The ‘Tooth’ About Pelagornithids

Seabirds are interesting animals. This rather loosely defined group (every definition always throws up some exceptions) contains some of the most familiar species of birds such as the chip-stealing seagulls or the tuxedoed gentlemen of the sea, the penguins. Yet there are some seabird groups that are not well known by the majority of people. One such group is the pelagornithids and this is a situation I feel needs rectified. This strange and enigmatic bird group lived for over 50 million years (Bourdon, 2011), achieving a global distribution and only disappearing from the skies around 2.5 million years ago. But what exactly is it about the pelagornithids that makes them so enigmatic? Read on and you will find out… There are several factors why the pelagornithids are considered enigmatic. The first one is to do with their anatomy and is perhaps best shown using a picture. Look at the below reconstruction of a pelagornithid by the fantastic palaeo-artist Peter Trusler. Now, bearing in mind what you know about modern birds, what is strange about this picture? What does this bird have that we wouldn’t necessarily associate with the birds we see today? Figure it out yet? If you said “teeth” then award yourself one science and move to the top of the class! This is a bird, but with teeth. How strange is that? One of the more commonly used names for the group is the bony-toothed birds. To confuse matters more, these are not true teeth. Rather than being situated in alveoli and possessing a root, crown, enamel and dentine, pelagornithid ‘teeth’ are actually hollow bony outgrowths of the jaws (Mayr, 2011). It is believed that pelagornithids used these structures to trap their prey (squid, soft skinned fish) within their beak after they had taken it from the water, possibly as they skimmed the sea surface. The second factor in the enigmatic nature of the pelagornithids is a taxonomic one. Despite being known to science for over 150 years (the first pelagornithid material was found in France in 1857 (Lartet, 1857)), nobody still has any real clue to which group the pelagornithids are most closely related to. Various analyses has seen them allied with the Pelecaniformes (pelicans and relatives) (most studies in late 19th and early 20th centuries), the Procellariiformes (albatrosses, petrels and relatives) (Harrison and Walker, 1976) and the Anseriformes (ducks and relatives) (Bourdon, 2005). They have even been placed in their own order, the Odontopterygiformes (Howard, 1957); such is their stubbornness to ally with one particular group. Finally, the most recent phylogenetic analysis has found that pelagornithids may have even been outside of Neoaves (the group that every living bird species belongs to) altogether! The title of one paper sums them up very well: Cenozoic mystery birds (Mayr, 2011)! The third reason why pelagornithids are just that little bit special is their size. The largest flying bird alive today in terms of wingspan is the wandering albatross (Diomedea exulans), which has a wingspan of up to 3.5 m. A well preserved pelagornithid skeleton from the late Miocene of Chile, was found to have a skeletal wingspan alone that spanned 4.5 m. Once you add the large primary feathers to that skeleton you end up with a flying bird that had a wingspan of between 5.5 – 6 m. That is one seriously big bird! These animals were the biggest things in the skies since the pterosaurs went extinct some 66 million years ago. Perhaps the next time a seagull steals one of your chips when you’re at the beach, you should be grateful that it wasn’t one of these guys, who may have been more likely to take your whole hand off!