‘Tubby’ Pterosaurs

Most pterosaurs
have an elliptical and taller than wide torso in cross section. That gives them a relatively narrow torso.

Deeper torso
Earlier we looked at pterosaurs with a deep torso, like Rhamphorhychus deepened principally by a large prepubis.

Wider torso
A few pterosaurs, especially among the anurognathids, have a wider that tall torso. Previously unrecognized, its time to take a look at these ‘tubby’ pterosaurs.

Dendrorhynchoides with the wider than tall torso in cross section.

Figure 1. Dendrorhynchoides, a basal anurognathid with a wider than tall torso in cross section. Scapula/coracoid in blue. Ribs and sternal complex in anterior view in red. Dorsal view of sternal complex in outline (below.)

Figure 1. Jeholopterus. Most workers avoid and overlook details like these, but here are the gastralia, ribs and sternal complex, along with a cross section of the torso, wider than tall.

Figure 2. Jeholopterus. Most of today’s workers avoid and overlook details like these. I was one of them until just recently~!  Reconstructions from tracings reveal so much! Here are the gastralia (in red), ribs and sternal complex (in green), along with a cross section of the torso, wider than tall (upper right). Note the posterior cervicals here are also much wider than tall, unless they were much deeper than is shown here. 

We knew that the skull of the flathead pterosaur was much wider than tall, but here the torso is also shown in cross section.

Figure 3. We knew that the skull of the flathead pterosaur was much wider than tall, but here the torso is also shown in cross section, likewise wider than tall.

Wider than tall torso – basal fenestrasaurs
Cosesaurus and Longisquama both have a typical torso, but Sharovipteryx has a wide, circular (in dorsal view), flat torso that contributed to its gliding abilities. Click the link to see it.

Wider than tall torso – pterosaurs
Some, but not all anurognathid pterosaurs trend toward a wider than tall torso. Dendrorhynchoides (Fig. 1) has a very wide sternal complex and robust ribs.  Jeholopterus (Fig. 2) likewise has wide ribs and elongate gastralia. The flathead pterosaur (SMNS 81928, Fig. 3) also has a wider than deep torso.

In addition
the flightless pterosaur (Sos 2428) and its tiny phylogenetic predecessor, BSPG 1911 I 31 (no. 42 in the Wellnhofer 1970 catalog), both have extended gastralia and ribs that widen the torso.

Limb interactions
Even though these pterosaurs have a wide torso, the hind limbs do not bang up against their wider bellies. The elbows could not have been tucked in as tightly as in narrower pterosaurs, but that probably did not pose a problem with obliquely deployed elbows. The knees would have tucked in below the gastralia that supported the belly in erect anurognathids or the knees would have splayed in those pterosaurs with less than a fully erect femur, as determined by the angle of the femoral head to the shaft, discussed earlier.

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