NOT a new Zhenyuanopterus: XHPM1088

Very, very close, but no cigar.

And not a juvenile either.
A new paper by Teng et al. (2014) reports on a small partial Zhenyuanopterus (XHPM1088, Fig. 1) that does quite fit the morphology of the holotype. No worries. They said it was a juvenile with some odd sorts of allometry going on.

I hate to say it, but we can blame Chris Bennett for this bit of wishful thinking as his 1995 and 1996 papers on Solnhofen pterosaurs opened the doors to letting almost any small specimen become the juvenile of any somewhat similar, but much larger specimen based on the false notion of allometry during ontogeny. Several specimens falsify that little fantasy, including all the embryos now known.

Phylogenetic analysis would have put a stop to such nonsense, but no analysis was undertaken, either in 1995, 1996 or 2014.

Figure 1. XHPM1088 in situ. Only the posterior half is preserved here.

Figure 1. XHPM1088 (mistakenly referred to Zhenyuanopterus) in situ. Only the posterior half is preserved here.

Here’s the problem
The new specimen has a relatively long and robust tail (15 caudals) and a more robust forelimb than hindlimb, plus a Yixian Formation (Early Cretaceous) locality. These facts identified this pterosaur as Zhenyuanopterus to its authors. With identical length ratios between the humerus and femur, Teng et al. thought growth was isometric in these bones, but not others. The scapula has an odd sort of shape otherwise found only in Zhenyuanopterus. However the coracoid was not the same shape or size ratio (Fig. 1). They thought the length of the coracoid would slow dramatically during growth compared to other bones, not realizing that taxa just outside of Zhenyuanopterus (i.e. Boreopoterus, Arthurdactylus, Fig. 2) had a similar long, straight coracoid. They also blamed the coracoid length problem on the holotype of Zhenyuanopterus, saying it was not well-preserved and giving it a longer redicted length based on XHPM1008. That’s not good Science, especially when the coracoids are well preserved and articulated in the holotype.

Unfortunately
Teng et al. thought one of the unique characters of Zhenyuanopterus was its small feet, but the reality is ALL ornithocheirids (more derived than the JZMP embryo) had tiny feet.

Figure 2. The partial pterosaur XHPM1088 to scale with Boreopterus and Zhenyuanopterus and also scaled up to a similar humerus length with Zhenyuanopterus.  Note the coracoids don't match. This is one of the few pterosaurs in which the tibia is shorter than the femur. Boreopterus is similar in this regard.

Figure 2. Click to enlarge. The partial pterosaur XHPM1088 to scale with Boreopterus and Zhenyuanopterus and also scaled up to a similar humerus length with Zhenyuanopterus. Note the coracoids don’t match. This is one of the few pterosaurs in which the tibia is shorter than the femur. Boreopterus is similar in this regard.

A beautiful illustration of Zhenyuanopterus is included in the paper (Fig. 3) sadly flawed by bat-like, deep chord wing membranes and an odd sort of hanging posture for a pterosaur, especially one with such small feet. Some traditions are very hard to kill.

Zhenyuanopterus-illustration

Figure 3. Zhenyuanopterus illustration by Zhao Chuang, a very talented artist. Sadly the wing membranes are wrong and the hanging posture is unlikely based on the tiny feet.

I encourage pterosaur workers
to start putting bones together in reconstructions, then adding new taxa to good phylogenetic analyses before assigning a juvenile status to a small pterosaur that doesn’t match a large one. Here’s a new genus that Teng et al. could have named, but didn’t.

Reference
Teng F-F, Lü J-C, Wei X-F, Hsiao Y-F and Pittman, M 2014. New Material of Zhenyuanopterus (Pterosauria) from the Early Cretaceous Yixian Formation of Western Liaoning. Acta Geologica Sinica (English) 88(1):1-5.

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