Pterosaurs of the Kem Kem Beds

Update 10/4/2022: This post is five years old and very outdated. A lot of newer research on Kem Kem pterosaurs has occurred since this post, including the naming of many new taxa. Do not use this as a source anymore.

The Kem Kem Beds lie on the border of Morocco and Algeria. This formation produces fossils that date to the Cenomanian, which reveal a coastal deltaic wetland environment. It’s most famous for the various large theropod dinosaurs such as Carcharodontosaurus and Spinosaurus (leading to the infamous Stromer’s Riddle – why are there so many large predatory dinosaurs in the same time and place?)

All of the pterosaur fossils from Kem Kem seem to hail from the Aoufous Formation (~95 Ma) and all come in the form of isolated bones, but given this quality of preservation a surprisingly high pterosaur diversity is known. At least five distinct taxa can be distinguished, indicating a probably Azhdarchoid-dominated assemblage. Chiarenza and Cau 2016 proposed that the high diversity of the Beds is exaggerated by ambiguous stratigraphy, and that the theropods, and by extension other fauna, hail from different units that were laid down at different times. Hence, they weren’t all contemporaneous. The same could apply for other fauna, including pterosaurs. But even if this weren’t the case (and they were all contemporaneous), Stromer’s Riddle likely wouldn’t apply to the pterosaurs – the diversity in jaw shapes in the recovered pterosaurs imply they all probably exploited different niches.

Anhanguerians

Only one toothed pterosaur, Siroccopteryx, is currently named from the Kem Kem formation. There are a lot of isolated teeth, however, and they fall into four distinct morphotypes (Wellnhofer and Buffetaut 1999). It’s unknown whether this might hint at higher diversity or if they could have all come from different positions in one pterosaur’s mouth.

Siroccopteryx moroccensis

siroccopteryx_coloborhynchus_by_hyrotrioskjan-d8ag6l3
Life restoration of Ernst Stromer, with Siroccopteryx for scale. By Joschua Knüppe, used with permission.

The first pterosaur named from Kem Kem, Siroccopteryx is an Ornithocheirid closely related to Coloborhynchus. In fact I’d say it was a species of Coloborhynchus if Coloborhynchus didn’t live 40 million years earlier. The only known remains are, like many old world Anhanguerians, a snout tip, which is basically only useful at telling us what it’s related to. It was fairly medium-sized and like most Anhanguerians probably piscivorous. A handy diet for a coastal environment.

Azhdarchids

Azhdarchids are more well-represented from Kem Kem. Not only are there two named species based on skull material, there are at least two morphs of cervical vertebrae (whether the differences are taxonomic or due to position in the neck are unclear) and an isolated humerus that could pertain to either. Interestingly, the two Azhdarchid species here might be related…

Alanqa saharica

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Life restoration of Alanqa. By Joschua Knüppe, used with permission.

Alanqa was named in 2010 based on a mandible that was at first interpreted as a possible Pteranodontid snout. More mandible and rostrum chunks were referred to it. The jaws are notable for being very long straight, even when compared to other Azhdarchids. What’s also notable is that near the back of the mandible was a pair of ridges on the occlusal face. A piece of palate was later found with similar ridges, and it’s likely this portion was positioned so the ridges met when the jaws closed (Martill & Ibrahim 2015).

It’s uncertain what these ridges were used for – Martill & Ibrahim suggested crushing hard-shelled prey, attachment for turkey-like snoods, attachment for “cheeks”, or simple display features. I personally am inclined towards the first or last options; there’s no evidence for any cheek-like structures in pterosaurs, and being at least partially in the inside of the mouth a soft-tissue attachment would be awkward. The ridges could indicate Alanqa was at least partially durophagous, crushing hard-shelled aquatic invertebrates. This would make it similar ecologically to modern openbill storks or oystercatchers.

Xericeps curvirostris

Xericeps-skull4.png
Reconstruction of the skull of Xericeps. Scale bar = 10 cm.

Xericeps was named by Martill and colleagues in 2017 off another mandible with paired ridges. Unlike Alanqa, the mandible is rounder in cross-section and gently curves upward. It’s been likened to the jabiru by Joschua Knüppe (I see a pattern here in comparing Azhdarchids to storks…). Ridges like these combined with a pointed/upturned anterior snout may have been an attempt at being a “toothless heterodont”, being able to process different foods (e.g. small vertebrates vs. shelled invertebrates) in different areas of the mouth (Headden, pers. comm.). The different shape of the jaws relative to Alanqa imply niche partitioning between these two pterosaurs.

What’s interesting is that both the Kem Kem Azhdarchids have almost identical paired parallel ridges near the back of the mandible (and in Alanqa, maybe the palate too). These mandibular ridges differ from the independently-evolved horizontal ridge in Bakonydraco and “Huaxiapterus benxiensis” and the single anterior ridge in Thalassodromeus. My analysis currently has Alanqa and Xericeps form a clade that may include Argentinadraco, which also has similar mandibular ridges.

Rodrigues et al. 2011 describe another fragment of rostrum, CMN 50859, which was broadly referred to Dsungaripteroidea (=Ornithocheiroidea) indet. based on the lack of diagnostic features. I think it might be Xericeps. Both have a convex ventral margin and a roughly oval cross-section.

xlebw0k3syczpwsqmwwt_xericeps_joschua-knuppe
Life restoration of Xericeps. By Joschua Knüppe, used with permission.

Other Pterosaurs

Kem Kem “Pteranodontid”

Another mandible fragment, MN 7054-V, was described by Kellner et al. 2007 and proposed to be a Pteranodontid. Very little anatomical information can be gleaned from this fossil, but a few things can be determined: it lacks teeth, is roughly triangular in cross-section, gently curves upward and doesn’t have any foraminae. The lack of foraminae probably excludes it from Azhdarchidae (Ibrahim et al. 2010), and the gentle upturn and lack of prominent tomia probably exclude it from Tapejaridae or Thalassodromidae. This leaves two possible clades – Pteranodontidae and Chaoyangopteridae. Around this time, unambiguous Pteranodontians are unknown in the fossil record, but Chaoyangopterids may be if Microtuban turns out to be one. The fossil is significantly less elongate than Pteranodontian mandibles but closer to (though still shorter than) that of Shenzhoupterus in length, and proportionally wider than Pteranodon mandibles seem to be, more closely resembling Lacusovagus in this respect. So take this with a grain of salt, but I think it might hint at a slightly short-snouted Kem Kem Chaoyangopterid.

kem kem chaoyangopterid
Very hypothetical reconstruction of MN 7054-V as a Chaoyangopterid. Scale bar = 5 cm.

Kem Kem Tapejarid

Kem Kem tapejarid
The beak chunk of the Tapejarid, in dorsal/ventral (a) and lateral (b) views. From Wellnhofer and Buffetaut 1999. Scale bar= 5 cm.

Finally, there’s this last little beak chunk, BSP 1997 I 67. It’s hard to tell whether it’s a mandible or a rostrum, but in any case this specimen shows the beginning of a deep crest. Contra Averianov 2014, it probably isn’t Alanqa; no Azhdarchid has a similar crest or similarly narrow jaws, and this fragment lacks the paired foraminae at the front of the jaw seen in Alanqa and several other Azhdarchids (they’re apparent even in tiny specimens referred to Azhdarcho, so they probably didn’t appear with age). Whatever it is, it seems to fit most among Tapejarids (possibly a basal one due to the relatively gentle curvature). This specimen implies a fairly large Tapejarid, similar in size to Tupandactylus. Assuming it was other Tapejarids, it was probably omnivorous/predominantly herbivorous, rounding out the ecological diversity in Kem Kem pterosaurs.

References
Averianov, A. (2014). “Review of taxonomy, geographic distribution, and paleoenvironments of Azhdarchidae (Pterosauria)“. ZooKeys 432: 1-107.
Chiarenza, A.A.; Cau, A. (2016). “A large abelisaurid (Dinosauria, Theropoda) from Morocco and comments on the Cenomanian theropods from North Africa“. PeerJ 4: e1754.
Ibrahim, N.; Unwin, D.M.; Martill, D.M.; Baidder, L.; Zouhri, S. (2010). “A New Pterosaur (Pterodactyloidea: Azhdarchidae) from the Upper Cretaceous of Morocco“. PLoS ONE 5(5): e10875.
Kellner, A.W.A.; Mello, A.M.S.; Ford, T. (2007). “A survey of pterosaurs from Africa with the description of a new specimen from Morocco“. In: Paleontologia: Cenários de Vida pp. 257-267.
Martill, D.M.; Ibrahim, N. (2015). “An unusual modification of the jaws in cf. Alanqa, a mid-Cretaceous azhdarchoid pterosaur from the Kem Kem beds of Morocco“. Cretaceous Research 53: 59-67.
Martill, D.M.; Unwin, D.M.; Ibrahim, N.; Longrich, N. (2017). “A new edentulous pterosaur from the Cretaceous Kem Kem beds of south eastern Morocco“. Cretaceous Research, in press.
Rodrigues, T.; Kellner, A.W.A.; Mader, B.J.; Russell, D.A. (2011). “New Pterosaur Specimens from the Kem Kem Beds (Upper Cretaceous, Cenomanian) of Morocco“. Rivista Italiana di Paleontologia e Stratigrafia 117(1): 149-160.
Wellnhofer, P.; Buffetaut, E. (1999). “Pterosaur remains from the Cretaceous of Morocco“. Paläontologische Zeitschrift 73 :133-142.

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