Meet Mimodactylus, a small ornithocheirid from Lebanon

Figure 1. Mimodactylus in situ from Kellner et al. 2019.

Figure 1. Mimodactylus in situ from Kellner et al. 2019.

Mimodactylus libanensis (Kellner et al. 2019; Late Cretaceous, 95mya; MIM (no number), Lebanon) is known from a virtually complete specimen (Figs. 1, 2), with the top of the skull still buried in the sediment (Fig. 3). Originally it was considered closest to Haopterus, together comprising the Mimodactylidae. This is a pterosaur I was introduced to over ten years ago. Back then Roy Nohra, one of the co-authors, sent me photos of the unprepared slabs from which I created this bipedal reconstruction (Fig. 2) prior to the publication of Kellner et al.

Figure 1. a basal ornithocheirid, undescribed, from Lebanon.

Figure 2. Mimodactylus reconstruction created several years ago, prior to fossil preparation and publication.

Here,
in the large pterosaur tree (LPT, 242 taxa), Mimodactylus nests between Yixianopterus and Haopterus — closer to Yixianopterus. So the LRT does not support the newly erected clade Mimodactylidae. Yixianopterus was omitted from the cladogram of Kellner et al. Once again, taxon exclusion is the number one problem.

Figure 1. Mimodactylus skull in situ and reconstructed. Kellner et al. misidentified the maxillary palate as the palatine. This is repaired in the reconstruction below.

Figure 3. Mimodactylus skull in situ and reconstructed. Kellner et al. misidentified the maxillary palate as the palatine (PL), apparently unaware that this was correctly identified by several authors years ago. This is repaired in the reconstruction below.

Apparently seven co-authors were not enough
to edit out the seven mistakes in the basic understanding of pterosaurs found in this long-awaited paper.

  1. The broad maxillary palate was misidentified as the palatine. This correction was made by Peters 2000 and later by Osi et al. 2010 and Pinheiro and Schultz 2012. The actual tiny pterygoids and ectopalatine (ectopterygoid + palatine) were not identified.
  2. The manual digits are aligned 1–4 palmar side down in flight in pterosaurs, not palm side anterior in flight with #3 on the top as shown in Kellner et al.
  3. All pterosaurs have 8 cervical vertebrae, not 6
  4. The brachiopatagium stretches between the wingtip and elbow, not the tail tip
  5. The feet of ornithocheirid pterosaurs, and Mimodactylus, too, are half the size pictured.
  6. The Kellner et al. cladogram (Supp Data) mistakenly includes the archosauriforms Ornithosuchus, Herrerasaurus and Scleromochlus as outgroup taxa, none of which are related to pterosaurs. Pterosaurs nest within Lepidosauria in the large reptile tree (LRT, 1611+ taxa). Also see Peters 2000, 2007.
  7. Kellner et al. wrote, “dorsal vertebrae not fused into a notarium, it is likely that it was a very young animal at the time of death, having reached an ontogenetic stage between 2 and 32.” No phylogenetic sisters in the LPT have a notarium. Kellner et al. are unaware that as lepidosaurs pterosaurs have a distinctly different ontogenetic pattern of ossification. Their cladogram suffers from massive taxon exclusion.
Figure 1. Original from Kellner et al. 2019 showing the several basic morphology mistakes made by their artist.

Figure 4. Original Mimodactylus illustration from Kellner et al. 2019 showing the several basic morphology mistakes made by their artist.

The cladogram of Kellner et al.
(Fig. 5) continues several myths based on taxon exclusion of the tiny Solnhofen pterosaurs, all of which were outgroups to all known Cretaceous pterosaurs. I have colorized clades that appear in the LPT because they type size they used was way too small to read. Yixianopterus is not present here and Mimodactylus is not closely related to the istiodactylids in the LRT, contra Kellner et al. 2019. These authors simply have no idea what the tree topology of the pterosaur looks like when small taxa are included. Nor do they understand that pterosaurs arose from tritosaur lepidsosaurs, not a scattershot of unrelated and dissimilar archosauriforms.

Figure 3. Cladogram from Kellner et al. 2019. Color overlays show clades recovered in the LPT.

Figure 5. Cladogram from Kellner et al. 2019. Color overlays show clades recovered in the LPT. If you find this difficult to read, you’re in the majority. This cladogram does not include taxa listed in the SuppData in which Anurognathus nests as the basalmost pterosaur.

A subset of the LPT
(Fig. 6) includes several pertinent taxa omitted by Kellner et al. 2019. Even so, Haopterus nests close by, but Pteranodon and kin do not. Not sure if you ask yourself this question, but I do: What does it mean when scientists refuse to test competing hypotheses for twenty years? … and continue traditions they know don’t make sense?

Figure 1. Subset of the LPT with the addition of Mimodactylus within the clade Scaphognathia.

Figure 6. Subset of the LPT with the addition of Mimodactylus within the clade Scaphognathia.

Here’s Haopterus
(Fig. 7) a taxon closely related to Mimodactylus in both cladograms. Note the tiny feet, skull shape, robust tail, and palate morphology, all instructive with regard to Mimodactylus.

Figure 6. Haopterus is close to Mimodactylus and provides a bauplan for a bipedal stance. Note the tiny feet and palate morphology.

Figure 7. Haopterus is close to Mimodactylus and provides a bauplan for a bipedal stance. Note the tiny feet, pelvis, skull and palate morphology.

And here’s Yixianopterus
the basalmost ornithocheirid in the LPT. Mimodactylus is more closely related to this taxon than to Haopterus. Kellner et al. 2019 omitted Yixianopterus from their analysis.

Figure 2. Reconstruction of Yixianopterus. Roadkill fossils really need at least this much reconstruction to make then intelligible. And don't ignore them in phylogenetic studies. Nothing spectacular here, which means it is more likely to be phylogenetically important.

Figure 8. Reconstruction of Yixianopterus. This is the basalmost ornithocheirid in the LPT.

Believe it or not,
Peters 2009 was actually cited in this paper based on the evidence of a ‘clear articulation’ of the pteroid with the radiale and medial orientation of the free end, contra prior studies on pteroid orientation. That shouldn’t be a citation. It’s just the way it has always been.

Figure 8. Artwork in Kellner et al. of Mimodactylus by Julius Csotonyi. Second frame shows repairs to morphology needed to bring this illustration up to date. Figure 8. Artwork in Kellner et al. of Mimodactylus by Julius Csotonyi. Second frame shows repairs to morphology needed to bring this illustration up to date.

Figure 9. Artwork in Kellner et al. of Mimodactylus by Julius Csotonyi. Second frame shows gross repairs to morphology needed to bring this illustration up to date. 

 

References
Kellner AWA et al. (6 co-authors) 2019. First complete pterosaur from the Afro-Arabian continent: insight into pterodactyloid diversity. Nature.com/ScientificReports 9:17875. PDF
Ösi A, Prondvai E, Frey E and Pohl B 2010. New interpretation of the palate of pterosaurs. The Anat Rec 293: 243–258. doi: 10.1002/ar.21053.
Peters D 2000b.
 A Redescription of Four Prolacertiform Genera and Implications for Pterosaur Phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106 (3): 293–336.
Peters D 2009. A reinterpretation of pteroid articulation in pterosaurs. Journal of Vertebrate Paleontology 29:1327-1330.
Pinheiro FL and Schultz CL 2012. An Unusual Pterosaur Specimen (Pterodactyloidea, ?Azhdarchoidea) from the Early Cretaceous Romualdo Formation of Brazil, and the Evolution of the Pterodactyloid Palate. PLoS ONE 7(11): e50088. doi:10.1371/journal.pone.0050088

wiki/Mimodactylus

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