Owls, Part 2: Giant Fossil Owls and Stolas

It’s time for the next installment of my OWLS! series of blog posts! This one is going to be a little bit different from my other posts…although, if you’ve read any of my Bigfoot or ghost posts you may not be surprised at the theme of this post.

My research takes me down a few interesting rabbit holes. One of these holes introduced me to J. A. S. Collin de Plancy’s Dictionnaire Infernal when I searched for “giant owls.” I was looking at adaptations that cursorial (ground-running or walking) birds have in the tarsometarsus bones. That is where I encountered Stolas.

Stolas is my favorite (is favorite the right word?) character of Collin de Plancy’s demon mythology from the perspective of both an owl fanatic and a palaeontologist. Collin de Plancy describes Stolas on page 635-6 of the Dictionnaire Infernal:

“Stolas, grand prince des enfers, qui apparaît sous la forme d’un hibou ; lorsqu’il prend celle d’un homme et qu’il’se montre devant l’exorciste, il enseigne : l’astronomie, ainsi que les propriétés des plantes et la valeur des pierres -précieuses. Vingt-six légions leire connaissent pour[;] general.”

Here is my extremely rusty high school French (with a double-check in Google Translate) translation:

“Stolas, great prince of Hell, who appears in the form of an owl; when he takes that of a man and shows [himself?] before the exorcist, he teaches astronomy, as well as the properties of plants and the values of precious stones. Known for Twenty-six legions; general.”

Stolas: “Go ahead: run. I dare you.” Image from Collin de Plancy, Dictionnaire Infernal.

If Stolas were real, he’d likely be a great resource of information for many in astronomy, botany, and geology. The geology link of Stolas is what makes the connection of Stolas to paleontology even more interesting. As a field palaeontologist I would find a twenty-six-legion strong field crew very useful.

Most of the demonic entities in the Dictionnaire Infernal (and earlier works on the same subject) appear as human-animal hybrids or large versions of familiar animals. Collin de Plancy does not give us a sense of scale but one’s brain does jump to “large,” or at least larger than life, when talking about demons. The dimensions of Stolas are fascinating: the woodcuts of Collin de Plancy show an owl with rather long legs, standing on the ground. The legs are longer than the body. There’s a lot going on with the appearance of Stolas that suggests he is a walker. It is unlikely that Stolas’ teeny owl body with those teeny owl wings and itty-bitty tail could haul around those legs during flight (especially while wearing his resplendent crown.)

Bestiaries and Owls

Owls appear frequently in the medieval literature, particularly in bestiaries. Bestiaries (no, not bestiality, although the root of both words is the same) depict animals both real and fanciful, from the Amphisbaena (a serpent with a head at either end), to odd interpretations of real animals. Did you know the Barnacle Goose grows from trees, dangling from their beaks? According to the Harley Bestiary (c. 1230-1240), that’s where Barnacle Geese come from!

Barnacle Goose img4465
British Library, Harley MS 4751, Folio 36r

Or how about bees: did you know that bees come from the decay of the putrid flesh of calves or oxen (Isidore of Seville, 7th century CE)? Some explanations are implausible, others are darn ridiculous, but they were interpretations based on observations made at the time. The prevailing wisdom of the day, according to the bestiaries, was that owls were dirty, slothful birds that pollute their nests with their own dung. Barn owls do build up a layer of pellets in their nests when the young are still in house and feeding, but most birds are pretty good at keeping waste out of their nests. It was common knowledge that owls frequent graveyards and tombs, and their cries are harbingers of an impending death. It’s not a glowing letter of recommendation.

Owls and their portrayal in bestiaries is a whole other post, but these bestiaries were written in the 12th – 16th centuries. Bestiaries were not immune to the prevailing attitudes of the day. Some of these ideas were, well, racist and antisemitic as flock. With the negative interpretations associated with owls, it makes sense that someone with an interest in both the natural and the spiritual world would have a demon appear as a larger-than-life owl, ready to run you down if you lost your nerve during a demon summoning. We can safely say that Collin de Plancy and Friends didn’t actually summon Stolas (or any demon) to pose for a sketch artist. We can chalk up mystic depictions of demonic giant walking owls as a stroll down Imagination and Theology Lane.

The Giant Cuban Owl

Fast forward to Cuba, 1954, where we actually have knowledge of a giant owl. The Cuban Giant Owl Ornimegalonyx was an owl of the Late Pleistocene (126,000 – 11,700 years ago, also known as the Ice Age). Ornimegalonyx was discovered on January 2, 1954 and was recognized as the remains of a large predatory bird. The discovery site was a large cavern called Pio Domingo Cave located in the Sierra de Sumidero, opposite Pica-Pica Valley in Pinar del Rio. Ornimegalonyx was originally described by Oscar Arrendondo (1958) in a publication called El Cartero Cubano. Oscar Arrendondo originally used Ornimegalonyx arrendondoi as a provisional name, and he later uses Ornimegalonyx oteroi as the official name in his 1958 publication describing the type specimen. Arrendondo used the name “oteri” in honor of speleologist (scientists who study caves) and expedition member Juan N. Otero (Arrendondo, 1958). The type material (the bones that everyone has to look at if you want to work on fossilized giant owls) consists of a fragmentary femur (thigh bone), three fragments of a tibiotarsus (shin bone), an incomplete tarsometatarsus (the lower part of the “backwards-looking-knee” of a bird – it’s the same as our ankle), and some toe bones (phalanges).

Cuban Owl legs
Image of leg bones from Ornimegalonyx (Arrendondo 1976)

Original descriptions of Ornimegalonyx have it belonging to the group Phorusrhacidae (also known as “terror birds”) because of the large size. Back in 1958, large owls were not on people’s radar. This small collection of bone fragments doesn’t sound like a lot on which to base the naming of a new critter, but there are parts of owl leg and foot bones that are Classic Owl. Ornimegalonyx was estimated to have stood about 1.1 m (3’7”) tall and likely weighed around 9 kg (20 lbs).

The best Ornimegalonyx image ever. Twilight Beasts introduced me to this image (link here) and blog where this and other great images come from (link here). Check out the Terror Bird image when you visit (because of course you’re going to visit the site)!

As owls go, Ornimegalonyx (orni = bird; mega = large) lives up to its name. Let’s look at its size in comparison to a fairly well-known and our largest owl alive today, the Eurasian Eagle-owl (Bubo bubo). The leg bones, the femur (thigh bone) plus the tibia (shin bone) plus the metatarsals of an Eurasian Eagle-owl are 10.8 cm, 15.5 cm, and 8.4 cm, respectively. We can estimate the leg length of the Eurasian Eagle-owl (give or take some soft tissue and cartilage) at 34.7 cm (or about 13.6 inches) long. The leg bones of Ornimegalonyx are 15.4 cm, 25.0 cm, and 14.7 cm. The estimated leg length of Ornimegalonyx is 55.1 cm (or 21.7 inches). This is how Arrendondo estimated the height of Ornimegalonyx at about 1.1 meters (3`7”)! Compare that to the height of the Eurasian Eagle-owl at 75 centimeters (around 30 inches). That’s a big owl! Most artistic reconstruction of Ornimegalonyx show a critter similar in shape to a Burrowing Owl (Athene cunicularia) due to the long legs and the interpretation that Ornimegalonyx spent more time running and walking than flying.

Was Ornimegalonyx unable to fly like our present-day owls? That’s an interesting question that’s still being examined. It’s definitely not the overall size of Ornimegalonyx that would have kept it grounded. The Secretarybird (Sagittarius serpentarius) is slightly taller than Ornimegalonyx at about 1.3 meters (4.3 feet tall). It is not even the estimated weight of Ornimegalonyx (uncited at around 9 kilograms) that would have made flying untenable: the Andean Condor weighs in at 15 kilograms.

Ornimegalonyx was not taller than a Secretarybird or heavier than an Andean Condor. Ornimegalonyx may have not been a “feathery death from above” kind of owl, but more of an “I will run you down” owl. Arrendondo (1976) states that the sternum (that’s the breastbone) doesn’t have a large enough keel (the bony projection in the middle of the breastbone) to hold the chest muscles required for a flying bird. Think of carving up the white meat of a turkey breast during the holidays: those are the flapping muscles of the downstroke of the wings, the pectoralis major and pectoralis minor. There’s enough of the sternum preserved of Ornimegalonyx to make a decent reconstruction.

Cuban owl sternum
Sternum and keel of Ornimegalonyx (Arrendondo 1976).

The keel of Ornimegalonyx is not as large as that of a Burrowing Owl or of the similarly-sized Secretarybird. Even vultures have a comparatively larger sternal keel than that of Ornimegalonyx, and vultures are more known for soaring on thermals than for dive-bombing stealthy death from above. Given that Ornimegalonyx didn’t have a lot of room on its breastbone to attach flapping muscles, it likely spent a great deal of time on the ground, terrorizing the Ice Age mammals. However, new specimens and more investigation will shed light on this in the future.

secretary bird
Skeleton of the Secretarybird (similar in size to the Giant Cuban Owl) on the BHL Biodiversity Heritage Library by Eduard d’Alton for his & Christian Heinrich Pander, Die Vergleichende Osteologie (1821-38). Contributed for digitization by Smithsonian Libraries (@silibraries). You can see the keel is pretty deep on the sternum.

Did Ornimegalonyx Inspire the Idea of Stolas?

Would Collin de Plancy have known about Ornimegalonyx, or preserved remains of creatures that would have inspired visions of demons, when he wrote Dictionnaire Infernal (1818; illustrated version in 1863)? We don’t have any reason to assume Collin de Plancy himself had any knowledge of giant fossil owls. As far as I know, there is no documented contact between Collin de Plancy and Cuba (I’m still looking.)

Theological interpretations of the natural world happened at late as the 1800s. Fossilized meat-eating dinosaur (theropod) footprints were described as the footprints of Noah’s Raven by Elihu Dwight as late as the 1800s. Edward Hitchcock later described these same tracks as those belonging to an extinct bird in the 1830s. Scriptural-based interpretations of natural phenomena were still prevalent when the Dictionnaire was written. Heck: these types of explanations for natural phenomena still happen today, so we really can’t side-eye past historians and naturalists too much if they assumed that demons appeared in owl-form.

The likelihood of Collin de Plancy having heard tell of fossils of Ornimegalonyx, or skeletons of a Stolas-like demon from Spanish colonies is possible. Spanish colonization of Cuba began during the 1492 expeditions, and was briefly colonized by Great Britain in 1762. French colonization of Cuba began in the 18th century and increased into the 19th century.  People were aware of fossils during this time. In the 1400s there was recognition that the phenomena that we call fossils were the remains of ancient life. Fossils were even described by Aristotle (348-322 BC) as being once-living organisms that were “petrified.” Unfortunately, I haven’t come across records of pre-1900s discoveries of fossils on Cuba. Columbus was likely aware of amber (http://www.nytimes.com/books/first/p/poinar-amber.html) as amber was used by the indigenous peoples who Columbus viciously exploited on the island of Hispainola. However, it seems unlikely that Columbus would have paid much attention to fossilized animals of Cuba, and there certainly has never been a report of a fossilized giant owl encased in amber.

Just because colonists may not have heard about giant fossil owls doesn’t mean they were unknown. People may have encountered Ornimegalonyx. There are records of people from the Palaeolithic Periods after the Ice Ages (Guanahatabey and Siboney cultures) living in Cuba.

It’s not often we have a real-life version of a mythical character such as Stolas. It doesn’t “prove” that Stolas is the real deal, or that owls represent demons. We still have a lot of work to do to shake off some of the negative associations people have with wildlife. Wolves, bats, owls, ravens, vultures: these are animals that are still associated with hunting, death, night, and evil doings. These animals are not evil: it’s only our associations and biases that interprets them as such. The more we learn about how wonderfully complex our natural world is the easier it will be (I hope) to exorcise the demons of our biases from these misunderstood animals.


Arrendondo 1958. Aves gigantes de nuestro pasado prehistorico: El Cartero Cubano, v. 17, no. 7 (July), p. 10-12, unnumbered text-figs.

Arredondo, Oscar and Olson, Storrs L. 1976. “The great predatory birds of the Pleistocene of Cuba.” in Collected Papers in Avian Paleontology Honoring the 90th Birthday of Alexander Wetmore, 169–187.

Owls, Part 1: Fossil Owls

Hello Dear Readers!

Live nest cam season is here (and sadly it is now past: too many major life changes happened that put this blog post on hold)! Nest cams are windows into the wonderful world of a very important time in the lives of our present-day theropods: mate interactions, nesting, brooding, and raising young.

Besides being completely fascinating, watching owls (and hawks, and osprey, and albatross) nest and raise young is that we know that Cretaceous theropods also courted their mates (1), constructed nests, laid eggs, and cared for their young. Here’s a link to an earlier blog post where I cover theropod nesting, brooding, and determining the sex of a theropod: http://birdsinmud.blogspot.com/2017/04/theropods-or-tender-pods-softer-side-of.html  There is a lot that we can learn about the lives of extinct theropods by studying our present day theropods!

Other than the previous blog post on the tender side of theropods where I link to owl nest cams I realized, while watching the Barred Owl snooze in her next box, that I have never written about owls as their own topic.

I think I may have ruffled some feathers on this Barred Owl.

So let’s talk about owls! I want to do a series of blog posts that highlight all that is fascinating about owls – I find everything about owls fascinating, so who knows how many posts this will be!

To start our conversation about owls we have to start at the beginning, which means we’ll be looking at the fossil history of owls!

Owl Features…In Bones

To talk about owls we have to talk about what features make owls what they are. If we don’t know what makes an owl an owl, we can’t figure out when owls first evolved. I’m only going to talk about owls as we recognize them from their skeletons because that’s what we have to work with as palaeontologists.

Owls belong to an order of birds called Strigiformes. This term was first coined by Wagler in 1830. To get into Club Strigiformes, you’d have to have the following characteristics:

  • Large, round, front-facing eyes (can fossilize),
  • Bony ring in the eye socket (sclerotic ring) is a solid, elongate tube (can fossilize),
  • Eyes in a circular or heart-shaped disk of radiating feathers (not skeletal),
  • Relatively large head (can fossilize),
  • Holes in the neck vertebrae where the arteries run through are about 10X the size of the artery (can fossilize),
  • Sharply hooked beaks (can fossilize, but shared with other birds of prey),
  • Hooked talons (can fossilize, but shared with other birds of prey), and
  • Feathers with serrated edges to reduce noise in flight (not skeletal).

Those are very general characteristics of an owl’s body. When we get down to the nitty-gritty of “How do I know my fossil bird is an owl?” we are dealing with parts of a bird skeleton that are more likely to fossilize than others. Skulls, with their thin braincases and thin bony struts, may not fossilize well (but it does happen). Bones that are relatively more sturdy, typically limb bones, have a better chance at fossilizing. This is why many of the oldest owl fossils are just that: limb bones or parts of limb bones. The most common limb bone of fossilized early owls that shows up in the scientific literature is one of my favorite bones, the tarsometatarsus.

Great Horned Owl tarsometatarsus, seen from the back. This is a stout, sturdy set of three fused metatarsals. http://www.boneid.net/product/great-horned-owl-bubo-viginianus-right-tarsometatarsal-posterior-view/

If you picture a bird leg, you are probably familiar with the “backward knee” look that they have. That “backward knee” isn’t the knee at all: that’s the equivalent of our angle joint between the tibiotarsus and the tarsometatarsus. Remember those “if dogs wore pants” memes that circulated a few years ago? Well, if birds (and extinct theropod dinosaurs) wore shoes, they would look something like this:

theropod shoes
This glorious bit of artwork was painstakingly sketched over the course of five minutes using a page from my quasi-bullet journal. Theropods likely wouldn’t want to wear high heels: it would interfere with the “spring” in their step.

The tarsometatarsus is one of my favorite bones in a bird skeleton because there’s a lot of identifying information in the area where the tarsometatarsus connects to the tibia and where the toes connect to the tarsometatarsus. I focused on the tarsometatarsus of shorebirds for my doctoral thesis because I wanted to understand the link between footprint shape and foot bones. [Results in progress.]

One of the obvious features of a bird of prey tarsometatarsus is the huge roller surfaces of the distal end – where the toes attach. Birds of prey are a lot like their extinct meat-eating dinosaur cousins: they do a lot of their prey catching with their feet. Those toes gotta be able to grip it good, so the roller surfaces are nice and robust. Check out the tarsometatarsus of a Bald Eagle.

Bald Eagle tarsometatarsus. The inner toe (digit II) is LARGE, and the roller surfaces are all in a line. https://royalbcmuseum.bc.ca/Natural_History/Bones/Species-Pages/BAEA.htm

Now, check out the tarsometatarus of a Great Horned Owl! Do you see the one roller surface – the outer roller – that is twisted?


This is a bony feature of a special owl foot trait, called the zygodactyl foot. Check out the feet of the Eurasian Eagle Owl coming in for a landing. Do you see how the outer toe is facing more backward than forwards? That’s a zygodactyl owl foot.



Even long-legged owls like the Burrowing Owl have a fourth/outer roller surface that is twisted!

Burrowing Owl. https://www.audubon.org/field-guide/bird/burrowing-owl
Burrowing Owl TMT.jpg
Burrowing Owl tarsometatarsus from Aves3D. It doesn’t really sit straight because of the fourth distal metatarsal “twist.” https://aves3d.org/public_images/show_image/5654?specimen_element_id=473&specimen_id=152

One feature that diurnal (active in the daytime) predatory birds have is a built-in sun-visor over each eye. This sun-visor is called the supraorbital process. In diurnal birds this ridge can be very pronounced, but in nocturnal birds this visor is smaller. In diurnal owls (Great Horned Owls are an example) the ridge is well-developed!

Skulls unlimited Great Horned Owl skull
Great Horned Owl skull from Skulls Unlimited. See the flange of bone above the round tube of bone? That’s the bony “sun visor.” https://www.skullsunlimited.com/products/replica-great-horned-owl-skull-bc-072

In the Boreal Owl skull, we don’t see that bony sun visor: the edge of the upper eye socket is rounded and smooth. But check out those asymmetrical ear openings! This feature allows sound to come into the owl’s ears at two different levels, giving the owl precision targeting of small furry/feathery/fluttery prey. If you’re hunting at night, you need to pull out all the tricks to get a tasty meal!

Boreal Owl Skull

These are two out of MANY features that make an owl an owl if all you find is the skeleton. That’s what we deal with when we talk about fossil owls.

Fossil Record of Owls: The Wise Oldest Owl

You might find this surprising, but owls have been around for a long time! We don’t yet have any definite owls from the Cretaceous Period, but in the time immediately after the Cretaceous – Paleogene extinction (when non-birdy dinosaurs went extinct 66 million years ago) owls are there! This suggests that owls – or very early versions of owls – may have evolved in the latest Cretaceous Period (2). Why is this? It’s because the “owly” features are fairly well-developed, and bony features take time to evolve in groups of animals.

That’s not to say that people haven’t thought they had evidence of Cretaceous owls. Bradycneme draculae (3) was described by Harrison and Walker in 1975 from the Maastrichtian (70 – 66 million years ago) age deposits of Transylvania (yes, they went there.) Following the description of Bradycneme as a Cretaceous owl, many researchers started to compare the end of the tibia (that’s the shin bone) to bones of theropod dinosaurs. It is very likely that Bradycneme is actually a funky little theropod called an alvarezsaurid (4).

Here’s an image of Patagonychus, an alvarezsaurid. Check out the wee little arms!

Patagonychus. https://en.wikipedia.org/wiki/Alvarezsauridae

Our first Wise Oldest Owl comes from the lower Paleocene deposits of Colorado, USA (Tiffanian: 60.2 – 56.8 million years ago). Ogygoptynx wetmorei is known as a “protostrigid:” it’s really really close to being an owl it’s scary, and it has features that are seen in both typical owls (like Great Horned Owls) and the Barn Owl kind of owl. Ogygoptynx is known from a tarsometatarsus (5).

Ogypt tmt
Ogygoptynx wetmorei tarsometatarsus. There’s a slight twist in the outer toe roller surface (you can tell the outer tarsometatarsus because of the small hole between metatarsals III and IV). The outer metatarsal roller surface is also slightly separated from the rest of the “bundle” of fused metatarsals (5).

Our next Wise Oldest Owl is Berruornis, which comes from the upper Paleocene deposits (59 – 56 million years ago) of the Reims area of northeast France. Berruornis is known from – surprise! – a nice sturdy tarsometatarsus! One of the owly features of Berruornis is seeing the fourth distal tarsometatarsus – the roller surface – starting to get that zygodactyl twist! Berruornis fossils are also found from the Late Paleocene rocks in Germany.

Tarsometatarsus of Berruornis. If you check out the middle image, you can see the small “twist” in the fourth roller surface as it peeks around the shaft (6).

This kickstarts my blog series on OWLS! The next post will focus on one fossil owl in particular…and this owl has some interesting mythological connections! Stay tuned!


1.  Lockley MG, McCrea RT, Buckley LG, Lim JD, Matthews NA, Houck KJ, Gierliński GD, Surmik D, Kim KS, Xing L, Kong DY, Cart K, Martin J, Hadden G. 2016. Theropod courtship: large scale physical evidence of display arenas and avian-like scrape ceremony behavior by Cretaceous dinosaurs. Scientific Reports 6, Article number: 18952 (2016)

2. Harrison CJO, Walker CA. 1975. The Bradycnemidae, a new family of owls from the Upper Cretaceous of Romania. Palaeontology 18(3): 563-570.

3. Naish D, Gareth J. 2004. Heptasteornis was no ornithomimid, troodontid, dromaeosaurid or owl: the first alvarezsaurid (Dinosauria: Theropoda) from Europe. Neues Jahrbuch für Geologie und Paläontologie Monatshefte 7: 385-401.

4. Kurochin EN, Dyke GJ. 2011. The first fossil owls (Aves: Strigiformes) from the Paleogene of Asia and a review of the fossil record of Strigiformes. Paleontological Journal 45(4): 445-458.

5. Vickers-Rich P,  Bohaska DJ. 1981. The Ogygoptyngidae, a new family of owls from the Paleocene of North America. Alcheringa 5(2): 95-102.

6. Mourer-Chauvire C. 1994. A large owl from the Palaeocene of France. Palaeontology 37: 339-348.