Another “Wingless, Juvenile” Rhamphorhynchus

Rhamphorhynchus sp. (BSPG 1960 I 470a) was considered a juvenile without a head or wings. The specimen appears to be largely unprepared. Earlier we looked at another purportedly wingless Rhamphorhynchus (BML-37012, No. 85 in the Wellnhofer 1975 catalog), also from the Solnhofen formation, in which the wings were buried.

juvenile Rhamphorhynchus BSPG 1960 I 470a in situ

Figure 1. Click to enlarge. The purported juvenile Rhamphorhynchus BSPG 1960 I 470a in situ (above) and traced in black. Buried elements (skull, wings) traced in gray. This specimen demonstrates the value of using Digital Segregation to trace buried elements. Digging into the matrix using this map should reveal more bones.

As Before…
When a fossil specimen is discovered by splitting Solnhofen limestones, typically many bones remain invisible, hidden beneath a thin blanket of limestone at the separation layer. Preparators can usually create a precise outline of the specimen, even when the bones are rather deep, because preparators can see the general direction of the fossil (head on one end, tail on the other) and the exact location of other elements are often betrayed by a slight rise in the matrix. Like a blanket over a child in bed, the limestone tells you exactly where to dig.

Above, Rhamphorhynchus intermedius (n28 in the Wellnhofer 1975 catalog) was recovered as a sister to BSPG 1960 I 470, below.

Figure 2. Above, Rhamphorhynchus intermedius (n28 in the Wellnhofer 1975 catalog) was recovered as a sister to BSPG 1960 I 470, below. If your computer screen is set to 72 dpi these two specimens will be shown at full scale. Both are among the most primitive known species of Rhamphorhynchus. Unlike the BML specimen reconstructed earlier, the BSPG specimen had a relatively small skull, based on the size of the mandible.

Reconstruction and Phylogenetic Analysis
We can’t just trace ephemeral elements without testing them in a reconstruction and phylogenetic analysis. The reconstruction is shown in Figure 2 alongside its phylogenetic sister, Rhamphorhynchus intermedius. The relatively short neck and robust torso mark these as primitive for the genus. The pedal phalangeal patterns are also primitive. The very wide jaws of the BSPG specimen are similar to those found in a more derived sister, also tiny, the BMM specimen.

A better test would be for a preparator to dig into the matrix where I have mapped the buried elements.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

References
Wellnhofer P 1975a. Teil I. Die Rhamphorhynchoidea (Pterosauria) der Oberjura-Plattenkalke Süddeutschlands. Allgemeine Skelettmorphologie. – Paleontographica A 148: 1-33.
1975b. Teil II. Systematische Beschreibung. – Paleontographica A 148: 132-186.
1975c. Teil III. Paläokolgie und Stammesgeschichte. – Palaeontographica 149: 1-30.
Wellnhofer P 1991. The Illustrated Encyclopedia of Pterosaurs. London, Salamander Books, Limited: 1-192.