million years ago. At that time, the early Paleogene jungle hothouse had ended. The climate was drying and cooling, and in parts of the world forests were giving way to savannah and scrubland, as was in Quercy. But that didn't stop birds. They started to take advantage of these new wide open spaces.
Aegialornis: An enigmatic bird that was closely related to swifts. Unlike swifts, it could perch and hold on to branches, but it was also an incredible flyer.
Quercypsitta: A unique group of not well known stem-parrots which likely resembled the earlier Halcyornithids, corvid-like stem-parrots from Europe and North America.
Palaeoglaux: Also known from the Messel Pit, this early relatively small owl may have been a diurnal hunter of small prey and had peculiar body feathers.
Sylphornis: A mysterious member of the piciformes with unique morphology, resembling jacamars and puffbirds.
Paraortyx: One of the earliest true phasianid galliforms, related to partridges, pheasants and chickens. It likely had a similar lifestyle to them, only taking flight when necessary.
Pelargopappus: An early relative of the long-legged secretarybird, this Eocene relative stalked the plains in a similar manner, stomping down on any prey it could catch.
Strigogyps: An omnivorous turkey-sized member of the cariamiform family, it is also known from the middle Eocene of Germany.
Archaeoganga: A relatively large and one of the earliest members of that wonderful desert bird clade, the sandgrouse.
Palaeoglaux artophoron, a basal owl from the Middle Eocene of Germany, living around 47 million years ago. Although not quite the oldest known fossil owl, it’s represented by much more complete remains.
About the size of a modern little owl or burrowing owl (~22cm/8.5″ long), it had some unusual plumage on its back -- long thin “ribbon-like” feathers, membranous and without barbs. Similar feathers are known in some modern birds, but all are used for display purposes. And, since visual display is much less effective in the dark, this suggests that Palaeoglaux was more diurnal than most of its living relatives.
