Good tidings and well-wishes!
Birds have always enjoyed a certain popularity among naturalists. Who could forget John James Audubon’s paintings of North American avians? And one would be hard-pressed to locate a biologist (or scientist of any discipline) who hasn’t heard of Darwin’s world-famous finches which helped to pioneer the concepts of biogeography and natural selection itself. Indeed, one of the first scientific predictions Darwin made in his Earth-shaking book “On The Origin Of Species By Means Of Natural Selection” was that birds evolved from reptiles with unfused metacarpals among other anatomical features, and two years later (in 1860), Archaeopteryx lithographicawas discovered in the Solnhofen limestone of Germany. Since then, avians have become one of the most heavily-researched groups in the history of evolutionary study; in fact, the re-emergence of the hypothesis that birds are descended from theropods helped trigger the dinosaur reniassance during the 196o’s and 70’s which forced the scientific community to view these “fearfully-great lizards” with an esteem that hadn’t occurred for over half of a century.
It therefore comes as no surprise that paleo-ornithologists have unearthed an enormous amount of bizarre and captivating fossilized remains of their beloved feathered critters. There are the towering Phorusrhacids of the Americas, the wingless moasof New Zealand, and the loon-like Hesperornithids of the extinct Western-Interior Seaway to name a few. The latter group was of particular interest to the legendary paleontologist Othneil Charles (O.C.) Marsh due to its evolutionary implications as evidenced by what was arguably the most distinct feature of its members: the presence of teeth. This discovery helped Marsh and “Darwin’s Bulldog”, Thomas Huxley, to solidify the relationship between birds and reptiles.
One would be mistaken, however, to say that birds with teeth or tooth-like structures were purely a thing of the Mesozoic.
Enter the Pelagornithidae, also known as the “pseudodontorns”, a hugely successful group of albatross-like seabirds which lived from the late Paleocene to the late Pliocene and which have been found in such diverse localities as Great Britain, Europe, both North American coasts, Japan, Africa, New Zealand, and possibly even Antarctica. These animals were members of the Order Pelecaniformes which also contains modern pelicans, boobies, gannets, frigatebirds, and cormorants among others.
By avian dinosaur standards, Pelagornithids are fairly well-known, which comes as no surprise when one examines their extraordinary remains. Initially, their most striking feature is sheer size. Fossil remains have suggested that these creatures could have achieved wingspans of nearly seven meters, rendering the largest individuals nearly twice the size of a modern albatross. As Gregory S. Paul explains in his book “Dinosaurs Of The Air: The Evolution And Loss Of Flight In Dinosaurs And Birds”:
“The longest wing feathers [of Pelagornithids] should have been well over a meter long! These lightly built superbirds should have weighed 50 kilograms. These avian giants came close to matching the biggest marine pterosaurs in wingspan and especially in heft. Pseudodontorns further mimicked [(some)] giant pterosaurs by retaining the long jaws and necks with which to snatch up sea life while on the wing.”
Michael Habib has subsequently written in an abstract for a 2006 symposium dedicated to the Calvert Marine Museum’s fossil club that
“Despite their impressive size and extreme adaptations for soaring, little work has been done on the flight performance of pseudodontorns. I have used anatomical information from Miocene pseudodontorns, along with methods from mechanical engineering, to estimate body weight, flight speed, and launch ability in large pseudodontorn birds. Pseudodontorns would have been champion gliders, exceeding even modern albatrosses in their average soaring speeds. Previous estimates of body weight are likely too low; pesudodontorns were probably heavier and faster than earlier estimates have suggested.”
The albatross-like lifestyle is further evidenced by thin and lengthy bones throughout the forearm in addition to a head morphology of the humerus which would have reduced shoulder mobility and in so doing stiffened their rather narrow wings to better facilitate long-distance soaring.
While the massive proportions of these birds are indeed quite impressive (among the avians, only the notorious teratorns exceeded them in size), they are by no means the group’s only distinctive feature. These animals were (almost certainly) dining on fish and squid, creatures which are infamously difficult to grip. To combat this, evolution lined their jaws with dozens of straight, tooth-like projections.
(For a copy of the press release accompanying this photo, do go here)
To assist in this effort, the beak itself was very robust and may have weighed the skull down to such a degree that these beasts may have had to hold their heads between their shoulders while in flight as modern pelicans do.
Okay, then: on to Pelagornis itself. While Osteodontornis is probably the best-known Pelagornithid (and one of the largest), Pelagornis was the first to be discovered and, unsurprisingly, inspired the family’s name. In “Catalogue Of Fossil Birds In The British Museum (Natural History)” (a facsimile reprint of the 1891 edition), Richard Lydekker writes that the genus is
“Founded upon the humerus, which presents many of the general characters of that of Sula- such as the small size of the proximial extremity, the slight development of the delto-pectoral crest, and the absence of an ectepicondylar proccess; but is distinguished by the absence of a olecranal fossa (in which respect toPelecanus), and the abortion of the bicipital surface.”
The only described species as of this writing (that I know of) is Pelagornis miocaenus which was named in 1857 by the French paleontologist Edouard Lartet and was unearthed in the Miocene of France. Another humerus has been subsequently found and in 2007 Gerald Mayr, Cornelis Hazevoet, Pedro Dantas, and M´rio Cachão tentatively assigned the sternum of a very large Pelagornithid discovered in Portuguese Miocene rocks to the genus. Their abstract is available here.
While all remains of Pelagornis thus far have been woefully incomplete, it nevertheless hails from a truly amazing group which is just beginning to receive the attention it deserves.
May the fossil record continue to enchant us all!