Pterodactylus fossils from the Solnhofen Limestone were the first identified pterosaurs in the fossil record, dating back to turn of the 19th century (see brief historical overview in Augustin et al., 2022). This specimen is a replica of a fossil hosted at the Bayerische Staatssamlung für Paläontologie in Munich, Germany, first described by Broili (1938) and attributed by him to the species Pterodactylus scolopaciceps. The specimen is remarkable not only for its completeness and articulation but also for the preservation of soft tissue outlines.

The taxonomy of Pterodactylus has been complex and controversial. This specimen was later attributed to Pterodactylus kochi (Wellnhofer, 1970) or Pterodactylus antiquus (Jouve, 2004; Bennett, 2013) due to synonymization. Alternatively, it has been placed into a separate genus under the species name Aerodactylus scolopaciceps (Vidovic & Martill, 2014). A thorough study by Smyth & Unwin (2024) highlighted the diagnostic characters of Pterodactylus antiquus, firmly establishing this taxonomic attribution for the specimen.

Both Pterodactylus and Rhamphorhynchus are found in correlative strata of the Solnhofen Limestone (Barrett et al., 2008), suggesting that they lived together in the same region. While the sharp teeth of both organisms indicate a fish-based diet, they represent significantly different kinds of pterosaurs. Pterodactylus belonged to a group of short-tailed pterosaurs with diminutive (or absent) fifth toes (pterodactyloids), while Rhamphorhynchus was a non-pterodactyloid, with a long tail and fully developed fifth toes (Witton, 2013).

The relatively small size of this specimen illustrates an interesting feature observed in pterosaur fossils from the Solnhofen Limestone: the vast majority seem to represent juvenile to sub-adult individuals (Bennett, 1996). This could be interpreted as a result of differential mortality rates (with higher mortality in younger individuals), ecological niche partitioning (e.g., younger pterosaurs occupied different environments, closer to the Solnhofen basins, than adult individuals), or sedimentological/taphonomic biases (e.g., the processes responsible for transport and burial of carcasses may have preferentially preserved smaller individuals) (Bennett, 1996; 2018). Intriguingly, the preferential preservation of juvenile individuals in the Solnhofen fossils has been noted for other groups of vertebrates (Bennett, 1996; Kemp, 2002) and even some invertebrates (see Mesolimuls walchi).

References:

Augustin, F.J., Kampouridis, P., Hartung, J., Albersdörfer, R. and Matzke, A.T., 2022. The geologically oldest specimen of Pterodactylus: a new exquisitely preserved skeleton from the Upper Jurassic (Kimmeridgian) Plattenkalk deposits of Painten (Bavaria, Germany). Fossil Record, 25(2), pp. 331-343. doi:10.3897/fr.25.90692.

Barrett, P.M., Butler, R.J., Edwards, N.P. and Milner, A.R., 2008. Pterosaur distribution in time and space: an atlas. Zitteliana, pp. 61-107.

Bennett, S.C., 1996. Year-classes of pterosaurs from the Solnhofen Limestone of Germany: taxonomic and systematic implications. Journal of Vertebrate Paleontology, 16(3), pp. 432-444.

Bennett, S.C., 2013. New information on body size and cranial display structures of Pterodactylus antiquus, with a revision of the genus. Paläontologische Zeitschrift, 87, pp. 269-289.

Bennett, S.C., 2018. New smallest specimen of the pterosaur Pteranodon and ontogenetic niches in pterosaurs. Journal of Paleontology, 92(2), pp. 254-271.

Jouve, S., 2004. Description of the skull of a Ctenochasma (Pterosauria) from the latest Jurassic of eastern France, with a taxonomic revision of European Tithonian Pterodactyloidea. Journal of Vertebrate Paleontology, 24(3), pp. 542-554.

Kemp, R.A., 2002. Generation of the Solnhofen tetrapod accumulation. Archaeopteryx, 19, pp. 11-28.

Smyth, R.S. and Unwin, D.M., 2024. Re-evaluation of Pterodactylus antiquus and Diopecephalus kochi: two troublesome taxonomic concepts. Journal of Systematic Palaeontology, 22(1), p.2421845. doi:10.1080/14772019.2024.2421845.

Vidovic, S.U. and Martill, D.M., 2014. Pterodactylus scolopaciceps Meyer, 1860 (Pterosauria, Pterodactyloidea) from the Upper Jurassic of Bavaria, Germany: the problem of cryptic pterosaur taxa in early ontogeny. PloS one, 9(10), p.e110646. doi:10.1371/journal.pone.0110646.

Wellnhofer, P., 1970. Die Pterodactyloidea (Pterosauria) der Oberjura-Plattenkalke Suddeutschlands. Bayerische Akademie der Wissenschaften, Mathematisch-Wissenschaftlichen Klasse, Abhandlungen 141: 1–133.

Witton, M. P., 2013. Pterosaurs: Natural History, Evolution, Anatomy. Princeton University Press. pp. 90-94. http://www.jstor.org/stable/j.ctt2jc95p