Anurognathid flying abilities – Rio Ptero Symposium

Earlier we talked about various Rio Ptero Symposium abstracts here, here, here, and here.

Today we look at anurognathids
Habib and Witton wrote, “The ration of humeral to femoral section modulus in Anurognathus ammoni is significantly lower than that for pterosaurs.” Habib is famous for reporting the humerus in pterosaurs was much stronger than the femur and so concluded that pterosaurs launched by leaping with their hind limbs to compress their forelimbs in preparation for a forelimb launch. This odd and, so far, unsupported by footprint evidence, hypothesis was covered earlier here and here.

But getting back to that ratio
Here are the two specimens attributed to Anurognathus (Fig. 1) in which the humerus is no thicker at its smallest diameter than the femur. In most pterosaurs the humerus is thicker. There are other notable exceptions here.

Figure 1. The flat-head pterosaur, a private specimen (on the left) attributed by Bennett (2007) to Anurognathus ammoni (on the right).

Figure 1. The flat-head pterosaur, a private specimen (on the left) attributed by Bennett (2007) to Anurognathus ammoni (on the right). There are several generic differences here, readily observed.

Habib and Witton report that:

  1. Anurognathids had short faces – this is based on the bad reconstruction of the flathead anurognathid (Bennett 2007) which was misinterpreted with a giant orbit (actually a maxilla) in the front half of the skull, different than ALL other pterosaurs.
  2. Anurognathids had a wingspan up to .9m (Habib and Witton did not consider the IVPP embryo, 8x larger than most other anurognathids and Dimorphodon? weintraubi, which nests with anurognathids in the large pterosaur tree).
  3. Anurognathids include only 4 species (the large pterosaur tree found 9 + 3 more protoanurognathids)
  4. Much of anurognathid osteology has been documented (actually only the post-crania has been accurately traced, the skulls have not been successfully reconstructed in the literature, but can be found here).
  5. Anurognathids are the only probable pterosaurian aerial insectivores, ignoring the many small to tiny pterosaurs (and their 8x smaller juveniles!) that could only have fed on the tiniest of insects.
  6. Their estimate for the wingspan of [the small, flathead] Anurognathus ammoni at 22 cm deletes the distal wing phalanges.
  7. Habib and Witton note “the average humeral breadth at midshaft relative to body mass is greatest in those birds and bats that habitually sustain hovering and feed on nectar, but the relative humeral diameter also tends to be greater than average in those species that hawk insects on the wing” – but this can’t pertain to pterosaurs as giant ornithocheirids greatly exceed those ratios when compared to anurognathids.
  8. Anurognathids had “dorsally-facing eyes” – wow, that’s weird and unsupported by ANY fossil reconstructions.  Even the bad Bennett (2007) reconstruction had a broad skull roof with laterally-facing eyes.
  9. Anurognathids probably performed “perch and chase” methods of hunting, as well as, or instead of sustained hunting flights. – This idea may come from deleting the distal wing phalanges (Bennett 2007), making the pterosaur less of a long-wing nighthawk analog. Odd that Habib and Witton do this because Jeholopterus and Batrachognathus, the two most derived anurognathids have a full complement of four wing phalanges plus the ungual.

Habib and Witton compare the gape of anurognathids to the freckled nightjar (Caprimulgus tristigma) as we did earlier with the common swift (Apus apus). That’s valid.

The skull and skeleton of Apus apus,

Figure 2. The skull and skeleton of Apus apus, the Common Swift.

Habib and Witton omitted any reference to the vampire anurognathid, Jeholopterus, or any reference to its unique morphology, including its incredible long curved hand claws, the super strong feet and, of course, the fangs, but do note that anurognathids “would have been competent leapers and ground launchers that may indicate a unique life history or ecology.” That I can agree with.

Too bad Habib and Witton did not touch on the right angle, dinosaur-like, femoral articulations to the pelvis, their extraordinarily long feet and even longer fifth toes. They didn’t discuss their unique and sensitive palatal bones or their extremely wide bodies.

As readers know, I have not been charitable with the works of Mike Habib and Mark Witton, but rather critical. I only wish they would start making accurate reconstructions from precise tracings and then create their own phylogenetic analyses over a wide gamut of pterosaurs so these problems would go away.

Bennett SC 2007. A second specimen of the pterosaur Anurognathus ammoni. Paläontologische Zeitschrift 81(4):376-398.
Habib MB and Witton M 2013. Functional morphology of anurgnathid pterosaurs and the evolution of insectivore in the Pterosauria. Rio Pterosaur Symposium 2013:74-76.


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