Pterosaur soft tissues

This is just a quick survey of *what* soft tissues are known or can be directly inferred in pterosaurs based on a variety of specimens. I won’t be going into the details of which specimens preserve which bits, how, where you can see them, what they mean or how they function – that would take pages and pages. This is meant just as a quick overview to show what can be gleaned from the fossils and it is far more than you might think (pterosaur courtesy of Dino Frey). While of course we can infer that as vertebrates pterosaurs had eyes, hearts, lungs, livers, kidneys, skin, and muscles these are rarely if ever recorded in the fossil record at all, and of course the fragmentary nature of the pterosaur fossil record (compared to say, dinosaurs) means that these events should be far rarer. However the ‘damage’ is offset by the fact that a great many pterosaurs come from lagerstaaten deposits of exceptional quality, and thus a great many features are preserved on occasion.

Various pterosaur soft tissues

Various pterosaur soft tissues

Obviously some names come up again and again, because if the preservation is good enough to save one feature, it can probably save quite a few so this might get a little repetitive in places. Anyway, in no particular order:

There are several beaks known for pterosaurs (both upper and lower) including Tapejara and Rhamphorhynchus.

Throat pouches (like those of a pelican) can be seen in Pterodactylus and can be inferred in Ludodactylus.

As mentioned before there are lots of soft tissue crests known, often combined with bony parts (but not necessarily) such as with Pterorhynchus, Tapejara and Germanodactylus.

Claws (both manual and pedal) show up in Jeholopterus well, in addition to several azhdarchid specimens, and others, and impressions of them can be seen in footprints too.

Also known from both prints and actual preserved tissue are the webbing between toes, with the dark wing Rhamphorhynchus being an exceptionally good example.

There is also evidence for webbing between some of the fingers based on prints, but not to my knowledge in fossils. However, as these parts of the hand are usually prepared clear of the matrix, examples have been lost in the past (traces still remain).

Although it is inferred in pretty much every rhamphorhyncoid, only Rhamphorhynchus, Sordes and Pterorhynchus preserve a tail vane (although there are many examples for the former).

Famously, some pterosaurs have ‘fur’ (well, pseudo-hair-filament-fibre-things). Most obvious is Sordes, but these can also be seen in Jeholopterus, Pterodactylus and others.

The most prominent feature (soft or otherwise) is the wing itself – more properly the brachiopatagium. Whole wings (or substantial parts) are known for Eosipterus, Eudimorphodon, Rhamphorhynchus, and Dendrorhynchoides among others, as well as several azhdarchoid bits.

The forewing or propatagium is rarely preserved, or more likely, is commonly prepared off the slab (something that is evident in many old Solnhofen specimens) but good examples are known in Pterodactylus and Jeholopterus.

Finishing off wings, the rear wing, (uropatagium or crurupatagium depending on your preference) is again uncommon, but with good records in Jeholopterus, Sordes, and Rhamphorhynchus.

Against the odds, there is even an example of actual muscle tissue preserved (and not just in the wings, or inferred from the bones). The new Anurognathus specimen, when seen under UV clearly has the traces or original muscles on the upper arms and legs – quite a feat of preservation after 145 million years.

Several pterosaurs have preserved stomach contents (including one exceptional Rhamphorhynchus) which allows us to infer the position of the gut in the animal. One also shows some kind of discolouration and structure that just might be a cast of part of the intestines.

Although these is still some debate over whether or not pterosaurs had a tendon in the trailing edge of the wing, there is definitely an indication of *something* there in several specimens from the Solnhofen – notably in Pterodactylus.

Brains cannot of course be recovered, but like all reptiles, the bony braincase can give us a general idea of the shape of the brain inside and what area were large and small and thus a simple look at some aspects of their biology. However, going a step further you can scan the internal architecture of the skull (if it is uncrushed) and see things in far greater detail. Larry Witmer did just this a few years back for Anhanguera and Rhamphorhynchus.

Like the brain, we can only infer some general features of the eye, but the size and depth of the orbit and the size of the sclerotic ring can give us an indication of visual acuity or the ability of the eye to operate in low light conditions.

A combination of footprints and real specimens show us that the foot pads of pterosaurs had small, but thick scales that would have protected the soles of the feet. Skin from the rest of the body is rare, but small fragments are in evidence from Sordes, and from an indeterminate pterosaur from Brazil.

Sadly there is no direct evidence of the air sac system, but the pneumatic nature of the bones and the pneumatopores that lead to them are a clear indication that they existed with Rhamphorhynchus being a good example.

That’s about if for soft tissues in pterosaurs. This really is an incredibly brief round-up but it represents a large number of specimens across a wide range of taxa, there are probably well over a hundred pterosaurs known with various soft tissue parts preserved, and far more where sadly it has been eroded unknowingly in the past by preparators. However, what is noticeable is just how much information is available – a large and diverse part of pterosaur soft tissue anatomy can be directly observed or inferred (and often in ways beyond that which can be done in other vertebrates e.g. through the sclerotic ring). We really do know a lot in some ways about pterosaurs that other palaeontologists can largely only dream of, but as ever, the answers are somewhat cryptic, open to multiple (often contradictory) interpretations, and often are little more than hints or nods towards the information we would really like.

This is par for the course in palaeontology, but there is a difference between having no information, and having just enough to not tell you anything meaningful, while hinting at what you really want to know! Many soft-tissue specimens represent little more than just beautiful fossils with actual scientific information available in the material highly limited or non-existent, but there are those which can tell us a huge amount (the dark wing, Sordes, Jeholopterus, the Vienna specimen) and these are justifiably highly prized.

9 Responses to “Pterosaur soft tissues”

  1. 1 Nathan Myers 30/07/2008 at 10:23 am

    Thank you for this. Digested information like this is available nowhere else.

    Has there been any plausible explanation of what the sclerotic ring is good for, or why archosaurs’ orbits are often so much bigger than the eye must have been?

  2. 2 David Hone 30/07/2008 at 11:23 pm

    There are several recent papers on the sclerotic ring in various archosaurs. It definitely provides support for the eye and potentially increses acuity, beyond that little is known. Orbits are awkward as the sclerotic ring is not always related to the diameter of the orbit, or more importantly the depth. Quite simply, more work is needed.

  3. 3 kattato Garu 11/03/2011 at 9:54 am

    Hi David, this is a great review. Is the a comparable review somewhere of pterosaur integumantary structures?

    • 4 David Hone 11/03/2011 at 9:57 am

      Well I never wrote one…. I do talk in various places on here about skin and pycnofibers but in short there’s rather less of them believe it or not, so there’s not much to say beyond what has been discussed repeatedly for things like Sordes and Jeholopterus. Glad you like the post though.

  4. 5 Terrance Taddeo 23/04/2011 at 2:31 pm

    I was enjoying this piece until you referred to pterosaurs as “reptiles.” Physiologically and behaviorally they could could not have been reptiles any more than are birds or bats.

    • 6 David Hone 23/04/2011 at 3:17 pm

      But they are reptiles since they descended from reptilian ancestors and are part of the clade Reptilia. Behaviour and physiology have nothing to do with it (and in any case, we know very little about either for pterosaurs).

      • 7 Robert lizard 16/05/2014 at 4:36 am

        Aren’t pterosaurs pretty much the freaks of nature, there is no creatures like them today nor any like them before the Triassic. They are very unique.

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