If you're just in this for the dinosaurs, you may have gotten the impression that there aren't any Mesozoic fossils between, say, Egypt and Pakistan. This is not true; the Middle East just happens to specialize in marine Mesozoic rocks and fossils, so dinosaurs are
not well represented. (Of course, these include the inevitable titanosaurs.) They're there, although as bits and pieces so far; eventually someone will name one. Pterosaurs are somewhat better known; before 2019 there was the azhdarchid
Arambourgiana philadelphiae from Jordan and the much smaller azhdarchoid
Microtuban altivolans from Lebanon. Now,
Mimodactylus libanensis makes a third named pterosaur from this region, and is by far the best represented.
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| The type specimen of Mimodactylus libanensis (Figure 2 in Kellner et al. 2019, which see for full caption). The scale bar for a is 50 mm (2.0 in), and 10 mm (0.39 in) for the three insets. CC-BY-4.0. |
Genus and species:
Mimodactylus libanensis. The "Mim-" part is a reference to the Mineral Museum (MIM) of Beirut, Lebanon, where the type specimen is housed, and the ptraditional pterosaur "dactylus" comes from the Greek "dactylos", usually given as "finger" where pterosaurs are concerned. The species name refers to Lebanon (Kellner et al. 2019). Together, we get something like "Mineral Museum finger of Lebanon".
Citation: Kellner, A. W. A., M. W. Caldwell, B. Holgado, F. M. Dalla Vecchia, R. Nohra, J. M. Sayão, and P. J. Currie. 2019.
First complete pterosaur from the Afro-Arabian continent: insight into pterodactyloid diversity. Scientific Reports 9:17875. doi:
10.1038/s41598-019-54042-z.
Stratigraphy and geography: The type and only known specimen is from the Hjoûla Lagerstätte of the Sannine Limestone, of late
Cenomanian age (early Late Cretaceous). It was found near Hjoûla in the northern part of Mount Lebanon Governorate, west and a little north of central Lebanon (Kellner et al. 2019). You may already know that Arabia has only recently split away from the African continent, geologically speaking. Back in the mid-Cretaceous, the two landmasses were still firmly connected and moving north, shrinking the Tethys Sea. Lebanon and other nearby areas were shallow marine settings on the leading edge of the tectonic action.
Holotype: MIM F1, a mostly complete and articulated to semi-articulated skeleton (Kellner et al. 2019). The skeletal restoration shows a few parts to be absent, such as the
ilium and the top of the head, but I would not be surprised if at least some of these parts are actually present in the block but inaccessible.
The type specimen of
Mimodactylus libanensis was a little fellow; Kellner et al. (2019) estimated its wingspan at approximately 1.32 m (4.33 ft). If that's a little abstract for you, the lower jaws are 102 mm long (4.02 in), and the humerus is 52 mm long (2.0 in). Kellner et al. (2019) interpreted it as a young individual, because many of the bones that fuse in adult pterosaurs were still unfused; for instance, no notarium (fusion of several dorsal vertebrae to brace the shoulders). Despite its youth, it is clearly not an example of either of the previously known pterosaurs from Lebanon, contemporaneous
Microtuban and an unnamed
ornithocheiroid. Rather, it was more closely related to one of the lesser-known groups of mid-Cretaceous pterosaurs, the
istiodactylids (Kellner et al. 2019).
The istiodactylids are noted for having a small number of short pointed teeth, crowded toward the
anterior end of relatively blunt and broad jaws ("relatively" meaning it doesn't come to a point, more or less). The breadth of the business end of the skull is sometimes compared to a duck's bill, but that's an exaggeration.
Istiodactylus itself has one of those quaint, frustrating histories involving an early specialist (Harry Govier Seeley) inexplicably assigning a specimen to a genus known from completely non-overlapping material: in this case, a partial skull of a pterosaur placed in
Ornithodesmus, otherwise represented solely by the hip vertebrae of what turned out to a dromaeosaur. Kellner et al. (2019) found
M. libanensis to be near but just outside of Istiodactylidae proper, paired with the Chinese pterosaur
Haopterus gracilis. They created Istiodactyliforms for
M. libanensis and the istiodactylids, and Mimodactylidae for
M. libanensis's branch.
M. libanensis has the istiodacylid-type crowding of small conical pointed teeth at the front of relatively broad jaws. There are some proportional differences in the wing compared to istiodactylids (the humerus being relatively shorter than some other elements), and overall the wings are relatively long as pterosaurs go, but the foot is similar to istiodactylids in being proportionally small. The pteroid (the rod-like projecting bone in the pterosaur wrist) is articulated pointing toward the body, for those of you keeping track of this historically controversial bone (Kellner et al. 2019).
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| The jaws of M. libanensis (Figure 3 in Kellner et al. 2019, which see for full caption). The scale bar for a is 10 mm (0.39 in), and for b is 1 mm (0.04 in). CC-BY-4.0. |
Istiodactylids are often interpreted as preferring terrestrial areas and having scavenging habits.
M. libanensis, on the other hand, is only known from a marine formation, and although its teeth are similar to istiodactylids, they aren't exactly the same. Kellner et al. (2019) looked in detail at a couple of hypotheses that would fit with the short pointed teeth. They decided insectivory was possible but questionable, because of the long wings and absence of insects (so far) in the host sediments. Instead, they proposed
M. libanensis was going after
decapod crustaceans in the shallow waters. The Hjoûla Lagerstätte, as the "lagerstätte" makes clear, is already known for producing well-preserved fossils, primarily of fish and crustaceans.
References
Kellner, A. W. A., M. W. Caldwell, B. Holgado, F. M. Dalla Vecchia, R. Nohra, J. M. Sayão, and P. J. Currie. 2019.
First complete pterosaur from the Afro-Arabian continent: insight into pterodactyloid diversity. Scientific Reports 9:17875. doi:
10.1038/s41598-019-54042-z.
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