Was Rhamphorhynchus a skim feeder?

Whilst translating a passage from Peter Wellhofers' work on the Rhamphorhynchoidea, I came across this specimen from the collection of Karl Strobl.

Specimen No. 28: Fig. 24; Plate. 8, Fig. 1-3. Wintershof. Sammlung KARL STROBL, Eichstätt.
Part and counterpart of an entire skeleton with excellent preservation.

The individual is seen from the side; the arms are pushed forwards, the flight fingers in parallel with backbone extend backwards. Impressions of the flight skin and the narrow, lance shaped tail sail are present. The lower jaw extremity is relatively high, blunted in front. The upper edge line of the skull is concave. The front edge of the Infra-temporal opening is formed by the Quadrato-jugale. The cranial length measures 55.5mm.
The gastral skeleton consists of 6 curved bones still in situ; the middle pieces are displaced forwards. The Pubis is widened ventral, so that to the Ischium appears as a bay than rather a round opening. The Prepubis is strengthened centrally and hook-shaped (fig. 10 e).
Within the body cavity is a compressed fish tail and numerous single fish bone fragments indicating the stomach contents. Beside this lies 6-7mm long bananas-shaped small sausages like gastric stones of 1.5mm diameter and with zigzag-shaped textured surface (ref. fig. 44 b).

This specimen clearly shows that this individual had eaten a fish which was swallowed whole, head first. The use of gastric stones to aid mechanical digestion is an indication of a more specialised digestive system. This rhamphorhynchus may have had a gizzard, similar to that seen in birds, or a muscular and thick stomach wall to enable the churning of contents to allow the enzymes and gastric stones to break down the food both chemically and mechanically.

Very few pterosaurs give information about stomach contents, and in this case it leads to a question about fishing methods. Did rhamphorhynchus use a surface skimming technique to fish, or was it a shallow diver. It is impossible to say for certain, but the evidence is compelling. The jaws would certainly be able to scoop up a fish from near the surface of the water. and such a technique would have needed a very precise flying skill and good control of the jaws and neck.

The jaw on this specimen shows an impression of an upturned bony sheath at the end of the lower jaw. Such a structure, being free of teeth, would lend itself to surface skimming. This is a strong clue to the feeding habits of this type of Rhamphorhynchus and the group as a whole.

Wellnhofer, P. 1975 Die Rhamphorhynchoidea (Pterosauria) der Oberjura-Plattenkalke Süddeutschlands. Teil II. Systematische beschreibung. Paläontographica A 148, 132–186.

The Rhamphorhynchoidea

In 1975, Peter Wellnhofer wrote a classic monograph on the Rhamphorhynchoidea. This set of 3 linked works has been the baseline for the study of this group of pterosaurs since then. It is a well organised work with analysis split into skeletal morphology, systematics and Palaeoecology. The texts were originally in German and as far as I am aware, they have not been translated wholesale into English. Recently, I started to translate part 2 for my own use. I would love to publish my translation, which will be a new work, but the original text is not out of copyright until 2025. I can only find paper copy, but I have been told that there is an electronic copy in German. This has eluded me, so I am transcribing and translating from the original text.

Wellnhofer, P. 1975 Die Rhamphorhynchoidea (Pterosauria) der Oberjura-Plattenkalke Süddeutschlands. Teil I. Allgemeine Skelletmorphologie. Paläontographica A 148 , 1–33.11 plates.

Wellnhofer, P. 1975 Die Rhamphorhynchoidea (Pterosauria) der Oberjura-Plattenkalke Süddeutschlands. Teil II. Systematische beschreibung. Paläontographica A 148, 132–186.

Wellnhofer, P. 1975 Die Rhamphorhynchoidea (Pterosauria) der Oberjura-Plattenkalke Süddeutschlands. Teil III. Palökologie und Stammesgeschichte. Paläontographica A 149, 1–30. 13 plates

The problem in translating any text is the transfer of meaning. There are words in German that can have several possible meanings in English. This also works the other way around. The bulk of the meaning is transferable with a high level of confidence in the result, but there are some areas where the meaning has to be a best guess. This type of translation is often referred to as a Gist Translation. This means that in some cases, the reader may need to refer to the original text to grasp the full meaning of a sentance of passage. It is for this reason that translations should only be attempted from the original documents. Another of Peters texts that I have frequently used is the Handbook of Paleoherpetology, Part 19. This text is also only available in German, so people who are not able to read that language can only look at the wonderful line drawings and be amazed. This is of course, another text that sets the baseline for the study of pterosaurs in general. It is a little dated now, but still a valuable resource. The original text is still available to purchase on the Internet.

Wellnhofer, P. & Khun, O. 1978 Handbuch der Paläoherpetologie. Teil 19. Pterosauria. Stuttgart: Verlag Gustav Fischer.

These texts defined the study of pterosaurs for a whole generation of researchers. It would be beneficial to the subject to have them available on line both in their original German text and in English. The main difficulty is in gaining permission to freely allow access without infringing copyright law. Watch this space!

The Frog Mouthed Pterosaurs

Anurognathus ammoni, a pterosaur from the upper Jurassic Solenhofen limestones of Bavaria, was first published in 1923 by Dodderlein. This was recognised as a very unusual small pterosaur, having a very broad and short jaw. Nothing had been seen like this before. The specimen was poorly preserved and the bones were somewhat disarticulated, but the animal clearly has short blunt teeth which were not suited to tearing flesh. "Frog Jaw" was thought to be an insectivore, possibly catching is prey on the wing or on leaves and branches around forested areas.
A second, well articulated specimen of Anurognathus ammoni was described by Bennet in 2002 and this specimen shows the skeletal anatomy of the pterosaur very clearly.
Another frog mouthed species, Batrachognathus volans, is known from the Karatau Mountains, Upper Jurassic sediments of Kazakhstan. This species was described by Rjabinin in 1948. The specimen is a partial skeleton including a disarticulated skull which clearly shows a wide jaw. This specimen shows some similarities with Anuroghnathus, but enough differences to classify it as a different species.
Dendrorhynchoides curvidentatus is a Tithonian species that was collected from the Chaomidianzi Formation, Zhangijagou locality from the Lower Yixian Formation near Beipiao City, Western Liaoning Province, China. It was published in 1998 and is one of several fine specimens to come out of this part of China. This is a very good fossil of this type of pterosaur and it has been restored after a preparator doctored the fossil in an attempt to make it more salable.
Jaholopterus ninchengensis is a compete Anurognathid with some soft part preservation from the Lower Yixian Formation at Nincheng, Inner Mongolia. This specimen is known as the Nincheng Rehe Pterosaur and is in the Institute of Vertebrate Paleontology and Paleoathropology in Beijing. The specimen caused quite a stir when it was published in 2002.

These 5 specimens are the major contingent of the classification Anurognathidae. There are a few fragmentary remains, like a jaw fragment from the Middle Jurassic Stonesfield Slate which is in The National Museum of Wales, Cardiff. The Anurognathids were probably quite widespread in distribution, but I suspect that they were forest dwelling pterosaurs, living in places where fossilization is a rare process. The scientific community is probably quite lucky to have this many specimens of this pterosaur lineage to work with.

Döderlein L., 1923, Anurognathus ammoni, ein neuer Flugsaurier. Sitzungsberichte der Bayerischen Akademie Wissenschaften, math.-naturwiss. Klasse, 1923, München. Pp. 117- 64, figs. 1-7.

Bennett S. C., 2002, A second specimen of Anurognathus from the Solnhofen Limestone of South Germany. Journal of Vertebrate Paleontology 22 (supp. 3), 36A

Rjabinin A. N., 1948, Remarks on a flying reptile from the Jurassic of the Kara-Tau, Akademia Nauk, Paleontological Institute, Trudy, 15(1): 86-93, 1 plate, Moscow and Leningrad.

Ji S.-A. and Ji Q., 1998, A new fossil pterosaur (Rhamphorhynchoidea) from Liaoning. Jiangsu Geology 22(4): 199-206.

Wang X., Zhou Z., Zhang F. and Xu W., 2002, A nearly complete articulated rhamphorhynchoid pterosaur with exceptionally well-preserved wing membranes and "hairs" from Inner Mongolia, Northeast China. Chinese Science Bulletin vol. 47(3), pp. 226-232.