The small pterosaur[n1] Rhamphorhynchus is known from a large host of specimens from the Late Jurassic of central to western Europe, mostly Germany and surrounding countries. It is known from complete specimens, to well-preserved partial, to utter crap. It is known from squished, 2D preserved specimens, and from 3D preserved fully prepared ones. Once, it was known from a large host of species, but numerous studies in the the mid-1990s indicate that most of these are probably a single species, merely ontogenetically different. There’s some quibbling that can be had about the ontogeny, as the jaw in Rhamphorhynchus spp. varies considerably, but we’ll get around to that some time later.
Rhamphorhynchus represents a small challenge to reconstruction given the enmeshing of its teeth: long, curving teeth splay anterior and lateral to the jaw, fewer on the mandible than the upper jaw, with prow-like edentulous tips. The jaw tips are toothless, but some specimens show evidence of soft-tissue projecting from them, best described by Wellnhofer (1975), who noted that in “gemmingi“-type specimens the straight prows bore straight or slightly upturned beak like shapes showing banding:
“Intermedius“- and “longicaudus“-type specimens, however, have mandibles with pronounced curves, and the shape of the soft-tissue seems to reflect this, while the premaxilla of the “intermedius“-type shown above also bears a hook (this one downward-oriented) but the underlying bony beak does not suggest such a structure is present.
There is banding in this tissue, which suggests there are layering issues involved: the structure so perceived is either split such that we are perceiving the interior, banded segments of tissue or that, rather, the material represented is not all of one material, but comprises a series of soft or hard tissues other than bone, such as cartilage, or even more pliable soft-tissues associated with the dermis. Tissue analysis through a variety of non-invasive (or even invasive, sorry guys!) techniques would have to be performed to differentiate if the banding did represent distinct tissue types, growth, etc. I’ve chosen to take the road most traveled and interpret the structures as being keratin, but I will warn you that, even interpreted as rhamphotheca, the extreme thickness and protuberance of the structures from the jaw tips may belie their use as a semi-hard, rhamphothecal tissue; that there isn’t a lot of data on the structure of the jaws at the tips of rhamphorhynchids to answer the question of what, and how much, of a rhamphotheca might be present. So I tend to be inclined to present the reconstruction I’d offer without keratin at all, but it does help with the reconstruction that is now part of my banner. The issue, of course, is that when the jaws closed, the tips of these structures may very well have touched, or even crossed, and that would certainly be true in the “intermedius“-type seen above though the “gemmingi“-type would likely not.
Note that even were the tip of the upper “rhamphotheca” shown here turned upwards, the tips might still touch.
It’s been noted that Rhamphorhynchus, like many Solnhofen pterosaurs, was piscivorous, but it is hard to reconcile this with incidental recovery: All of the Eocene birds from the Green River Formation, birds collected from the Jiufotang and Yixian Formations, etc., are collected from lacustrine, marine, or estuarine environment, and for pterosaurs from the Jiufotang, Yixian, Solnhofen, and especially Santana and Crato Formations, virtually the entire fauna is known from what are certainly collected remains recovered from an anoxic (oxygen-deprived) low-energy body of water, which is conducive to preserving body fossils of small animals. Not all of these species recovered were aquatic or aerial, indicating that this preservational regime would tend to collect animals that gathered or were transported to the deposit regardless of where they might otherwise inhabit. And what this means is that it is not necessarily true that all such animals are piscivorous. But I will eventually get around to discussing this topic when I can cover it in greater depth; needless to say, the topic suggests at least a perspective that differs with Rhamphorhynchus (any species, if polyspecific) being piscivorous.
Taxonomic note: Rhamphorhynchus muensteri was originally named by Georg August Goldfuß (Goldfuss) in 1831 as Ornithocephalus muensteri. Hermann von Meyer in 1846 coined the name Rhamphorhynchus and moved muensteri into it. This had been the “law of the land” (followed by most workers, including Wellnhofer, 1975) until Bennett (1995) provided ample data that suggested all Rhamphorhynchus species were ontogenetic morphs (or “semaphoront,” not his term [edited: the quoted term was originally "biont," but the term "semaphoront"[n2] was meant instead, and is now used]), and thus would all become muensteri.
[n1] Relatively speaking. Rhamphorhynchus was about the same size as contemporaneous Pterodactylus, with a wingspan as an adult exceeding 1m.
[n2] Hennig’s use of the term (1966) denotes, as in insects, particular (and distinct) phases in the life cycle of an organism. It has been adapted for use by some biologists to reference “classes,” as in ceratopsians, hadrosaurs, Bennett’s year-classes of Rhamphorhynchus (1995) and Pterodactylus (1996). I find the term ugly, but it has some usefulness.
Bennett, S. C. 1995. A statistical study of Rhamphorhynchus from the Solnhofen Limestone of Germany: Year-classes of a single large species. Journal of Paleontology 69: 569-580.
Bennett, S. C. 1996. Year-classes of pterosaurs from the Solnhofen Limestone of Germany: Taxonomic and systematic implications. Journal of Vertebrate Paleontology 16 (3): 432-444.
Goldfuß, G. A. [Goldfuss] 1831. Beiträge zur Kenntnis verscheidener Reptilien ver Vorwelt (Contributions to the knowledge of primitive reptiles of the ancient world). Nova Acta Academiae Leopoldinae 15: 61-128.
Hennig, E. H. W. 1966. Phylogenetic Systematics. University of Illinois Press (Chicago). (Translated by Davis and Zangerl.)
von Meyer, H. 1846. Pterodactylus (Rhamphorhynchus) gemmingi aus dem Kalkschiefer von Solenhofen (Pterodactylus (Rhamphorhynchus) gemmingi from the Solnhofen shales). Palaeontographica 1: 1-20.
Wellnhofer, P. 1975. Die Rhamphorhynchoidea (Pterosauria) der Oberjura-Plattenkalke Süddeutschlands (Rhamphorhynchoidea (Pterosauria) from the Upper Jurassic limestones of southern Germany). Palaeontographica, Abteilungen A 148: 1-33.